GLERL Publications with Abstracts
January 2008 - December 2008
|Capitalized names represent GLERL authors.
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Arhonditsis, G.B., C.A. STOW, H.W. Paerl, L.M. Valdes-Weaver, L.J. Steinberg, and K.H. Reckhow. Delineation of the role of nutrient dynamics and hydrologic forcing on phytoplankton patterns along a freshwater-marine continuum. Ecological Modelling 208:230-246 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080045.pdf
We examined the spatiotemporal phytoplankton community patterns and identified the nature of the underlying causal mechanisms in a freshwater-saltwater continuum, the Neuse River Estuary (North Carolina, USA). We used a Bayesian structural equation modeling (SEM) approach that considers the regulatory role of the physical environment (flow, salinity, and light availability), nitrogen (dissolved oxidized inorganic nitrogen and total dissolved inorganic nitrogen), phosphorus, and temperature on total phytoplankton biomass and phytoplankton community composition. Hydrologic forcing (mainly the river flow fluctuations) dominates the up-estuary processes and loosens the coupling between nutrients and phytoplankton. The switch from an upstream negative to a downstream positive phytoplankton-physical environment relationship suggests that the elevated advective transport from the upper reaches of the estuary leads to a phytoplankton biomass accumulation in the mid- and down-estuary segments. The positive influence of the physical environment on the phytoplankton community response was more evident on diatom, chlorophyte and cryptophyte dynamics, which also highlights the opportunistic behavior of these taxa (faster nutrient uptake and growth rates, tolerance on low salinity conditions) that allows them to dominate the phytoplankton community during high freshwater conditions. Model results highlight the stronger association between phosphorus and total phytoplankton dynamics at the upstream freshwater locations; both nitrogen and phosphorus played a significant role in the middle section of the estuary, while the nitrogen-phytoplankton relationship was stronger in the downstream meso-polyhaline zone. Finally, our analysis provided evidence of a protracted favorable environment (e.g., longer residence times, low DIN concentrations and relaxation of the phosphorus limitation) for cyanobacteria dominance as we move to the down-estuary area, resulting in structural shifts on the phytoplankton community temporal patterns.
BELETSKY, D., and D.J. SCHWAB. Climatological circulation in Lake Michigan. Geophysical Research Letters 35( L21604, doi:10.1029/2008GL035773):5 pp. (2008).
Maps of climatological circulation in Lake Michigan are presented for the first time. They are based on ten years continuous modeling of lake hydrodynamics from 1998-2007 using observed meteorological data as the forcing function. Model results show a remarkably stable largescale cyclonic circulation pattern during both stratified and unstratified conditions. Lake-averaged mean current speed is about 2 cm/s, but currents can reach 10 cm/s in some locations. The model results are confirmed by long-term current observations.
Costantini, M., S.A. LUDSIN, D.M. MASON, X. Zhang, W.C. Boicourt, and S.B. BRANDT. Effect of hypoxia on habitat quality of striped bass (Morone saxatilis) in Chesapeake Bay. Canadian Journal of Fisheries and Aquatic Sciences 65:989-1002 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080010.pdf
Eutrophication-induced hypoxia may affect both benthic and pelagic organisms in coastal systems. To evaluate the effect of hypoxia on pelagic striped bass (Morone saxatilis), we quantified the growth rate potential (GRP) of age-2 and age-4 fish in Chesapeake Bay during 1996 and 2000 using observed temperature, dissolved oxygen, and prey abundance information in a spatially-explicit bioenergetics modeling framework. Regions of the Bay with bottom hypoxia were generally areas with high quality habitat (i.e., GRP > 0 g·g-1·day-1), primarily because prey fish were forced into warm, oxygenated surface waters suitable for striped bass foraging and growth. In turn, by concentrating fish prey above the oxycline and removing bottom waters as a refuge, hypoxia likely enhanced striped bass predation efficiency and continued to the recovery of striped bass during the mid-1990s, a time when the striped bass fishery also was closed. This short-term positive effect of hypoxia on striped bass, however, appears to have been counterbalanced by a long-term negative effect of hypoxia in recent years. Ultimately, hypoxia-enhanced operation efficiency, combined with an abundance of striped bass due to restricted harvest, appears to be causing overconsumption of prey fishes in Chesapeake Bay, thus helping to explain poor growth and health of striped bass in recent years.
CROLEY, T.E. II. The once-Great Lakes. Proceedings, Climate Change in the Great Lakes Region, Starting a Public Discussion, Green Bay, WI, March 2007. University of Wisconsin Sea Grant Institute, pp. 65-69 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080009.pdf
This presentation reviewed the results of a study of hydrological effects of climate change in the Great Lakes region conducted by the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory. To establish a climate baseline, researchers collected daily precipitation and maximum-minimum air temperature data for 1948-99 from 1,800 meteorological stations around the Great Lakes, and temperature, wind speed, humidity, and cloud cover over the lakes from 40 stations. Using these data to represent present climate conditions, three different general circulation models were used to simulate four future climate scenarios: "warmer and dry," "hot and dry," "warmer and wet," and "hot and wet." This enabled the scientists to determine the effects of the full range of projected maximum/minimum air temperatures and high/low precipitation amounts for hydrological analysis. Evaporation and precipitation are the two most important factors controlling Great Lakes water levels.
CROLEY, T.E. II., and C. He. Spatially distributed watershed model of water and materials runoff. In Wetland and Water Resource Modeling and Assessment: A Watershed Perspective. W. Ji (Ed.). Part II, Wetland Hydrology and Water, Chapter 9. CRC Press, Taylor and Francis Group, Boca Raton, FL, pp. 99-112 (2008).
Agricultural nonpoint source contamination of water resources by pesticides, fertilizers, animal wastes, and soil erosion is a major problem in much of the Laurentian Great Lakes Basin, located between the United States and Canada. Point source contaminations, such as combined sewerage overflows (CSOs), also add wastes to water flows. Soil erosion and sedimentation reduce soil fertility and agricultural productivity, decrease the service life of reservoirs and lakes, and increase flooding and costs for dredging harbors and treating wastewater. Improper management of fertilizers, pesticides, and animal and human wastes can cause increased levels of nitrogen, phosphorus, and toxic substances in both surface water and groundwater. Sediment, waste, pesticide, and nutrient loadings to surface and subsurface waters can result in oxygen depletion and eutrophication in receiving lakes, as well as secondary impacts such as harmful algal blooms and beach closings due to viral and bacterial and/or toxin delivery to affected sites. The U.S. Environmental Protection Agency (EPA) has identified contaminated sediments, urban runoff and storm sewers, and agriculture as the primary sources of pollutants causing impairment of Great Lakes shoreline waters (USEPA 2002). Prediction of various ecological system variables or consequences (such as beach closings), as well as effective management of pollution at the watershed scale, require estimation of both point and nonpoint source material transport through a watershed by hydrological processes. However, currently there are no integrated fine-resolution spatially distributed, physically based watershed scale hydrological/water quality models available to evaluate movement of materials (sediments, animal and human wastes, agricultural chemicals, nutrients, etc.) in both surface and subsurface waters in the Great Lakes watersheds.
CROLEY, T.E. II., and C.F.M. Lewis. Warmer and drier climates that make Lake Huron into a terminal lake. Aquatic Ecosystem Health and Management 11(2):153-160 (2008).
Paleo-hydrologists have adjusted for glacial isostatic uplift and compared the original elevations of paleo-water level indicators and basin outlets for Lake Huron, revealing that Huron lake levels fell tens of meters below its lowest possible outlet (becoming a terminal lake) about 7,900 14C years BP. This corresponds to when the upper Great Lakes stopped receiving glacial melt inflow and became dependent for water supply on precipitation alone, as at present. Since these researchers accounted for differential isostatic effects, they surmised that the upper Great Lakes were impacted by severe dry climate. To understand possible climate changes that led to the closure, the Great Lakes Environmental Research Laboratory applied their Advanced Hydrologic Prediction System to explore deviations from present climates that could force the upper Great Lakes to become terminal. GLERL modeled the steady-state water balance of the present upper Great Lakes with pre-development natural water flow conditions by employing lake outflow-depth rating curves (using estimated sill elevations) reasonable for a natural system and by using dynamic lake areas controlled by observed hypsometric relations for each lake. By using systematic shifts in precipitation and temperature relative to the present base climate, GLERL showed the temperature rises and precipitation drops required for a terminal lake; they may be less extreme if additional effects of past differences in wind speed and insolation are also considered.
CROLEY, T.E. II., D.F. Raikow, C. He, and J.F. Atkinson. Hydrological resource sheds. Journal of Hydrologic Engineering 13(9):873-885 (2008).
When we consider a location with a material e.g., water, pollutant, sediment passing through it, we can ask: “Where did the material come from and how long did it take to reach the location?" We can quantify the answer by defining the areas contributing to this location during various time periods as "resource sheds." Various resource sheds and their source material distributions are rigorously defined and properties derived. For watershed hydrology, we compute resource sheds and their source distributions with a spatially distributed hydrology model by tracing water departing from a "cell" say 1 km2 over one time interval, traveling through intermediate cells soil, groundwater, and surface zones, and arriving at the watershed mouth in another time interval. This requires modeling all cells, but only tracing contributions from one at a time. By then combining these simulations for all cell loadings, we construct a map of the contributions over the entire watershed for specific departure and arrival time intervals. We then combine results of several sets of simulations to determine the source distribution for any time period and infer resource sheds from these mappings. We give examples for the Maumee River watershed in northern Ohio, discuss computation reduction, and suggest future extensions to other materials. DOI: 10.1061/ ASCE 1084-0699 2008 13:9 873
Deal, C., M. Jin, and J. WANG. The significance of water column nitfciation in the southeastern Bering Sea. Chinese Journal of Polar Research 19(2):185-192 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080064.pdf
Nitrate is considered the nutrient that limits new primary production in the southeastern Bering Sea shelf. Nitrate regenerated through biological nitrification has the potential to significantly support primary production as well. Here we use measurements of the specific rate of water column nitrification in a I-D ecosystem model to quantify the resupply of nitrate from nitrification in the middle shelf of the southeastern Bering Sea. Model sensitivity studies reveal nitrification rate is an important control on the dominant phytoplankton functional type, and the amount of nitrate in summer bottom waters and in the winter water column. Evaluation of nitrification using the model supports the hypothesis that increases in late-summer nitrate concentrations observed in the southeastern Bering Sea bottom waters are due to nitrification. Model results for nitrate replenishment exceed previously estimated rates of 20-30% based on observations. The results of this study indicate that nitrification, potentially the source of up to ~ 38% of the springtime water column nitrate, could support ~ 24% of the annual primary production.
Dettmers, J.M., C.P. Madenjian, P.J. Allen, S.A. POTHOVEN, and T.F. NALEPA. Impacts of recent invasive species on nearshore fishes. In The State of Lake Michigan in 2005. D.F. Clapp and W. Horns (Eds.). Great Lakes Fishery Commission Special Publication 08-02. Great Lakes Fishery Commission, Ann Arbor, MI, pp. 19-26 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080066.pdf
Invasive species have impacted Lake Michigan’s fisheries for 70 years. The passage through the Welland Canal by sea lamprey, after it invaded Lake Ontario, led to its establishment in Lake Michigan where it was first seen in 1936 (Christie and Goddard 2003). A combination of overfishing and sea lamprey predation led to the extirpation of lake trout (Coble et al. 1990; Hansen 1999) and to the extirpation or extinction of several deepwater ciscoes endemic to the Great Lakes (Coon 1999). Alewives, probably through interference with reproduction, likely caused the decline in abundances of deepwater sculpins and yellow perch during the 1960s and may have delayed the recovery of burbot in Lake Michigan until the 1980s (Madenjian et al. 2002). From 1959 to 1999, the rate of new introductions into the Great Lakes has increased to more than one species per year (Grigorovich et al. 2003), resulting in the establishment of numerous invaders during the past 20 years. In this report, we focus on (1) the status of six recent invasive species during 2000-2004, (2) the identity of other species that could invade in the near future, (3) examples of their impacts on the nearshore fish community, and (4) the implications for fishery management.
Dufour, E., T.O. HÖÖK, W.P. Patterson, and E.S. RUTHERFORD. High resolution isotope analysis of young alewife Alosa pseudoharengus otoliths: assessment of temporal resolution and reconstruction of habitat occupancy and thermal history. Journal of Fish Biology 73:2434-2451 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080049.pdf
Otoliths of age 0 year alewife Alosa pseudoharengus collected in different Lake Michigan habitats were microsampled, and carbon and oxygen isotope ratios (δ18Ootolith and δ13Cotolith) of resulting microsamples were quantified. To assess the temporal resolution of the method, age and otolith growth rates were also estimated by counting otolith daily growth increments. Core and outer intra-otolith samples averaged 36 and 23 days, respectively. Because of the accretionary nature of otolith growth, a habitat switch by a larva occurring between 0 and 18 days post-hatch may not be recognized by this approach. Taking this temporal resolution into account, A. pseudoharengus habitat occupancy and thermal history in nearshore Lake Michigan, and a connecting drowned river-mouth lake were documented. Comparisons between δ18Ootolith and δ13Cotolith profiles, and isotope values of Lake Michigan habitats suggested that movements by individual fish between a nearshore area of Lake Michigan proper and drowned river-mouth lake habitats were rare. Some individuals evidently moved between habitats, and such movements occurred during different periods of ontogeny. Thermal reconstructions, based on δ18Ootolith values suggested that during early life (e.g. first month of life) young A. pseudoharengus appeared to inhabit microhabitats with temperatures greater than mean epilimnetic temperatures. This study demonstrates not only the utility of intra-otolith geochemical analysis to describe the complexity of fish behaviour in fresh water but also identifies limitations of the present approach.
DYBLE, J., G.L. FAHNENSTIEL, R.W. Litaker, D.F. Millie, and P.A. Tester. Microcystin concentrations and genetic diversity of Microcystis in the lower Great Lakes. Environmental Toxicology 23:507-516 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080028.pdf
The resurgence of Microcystis blooms in the lower Great Lakes region is of great concern to public and ecosystem health due to the potential for these colonial cyanobacteria to produce hepatoxic microcystins. A survey of Microcystis cell densities and microcystin concentrations during August 2004 showed particularly high concentrations of both cells and toxin in the nearshore regions of Saginaw Bay (Lake Huron) and western Lake Erie, often exceeding the World Health Organization's recommended drinking water limit of 1 ug L-1. The dominant congener of microcystin in both basins was microcystin-LR (MC-LR), whereas the second most abundant congeners, accounting for up to 20-25% of the total microcystin concentrations, were MC-LA in Saginaw Bay and MC-RR in western Lake Erie. Multiplex PCR assays of Microcystis colonies isolated from these two regions showed that a much greater percentage of the Microcystis colonies from Saginaw Bay carried the mcyB gene necessary for microcystin production, in comparison with those from western Lake Erie. The mcyB genotypes sequenced separated into two distinct phylogenetic clusters, with Microcystis originating from Lake Erie predominantly in one branch and from Saginaw Bay present in both branches. These results indicate that the genetic composition of the bloom could impact the concentrations and congeners of microcystin produced and that the cell count methods currently being used to gauge public health threats posed by Microcystis blooms may not sufficiently assess actual bloom toxicity.
EADIE, B.J., J.A. ROBBINS, J. Val Klump, D.J. SCHWAB, and D.N. Edgington. Winter-spring storms and their influence on sediment resuspension, transport, and accumulation patterns in southern Lake Michigan. Oceanography 21(4):118-135 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080029.pdf
The Episodic Events-Great Lakes Experiment was designed to quantify the impacts of major late winter-early spring storms on sediment-water exchange, sediment, and associated constituent transport and resultant influence on well-characterized sediment distributions in southern Lake Michigan. Prior to this project, only very sparse data were available during the late winter-early spring period for any of the Great Lakes, primarily because of strong storms and ice conditions. The observation strategy consisted of moored arrays of current meters, thermistors, and sequencing traps, along with shipboard surveys. In addition, process measurement cruises were conducted along with special cruises for sedimentwater interface sampling using a remotely operated vehicle, particle transformation measurements, and sediment collection. A summary of conclusions include: (1) particles, predominantly from the western shore of the lake, are resuspended and transported in a coastal band toward the major sediment depositional region in the southeastern portion of the lake, (2) transport rates, measured by 234Th, are on the order of kilometers per day, (3) the magnitude of resuspended sediments from a single major storm is 1-5 x 106 kg, larger than annual external input of fine-grained materials to the southern basin, (4) resuspension surrogates based on 50 years of wave data show an interannual variability in major storm events that ranges over an order of magnitude, and (5) trap and 7Be evidence indicates that the events appear to be primarily responsible for the complicated sediment accumulation patterns in the southern basin of Lake Michigan.
FAHNENSTIEL, G.L., D.F. Millie, J. DYBLE, R.W. Litaker, P.A. Tester, M.J. McCORMICK, R. Rediske, and D. Klarer. Microcystin concentrations and cell quotas in Saginaw Bay, Lake Huron. Aquatic Ecosystem Health and Management 11(2):190-195 (2008).
Distribution of the toxin microcystin was studied in Saginaw Bay, Lake Huron during two summer (August) cruises in 2003-2004. Intracellular microcystin concentrations averaged 1.1 ug l-1(range 0.01-3.5 ug l−1), and extracellular concentrations averaged only 0.09 ug l-1(range 0.01-0.18 ug l-1). Highest microcystin concentrations were found in the nearshore regions of the bay, which were shallow and had high total phosphorus concentrations. Microcystin concentrations were strongly correlated with Microcystis aeruginosa abundance (r = 0.8). M. aeruginosa abundance was strongly correlated with total phosphorus, and growth rates were negatively correlated with C:P ratio. Particulate nutrient ratios suggested that Saginaw Bay algae were severely phosphorus deficient. Microcystin cell quotas for M. aeruginosa averaged 140 fg cell-1, and were not correlated with any environmental factor or growth rates. In Saginaw Bay, phosphorus availability primarily influences microcystin concentrations through direct control of M. aeruginosa abundance and growth rates, and not through direct control of cellular microcystin synthesis.
Ge, J., J. Qi, and B.M. LOFGREN. Use of vegetation properties from EOS observations for land-climate modeling in East Africa. Journal of Geophysical Research 113(D15101, doi:10.1029/2007JD009628):15 pp. (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080023.pdf
Land use/cover change has been recognized as a key component in global climate change. Information on land surface biophysical properties and climatic variables based on in situ data fail to resolve the fine-scale variability that exists in many parts of the world, including East Africa. In this study, we used the NASA's Earth Observing System (EOS) products to improve the representation of the land surface in a regional climate model as well as assess the model performance. The Moderate Resolution Imaging Spectroradiometer (MODIS) data of leaf area index (LAI) and vegetation fractional cover (VFC) were directly incorporated in the Regional Atmospheric Modeling System (RAMS). The model was validated in terms of the land surface temperature (LST), utilizing the MODIS LST data from both Terra and Aqua satellites. Compared with the built-in land surface, the ingested MODIS LAI and VFC greatly improved the spatial and temporal dynamics of vegetation in East Africa. Three experiments were carried out for the year of 2003 to test the impacts of land surface conditions. The results showed that the spatial, seasonal, and diurnal characteristics of the RAMS simulated LST were improved because of MODIS LAI and VFC. Specifically, the Intertropical Convergence Zone (ITCZ)-related migration, bimodal temporal variation, and monthly averaged diurnal cycles of LST were more realistically reproduced. The need to realistically represent the spatial and temporal distribution of vegetation is thus highlighted, and the value of the EOS observations for the land-climate modeling is demonstrated.
Ge, Z., and P.C. LIU. Long-term wave growth and its linear and nonlinear interactions with wind fluctuations. Annales Geophysicae 26:747-758 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080012.pdf
Following Ge and Liu (2007), the simultaneously recorded time series of wave elevation and wind velocity are examined for long-term (on Lavrenov's 4-scale or 3 to 6 h) linear and nonlinear interactions between the wind fluctuations and the wave field. Over such long times the detected interaction patterns should reveal general characteristics for the wave growth process. The time series are divided into three episodes, each approximately 1.33 h long, to represent three sequential stages of wave growth. The classic Fourier domain spectral and bispectral analyses are used to identify the linear and quadratic interactions between the waves and the wind fluctuations as well as between different components of the wave field. The results show clearly that as the wave field grows the linear interaction becomes enhanced and covers wider range of frequencies. Two different wave-induced components of the wind fluctuations are identified. These components, one at around 0.4 Hz and the other at around 0.15 to 0.2 Hz, are generated and supported by both linear and quadratic windwave interactions probably through the distortions of the waves to the wind field. The fact that the higher-frequency wave-induced component always stays with the equilibrium range of the wave spectrum around 0.4 Hz and the lower frequency one tends to move with the downshifting of the primary peak of the wave spectrum defines the partition of the primary peak and the equilibrium range of the wave spectrum, a characteristic that could not be revealed by short-time wavelet-based analyses in Ge and Liu (2007). Furthermore, these two wave-induced peaks of the wind spectrum appear to have different patterns of feedback to the wave field. The quadratic wave-wave interactions also are assessed using the auto-bispectrum and are found to be especially active during the first and the third episodes. Such directly detected wind-wave interactions, both linear and nonlinear, may complement the existing theoretical and numerical models, and can be used for future model development and validation.
HAND, C.P., S.A. LUDSIN, B.J. Fryer, and J.E. Marsden. Statolith microchemistry as a technique for discriminating among Great Lakes sea lamprey (Petromyzon marinus) spawning tributaries. Canadian Journal of Fisheries and Aquatic Sciences 65:1153-1164 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080015.pdf
Laurentian Great Lakes fishery management agencies are seeking ways to identify natal origins of pamsitic- and spawning-phase sea lamprey (Petromyzon marinus) so that efforts to control this invasive species can be prioritized. We developed laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as a technique to quantify elemental concentrations in larval sea lamprey statoliths and explored the use of statolith microchemistry as a tool to discriminate among larval sea lamprey production streams. Our analyses demonstrate that (i) traversing across the statolith with the laser is preferable to drilling down through its apex, (ii) preserving specimens in 95% ethanol versus freezing them has minimal effects on elemental concentrations, (iii) a minimum of 15 individuals per stream should accurately depict stream-specific statolith elemental signatures, and (iv) LA-ICP-MS is preferable to particle-induced X-my emission (PIXE) for statolith analysis, based on higher precision, lower cost, reduced sampling-time requirements, and wider availability. Using LA-ICP-MS, we could discriminate among larvae from 13 streams located in Lakes Michigan, Huron, and Superior with 82% classification accuracy, indicating that this tool holds promise for determining natal origins of sea lamprey in the Great Lakes.
HAWLEY, N. A digital data base for the particle size distribution of bottom sediments in Lake Michigan. NOAA Technical Memorandum GLERL-145. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 17 pp. (2008). http://www.glerl.noaa.gov/ftp/publications/tech_reports/glerl-145/tm-145.pdf
This document describes a map of the size distribution of bottom sediments in Lake Michigan. The data set combines measurements of the bottom sediment size distribution made by several previous investigations. The results are presented on the same 2 km grid presently used for forecasting waves and currents in the lake.
He, C., and T.E. CROLEY II. Estimating nonpoint source pollution loadings in the Great Lakes watershed. In Wetland and Water Resource Modeling and Assessment: A Watershed Perspective. W. (Ed.) Ji. Part III, Water Quality and Biogeochemical Processes, Chapter 10. CRC Press, Taylor and Francis Group, Boca Raton, FL, 115-127 (2008).
Nonpoint source pollution is the leading source of impairment of U.S. waters (U.S. Environmental Protection Agency [EPA] 2002). In the Great Lakes basin, contaminated sediments, urban runoff and combined sewerage overflows (CSOs), and agriculture have been identified as the primary sources of impairments of the Great Lakes shoreline waters (U.S. EPA 2002). The problems caused by these pollutants include toxic and pathogen contamination of fisheries and wildlife, fish consumption advisories, drinking water closures, and recreational restrictions (U.S. EPA 2002). Management of these problems and rehabilitation of the impaired waters to fishable and swimmable states require identifying impaired waters that are unable to support fisheries and recreational activities and tracking sources of both point and nonpoint source material transport through a watershed by hydrological processes. Such sources include sediments, animal and human wastes, agricultural chemicals, nutrients, and industrial discharges, and so forth.
He, C., T.E. CROLEY II, and Q. Feng. Modeling water movement between the glacial, agricultural oasis and desert in the Heihe Watershed, Northwest China. Proceedings, Fifth International Conference on Geographic Information Systems, Istanbul, Turkey, July 2-5, 2008. 147-153 pp. (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080036.pdf
Irrigated farming accounts for more than 80 percent of the total water uses in arid Northwest China. Over the past few decades, rapid population growth, agricultural irrigation expansion, and industrial development have led to groundwater depletion, river flow reduction, and farmland salinization, and ecosystem deterioration in the region. In the context of climate change, how much water will be available to support domestic, irrigation, and industrial supplies while satisfying the needs for maintenance of ecosystems in Northwest China? This paper describes the preliminary work of adapting the U.S. Department of Commerce'ss National Oceanic and Atmospheric Administration's Distributed Large Basin Runoff Model to the Heihe Watershed (the second largest inland river in arid Northwestern China, with a drainage area of 128,000 km2) for understanding glacial/snow melt, groundwater, surface runoff, and evapotranspiration, and for assessing hydrological impacts of climate change and glacial recession on water supply in the middle and lower reaches of the Watershed. Keywords: Glacial Recession, Distributed Large Basin Runoff Model, (DLBRM), Heihe Watershed in Northwestern China, and Water Shortage.
He, C., C. DeMARCHI, and T.E. CROLEY II. Modeling spatial distributions of nonpoint source pollution loadings in the Great Lakes watersheds by using the distributed large basin runoff model. Proceedings, AWRA 2008 Spring Specialty Conference, San Matteo, CA, March 17-19, 2008. 7 pp. (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080037.pdf
The NOAA Great Lakes Environmental Research Laboratory, Western Michigan University, and the University of Michigan are jointly developing a physically based, spatially-distributed hydrology model to simulate spatial and temporal nonpoint source material distributions in the Saginaw Bay watersheds, which drains into Lake Huron. Multiple databases of meteorology, land use, topography, hydrography, soils, and agricultural statistics were used to estimate nonpoint source loading potential in the study watersheds. Animal manure production was computed from tabulations of animals by zip code area for the census years of 1987, 1992, 1997, and 2002. Relative chemical loadings for agricultural land use were calculated from fertilizer and pesticide applications for the same periods. These estimates are to be used as the input to the distributed water quality model for simulating pollutant transport through surface and subsurface processes to Great Lakes waters. These simulations, once verified with the in situ Saginaw Bay water quality data, will provide important information to researchers and decision makers for developing the Total Maximum Daily Load programs to minimize the nonpoint source pollution in the watersheds.
HÖÖK, T.O., E. Gorokhova, and S. Hansson. RNA:DNA ratios of Baltic Sea herring larvae and copepods in embayment and open sea habitats. Estuarine, Coastal, and Shelf Science 76:29-35 (2008).
Elucidation of important nursery habitats for young fish can aid in the management and assessment of fish stocks. Herring (Clupea harengus) in the Baltic Sea primarily spawn in coastal areas, but larvae are also present in off-shore, open sea areas. To investigate if sheltered coastal habitats provide a better growth environment for larval herring, we compared short-term growth (as indexed by whole body RNA:DNA ratios) of larval herring from three habitat types of the northwest Baltic proper (sheltered inner bay, exposed outer bay, and open sea). In addition, we compared individual RNA content of adult female Eurytemora affinis (a common Baltic copepod) among these different habitats. High RNA levels in these copepods indicate high production of nauplii, which are important food for larval herring. Both RNA:DNA ratios of larval herring and RNA content of E. affinis were significantly greater in embayment habitats, suggesting that the sheltered coastal areas are high quality nursery habitats for young Baltic herring.
HÖÖK, T.O., E.S. Rutherford, T.E.I. CROLEY, D.M. MASON, and C.P. Madenjian. Annual variation in habitat-specific recruitment success: Implications from an individual-based model of Lake Michigan alewife (Alosa pseudoharengus). Canadian Journal of Fisheries and Aquatic Sciences 65:1402-1412 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080021.pdf
The identification of important spawning and nursery habitats for fish stocks can aid fisheries management, but is complicated by various factors, including annual variation in recruitment success. The alewife (Alosa pseudoharengus) is an ecologically important species in Lake Michigan that utilizes a variety of habitats for spawning and early life growth. While productive, warm tributary mouths (connected to Lake Michigan) may contribute disproportionately more recruits (relative to their habitat volume) to the adult alewife population than cooler, less productive nearshore habitats, the extent of interannual variation in the relative contributions of recruits from these two habitat types remains unknown. We used an individual-based bioenergetics simulation model and input data on daily temperatures to estimate alewife recruitment to the adult population by these different habitat types. Simulations suggest that nearshore lake habitats typically produce the vast majority of young alewife recruits. However, tributary habitats may contribute the majority of alewife recruits during years of low recruitment. We suggest that high interannual variation in the relative importance of habitats for recruitment is a common phenomenon, which should be considered when developing habitat management plans for fish populations.
HU, H., and J. WANG. Modeling the ocean circulation in the Bering Sea. Chinese Journal of Polar Research 19(2):193-211 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080063.pdf
With parameterized wave mixing, the circulation and the tidal current in the Bering Sea were simulated simultaneously using the three-dimensional Princeton Ocean Model. The simulated circulation pattern in the deep basin is relatively stable, cyclonic, and has little seasonal change. The Bering Slope Current between 200-1000 m isobaths was estimated to be 5 Sv in volume transport. The Kamchatka Current was estimated to be 20 Sv off the Kamchatka Peninsula. The Bering shelf circulations vary with season, driven mainly by wind. These features are consistent with historical estimates. A counter current was captured Howing southeastward approximately along the 200 m isobath of the Bering Slope, opposite to the northwestward Bering Slope Current, which needs to be validated by observations. An upwelling current is located in the shelf break (120-1000 m) area, which may imply the vertical advection of nutrients for supporting the Bering Sea Green Belt seasonal plankton blooms in the breakslope area. The Bering Slope Current is located in a downwelling area.
Jin, M., C. Deal, and J. WANG. A coupled ice-ocean ecosystem model for 1-D and 3-D applications in the Bering and Chukchi Seas. Chinese Journal of Polar Science 19(2):218-229 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080065.pdf
Primary production in the Bering and Chukchi Seas is strongly influenced by the annual cycle of sea ice. Here pelagic and sea ice algal ecosystems coexist and interact with each other. Ecosystem modeling of sea ice associated phytoplankton blooms has been understudied compared to open water ecosystem model applications. This study introduces a general coupled ice-ocean ecosystem model with equations and parameters for 1-0 and 3-D applications that is based on 1-0 coupled ice-ocean ecosystem model development in the landfast ice in the Chukchi Sea and marginal ice zone of Bering Sea. The biological model includes both pelagic and sea ice algal habitats with 10 compartments: three phytoplankton (pelagic diatom, flagellates and ice algae: D, F, and Ai) , three zooplankton (copepods, large zooplankton, and microzooplankton: ZS, ZL, ZP). three nutrients (nitrate + nitrite, ammonium, silicon: N03, NH4 , Si) and detritus ( Det). The coupling of the biological models with physical ocean models is straightforward with just the addition of the advection and diffusion terms to the ecosystem model. The coupling with a multi-category sea ice model requires the same calculation of the sea ice ecosystem model in each ice thickness category and the redistribution between categories caused by both dynamic and thennodynamic forcing as in the physical model. Phytoplankton and ice algal self-shading effect is the sole feedback from the ecosystem model to the physical model.
Jin, M., J. WANG, K. Mizobata, H. HU, and K. Shimada. Observations and modeling of the ice-ocean conditions in the coastal Chukchi and Beaufort Seas. Acta Oceanologica Sinica 27(3):79-87 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080047.pdf
The Chukchi and Beaufort Seas include several important hydrological features: inflow of the Pacific water, Alaska coast current (ACC), the seasonal to perennial sea ice cover, and landfast ice along the Alaskan coast. The dynamics of this coupled ice-ocean system is important for both regional scale oceanography and large-scale global climate change research. A number of moorings were deployed in the area by JAMSTEC since 1992, and the data revealed highly variably characteristics of the hydrological environment. Regional high-resolution coupled ice-ocean model of the Chukchi and Beaufort Seas was established to simulate the ice-ocean environment and unique seasonal landfast ice in the coastal Beaufort Sea. The model results reproduced the Beaufort gyre and the ACC. The depth-averaged annual mean ocean currents along the Beaufort Sea coast and shelf break compared well with data from four moored ADCPs, but the simulated velocity had smaller standard deviations, which indicate small-scale eddies were frequent in the region. The model results capture the seasonal variations of sea ice area compared with remote sensing data, and the simulated sea ice velocity showed an almost stationary area along the Beaufort Sea coast that was similar to the observed landfast ice extent. It is the combined effects of the weak oceanic current near the coast, a prevailing wind with an onshore component, the opposite direction of the ocean current, and the blocking by the coastline that make the Beaufort Sea coastal areas prone to the formation of landfast ice.
JOHENGEN, T.H., B.A. Biddanda, and J.B. Cotner. Stimulation of Lake Michigan plankton metabolism by sediment resuspension and river runoff. Journal of Great Lakes Research 34:213-227 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080022.pdf
Previous work during a major sediment resuspension event (March 1988) in southern Lake Michigan demonstrated that nutrients and carbon derived from resuspended sediment stimulated intense winter heterotrophic production while simultaneously decreasing light availability and autotrophic biomass. However, the role of riverine inputs on plankton metabolism remained unclear. Here we present results from a simulated enrichment experiment (March 2000) designed to examine the influence of resuspended sediments and riverine inputs on Lake Michigan plankton dynamics. Lake water amended with realistic levels of river water, coastal resuspended sediment and river water + sediment all showed enhanced heterotrophic bacterial production and plankton respiration rates, relative to the lake water control. Bacterial production increased by approximately 4 in river water treatments and by a factor of 2.5x for the sediment only treatment compared to lake water controls. Rates of net primary production were stimulated by river water (8.5x) and resuspended sediment (3x), but most by a combination of river water + sediments (11x). Community respiration showed a similar response with rates approximately 8x higher in river water amendment treatments and 3.5x higher in the sediment treatment. Extrapolating experimentally determined production rates to the southern Lake Michigan basin indicated that heterotrophic and autotrophic production in this nearshore region may be enhanced by as much as 3x and 5.2x due to these source inputs. Indeed, field measurements throughout southern Lake Michigan from 1998-2000 support these experimental results. Experimental and field observations suggest that both seasonal riverine inputs and episodic resuspended sediments influence the regional scale ecosystem metabolism and biogeochemistry in Lake Michigan.
Jonas, J., R.M. Claramunt, and E.S. RUTHERFORD. Salmonine reproduction and recruitment. In The State of Lake Michigan in 2005. D.F. Clapp and W. Horns (Eds.). Great Lakes Fishery Commission Special Publication 08-02. Great Lakes Fishery Commission, Ann Arbor, MI, pp. 65-70 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080067.pdf
Fostering self-sustainability and protecting the genetic diversity of fish stocks are key features of the goals and guiding rinciples in the fish community objectives for Lake Michigan (Eshenroder et al. 1995). Reliance on natural feedbacks between predator and prey to control recruitment can provide more-effective self-regulation, leading to greater system resilience and stability, than external actions, such as stocking or harvest, which entail time lags (Christie et al. 1987). The genetic fitness of self-sustaining populations likely exceeds that of stocked populations (Berejikian et al. 1999, 2001; Kostow et al. 2003), because self-sustaining populations benefit from natural selection and are able to adapt to unique and specific conditions in localized environments (Falkner and Falkner 2000). Natural recruitment of Lake Michigan salmonine populations has been quantified historically by mark-and-recapture studies of hatchery-released fish, by counting out-migrating wild smolts in tributary streams, and, more recently, by surveys of lake trout eggs and fry on spawning reefs. Because hydrologically stable, groundwater-fed streams most conducive to natural reproduction of anadromous salmonids (Carl 1983; Seelbach 1985) are generally found in just the northern and eastern areas of the lake’s basin, measures of smolt out-migration or of returning adults in streams can be difficult to translate into the whole-lake population, which also comprises stocked fish. In contrast, if recruitment of wild fish is quantified through recreational fisheries and independent assessments in the open lake, information regarding stream-specific influences on the lakewide population is not obtained. Given limited monitoring efforts, the recruitment dynamics of salmonines continues to be incompletely understood. Here we report on natural recruitment of four of the lake’s major salmonines: coho salmon, Chinook salmon, steelhead, and lake trout. We do not report on brown trout because, although it is a major salmonine, its level of natural reproduction is minimal (Keller et al. 1990).
Kapo, K.E., G.A. BURTON, D. de Zwart, L. Posthuma, and S.D. Dyer. Quantitative lines of evidence for screening-level diagnostic assessment of regional fish community impacts: A comparison of spatial database evaluation methods. Environmental Science and Technology 42(24):9412-9418 (2008).
Determination of local ecological impacts and stressor identification in aquatic ecosystems is increasingly needed and required for designing effective watershed management plans in various jurisdictions. Spatial database evaluation methods applied to available environmental data resources can provide screening-level, geographically based stressor identification hypotheses. Cross-comparison of the output of independent methods is a critical step to address common concerns with the interpretation of output, identify strengths and weaknesses, and reduce uncertainty. Two current approaches were compared in this study: (1) the "Effect and Probable Cause" (EPC) method and (2) a GIS "Weights-of-Evidence/Weighted Logistic Regression" (WOE/WLR) method. The methods were applied to the same Ohio (U.S.) spatial data resources to link impacts on local fish assemblages with various natural and anthropogenic stressors. The methods generally yielded significantly similar results in the identification of stressors and their relative influence. However, key differences were also observed between the methods which reflected the distinctive objectives and sensitivities of each. The findings show that scientific interpretation of analysis output requires an understanding of method characteristics, and suggests the potential value of utilizing multiple methods as quantitative lines of evidence in screening-level regional diagnostic assessment.
Kelley, J.G.W., A.-J. Zhang, P. Chu, and G.A. LANG. Skill assessment of NOS Lake Ontario Operational Forecast System (LOOFS). NOAA Technical Memorandum NOS CS 13. NOAA Office of Coast Survey, Coast Survey Development Lab, Silver Spring, MD, 40 pp. (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/2008tmNOS_CS13.pdf
This document describes the Lake Ontario Operational Forecast System (LOOFS) and an assessment of its skill. The lake forecast system, based on a hydrodynamic model, uses near real-time atmospheric observations and numerical weather prediction forecast guidance to produce three-dimensional forecast guidance of water temperature and currents and two-dimensional forecasts of water levels for Lake Ontario. LOOFS is the result of technology transfer of the Great Lake Forecasting System (GLFS) and Great Lakes Coastal Forecasting System (GLCFS) from The Ohio State University (OSU) and NOAA’s Great Lakes Environmental Research Laboratory (GLERL) to NOAA's National Ocean Service (NOS).
Kerfoot, W.C., J.W. Budd, S.A. Green, J.B. Cotner, B.A. Biddanda, D.J. SCHWAB, and H.A. VANDERPLOEG. Doughnut in the desert: Late-winter production pulse in southern Lake Michigan. Limnology and Oceanography 53(2):589-604 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080008.pdf
Contrary to expectations of fairly uniform and unstratified waters, sea-viewing wide field-of-view sensor (SeaWiFS) and moderate-resolution imaging spectroradiometer (MODIS) imagery revealed a spatially complex chlorophyll a pattern, termed the "doughnut," in southern Lake Michigan during March to April. Phosphorus rich coastal waters and sediments are entrained along gyre convergence zones and moved into deeper waters, stimulating a ring of production. Cross-lake surveys (April 2001 and April 2006) with two separate profiling instruments (vertical Seabird CTD casts, horizontal Acrobat tows) uncovered columnar patterns for Chl a, temperature, and other variables (colored dissolved organic matter, transmissivity) consistent with a spatially complex, rotating gyre structure. Optical plankton counter transects, plankton net tows, and sonar documented that the spatial heterogeneity extends to higher levels of food webs (zooplankton). The horizontal and vertical patterns suggest a previously unrecognized coupling between late-winter storm-induced gyre formation, coastal water plus sediment capture, and deep-water productivity. The pulse may explain how certain zooplankton species characteristic of the Great Lakes can successfully overwinter through what was previously perceived as a very unproductive and resource-stressful period. The magnitude of the winter pulse may be linked to climate change, as higher temperatures and more frequent winter storms suppress coastal ice formation and encourage movement of nutrient-enriched waters and sediments into deeper waters.
Kiziewicz, B., and T.F. NALEPA. Some fungi and water molds in waters of Lake Michigan with emphasis on those associated with the benthic amphipod Diporeia spp. Journal of Great Lakes Research 34:774-780 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080052.pdf
To determine types of fungi in the water and associated with the benthic amphipod Diporeia spp., samples were collected at various depths in Lake Michigan in an area where the Diporeia population was in a severe state of decline. No fungi were found associated with living, freshly-dead, or dried Diporeia cultured separately from Lake Michigan water. When dead Diporeia and other organic substrates (snake skin and hemp seeds) were used to grow fungi in Lake Michigan water, a rich and diverse fungal and water mold community was revealed. A total of 31 species were found, with the most common genera being Achlya, Aphanomyces, Myzocytium, and Pythium. In general, species were homogeneously distributed in the water; that is, few differences were found in species richness between nearshore (10-15 m) and offshore (60-80 m) waters, and between near-surface (1 m) and near-bottom waters (1 m off bottom). Sampling occurred during the unstratified period (April and October) to maximize the number of species collected, which may have contributed to the uniform spatial pattern observed. While conclusions must be placed in context with our methods of detection, we found no evidence that a fungal infestation was associated with Diporeia in this region of the lake.
Kunkel, K., P. Bromirski, H. Brooks, T. Cavazos, A. Doug, D. Easterling, K. Emanual, P. Groisman, G. Holland, T. Knutson, J. Kosin, P. Komar, D. Levinson, R. Smith, J. Allen, R.A. ASSEL, S. Changnon, J. Lawrimore, K.B. Liu, and T. Peterson. Chapter 2: Observed changes in weather and climate extremes. In Weather and Climate Extremes in a Changing Climate: Regions of Focus: North America, Hawaii, Caribbean, and U.S. Pacific Islands. T.R. Karl, G.A. Meehi, C.D. Miller, S.J. Hassol, A.M. Waple, and W.L. Murray (Eds.). The U.S. Climate Change Science Program and the Subcommittee on Global Change Research, Washington, DC, pp. 35-80 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080019.pdf
Long-term upward trends in the frequency of unusually warm nights, extreme precipitation episodes, and the length of the frost-free season, along with pronounced recent increases in the frequency of North Atlantic tropical cyclones (hurricanes), the length of the frost-free season, and extreme wave heights along the West Coast are notable changes in the North American climate record.
Lewis, C.F.M., J.W. King, S.M. Blasco, G.R. Brooks, J.P. Coakley, T.E. CROLEY, D.L. Dettman, T.W.D. Edwards, C.W. Heil, J.B. Hubeny, K.R. Laird, J.H. McAndrews, F.M.G. McCarthy, B.E. Mediolo, T.C. Moore, D.K. Rea, and A.J. Smith. Dry climate disconnected the Laurentian Great Lakes. EOS Transactions 89(52):541-542 (2008).
Recent studies have produced a new understanding of the hydrological history of North America's Great Lakes, showing that water levels fell several meters below lake basin outlets during an early postglacial dry climate in the Holocene (younger than 10,000 radiocarbon years, or about 11,500 calibrated or calendar years before present (B.P.)). Water levels in the Huron basin, for example, fell more than 20 meters below the basin overflow outlet between about 7900 and 7500 radiocarbon (about 8770-8290 calibrated) years B.P. Outlet rivers, including the Niagara River, presently falling 99 meters from Lake Erie to Lake Ontario (and hence Niagara Falls), ran dry. This newly recognized phase of low lake levels in a dry climate provides a case study for evaluating the sensitivity of the Great Lakes to current and future climate change.
LIEBIG, J.R., and H.A. VANDERPLOEG. Selecting optical plankton counter size bins to optimize zooplankton information in Great Lakes studies. NOAA Technical Memorandum GLERL-143. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 16 pp. (2008). http://www.glerl.noaa.gov/ftp/publications/tech_reports/glerl-143/tm-143.pdf
Equivalent spherical diameter (ESD) size bins for the optical plankton counter (OPC) were determined so as to optimize the OPC for providing abundance of Great Lakes zooplankton species. By determining OPC ESDs for animals of known lengths (L) pumped through laboratory OPC, we derived the ESD/L ratio for a variety of species. Based on the size spectra of individual species lengths determined from net tows and application of previously determined ESD/L ratios, divisions for OPC size bins were selected so as to separate species or groups of species. Since there are differences in zooplankton composition and size within species between Lakes Michigan and Erie, the OPC size bins designated were not the same in the two lakes. This report describes the process used to determine OPC bin sizes and presents the results of an example from Lake Michigan and one from Lake Erie. In addition, ESDs calculated from zooplankton lengths may provide a size metric more useful than length because an ESD more closely resembles visual target strength than length.
LIU, P.C., H.S. Chen, D.-J. Doong, C.C. Kao, and Y.-J.G. Hsu. Monstrous ocean waves during Typhoon Krosa. Annales Geophysicae 26:1327-1329 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080018.pdf
This paper presents a set of ocean wave time series data recorded from a discus buoy deployed near northeast Taiwan in western Pacific that was operating during the passage of Typhoon Krosa on 6 October 2007. The maximum trough-to-crest wave height was measured to be 32.3 m, which could be the largest Hmax ever recorded. Keywords. Meteorology and atmospheric dynamics (Ocean-atmosphere interactions; Waves and tides) - Oceanography: physical (Surface waves and tides) the passage of hurricane Ivan in 2004. Holliday et al. (2006), on the other hand, discovered a recorded Hmax=29.1m from the Shipborne Wave Recorder onboard RRS Discovery on 8 February 2000 in the northeast Atlantic Ocean 250 km west of Scotland during a developing storm. While larger than usual wave heights during a typhoon or hurricane are to be anticipated, there is no tangible knowledge regarding what a typical wave height magnitude is. In this brief report we wish to present the above mentioned wave data as recorded at the Gueishantao Island buoy during Typhoon Krosa that has manifestly exceeded all the previous known extreme wave records.
LIU, P.C., and K.R. MacHutchon. Are there different kinds of rogue waves? Journal of Offshore Mechanics and Arctic Engineering 130:7 pp. (2008).
There is clearly no immediate answer to the question posted by the title of this paper. Inasmuch as that there are not much definitively known about rogue waves and that there is still no universally accepted definition for rogue waves in the ocean, we think there might just be even more than one kind of rogue waves to contend with. While the conventional approach has generally designated waves with Hmax/Hs greater than 2.2 as possible rogue waves, based on Rayleigh distribution considerations, there is conspicuously no provision as to how high the ratio of Hmax/Hs can be and thus not known how high can a rogue wave be. In our analysis of wave measurements made from a gas drilling platform in South Indian Ocean, offshore from Mossel Bay, South Africa, we found a number of cases that indicated Hmax/Hs could be valued in the range between 4 and 10. If this were to be the case, then these records could be considered to be "uncommon" rogue waves, whereas a record of Hmax/Hs in the range between 2 and 4 could be considered to comprise "typical" rogue waves. On the other hand, the spikes in the Hmax data could have been caused by equipment malfunction or some other phenomenon. Clearly, the question of whether or not there are different kinds of rogue waves cannot be readily answered by theoretical considerations alone and there is a crucial need for long-term wave time-series measurements for studying rogue waves. DOI: 10.1115/1.2917431
LIU, P.C., D.J. SCHWAB, C.H. Wu, and K.R. MacHutchon. Wave heights in a 4-D ocean wave field. Proceedings, OMAE 2008 ASME 27th International Conference on Offshore Mechanics and Arctic Engineering, Estoril, Portugal, June 15-20, 2008. 5 pp. (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080017.pdf
This paper presents a preliminary examination and analysis of a small suite of 4-D wave data to explore what new insight or inference we can garner -- particularly toward the realm where conventional approaches have not been traversed. While we caught a few glimpses that might indicate a need for new conceptualizations, it by no means to negates the vast positive contributions the conventional approaches have been made in the past century. We feel it is timely to encourage further 4-D ocean wave measurement and thereby facilitate fresh new states of study and understanding of ocean waves.
LOFGREN, B.M., and P. Bieniek. Large-scale 700 hPa height patterns associated with cyclone passage and strong winds on Lake Erie. Journal of Great Lakes Research 34:36-53 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080011.pdf
The difference in 700 hPa height patterns was examined on a seasonal basis between years with high numbers and low numbers of cyclone passages through Lake Erie, and high and low numbers of strong wind events at Cleveland Hopkins Airport. These show that both cyclones and strong wind events often are associated with atmospheric patterns resembling the negative phase of the North Atlantic Oscillation, or the negative phase of the Arctic Oscillation. Custom teleconnection indices were derived from these maps of 700 hPa height differences, and the seasonal means of each of these indices were linearly regressed against the number of cyclones and the number of strong wind events in that season for each year. This procedure led to moderate, but statistically significant, correlation coefficients. This gives some basis for probabilistic prediction of cyclone passages and strong wind events at Lake Erie. Actual application in prediction will require skill also in predicting the geopotential heights, and predictions generalized over larger areas may have greater significance and robustness.
Lohrenz, S.E., G.L. FAHNENSTIEL, and D.F. Millie, Coastal sediment dynamics and river discharge as key factors influencing coastal ecosystem productivity in southeastern Lake Michigan. Oceanography 21(4):60-69 (2008). http://www.tos.org/oceanography/archive/21-4_lohrenz.html
A central question addressed by the Episodic Events in the Great Lakes Experiment (EEGLE) was the extent to which the spring phytoplankton bloom in southern Lake Michigan is influenced by a recurrent coastal turbidity plume that results from wind-driven sediment resuspension and transport. Findings from a series of studies conducted as part of EEGLE during spring in 1998, 1999, and 2000 confirmed the importance of sediment processes as a factor influencing ecosystem productivity in southeastern Lake Michigan, but also identified interannual variability in river discharge as potentially important in regulating productivity in coastal waters. Here, we describe the application of satellite-derived and in situ optical observations to examine the impacts of the recurrent coastal turbidity plume (RCP) on light availability and phytoplankton productivity. A review and synthesis of prior work highlighted findings that sediment resuspension during the 1998 El Niño period, a time of intense winter storm activity and an unusually strong RCP, profoundly influenced optical properties in coastal waters, constraining phytoplankton growth and primary production. In contrast, in 1999, a moderate RCP coupled with relatively high discharge from the St. Joseph River led to a strong inner shelf optical signature indicative of elevated levels of dissolved organic matter and apparent enhancement of productivity. We speculate that future changes in climate are likely to alter sediment dynamics and river discharge with uncertain consequences for coastal ecosystem productivity and community structure in southeastern Lake Michigan
as well as in other coastal systems.
Lu, Y., S.A. LUDSIN, D.L. FANSLOW, and S.A. POTHOVEN. Comparison of three microquantity techniques for measuring total lipids in fish. Canadian Journal of Fisheries and Aquatic Sciences 65:2233-2241 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080041.pdf
To measure lipids in juvenile and adult fishes, we refined three microquantity approaches (microgravimetric, microcolorimetric sulfophosphovanillan (SPV), and Iatroscan thin layer chromatography - flame ionization detection (TLC-FID)) that were originally developed to measure lipids in small aquatic invertebrates. We also evaluated their precision and comparability by quantifying the total lipid content of age-1+ walleye (Sander vitreus), yellow perch (Perca flavescens), and lake whitefish (Coregonus clupeaformis) collected in Lake Erie (US-Canada), Lake Michigan (USA), and Muskegon Lake (Michigan, USA). Our findings demonstrate that (i) microquantity approaches provide estimates of total lipids in juvenile and adult fishes similar to those of more traditional macroquantity approaches, (ii) the microcolorimetric SPV and microgravimetric approaches produce near identical estimates of total lipid content, and (iii) the Iatroscan TLC-FID approach underestimates total lipids relative to the other approaches for individuals with high lipid levels. Ultimately, our research makes available additional techniques for measuring total lipid content of fishes that are less expensive than traditional techniques, owing to a reduced need for large quantities of samples and solvents.
Madenjian, C.P., D.V. O'Connor, R.R. Rediske, J.P. O'Keefe, and S.A. POTHOVEN. Net trophic transfer efficiencies of polychlorinated biphenyl congeners to Lake Whitefish (Coregonus clupeaformis) from their food. Environmental Toxicology and Chemistry 27(3):631-636 (2008).
Lake whitefish (Coregonus clupeaformis) were fed rainbow smelt (Osmerus mordax) in four laboratory tanks over a 133-d experiment. At the start of the experiment, 10 to 14 of the fish in each tank were sacrificed, and the concentrations of 40 polychlorinated biphenyl (PCB) congeners within these fish were determined. Polychlorinated biphenyl congener concentrations were also determined in the 15 lake whitefish remaining in each of the four tanks at the end of the experiment as well as in the rainbow smelt fed to the lake whitefish. Each lake whitefish was weighed at the start and the end of the experiment, and the amount of food eaten by the lake whitefish during the experiment was tracked. Using these measurements, net trophic transfer efficiency (ϒ) from the rainbow smelt to the lake whitefish in each of the four tanks was calculated for each of the 40 PCB congeners. Results showed that ϒ decreased exponentially as log Kow for the congeners increased from 6 to 8. Further, ϒ averaged 0.70 for the tetrachloro congeners but averaged only 0.45 for the higher chlorinated congeners.
McCORMICK, M.J., T.O. Manley, D. BELETSKY, A.J. FOLEY, and G.L. FAHNENSTIEL. Tracking the surface flow in Lake Champlain. Journal of Great Lakes Research 34:721-730 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080053.pdf
Understanding the hydrodynamics of Lake Champlain is a basic requirement for developing forecasting tools to address the lake's environmental issues. In 2003 through 2005, surface drifting buoys were used to help characterize the circulation of the main body and northeast region (Inland Sea) of the lake. Progressive vector diagrams of over-lake winds when compared to drifter trajectories suggest the presence of gyre-like circulation patterns. Drifter statistics suggest average current speeds of 10 cm s-1 and were predominantly northward (+ V) due to northerly-directed winds and lake geometry. Singleparticle eddy diffusivities on the order of 106 cm2 s-1 were calculated which is consistent with results from the Great Lakes and in some oceanic regions. However, the Lagrangian length and time scales, a measure of flow decorrelation scales, were in general smaller than seen in the Great Lakes, which is a natural consequence of the smaller basin size of Lake Champlain relative to the Great Lakes.
McCORMICK, M.J., and D.J. SCHWAB. Observations of currents in Saginaw Bay, Lake Huron. Aquatic Ecosystem Health and Management 11(2):182-189 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080060.pdf
During June 1991 through June 1994 six current meter moorings were deployed in the outer region of Saginaw Bay, Lake Huron to study the bay's dynamics and interaction with Lake Huron. Two current meters were configured on each subsurface mooring at 14 m below the water surface and 2 m above the bottom and current speed, direction and water temperature were recorded at 15 minute intervals. These data represent nearly 1.2 million observations and are the longest continuous set of observations conducted anywhere in Lake Huron and the first ever winter observations conducted in Saginaw Bay. The winter months showed the highest mean currents from the moorings closest to Lake Huron while the stratified season showed high mean currents at the moorings located in the bay proper. There was little consistency in mean flow vectors other than the bottom currents at the southeastern mooring which showed consistent flow from the bay into Lake Huron. Only a small fraction of the kinetic energy was contained in the mean flow. The variability in the orientation of the principal axes of variation on semiannual to inter-annual time scales suggests using caution in generalizing about circulation patterns based solely upon limited data sets.
Millie, D.F., G.L. FAHNENSTIEL, J. DYBLE, R.J. Pigg, R.R. Rediske, D.M. Klarer, R.W. Litaker, and P.A. Tester. Influence of environmental conditions on late-summer cyanobacterial abundance in Saginaw Bay, Lake Huron. Aquatic Ecosystem Health and Management 11(2):196-205 (2008).
The relationships among environmental conditions and phytoplankton assemblages were characterized during late summer (2003-2005) in Saginaw Bay, Lake Huron. Differences among sampling stations, arising primarily from spatial disparities in water-column optical properties and nutrient availability, were evident. Cyanobacteria and diatoms dominated phytoplankton assemblages, with the greatest total chlorophyll a concentrations occurring at the innermost portions of the Bay. Microcystis abundance was greatest in the Bay's upper reaches and decreased with increasing distance from the mouth of the Saginaw River. A suite of variables, indicative of annually-distinct meteorological and hydrological conditions and phosphorus-laden inflows, were identified to (collectively) best 'group' stations in a manner consistent with that of phylogenetic-group chlorophyll a concentrations and cyanobacterial biovolumes. However, a great deal of variability between abiotic and biotic patterns remained unexplained and several abiotic variables singularly corresponded with Microcystis abundance. Taken together, it appears that multiple environmental conditions (including annual/episodic meteorological patterns, seasonal/intermittent riverine inflows, annual phosphorus loading, etc.) interact with taxon-specific physiological traits to holistically influence late-summer phytoplankton abundance throughout inner Saginaw Bay.
Mizobata, K., S. Saitoh, and J. WANG. Interannual variability of summer biochemical enhancement in relation to mesoscale eddies at the shelf break in the vicinity of the Pribilof Islands, Bering Sea. Deep-Sea Research II 55:1717-1728 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080046.pdf
This study examined variability of the eddy field and primary production over the Bering Sea's eastern shelf break area during summer using a satellite multi-sensor data set. The eddy field and on-shelf nutrient flux below 50 m water depth were also investigated using a numerical model. The satellite altimeter data analysis and numerical experiments indicated that the eddy field was induced by perturbations of the Bering Slope Current system and/or instabilities in the Bering Sea basin via flow through the Aleutian passes. The distribution of high primary production roughly coincided with the high variability area of the eddy field. Numerical experiments showed a 70% increase in net on-shelf flux and 54% increase in net on-shelf transport by the generation/propagation of eddies along the shelf break. At Pribilof Canyon, towed CTD/fluorometer measurements during the summer of 2003 revealed a stable water column and high fluorescence (>10 ug L -1) in the area between the 200- and 1000-m isobaths at a time when there was a low level of on-shelf flux regardless of the eddy field. Conversely, the eddy-induced, on-shelf flux and stable water column can enhance primary production from spring to summer at the shelf break. Moreover, the eddy-induced on-shelf nutrient flux probably contributes to the primary productivity at the western shelf of the Pribilof Islands where the Bering Sea ecosystem is very dynamic. This eddy-related shelf break process can be applied to not only the Bering Sea shelf break but also all shelf break areas in which propagating eddies are found.
NALEPA, T.F., D.L. FANSLOW, G.A. LANG, D.B. LAMARAND, L.G. CUMMINS, and G.S. CARTER. Abundances of the amphipod Diporeia spp. and the mussels Dreissena polymorpha and Dreissena rostriformis bugensis in Lake Michigan in 1994-1995, 2000, and 2005. NOAA Technical Memorandum GLERL-144. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 25 pp. (2008). http://www.glerl.noaa.gov/ftp/publications/tech_reports/glerl-144/tm-144.pdf
This technical report provides basic results of benthic surveys conducted in Lake Michigan in 1994-1995, 2000, and 2005. The focus of these surveys was to assess lakewide trends in abundances of the amphipod Diporeia spp., the zebra mussel (Dreissena polymorpha), and the quagga mussel (Dreissena rostriformis bugensis). These lakewide surveys were an expansion of a monitoring program in the southern basin that has examined trends in the abundance and composition of the macroinvertebrate community since 1980 (Nalepa 1987, Nalepa et al. 1998). The original purpose of the monitoring program was to assess the response of the benthic community to phosphorus abatement efforts in the mid-1970s (Nalepa 1987). However, after D. polymorpha became established in the southwestern portion of the lake in 1989 (Marsden et al. 1993), the monitoring program detected several dramatic changes in the benthic community in the early 1990s. For one, the Diporeia population began to systematically disappear (Nalepa et al. 1998). Also, D. polymorpha rapidly expanded and soon became dominant in the nearshore region. To determine if the same dramatic changes in the southern basin were occurring over a broader lake area, the monitoring program was expanded in 1994-1995 to include the entire lake. Sampling in these two years was conducted jointly with several other Lake Michigan programs -- Environmental Monitoring and Assessment (EMAP) and Lake Michigan Mass Balance (LMMB). After 1994-1995, lakewide monitoring of Diporeia and Dreissena populations continued at 5-year intervals (i.e., in 2000 and 2005) as part of a regular monitoring program. The purpose of this report is to provide all abundance data collected in 1994-1995, 2000, and 2005, and to provide basic details of the lakewide sampling program, including station locations, sampling methods, and laboratory procedures. Data are presented with little attempt at interpretation; detailed analysis and discussions of relevance will be provided in other publications (see Nalepa et al. in press).
Olson, J.M., G. Alagarswamy, J.A. Andresen, D.J. Campbell, A.Y. Davis, J. Ge, M. Huebner, B.M. LOFGREN, D.P. Lusch, N.J. Moore, B.C. Pijanowski, J. Qi, P.K. Thornton, N.M. Torbick, and J. Wang. Integrating diverse methods to understand climate-land interactions in East Africa. Geoforum 39:898-911 (2008).
The questions of how land use change affects climate, and how climate change affects land use, require examination of societal and environmental systems across space at multiple scales, from the global climate to regional vegetative dynamics to local decision making by farmers and herders. It also requires an analysis of causal linkages and feedback loops between systems. These questions and the conceptual approach of the research design of the Climate-Land Interaction Project (CLIP) are rooted in the classical human-environment research tradition in Geography. This paper discusses a methodological framework to quantify the two-way interactions between land use and regional climate systems, using ongoing work by a team of multi-disciplinary scientists examining climate-land dynamics at multiple scales in East Africa. East Africa is a region that is undergoing rapid land use change, where changes in climate would have serious consequences for people's livelihoods, and requiring new coping and land use strategies. The research involves exploration of linkages between two important foci of global change research, namely, land use/land cover (LULC) and climate change. These linkages are examined through modeling agricultural systems, land use driving forces and patterns, the physical properties of land cover, and the regional climate. Both qualitative and quantitative methods are being used to illustrate a diverse pluralism in scientific discovery.
POTHOVEN, S.A., S.A. LUDSIN, T.O. HÖÖK, D.L. FANSLOW, D.M. MASON, P.D. Collingsworth, and J.J. VanTassel. Reliability of bioelectrical impedence analysis for estimating whole-fish energy density and percent lipids. Transactions of the American Fisheries Society 137:1519-1529 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080039.pdf
We evaluated bioelectrical impedance analysis (BIA) as a nonlethal means of predicting energy density and percent lipids for three fish species: yellow perch Perca flavescens, walleye Sander vitreus, and lake whitefish Coregonus clupeaformis. Although models that combined BIA measures with fish wet mass provided strong predictions of total energy, total lipids, and total dry mass for whole fish, including BIA provided only slightly better predictions than using fish mass alone. Regression models that used BIA measures to directly predict the energy density or percent lipids of whole fish were generally better than those using body mass alone (based on Akaike's information criterion). However, the goodness of fit of models that used BIA measures varied widely across species and at best explained only slightly more than one-half the variation observed in fish energy density or percent lipids. Models that combined BIA measures with body mass for prediction had the strongest correlations between predicted and observed energy density or percent lipids for a validation group of fish, but there were significant biases in these predictions. For example, the models underestimated energy density and percent lipids for lipid-rich fish and overestimated energy density and percent lipids for lipid-poor fish. A comparison of observed versus predicted whole-fish energy densities and percent lipids demonstrated that models that incorporated BIA measures had lower maximum percent error than models without BIA measures in them, although the errors for the BIA models were still generally high (energy density: 15-18%; percent lipids: 82-89%). Considerable work is still required before BIA can provide reliable predictions of whole-fish energy density and percent lipids, including understanding how temperature, electrode placement, and the variation in lipid distribution within a fish affect BIA measures.
POTHOVEN, S.A., and C.P. Madenjian. Changes in consumption by alewives and lake whitefish after Dreissenid mussel invasions in Lakes Michigan and Huron. North American Journal of Fisheries Management 28:308-320 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080005.pdf
Growth of alewives Alosa pseudoharengus and lake whitefish Coregonus clupeaformis has declined since the arrival and spread of dreissenid mussels in Lakes Michigan and Huron. Alewives are the main forage for the salmonids in Lake Michigan, and lake whitefish are the most important commercial species in both lakes. Bioenergetics modeling was used to determine consumption by the average individual fish before and after the dreissenid invasion and to provide insight into the invasion's effects on fish growth and food web dynamics. Alewives feed on both zooplankton and benthic macroinvertebrates, and lake whitefish are benthivores. Annual consumption of zooplankton by an average alewife in Lake Michigan was 37% lower and consumption of benthic macroinvertebrates (amphipods Diporeia spp., opossum shrimp Mysis relicta, and Chironomidae) was 19% lower during the post-invasion period (1995–2005) than during the pre-invasion period (1983-1994). Reduced consumption by alewives corresponded with reduced alewife growth. In Lakes Michigan and Huron, consumption of nonmollusk macroinvertebrates (Diporeia spp., opossum shrimp, Chironomidae) by the average lake whitefish was 46-96% lower and consumption of mollusks (mainly dreissenids and gastropods) was 2-5 times greater during the post-invasion period than during the pre-invasion period. Even though total food consumption by lake whitefish did not differ between the two periods in Lake Huron or the Southern Management Unit in Lake Michigan, post-invasion weight at age was at least 38% lower than pre-invasion weight at age. Under the current post-invasion diet regime, consumption by lake whitefish would have to increase by up to 122% to achieve pre-invasion growth rates.
Rao, Y.R., N. HAWLEY, M.N. Charlton, and W.M. Schertzer. Physical processes and hypoxia in the central basin of Lake Erie. Limnology and Oceanography 53(5):2007-2020 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080059.pdf
The circulation and exchange processes during summer stratification were examined using time-series data of horizontal velocity, temperature, and dissolved oxygen profiles during 2004 and 2005 in the mid-central basin of Lake Erie. The current and temperature spectra showed a prominent peak at around 18 h, indicating the presence of clockwise rotating inertial waves. The mean bottom currents were strong (>0.1 m s-1) and flowed in opposite direction to winds because of the surface pressure gradient due to wind set-up. The general range of horizontal exchange coefficients in the central basin is 0.2-1.2 m2 s-1. Vertical exchange coefficients varied from 1 x 10-5 to 1 x 10-4 m2 s-1. The high values usually occurred in the surface layer because of surface winds. The source of turbulent energy is current shear due to near-inertial oscillations in and above the thermocline and shearing stress due to the effect of mean currents and wave-induced motions during energetic wind events at the lake bottom. During strong wind episodes significant wave-induced currents were observed close to the bottom. The short-term oxygen depletion rates varied considerably between +0.87 mg L-1 d-1 and -1.16 mg L-1 d-1 in 2004 mainly because of physical processes in the central basin. When the hypolimnion depth is sufficiently thick (4 m), shortterm changes in dissolved oxygen concentrations were partly due to vertical mixing and partly due to horizontal transport and mixing.
Redalje, D.G., S.D. Lohrenz, M.J. Natter, M.D. Tuel, G.J. Kirkpatrick, D.F. Millie, G.L. FAHNENSTIEL, and F.M. VanDohal. The growth dynamics of Karenia brevis within discrete blooms on the West Florida Shelf. Continental Shelf Research 28:24-44 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080038.pdf
As part of the ECOHAB: Florida Program, we studied three large blooms of the harmful bloom forming dinoflagellate Karenia brevis. These blooms formed on the West Florida Shelf during Fall of 2000 off Panama City, and during Fall 2001 and Fall 2002 off the coastline between Tampa Bay and Charlotte Harbor. We suggest that these blooms represent two different stages of development, with the 2000 and 2001 blooms in an active growth or maintenance phase and the 2002 bloom in the early bloom initiation phase. Each bloom was highly productive with vertically integrated primary production values of 0.47-0.61, 0.39-1.33 and 0.65 g C m-2 d-1 for the 2000, 2001 and 2002 K. brevis blooms, respectively. Carbon specific growth rates were low during each of these blooms with values remaining fairly uniform with depth corresponding to generation times of 3-5 days. Nitrogen assimilation by K. brevis was highest during 2001 with values ranging from 0.15 to 2.14 umol NL-1 d-1 and lower generally for 2000 and 2002 (0.01-0.64 and 0.66-0.76 μmol NL-1 d-1 for 2000 and 2002, respectively). The highest K. brevis cell densities occurred during the 2001 bloom and ranged from 400 to 800 cells mL-1. Cell densities were lower for each of the 2000 and 2002 blooms relative to those for 2001 with densities ranging from 100 to 500 cells mL-1. The 2000 and 2001 blooms were dominated by K. brevis in terms of its contribution to the total chlorophyll a (chl a) pool with K. brevis accounting generally for >70% of the observed chl a. For those populations that were dominated by K. brevis (e.g. 2000 and 2001), phytoplankton C biomass (Cp,0) constituted <30% of the total particulate organic carbon (POC). However, in 2002 when diatoms and K. brevis each contributed about the same to the total chl a, Cp,0 was >72% of the POC. The fraction of the total chl a that could be attributed to K. brevis was most highly correlated with POC, chl a and salinity. Nitrogen assimilation rate and primary production were highly correlated with a greater correlation coefficient than all other comparisons.
REID, D.F. Ballast water and saltwater flushing: Closing a gap in the protection framework for the Great Lakes. ANS Update 14(1):2 pp. (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080035.pdf
Ballast water was identified as a vector for invasive species to the Great Lakes region in the late 1980s. In 1993 the U.S. established regulations for ships with (pumpable) ballast water to conduct open-ocean ballast water exchange (BWE) in order to conduct ballast operations in the Great Lakes (and upper Hudson River). Ships not carrying pumpable ballast water were not regulated. The recommendation for BWE was based on the idea that ballast water of coastal origin and containing coastal organisms would be replaced by mid-ocean seawater and organisms, the latter being far lower in population density and less likely to survive if discharged into the freshwater Great Lakes. However, the efficacy of BWE has been seriously questioned in recent years because of the continued discovery of new aquatic nonindigenous species (ANS) in the Great Lakes since 1993.
Richardson, C.J., R.S. King, S.S. Qian, P. Vaithiyanathan, R.G. Qualls, and C.A. STOW. Response to comment on "Estimating ecological thresholds for phosphorus in the Everglades". Environmental Science and Technology 42:6772-6773 (2008).
We thank Gaiser et al. for their comments (1) on our article (2). We support their contention that excess phosphorus has caused serious ecological effects and that caution must be taken when setting water quality standards to provide the best protection for an ecosystem. However, we disagree with their interpretation that our approach fails to protect wetlands because it bases thresholds on averages and with their view that “any” increase above ambient background concentrations causes an ecological imbalance.
Richardson, C.J., R.S. King, S.S. Qian, P. Vaithiyanathan, R.G. Qualls, and C.A. STOW. An ecological basis for establishment of a phosphorus threshold for the Everglades ecosystem. In The Everglades Experiment. Lessons for Ecosystem Restoration. C.J. Richardson (Ed.). Springer, New York, NY, 595-616 (2008).
Numerous studies have shown that the Everglades fen is a phosphorus-limited ecosystem (Steward and Ornes 1975a,b; Craft and Richardson 1993a; Koch and Reddy 1992; Richardson et al. 1999; Richardson and Qian 1999; Noe et al. 2001). From this it can be hypothesized that increases in phosphorus concentrations in the water column and the soils of the Everglades above the ecosystem's P assimilative capacity (Cha. 23) will result in significant imbalances in the structure and function of the Everglades ecosystem (Richardson and Qian 1999).
Richardson, C.J., P. Vaithiyanathan, R.G. Qualls, M.B. Bush, C.A. STOW, and M. Ho. Water quality, soil chemistry, and ecosystem responses to P dosing. In The Everglades Experiments. Lessons for Ecosystem Restoration. C.J. Richardson (Ed.). Springer, New York, NY, 385-416 (2008).
Our mesocosm study consisted of flumes or channels established in 1991 in two unimpacted slough communities in unenriched areas of WCA-2A (see Figs. 14.1 and 14.2, Chap 14, Plate 7). The word "mesocosm" here refers to an experimental enclosure where only phosphorus concentrations were chemically manipulated.
ROBERTS, J.J., and F.J. Rahel. Irrigation canals as sink habitat for trout and other fishes in a Wyoming drainage. Transactions of the American Fisheries Society 137:951-961 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080016.pdf
Irrigation canals can be a major source of mortality for fish in the Rocky Mountain region. Our study looked at how fish were affected by the irrigation canal system in the Smiths Fork, a tributary to the Bear River in western Wyoming. There are two native species of conservation concern in the Smiths Fork drainage: Bonneville cutthroat trout Oncorhynchus clarkii utah and northern leatherside chub Lepidomeda copei. Our objectives were to determine the relative abundance of each species within the canals and the fate of trout (Bonneville cutthroat trout and brown trout Salmo trutta) that enter canals. During the summer of 2003 we sampled 30 sites within the Covey Canal system, which is the largest canal system withdrawing water from the Smiths Fork. Because fish were observed to accumulate at certain spots in the canal system, we developed a sampling scheme that incorporated both random sample sites and sites known to attract fish. We estimated that between 6,300 and 10,400 fish encompassing 10 species were entrained in this canal system. The two most abundant species were speckled dace Rhinichthys osculus (29% of all fish) and mountain sucker Catostomus platyrhynchus (37% of all fish). Bonneville cutthroat trout and northern leatherside chub each comprised 2% of the total entrained fish. We implanted 30 Bonneville cutthroat trout and 13 brown trout with radio transmitters to determine whether entrained trout could leave the canal system when water levels were reduced in late summer. We found that 77% of the transmitter-implanted fish died within the canals, indicating that this system functions as sink habitat for Bonneville cutthroat trout and brown trout. Based on this mortality rate, we estimated that 120 Bonneville cutthroat trout (95% confidence interval, 75-165) and 299 brown trout (280-317) perished in the Covey Canal system during the summer of 2003.
ROBINSON, S.D., P.F. LANDRUM, P.L. VanHoof, and B.J. EADIE. Seasonal variation of polychlorinated biphenyl congeners in surficial sediment, trapped settling material, and suspended particulate matter in Lake Michigan, USA. Environmental Toxicology and Chemistry 27(2):313-322 (2008).
A unique time series of surface sediment, trapped settling material, and suspended particulate material polychlorinated biphenyl (PCB) samples were collected at a 45-m deep site off Grand Haven (MI, USA) over a 14-month period. Both concentrations and congener distributions remained constant for the sediments, although there were seasonal and interannual variability in the other matrices. Trapped settling material and suspended particulate material PCB concentrations were substantially lower (~50%) in 1997 than in the samples from December 1997 through July 1998. The cause could not be determined from the data collected, but there were some very large storms during the winter-spring period of 1998, resulting in major sediment resuspension throughout the southern basin. Observed seasonal variation in PCB concentration and congener distribution on particles likely was due to the changes in particle composition. These include particle size and the source of particles (such as the amount of resuspended sediment in trapped settling material), and the role of diagenesis of the organic matter on particles.
RUBERG, S.A., E. Guasp, N. HAWLEY, R.W. MUZZI, S.B. BRANDT, H.A. VANDERPLOEG, J.C. LANE, T.C. MILLER, and S.A. CONSTANT. Societal benefits of the real-time coastal observation network (ReCON): Implications for municipal drinking water quality. Marine Technology Society Journal 42(3):103-109 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080057.pdf
Environmental conditions on Lake Erie in summer 2006 produced hypoxic waters (1.2 mg/l), with characteristic low pH (7.2), low temperature (18°C) and high manganese levels, negatively impacting water processing at the Cleveland Water Department. A ReCON system deployed in 2005 recorded the onset of similar conditions and is used to explain the episodic nature of the event. Internal waves initiated by winds can propagate around the central basin of Lake Erie for several days explaining the cyclical nature of the event. Future deployments of a ReCON buoy system in Lake Erie's central basin will provide real-time observations of temperature and dissolved oxygen to water department managers. The buoy will function as an early warning system for the detection of low oxygen and the onset of internal waves responsible for delivering hypoxic waters to water intakes thus ensuring the quality of drinking water for approximately 1.5 million residents at Cleveland, OH.
RUTHERFORD, E.S. Lake Michigan's tributary and nearshore fish habitats. In The State of Lake Michigan in 2005. D.F. Clapp and W. Horns (Eds.). Great Lakes Fishery Commission Special Publication 08-02. Great Lakes Fishery Commission, Ann Arbor, MI, pp. 7-17 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080068.pdf
The importance of preserving and restoring habitat for fish was implicitly recognized in the guiding principles and goals of the Great Lakes Water Quality Agreement (GLWQA) (International Joint Commission 1988), in A Joint Strategic Plan for Management of Great Lakes Fisheries (hereafter, Joint Plan) (Great Lakes Fishery Commission 1997), and most recently in the Great Lakes Regional Strategy (Great Lakes Regional Collaboration 2005). The GLWQA of 1978 called for an ecosystem approach to restore and maintain the chemical, physical, and biological integrity of waters within the Great Lakes basin (Bertram et al. 2005) and recognized the interdependence of living organisms with their physical and chemical habitats (Trudeau 2005). Lake management plans (LaMPs) were established to address critical pollutants and other stresses to each lake and included development of remedial action plans for Areas of Concern (AOCs) that have serious pollution problems impairing beneficial use by humans, fish, or wildlife (U.S. EPA 2004a). In 2000, the Lake Michigan LaMP was developed to comply with provisions in the GLWQA and to guide management practices to maximize achievement of ecosystem goals and restore beneficial use impairments cited in the GLWQA. Many of the subgoals of the management plan (and the environmental indicators used to evaluate those subgoals) address restoration and protection of fish health, biotic integrity, and habitat productivity. Progress towards meeting the goals is reported on a biennial basis (e.g., U.S. EPA 2004b). The Great Lakes Regional Strategy (Great Lakes Regional Collaboration 2005) is a recent wide-ranging, cooperative effort to design and implement a strategy for the restoration, protection, and sustainable use of the Great Lakes, with specific suggestions for addressing impairments to fish communities in tributary, coastal wetland, and nearshore habitats.
Santagata, S., Z.R. Gasi?naite, E. Verling, J.R. Cordell, K. Eason, J.S. Cohen, K. Bacela, G. Quilez-Badia, T.H. JOHENGEN, D.F. REID, and G.M. Ruiz. Effect of osmotic shock as a management strategy to reduce transfers of non-indigenous species among low-salinity ports by ships. Aquatic Invasions 3(1):61-76 (2008).
Open-ocean ballast-water exchange (BWE) is currently the most common treatment used to reduce the ballast transfer of organisms and the subsequent risk of invasions among coastal ecosystems. Freshwater or estuarine organisms remaining after BWE often experience high mortality, due to osmotic shock caused by high-salinity exposure. We conducted 70 salinity tolerance experiments on 54 different taxa to measure mortality rates of freshwater and estuarine organisms after exposure to oceanic seawater (34 psu), simulating both flow-through (F-T) and empty-refill (E-R) BWE methods. We focused especially on larval and adult crustaceans from freshwater and mesohaline habitats adjacent to ports of the Baltic Sea, North Sea, Great Lakes, Chesapeake Bay, and San Francisco Bay. Animals from oligohaline habitats (0-2 psu) experienced the highest mortality: all individuals died in 82% of the F-T treatments and 88% of the E-R treatments. The effectiveness of both treatment types decreased with animals from low-salinity (2-5 psu, 100% mortality in 27% of F-T and 46% of E-R treatments) and mesohaline habitats (5-18 psu, 100% mortality in 40% of F-T and 52% of E-R treatments). In 43% of cases among all salinity categories, empty-refill treatments required less exposure time to cause significant mortality than flow-through treatments. Invertebrates that exhibited significant survivorship were most often peracarid crustaceans including widely introduced species of mysid shrimps and amphipods. Although salinity shock does not completely prevent the transfer of all low-salinity biota, BWE provides a useful management tool to reduce species transfers, especially considering the combined effects of removal and mortality.
Schertzer, W.M., R.A. ASSEL, D. BELETSKY, T.E.I. CROLEY, B.M. LOFGREN, J.H. SAYLOR, and D.J. SCHWAB. Lake Huron climatology, inter-lake exchange and mean circulation. Aquatic Ecosystem Health and Management 11(2):144-152 (2008).
Selected key features of the physical limnology, hydrology and climate influencing Lake Huron is presented. The lake is deep (229 m), consists of four interconnected bodies of water and currently there are no diversions into or out of the lake. Long-term annual summaries of meteorological and hydrological variables show that the lake affects spatial distributions across the basin. An estimate of the long-term hydrologic budget shows the relative importance of the major inflows, outflows and net basin supply. Long-term monthly average water level is 176.6 m. Monthly mean total heat flux ranges from -155 W m-2 in December to 154 W m-2 in June. Light attenuation is higher in Saginaw Bay and the nearshore compared to the mid-lake. Ice extent can be an important factor in the Lake Huron system with values ranging from <10% to >90% depending on winter severity. Surface and mean lake temperature for shallow North Channel are similar, however, large volumes of main Lake Huron and Georgian Bay results in mean temperatures nearly 10oC less than surface temperatures in summer. Inter-lake exchange at the Straits of Mackinac is about 2 cm s-1 but fluctuating flows can be up to 30 times larger. The averaged summer and winter circulation shows cyclonic patterns for Lake Huron.
SELLINGER, C.E., C.A. STOW, E.C. Lamon, and S.S. Qian. Recent water level declines in the Lake Michigan-Huron system. Environmental Science and Technology 42(2):367-373 (2008).
Great Lakes water levels have fluctuated over thousands of years. High water levels were a problem in the 1980s, but a recent sudden drop in Lakes Michigan and Huron has caused particular concern, in part because lower water levels are consistent with many global climate change scenarios. We examined water level data (1860–2006) representing Lakes Michigan and Huron to evaluate changes in both long-term and seasonal patterns over time, and explore relationships with candidate predictor variables. Our tools for this analysis included both Seasonal Trend decomposition using Loess (STL), and dynamic linear models (DLM). In addition to the recent decline, STL results reveal a sustained decline around 1900, a long-term periodicity of ∼30 years, and an unexpected correspondence with sunspot activity. DLM results indicate a relationship with precipitation over a three-year lagged period, which has been essentially unchanging from 1900 to present. Additionally, the DLM highlights an underlying lake level decline beginning in ∼1973 and continuing to the present, which may have been obscured by concurrently increasing precipitation into the 1990s. The current underlying decline might be related to a simultaneous evaporation increase, however, our model could not confirm this relationship, possibly due to the shorter period of record for evaporation data. We cannot be certain that the present observed water level drop is caused by factors related to global climate change, or that it portends a long-term problem. However, because the underlying decline has been ongoing for ∼33 years it may be prudent to include lower lake levels in future management planning.
STOW, C.A., E.C. Lamon, T.K. Kratz, and C.E. SELLINGER. Lake level coherence supports common driver. EOS Transactions 89(41):7 (2008).
Lake Superior, the world's largest lake by surface area (82,400 square kilometers) experienced record low water levels in 2007 [Holden, 2007]. In addition, Lakes Michigan and Huron (58,000 and 59,596 square kilometers, respectively), which behave hyraulically as one lake and which began declining in 1997, were at near-record low levels in 2007 [Sellinger et al. 2008]. The low levels that these three lakes are experiencing have raised concern that the Laurentian Great Lakes are beginning to realize predicted climate change effects [Magnuson et al., 1997].
WANG, H.-Y., T.O. HÖÖK, M.P. Ebener, L.C. Mohr, and P.J. Schneeberger. Spatial and temporal variation of maturation schedules of lake whitefish (Coregonus cleupaformis) in the Great Lakes. Canadian Journal of Fisheries and Aquatic Sciences 65:2157-2169 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080040.pdf
Fish maturation schedules vary greatly among systems and over time, reflecting both plastic and adaptive responses to ecosystem structure, physical habitats, and mortality (natural and fishing). We examined maturation schedules of commercially exploited lake whitefish (Coregonus clupeaformis) in the Laurentian Great Lakes (Lakes Michigan, Huron, and Superior) by estimating ages and lengths at 50% maturity, age-specific maturity ogives (age-specific probability of being mature), and probabilistic maturation reaction norms (PMRNs; a metric that accounts for effects of growth and mortality). Collectively, these estimates indicated variation in maturation schedules between sexes (i.e., males tend to mature at younger ages and shorter lengths than females) and among systems (midpoint estimates of PMRNs were smallest for Lake Michigan fish, intermediate for fish in the main basin of Lake Huron, and largest for fish in Lake Huron’s Georgian Bay and Lake Superior). Temporally, recent increases in age at 50% maturity in Lakes Huron and Michigan may primarily reflect plastic responses to decreased growth rates associated with ecosystem changes (e.g., declines of the native amphipod, Diporeia spp.). As plastic and adaptive changes in maturation schedules of fish stocks may occur simultaneously and require different management considerations, we recommend the concomitant analysis of multiple maturation indices.
WANG, J., M. Jin, J. Takahashi, T. Suzuki, I.G. Polyakov, K. Mizobata, M. Ikeda, F.J. Saucier, and M. Meier. Modeling Arctic Ocean heat transport and warming episodes in the 20th century caused by the intruding Atlantic water. Chinese Journal of Polar Research 19(2):159-167 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080061.pdf
This study investigates the Arctic Ocean warming episodes in the 20th century using both a high-resolution coupled global climate model and historical observations. The model, with.no flux adjustment, reproduces well the Atlantic Water core temperature (AWCT) in the Arctic Ocean and shows that four largest decadalscale warming episodes occurred in the 1930s, 70s, 80s, and 90s, in agreement with the hydrographic observational data. The difference is that there was no pre-warming prior to the 1930s episode, while there were two pre-warming episodes in the 1970s and 80s prior to the 1990s, leading the 1990s into the largest and prolonged warming in the 20th century. Over the last century, the simulated heat transport via Fram Strait and the Barents Sea was estimated to be, on average, 31. 32 TW and 14. 82 TW, respectively, while the Bering Strait also provides 15.94 TW heat into the western Arctic Ocean. Heat transport into the Arctic Ocean by the Atlantic Water via Fram Strait and the Barents Sea correlates significantly with AWCT (C =0.75) at 0lag. The modeled North Atlantic Oscillation (NAO) index has a significant correlation with the heat transport (C =0.37). The observed AWCT has a significant correlation with both the modeled AWCT ( C =0.49) and the heat transport (C =0.41) . However, the modeled NAO index does not significantly correlate with either the observed AWeT (C = O. 03) or modeled AWCT (C = O. 16) at a zero-lag, indicating that the Arctic climate system is far more complex than expected. Key words Arctic Ocean, heat transport, warming episodes, modeling.
WANG, J., K. Mizobata, H. HU, M. Jin, S. Zhang, W. Johnson, K. Shimada, and M. Ikeda. Modeling seasonal variations of ocean and sea ice circulation in the Beaufort and Chukchi Seas: A model-data fusion study. Chinese Journal of Polar Research 19(2):168-184 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080062.pdf
A 3. 8-km Coupled lee-Ocean Model (CIOM) was implemented to successfully reproduce many observed phenomena in the Beaufort and Chukchi seas, including the Bering-inflow-originated coastal ciurrent that splits into three branches: Alaska Coastal Water (ACW) , Central Channel, and Herald Valley branches. Other modeled phenomena include the Beaufort Slope Current (BSC), the Beaufort Gyre, the East Siberian Current (ESC), mesoscale eddies, seasonal landfast ice, sea ice ridging, shear, and deformalion. Many of these downscaling processes can only be captured by using a high-resolution CIOM. nested in a global climate model. The seasonal cycles for sea ice concentration, thickness, velocity, and other variables are well reproduced with solid validation by satellite measurements. The seasonal cycles for upper ocean dynamics and thermodynamics are also well reproduced, which include the formation of the cold saline layer due to the injection of salt during sea ice formation, the BSC, and the subsurface upwelling in winter that brings up warm, even more saline Atlantic Water along the shelfbreak and shelf along the Beaufort coast.
Waples, J.T., B.J. EADIE, J. Val Klump, M. Squires, J.B. Cotner, and G. McKinley. Chapter 7: The Laurentian Great Lakes. North American Continental Margins: A Synthesis and Planning Workshop. Report of the North American Continental Margins Group for the U.S. Carbon Cycle Scientific Steering Group and Interagency Working Group. U.S. Carbon Cycle Science Program, Washington, DC, pp. 73-81 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080024.pdf
North America’s inland ocean, the Great Lakes (Figure 7.1), contains about 23,000 km3 (5,500 cu. mi) of water (enough to flood the continental United States to a depth of nearly 3 m), and covers a total area of 244,000 km2 (94,000 sq. mi) with 16,000 km of coastline. The Great Lakes comprise the largest system of fresh, surface water lakes on earth, containing roughly 18% of the world supply of surface freshwater. Reservoirs of dissolved carbon and rates of carbon cycling in the lakes are comparable to observations in the marine coastal oceans (e.g., Biddanda et al. 2001) (Table 7.1). The drainage area of the Laurentian system (including the Saint Lawrence River) is approximately 1.0 million km2-- approximately one-third of the Mississippi River watershed or roughly 4% of the surface area of North America. The Great Lakes drain through the Saint Lawrence River, which flows approximately 1200 km before emptying into the largest estuary in the world, the Gulf of Saint Lawrence. This feature of the Great Lakes system is unique in relation to the other marginal regions: exchange with the open ocean is in only one direction, to the ocean. Because of the large size of the watershed, physical characteristics such as climate, soils, and topography vary across the basin. Terrestrial and atmospheric forcing is strongly latitude-dependent in this large basin. To the north, the climate is cold and the terrain is dominated by a granitic bedrock called the Canadian (or Laurentian) Shield consisting of Precambrian rocks under a generally thin layer of acidic soils. Conifers dominate the northern forests. In the southern areas of the basin, the climate is much warmer. The soils are deeper with layers or mixtures of clays, carbonates, silts, sands, gravels, and boulders deposited as glacial drift or as glacial lake and river sediments. The lands are usually fertile and have been extensively drained for agriculture. The original deciduous forests have given way to agriculture and sprawling urban development. This variability has strong impacts on the characteristics of each lake. The lakes are known to have significant effects on air masses as they move in prevailing directions, as exemplified by the 'lake effect snow' that falls heavily in winter on communities situated on the eastern edges of lakes. If the Lakes can frequently experience the degrees of CO2 undersaturation shown below, then the CO2 of the airmasses must be impacted as well.
WILSON, A.E., D.C. GOSSIAUX, T.O. HÖÖK, J.P. Berry, P.F. LANDRUM, J. DYBLE, and S.J. Guildford. Evaluation of the human health threat associated with the hepatoxin microcystin in the muscle and liver tissues of yellow perch (Perca flavescens). Canadian Journal of Fisheries and Aquatic Sciences 65:1487-1497 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080020.pdf
During the summer of 2006, the western basin of Lake Erie experienced a bloom of the toxigenic cyanobacterium Microcystis aeruginosa. Across 11 sites, intracellular, particulate-bound microcystin levels in the seston increased to levels that exceeded World Health Organization guidelines for drinking water exposure (1 mg toxin L-1). In contrast, toxin concentrations in yellow perch (Perca flavescens) muscle tissue (n = 68) declined from June to August, were negatively related to algal toxin levels, and never exceeded a conservative chronic exposure concentration estimated using proposed United States Environmental Protection Agency (US EPA) guidelines. Microcystin concentrations in yellow perch liver exceeded US EPA chronic exposure guidelines, were on average 125 times higher than muscle toxin concentrations per unit dry weight, and varied little throughout the summer. With current guidelines, humans do not appear to be at risk when consuming the muscle tissue of Lake Erie yellow perch collected during large-scale cyanobacterial blooms. However, this study highlights the need for a better understanding of the trophic transfer of cyanobacterial toxins through aquatic food webs in diverse ecosystems with an emphasis on understanding if these compounds could accumulate sufficiently to affect human health.
Wynne, T.T., R.P. Stumpf, M.C. Tomlinson, R.A. Warner, P.A. Tester, J. DYBLE, and G.L. FAHNENSTIEL. Relating spectral shape to cyanobacterial blooms in the Laurentian Great Lakes. International Journal of Remote Sensing 29(12):3665-3672 (2008).
A change in the spectral shape at 681 nm is used to distinguish blooms of cyanobacteria from blooms of other phytoplankton via MERIS satellite sensor imagery. During large cyanobacterial blooms, the spectral shape around 681 nm is not a positive quantity as scattering due to cyanobacteria overwhelms the fluorescence signal, thus creating a negative spectral shape. This relationship is consistent in both remotely sensed and in situ data.
Yang, X.Y., R.X. Huang, J. WANG, and D.X. Wang. Delayed baroclinic response of the Antarctic circumpolar current to surface wind stress. Science in China Series D: Earth Sciences 51(7):1036-1043 (2008).
The Antarctic Circumpolar Current (ACC) responds to the surface windstress via two processes, i.e., the instant barotropic process and the delayed baroclinic process. This study focuses on the baroclinic instability mechanism in ACC, which was less reported in the literatures. Results show that the strengthening of surface zonal windstress causes the enhanced tilting of the isopycnal surface, leading to more intense baroclinic instability. Simultaneously, the mesoscale eddies resulting from the baroclinic instability facilitate the transformation of mean potential energy to eddy energy, which causes the remarkable decrease of the ACC volume transport with the 2-year lag time. This delayed negative correlation between the ACC transport and the zonal windstress may account for the steadiness of the ACC transport during last two decades.
ZHANG, H., D.A. Culver, and L. Boegman. A two-dimensional ecological model of Lake Erie: Application to estimate dressenid impacts on large lake plankton populations. Ecological Modelling 214:219-241 (2008). http://www.glerl.noaa.gov/pubs/fulltext/2008/20080013.pdf
We constructed a complex ecological model of Lake Erie, EcoLE, based on a two-dimensional hydrodynamic and water quality model (CE-QUAL-W2).We used data from 1997 to calibrate the model, and data from 1998 and 1999 to verify it. The simulated surface and bottom water temperatures show good agreement with field observations. In spite of limitations of this 2D model and data availability, the simulated values of biological and nutrient state variables match well with field measurements. Although EcoLE's performance for the verification years is as good as that of the calibration year, the wide standard deviations of both field measurements and model simulations as well as the complexity of an ecosystem of this size make us consider our model more as a valid analytical tool rather than a predictive one at this moment. Nevertheless, we have constructed the first fine-scale dynamic ecological model of a large lake that couples hydrodynamics and detailed food web of lower trophic levels and is driven by real-time air temperature and wind conditions and the inputs from the atmosphere and tributaries. Using the model we investigate the impacts of zebra mussels (Dreissena polymorpha) and quagga mussels (D. bugensis) on phytoplankton of Lake Erie. The simulation results show that dreissenid grazing impacts on non-diatom edible algae (NDEA) are weakened by the boundary layer above the basin bottom. However, dreissenid grazing impacts on diatoms are less affected by the boundary layer due to the higher sinking rates of diatoms. Dreissenid mussels increase non-diatom inedible algae (NDIA) rapidly with increasing mussel population size, because the dreissenid population excretes a large amount of ammonia and phosphate. Our results indicate that dreissenid mussels have weak direct grazing impacts on algal biomass, while indirect effects of their nutrient excretion have a greater impact on the system.
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