GLERL Publication Abstracts: FY 2006

ASSEL, R. A. Classification of annual Great Lakes ice cycles: Winters of 1973-2002. Journal of Climate 18:4895-4905 (2005).

Annual seasonal average ice cover from 1973 to 2002 and associated dates of first ice, last ice, and ice duration are presented and discussed. The annual seasonal average ice cover of each Great Lake is used to define three ice cycle classes: mild, typical, and severe. About half of the severe ice cycles occurred from 1977 to 1982 and about half of the mild ice cycles occurred from 1998 to 2002. The seasonal progression of daily lake-averaged ice cover, spatial differences in ice cover, and differences among the Great Lakes for mild, typical, and severe ice cycles are discussed within the context of lake bathymetry and winter air temperatures. Seasonal average ice cover is larger on Lakes Superior, Erie, and Huron relative to Lakes Michigan and Ontario, because of shallower depths (for Erie and Huron) and lower air temperatures (for Superior) relative to Lakes Michigan and Ontario. This ice cycle classification scheme can be used to compare future Great Lakes ice cycle severity with this 30-winter benchmark.

ASSEL, R. A. Detroit River - Western Lake Erie Basin Indicator Project. Indicator: Lake Erie Ice Cover. U.S. EPA Web Site, pp. (2006).

No abstract

Barbiero, R. P., T. F. NALEPA, and M. L. Tuchman. Phytoplankton, zooplankton, and benthos. In The State of Lake Huron in 1999. M.P. Ebener (Ed.). Special Publication 05-02. Great Lakes Fishery Commission, Ann Arbor, MI, 33-41 (2005).

No specific FCOs for phytoplankton, zooplankton, and benthos exist. However, FCOs call for balancing predator abundance with prey-fish production, which is a function of plankton and benthos production. The Great Lakes National Program Office (GLNPO) of the U.S. Environmental Protection Agency has conducted regular surveillance monitoring of Lake Huron since 1983. The monitoring effort is focused on whole-lake responses to changes in loadings of anthropogenic substances, so sampling is restricted largely to the relatively homogeneous offshore waters. Data presented in this report are for phytoplankton and zooplankton communities sampled at 14 sites lakewide during spring (20-21 April) and summer (15-17 August), 1999. Sampling methods and limnological conditions during the surveys are described in Barbiero and Tuchman (2001) and Barbiero et al. (2001). The description of the benthos community is consolidated from a variety of unrelated studies.

Biddanda, B. A., D. F. Coleman, T. H. JOHENGEN, S. A. RUBERG, G. A. Meadows, H. W. VanSumeren, R. R. Rediske, and S. T. Kendall. Exploration of a submerged sinkhole ecosystem in Lake Michigan. Ecosystems 9:828-842 (2006).

Dissolution of the Silurian-Devonian aquifer in the Lake Huron Basin has produced several karst formations in the bedrock (sinkholes), through which groundwater emerges onto the lake floor. During September 2003, we explored a recently discovered submerged sinkhole ecosystem (55 m * 40 m * ~1 m) located at a depth of 93 m with a remotely operated vehicle (ROV) equipped with a conductivity-temperature-depth (CTD) system, an acoustic navigational system, a video camera, and a water sampling system. In addition to two morphotypes of benthic mats, a 1–2 m thick visibly cloudy near-bottom nepheloid-like layer (sinkhole plume) with a strong hydrogen sulfide odor prevailed just above the seepage area of clear water. Relative to lake water, water samples collected within the sinkhole plume were characterized by slightly higher (by 4°C) temperatures, very high levels of chloride (up to 175 mg l-1) and conductivity (1,700 µS cm-1), as well as extremely high concentrations of sulfate (1,400 mg l-1), phosphorus (3 mg l-1) and particulate organic matter (400 mg C l-1). Compared to background lake water, sinkhole plume water was characterized by approximately twofold lower C:N ratios and tenfold higher levels of dissolved organic carbon, bacterial biomass as well as heterotrophic bacterial production. Significant uptake of 14C-bicarbonate in dark incubations provided preliminary evidence for occurrence of chemosynthesis, possibly mediated by specialized Bacteria and Archea present in this submerged sinkhole ecosystem in the Laurentian Great Lakes.

BRANDT, S. B., J. Hendee, P. Levin, J. Phinney, D. Schuerer, and F. Schwing. Ecological forecasting. White Paper #5. In Ecosystem Science Capabilities Required to Support NOAA's Mission in the Year 2020. NOAA Technical Memorandum NMFS-F/SPO-74. S.A. Murawski and G.C. Matlock (Eds.). NOAA, National Marine Fisheries Service, Silver Spring, MD, 52-63 (2006).

The health of the U.S. economy is inextricably linked to the health of our Nation’s ecosystems and the goods and services they deliver to our economy. Each year, U.S. ecosystems provide over $227 billion in added value to the U.S. economy (CENR, 2001) as well as other harder-to-quantify services and benefits such as waste detoxification and decomposition, air and water purification, maintenance of biological diversity, and recreational and spiritual renewal (Daily et al., 1997). Coastal ecosystems, in particular, provide a wealth of fisheries resources and recreational benefits, and are a potential source of life saving pharmaceuticals. These important ecosystems can also directly impact human health from exposure to contaminated water (e.g., from urban and agricultural runoff, pollutants, coliform, and other pathogens, and toxic algae) or contaminated food (e.g., fish and shellfish).

Bundy, M. H., H. A. VANDERPLOEG, P. J. Lavrentyev, and P. A. Kovalcik. The importance of microzooplankton versus phytoplankton to copepod populations during late winter and early spring in Lake Michigan. Canadian Journal of Fisheries and Aquatic Sciences 62:2371-2385 (2005).

Feeding rates of the calanoid copepod Leptodiaptomus sicilis on natural assemblages of phytoplankton and microzooplankton were evaluated during late winter and early spring in Lake Michigan. Microzooplankton were the preferred food source for this copepod, and larger size fractions of phytoplankton were preferred to smaller size fractions. Ingestion rates of total chlorophyll a ranged from 2 to 14 ng·copepod–1·day–1, while ingestion rates of microzooplankton biomass ranged from 0.04 to 0.15 µg C·copepod–1·day–1. In these experiments, microzooplankton carbon accounted for 22%–74% of the total carbon ingested. Clearance rates of microzooplankton carbon were positively related to the larger size fractions of chlorophyll a and to total suspended solids. Measured ingestion rates of microzooplankton and phytoplankton carbon suggest that calanoid copepod populations have the potential to control microzooplankton production in late winter and early spring, and even with an abundance of phytoplankton carbon, food availability may limit the reproduction of L. sicilis. Because microzooplankton contribute significantly to the diet of these copepods, stimulation of the microbial food web by terrigenous inputs of nutrients and carbon may be transmitted to higher trophic levels (i.e., mesozooplankton and their predators) through heterotrophic flagellates and protozoans.

Bunnell, D. B., C. P. Madenjian, and T. E. CROLEY II. Long-term trends of bloater (Coregonus hoyi) recruitment in Lake Michigan: evidence for the effect of sex ratio. Canadian Journal of Fisheries and Aquatic Sciences 63:832-844 (2006).

Long-term population trends are generally explained by factors extrinsic (e.g., climate, predation) rather than intrinsic (e.g., genetics, maternal effects) to the population. We sought to understand the long-term population dynamics of an important native Lake Michigan prey fish, the bloater Coregonus hoyi. Over a 38-year time series, three 10- to 15-year phases occurred (poor, excellent, and then poor recruitment) without high interannual variability within a particular phase. We used dynamic linear models to determine whether extrinsic (winter and spring temperature, alewife predator densities) or intrinsic factors (population egg production, adult condition, adult sex ratio) explained variation in recruitment. Models that included population egg production, sex ratio, winter and spring temperature, and adult bloater condition explained the most variation. Of these variables, sex ratio, which ranged from 47% to 97% female across the time series, consistently had the greatest effect: recruitment declined with female predominance. Including biomass of adult alewife predators in the models did not explain additional variation. Overall our results indicated that bloater recruitment is linked to its sex ratio, but understanding the underlying mechanisms will require additional efforts.

Cardenas, M. P., D. J. SCHWAB, B. J. EADIE, N. HAWLEY, and B. M. Lesht. Sediment transport model validation in Lake Michigan. Journal of Great Lakes Research 31:373-385 (2005).

A multiple sediment type, three-dimensional hydrodynamic and sediment transport model was applied to Lake Michigan to simulate conditions during the Spring 2000 resuspension event. Model predictions were compared to data gathered by the EEGLE project including turbidity and downward mass flux. The model predictions for turbidity compared well to observed data, especially in capturing the distinctive peaks in turbidity due to advection that occurred in the area of the resuspension feature. The advection peaks seemed tied to the presence of a highly-resuspendable pool of sediments that was transported by weaker winds during early Spring 2000. The model predictions at depths of 40 m in the area of the resuspension feature were more problematic, as the observed data in one location showed a significant turbidity peak at the time of maximum winds. The model underestimated turbidity at that particular location, yet model predictions of a very similar turbidity peak were seen at a similar depth. The different turbidity predictions at these locations were due to underestimation of offshore flow by the hydrodynamic model. The model generally underestimated downward mass flux, though the predictions for the time-intervals that included the time of peak winds and the following week were good to excellent. These intervals generally showed the highest downward mass flux. This work highlights the importance of multiple sediment types, their associated critical shear stresses for resuspension, and the presence of a very easily resuspendable sediment layer. The availability of comprehensive data set was also important.

Carter, G., P. Restrepo, J. Hameedi, P. Ortner, C. E. SELLINGER, J. Stein, and T. Beechie. Freshwater issues. White Paper #3. In Ecosystem Science Capabilities Required to Support NOAA's Mission in the Year 2020. NOAA Technical Memorandum NMFS-F/SPO-74. S.A. Murawski and G.C. Matlock (Eds.). NOAA, National Marine Fisheries Service, Silver Spring, MD, 29-39 (2006).

Freshwater is our most precious and finite natural resource -- the total amount of freshwater in lakes, streams, rivers, and groundwater accounts for less than one percent of water on the Earth. As human populations increase, so does competition for water to meet societal needs versus to maintain the needs of the earth’s biological systems. Additionally, there are increasing demands for recreational use of water in streams, river, and lakes, and increasing awareness of interacting hydrological ecological, and social systems required for a healthy environment, dynamic economy, and equitable allocation and use of freshwater.

CARTER, G. S., T. F. NALEPA, and R. R. Rediske. Status and trends of benthic populations in a coastal drowned river mouth lake of Lake Michigan. Journal of Great Lakes Research 32:578-595 (2006).

Muskegon Lake was designated an Area of Concern because of severe environmental impairments from direct discharge of industrial and municipal wastes. Since diversion of all municipal and industrial wastewater in 1973, few studies have assessed ecological changes associated with improved water quality. We examined distributions and long-term changes in the benthic macroinvertebrate community at 27 sites. Distributions were evaluated relative to distance from the river mouth, water depth, grain size, and known areas of sediment contamination. Temporal changes were assessed relative to wastewater diversion. Oligochaeta and Chironomidae dominated the community, and the oligochaete trophic condition index indicated that, in 1999, the lake was generally mesotrophic to eutrophic. Cluster analysis resulted in four distinct site groupings. A cluster of sites near the river mouth had the highest total density (9,375 m–2) and lowest diversity (Shannon Weaver Index 1.05) suggesting an enriched habitat. A site cluster in the south central region had the lowest oligochaete density (2,782 m–2), lowest oligochaete trophic condition index scores (1.00), and highest diversity (2.24), suggesting the best habitat. The chironomid community in this site cluster was dominated by predatory species, possibly resulting from high concentrations of heavy metals at some sites. Densities of all major taxonomic groups increased significantly between 1972 and 1999. Decreasing proportions of oligochaetes (0.85 to 0.68) and increasing diversity suggest improved environmental conditions over this period. Evidence suggests that changes in Muskegon Lake’s benthic community were more a result of wastewater diversion than Dreissena invasion

Cowden, J. R., D. Watkins, and T. E. CROLEY II. Investigating urban land use effects on runoff by using the distributed large basin runoff model. Proceedings, The World Environmental and Water Resources Congress 2006: Examining the Confluence of Environmental and Water Concerns, Omaha, Nebraska, May 21-25, 2006. Environmental Water Resources Institute, American Society of Civil Engineers, 9 pp. (2006).

Urbanization is a growing trend world wide and presents many significant challenges in watershed planning. Distributed operational hydrology models can assist decision makers in understanding the effects of land use and urban development policies on large watersheds, including runoff quantity and quality. The National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory (GLERL) has developed the Distributed Large Basin Runoff Model (DLBRM) as a large-scale model for the Great Lakes basin. This paper illustrates how the daily DLBRM may be used to model runoff impacts of urbanization. Urbanization trends within the Clinton watershed of Southeastern Michigan are discussed, including analysis of stationary stream flow trends of the watershed. Calibration issues regarding temporal parameter variability are also addressed followed by urbanization scenario simulations within the Clinton watershed

CROLEY, T. E., II. Modified Great Lakes hydrology modeling system for considering simple extreme climates. NOAA Technical Memorandum GLERL-137. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 27 pp. (2006).

We (the Great Lakes Environmental Research Laboratory) want to simulate Great Lakes hydrology for simple hypothetical climate scenarios to understand the extremes necessary to cause closed (terminal) lakes, suspected to have occurred about 7,900 radiocarbon years ago. We use our Advanced Hydrologic Prediction System with some conditions estimated for this period. We use dynamic lake areas (which vary with lake depth) to correct modeled over-lake precipitation, runoff, and lake evaporation, and neglect existing diversions and consumptions. We use simple shifts in precipitation, air temperature, and humidity, relative to the present base climate, with 52 years of daily historical meteorology. For steady-state analysis of the interconnected Great Lakes, we employ lake outflow-depth rating curves (using estimated sill elevations) reasonable for a natural system and combine with a water balance for all the lakes connected by their channels. We consider the upper and lower Great Lakes separately with no river connection, as in the early Holocene basin configuration. We identify candidate climates that result in closed lakes by looking at lake outflows and levels, demonstrating that climate may have been the mechanism creating terminal lake status in the past. The lakes would close in the order: Erie, Superior, Michigan-Huron, and Ontario for increasingly drier and warmer climates. For a temperature rise of T �C and a precipitation drop of P% relative to the present base climate, conditions for complete lake closure range from 4.7 T + P > 51 for Erie to 3.5 T + P > 71 for Ontario

CROLEY, T. E. II. Using climatic predictions in Great Lakes hydrologic forecasts. In ASCE Task Committee Report on Climatic Variations, Climate Change, and Water Resources Engineering. J. Garbrecht and T. Piechota (Eds.) . American Society of Civil Engineers, Arlington, VA, 164-185 (2006).

The Great Lakes Environmental Research Laboratory’s (GLERL’s) Advanced Hydrologic Prediction System (AHPS) illustrates the technology for those interested in using climate predictions in water resources decisions. It provides 1-6-month probability outlooks for 25 hydrology variables over the 121 watersheds and 7 lake surfaces of the Great Lakes basin, including simultaneous water levels on all lakes. The system incorporates both current conditions, antecedent to a forecast, and multiagency, multi-area, multi-period climate outlooks of meteorology probabilities. Extended water level forecasts are evaluated over three periods to determine the value of antecedent conditions and meteorological outlooks in making them. The suitability of GLERL’s AHPS forecasts is also considered relative to existing US and Canadian forecasts. While the use of antecedent conditions adds considerably to Great Lakes forecasting ability, the use of existing meteorological outlooks adds little. GLERL’s AHPS appears better than, or as good as, other Great Lakes forecasts and offers the advantage of improvement as better near real time data streams and improved process models become available. Forecasts that utilize climate predictions are used in several water resource decision settings, as illustrated here

CROLEY, T. E. II., and C. He. Watershed surface and subsurface spatial intraflows model. Journal of Hydraulic Engineering 11(1):12-20 (2006).

We present new developments to the original, spatially lumped large basin runoff model (LBRM) of the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory. In addition to making it a two-dimensional, spatially distributed model, we modify it to allow muting flows between adjacent cells upper soil zones, lower soil zones, and groundwater zones. We modify the LERM continuity equations for these additional flows and add corresponding corrector terms to the original solution equations. We derive the flow network from elevation and hydrography and the LBRM automatically arranges eel) computations. We apply the newly modified LBRM to the Kalamazoo River watershed in Michigan and to the Maumee River watershed in Ohio. The simulations show that the Kalamazoo River has dominant groundwater storage, allowing delayed and sustained hydrologic responses to rainfall whereas the Maumee River lacks any significant groundwater storage, allowing a fast flashy response to rainfall. These results are characteristic of the study watersheds, indicating that the addition of subsurface intraflows in the model has improved watershed representation

DeMaster, D., M. Fogarty, D. M. MASON, G. Matlock, and A. Hollowed. Management of living marine resources in an ecosystem context. White paper #2. In Ecosystem Science Capabilities Required to Support NOAA's Mission in the Year 2020. NOAA Technical Memorandum NMFS-F/SPO-74. S.A. Murawski and G.C. Matlock (Eds.). NOAA, National Marine Fisheries Service, Silver Spring, MD, 15-28 (2006).

One of the four goals articulated in NOAA’s Strategic Plan is to “protect, restore and manage coastal and ocean resources through an ecosystem approach” (NOAA, 2004). This goal flows from the mandates and direction of such Federal laws, executive orders, courts, and international treaties as the Magnuson-Stevens Fishery and Conservation Management Act (MSFCMA), Endangered Species Act (ESA), National Environmental Policy Act (NEPA), Marine Mammal Protection Act, Coral Reef Conservation Act, Coastal Zone Management Act, National Marine Sanctuaries Act, International Commission for the Conservation of Atlantic Tunas, and Inter-American Tropical Tuna Commission. These directives reflect society’s desire for policies and institutions to manage the environment. When combined, they reflect the recognition that fishing is but one competing use of ecosystems that produces a broad set of ecological and societal benefits. But the benefits are not achieved without costs; thus, there is a need to manage LMRs in an ecosystem context. The critical need for a more holistic approach to managing the use of LMRs has been well articulated in a number of recent publications, including the U.S. Commission on Ocean Policy report (USCOP, 2004), U.S. Ocean Action Plan (CEQ, 2004), Pew Oceans Commission report (2003), Rappoport (1998), report to Congress by the Ecosystem Principles Advisory Panel (1999), report by the United Nations’ Food and Agriculture Organization (FAO, 2003), a series of essays published by the Marine Ecology Progress Series (Browman and Stergiou, 2004), and a series of National Research Council (NRC) publications (1994, 1999b, 1999c, 2001, 2002), as well as numerous references contained therein.

DYBLE, J., P. A. Tester, and R. W. Litaker. Effects of light intensity on cylindrospermopsin production in the cyanobacterial HAB species Cylindrospermopsis raciborskii. African Journal of Marine Science 28(2):309-312 (2006).

The role of light intensity on growth and the production of the hepatotoxin cylindrospermopsin (CYN) in the cyanobacterial harmful algal bloom species Cylindrospermopsis raciborskii was investigated using cultured isolates grown in N-free media under a series of neutral density screens. Maximum growth as indicated by chlorophyll a concentrations was measured at 75 µmol photons m-2 s-1, whereas maximum intracellular and extracellular CYN concentrations occurred in cultures grown under the highest light intensity (140 µmol photons m-2 s-1). During exponential growth phase, N-limited C. raciborskii cultures grown under light intensities of 18–75 µmol photons m-2 s-1 exhibited a strong linear relationship between light intensity and both intracellular and extracellular CYN concentrations. Extracellular CYN concentrations increased significantly as the culture moved from log to stationary growth phase. These results indicate that the highest intracellular toxin concentrations in the field are likely to occur in C. raciborskii populations that have been actively growing at light intensities of 75–150 µmol photons m-2 s-1 for more than two weeks, and that peak soluble toxin levels will be found at the end of a bloom.

FOLEY, A. J. III, T. F. NALEPA, G. K. Walker, and M. J. McCORMICK. Epibiont populations associated with Diporeia spp. (amphipoda) from Lake Michigan. Verh. Internat. Verein. Limnol. 29:1205-1211 (2006).

The benthic amphipod Diporeia spp. is the dominant benthic macroinvertebrate in the offshore region (>30 m) of the Laurentian Great Lakes and, as a detritivore, plays a critical role in the offshore food web. Diporeia feed on organic material that settles from the water column and, in turn, are fed upon by many fish species. This organism, therefore, serves as an important trophic link between lower and upper trophic levels (Gardner et al. 1990). Diporeia are currently declining in all the Great Lakes except Lake Superior (Dermott & Kerec 1997, Nalepa et al. 1998, Lozano et al. 2001, Dermott 2001). While declines have been coincidental with the introduction and spread of the zebra mussel (Dreissena polymorpha) and the quagga mussel (Dreissena bugensis), exact mechanisms for the negative response have not been clearly defined (Nalepa et al. 2004).

Gregson, B. P., D. F. Millie, C. Cao, G. L. FAHNENSTIEL, R. J. Pigg, and D. P. Fries. Simplified enrichment and identification of environmental peptide toxins using antibody-capture surfaces with subsequent mass spectrometry detection. Journal of Chromatography A 1123(2):233-238 (2006).

The development of a simplified assay for detection of congeners of the microcystin (MC) hepatotoxin is described that combines the extreme sensitivity of surface-enhanced laser desorption/ionization time-of-flight MS (SELDI TOF-MS) with the superior selectivity of immunoaffinity interactions. Using methods similar to those of conventional immunoassays, MC standards were captured and enriched on immunoreactive ProteinChips coated with an MC-antibody and analyzed by TOF-MS. Unlike with conventional immunoassays, individual congeners were resolved from mixed pools. Assay conditions were optimized for the quantification of MC from untreated raw pond water at concentrations as low as 0.025 µg L-1, well below the public health relevant guideline of 1 µg L-1.

HAWLEY, N., T. H. JOHENGEN, Y. R. Rao, S. A. RUBERG, D. BELETSKY, S. A. LUDSIN, B. J. EADIE, D. J. SCHWAB, T. E. CROLEY II, and S. B. BRANDT. Lake Erie hypoxia prompts Canada-U.S. study. EOS Transactions 86(32):313-319 (2006).

Because of its size and geometry, the central basin of Lake Erie, one of North America’s Great Lakes, is subject to periods in the late summer when dissolved oxygen concentrations are low (hypoxia). An apparent increase in the occurrence of these eutrophic conditions and ‘dead zones’ in recent years has led to increased public concern. The International Field Years for Lake Erie (IFYLE) project of the Great Lakes Environmental Research Laboratory (GLERL, a U.S. National Oceanic and Atmospheric Administration (NOAA) laboratory), was established in 2005 in response to this increase. This project is investigating the causes and consequences of hypoxia in the lake. As part of the effort, scientists from the United States and Canada conducted an extensive field study in 2005 to gather more information on the duration and extent of the hypoxic zone and its effects on the biota in the lake. This article gives a brief history and description of the problem and presents initial results from the field study. Preliminary results from 2005 indicate that, when compared with data collected in the past 25 years, the hypoxic region was one of the largest (approximately 10,000 square kilometers) ever documented in the lake. This is about half the maximum size of the hypoxic area in the Gulf of Mexico [Rabelais et al., 1999] and about five times larger than the maximum hypoxic area in the Chesapeake Bay [Hagy et al., 2004].

He, C., and T. E. CROLEY II. Spatially modeling nonpoint source pollution loadings in the Saginaw Bay watersheds with the DLBRM. Geographic Information Systems and Water Resources IV, AWRA Spring Specialty Conference, Houston, TX, May 8-10, 2006. American Water Resources Association, 8 pp. (2006).

Accurate nonpoint source (NPS) pollution accounting is essential to effective water quality and ecosystem management. The National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory and Western Michigan University are jointly developing a physically based, spatially-distributed hydrology model to simulate spatial and temporal NPS material distributions in the Saginaw Bay watersheds, draining into Georgian Bay in the Laurentian Great Lakes. 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 estimates by crop for the same periods. These estimates are used as the input to the distributed water quality model for simulating pollutant transport through surface and subsurface processes to Great Lakes waters. Visualization and GIS interfaces are developed to visualize the spatial and temporal distribution of the pollutant transport. 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 Environmental Protection Agency (EPA) mandated Total Maximum Daily Load programs to minimize the nonpoint source pollution in the watersheds

Hong, Y., A. Steinman, B. Biddanda, R. Rediske, and G. L. FAHNENSTIEL. Note. Occurrence of the toxin-producing Cyanobacterium Cylindrospermopsis raciborskii in Mona and Muskegon Lakes, Michigan. Journal of Great Lakes Research 32:645-652 (2006).

The bloom-forming and toxin-producing cyanobacterium Cylindrospermopsis raciborskii was observed in Muskegon and Mona lakes, drowned river-mouth tributaries of Lake Michigan. Morphological features of the taxon were similar to those described elsewhere. The species was observed only in late summer; elevated bottom water temperature, and perhaps phosphorus concentration, appears to be implicated in its appearance. Maximum abundances at any given site reached 393 and 0.9 trichomes/mL in Mona Lake and Muskegon Lake, respectively. Although these concentrations are low relative to other reports, the presence of this species in these two lakes from adjacent watersheds adds to a growing body of literature that suggests the distribution of C. raciborskii is on the increase in northern latitudes.

Hultquist, T. R., M. R. Dutter, and D. J. SCHWAB. Reexamination of the 9-10 November 1975 Edmund Fitzgerald storm using today's technology. Bulletin of the American Meteorological Society 87(5):607-622 (2006).

An intense autumn storm moved through the upper Great Lakes region on 10 November 1975, producing extremely hazardous wind and wave conditions on Lake Superior. The storm is particularly memorable because it is forever linked with the loss of the ship Edmund Fitzgerald (U.S. Coast Guard 1977), which occurred at approximately 0015 UTC (7:15 P.M. EST) 11 November 1975. There are numerous theories about the specific cause for the loss of the Edmund Fitzgerald, and this article makes no attempt to further investigate possible causes, but rather focuses on determining the most likely weather conditions throughout the storm. Meteorological observations from the storm were combined with modern numerical weather prediction models to provide detailed hindcasts of conditions throughout the storm. These hindcasts indicate that although severe wind and wave conditions did occur during the storm, the most extreme conditions were confined to a 6-h period in the late afternoon and early evening of 10 November 1975, during which time the Edmund Fitzgerald sank.

JAEGAR, A. L. Invasive species impacts on ecosystem structure and function. Master's Thesis. Michigan State University, Department of Fisheries and Wildlife, E. Lansing, MI, 210 pp. (2006).

Exotic species invasion is a worldwide threat to the integrity of aquatic ecosystems. To understand ecosystem level response to the introduction of exotic species, I compared food web characteristics of two eutrophic Great Lakes ecosystems - the Bay of Quinte, Lake Ontario, Canada, and Oneida Lake, New York, USA - before and after zebra mussel (Dreissena polymorpha) invasion using ecological network analysis (ENA) and a social network analysis method, cohesion analysis (CA). ENA quantifies ecosystem function through an analysis of food web transfers, while CA assesses ecosystem structure by organizing food web members into subgroups of strongly interacting predators and prey. In Oneida Lake and the Bay of Quinte, zebra mussel invasion increased food web organization and the potential for system development. Additionally, zebra mussel invasion stimulated benthic production in both systems. Effects on food web structure were strongest in the Bay of Quinte where zebra mussel invasion removed subgroup structure entirely. In Oneida Lake, over 33% of taxa changed subgroup association after invasion, with benthically associated subgroups gaining the most members. This analysis suggested that the effects of zebra mussel introduction are similar in ecosystems of comparable trophic status and that future invasions of eutrophic systems could have similar impacts on ecosystem structure and function.

JOSEPH, S. Beach closures and human health. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (2006).

During natural and human-made events, pollutants enter into the Great Lakes that pose a health risk to swimmers, boaters, and other recreationists. Microscopic pollutants, such as bacteria and viruses can be pathogenic (cause illness in humans). The symptoms and illnesses that these pathogens can cause vary based on multiple factors. Some people might get a sore throat or cold-like symptoms, others can get gastroenteritis (diarrhea). Usually the elderly, people with compromised immune systems, and young children are more at risk of illness from disease causing bacteria in the water. In order to protect people from getting sick your county, tribal, or state health department monitors the quality of Great Lakes beaches. There are two main bacteria, E.coli and Enterococci, that are monitored in recreational water. If the level of either bacteria is too high, they will close the beach until the bacteria level decreases

LEE, J. H., and P. F. LANDRUM. Development of a Multi-component Damage Assessment Model (MDAM) for time-dependent mixture toxicity with toxicokinetic interactions. Environmental Science and Technology 40(4):1341-1349 (2006).

A new mixture toxicity model was developed to predict the time-dependent toxicity of a mixture with toxicokinetic interactions directed specifically toward addressing biotransformation. The Damage Assessment Model (DAM), a toxicokinetic-toxicodynamic model that describes and predicts the time-dependent toxicity of a single compound, was extended to a multicomponent model for mixture toxicity. The model assumes that cumulative damage from the parent compound, metabolites, and/or a biotransformation inhibitor are additive, and the sum of the cumulative damage determines mixture toxicity. Since incorporation of the damage addition hypothesis into the DAM was equivalent to an independent action model for mixture toxicity, it was applied to describe the combined effect of mixture components with potentially dissimilar modes of action. From the multicomponent DAM, a time-dependent toxic unit model was derived and applied to determine the toxic units of mixture components. This model suggests a series of experimental designs required to assess the role of biotransformation in the toxicity of metabolized organic compounds and a data analysis method to separately estimate toxicodynamic parameters for the parent compound and metabolites.

LEE, J. H., and P. F. LANDRUM. Application of a Multi-component Damage Assessment Model (MDAM) for the toxicity of metabolized PAH in Hyalella azteca. Environmental Science and Technology 40(4):1350-1357 (2006).

Biotransformation and time-dependent toxicity of pyrene and fluorene, in the presence and absence of the biotransformation inhibitor 6-propylpiperonyl butyl diethylene glycol ether known as piperonyl butoxide (PBO), were investigated in Hyalella azteca. Toxicokinetics and biotransformation were determined in both short- and longterm experiments. For pyrene, the uptake rate coefficient (ku = 99 +- 9 L kg-1 h-1), elimination rate constant for parent compound (kep = 0.050 +- 0.008 h-1), biotransformation rate constant (km = 0.016 +- 0.003 h-1), and elimination rate constant for metabolites (kem = 0.021 +- 0.007 h-1) were determined from a short-term study. For fluorene, ku (130 +- 30 L kg-1 h-1) and kep (1.7 +- 0.2 h-1) were estimated based on km (0.015 +- 0.002 h-1) and kem (0.011 +- 0.002 h-1) determined from a long-term study. At steady state, the percent metabolites for pyrene and fluorene were 43% and 58%, respectively, determined from km/( km+ kem). Time dependent toxicity was determined as both lethal water concentration and lethal body residue in the presence and absence of PBO. Co-exposure to PBO decreased the median lethal residue (LBR50) for parent pyrene and shortened the median lethal time (LT50). Pyrene toxicity was explained by the body residues of parent pyrene and PBO, where the metabolites’ contribution was negligible. For fluorene, coexposure to PBO increased the LBR50 for parent fluorene and shortened the LT50. Thus, fluorene metabolites contributed significantly to the toxicity. Using a multicomponent damage assessment model, the toxicodynamic parameters, damage accrual rate coefficient, and damage recovery rate constant for parent pyrene and parent fluorene were very similar and estimated to be from 0.009 to 0.020 µmol-1 g h-1 and from 0.003 to 0.013 h-1, respectively, and the incipient LBR50 at the infinite time (LBR50(t = oo)) was from 0.24 to 0.46 µmol g-1, respectively. These values are similar to the reported (LBR50(t = oo)) for other nonpolar narcotics such as pentachlorobenzene (PCBz, 0.38 (0.13 µmol g-1) and dichlorophenylchloroethylene (DDE, 0.41 +- 0.19 µmol g-1). For fluorene metabolites, these values were 0.10 +- 0.03 µmol-1 g h-1, 0.034 +- 0.021 h-1, and 0.33 +- 0.23 µmol g-1, respectively. However, for pyrene metabolites, since toxicity of pyrene metabolites was negligible, the parameters could not be estimated.

LIEBIG, J. R., H. A. VANDERPLOEG, and S. A. RUBERG. Factors affecting the performance of the optical plankton counter in large lakes: insights from Lake Michigan and laboratory studies. Journal of Geophysical Research 111(C05S02):10 pp. (2006).

There has been a question as to whether the optical plankton counter (OPC) accurately measures zooplankton density and biomass in large lakes, oceans, and estuaries. Results from our Lake Michigan surveys in 1998–2000 often revealed poor agreement between the OPC-2T and 153-mm mesh plankton net samples. The most serious common problem was overestimation of zooplankton biomass by the OPC relative to net tows. Such overestimates have been attributed to the orientation of zooplankton assuming that their maximal silhouette area is detected by the OPC, coincidence, and the presence of nonzooplankton particles. Experiments using an OPC-1L with polymer microspheres, nylon rods, or live zooplankton confirmed that the OPC accurately counts and sizes zooplankton at low zooplankton concentrations typically found in Lake Michigan and that a shape factor correction often used need not be applied. Most overestimation of biomass was associated with the presence of nonzooplankton particles. Worst agreement was seen in shallow nearshore zones during periods of high total suspended matter (TSM), which consisted of fine sediments and large resuspended particles such as sediment phytoplankton aggregates, and benthic plant and animal debris. Best agreement was found under low TSM conditions associated with offshore waters during the stratified period.

Lindberg, W. J., T. K. Frazer, K. P. Portier, F. Vose, J. Loftin, D. J. Murie, D. M. MASON, B. Nagy, and M. K. Hart. Density-dependent habitat selection and performance by a large mobile reef fish. Ecological Applications 16(2):731-746 (2006).

Many exploited reef fish are vulnerable to overfishing because they concentrate over hard-bottom patchy habitats. How mobile reef fish use patchy habitat, and the potential consequences on demographic parameters, must be known for spatially explicit population dynamics modeling, for discriminating essential fish habitat (EFH), and for effectively planning conservation measures (e.g., marine protected areas, stock enhancement, and artificial reefs). Gag, Mycteroperca microlepis, is an ecologically and economically important warm-temperate grouper in the southeastern United States, with behavioral and life history traits conducive to large-scale field experiments. The Suwannee Regional Reef System (SRRS) was built of standard habitat units (SHUs) in 1991–1993 to manipulate and control habitat patchiness and intrinsic habitat quality, and thereby test predictions from habitat selection theory. Colonization of the SRRS by gag over the first six years showed significant interactions of SHU size, spacing, and reef age; with trajectories modeled using a quadratic function for closely spaced SHUs (25 m) and a linear model for widely spaced SHUs (225 m), with larger SHUs (16 standardized cubes) accumulating significantly more gag faster than smaller 4-cube SHUs (mean1/72.5 gag/16-cube SHU at 225-m spacing by year 6, compared to 24.2 gag/4-cube SHU for same spacing and reef age). Residency times (mean 1/4 9.8 mo), indicative of choice and measured by ultrasonic telemetry (1995–1998), showed significant interaction of SHU size and spacing consistent with colonization trajectories. Average relative weight (Wr) and incremental growth were greater on smaller than larger SHUs (mean Wr 1/4 104.2 vs. 97.7; incremental growth differed by 15%), contrary to patterns of abundance and residency. Experimental manipulation of shelter on a subset of SRRS sites (2000–2001) confirmed our hypothesis that shelter limits local densities of gag, which, in turn, regulates their growth and condition. Density-dependent habitat selection for shelter and individual growth dynamics were therefore interdependent ecological processes that help to explain how patchy reef habitat sustains gag production. Moreover, gag selected shelter at the expense of maximizing their growth. Thus, mobile reef fishes could experience density-dependent effects on growth, survival, and/or reproduction (i.e., demographic parameters) despite reduced stock sizes as a consequence of fishing.

Liu, L., M. S. Phanikumar, S. L. Molloy, R. L. Whitman, D. A. Shively, M. B. Nevers, D. J. SCHWAB, and J. B. Rose. Modeling the transport and inactivation of E. coli and Enterococci in the near-shore region of Lake Michigan. Environmental Science and Technology 40(16):5022-5028 (2006).

To investigate the transport and fate of fecal pollution at Great Lakes beaches and the health risks associated with swimming, the near-shore waters of Lake Michigan and two tributaries discharging into it were examined for bacterial indicators of human fecal pollution. The enterococcus human fecal pollution marker, which targets a putative virulence factors the enterococcal surface protein (esp) in Enterococcus faecium, was detected in 2/28 samples (7%) in the tributaries draining into Lake Michigan and in 6/30 samples (20%) in Lake Michigan beaches. This was indicative of human fecal pollution being transported in the tributaries and occurrence at Lake Michigan beaches. To understand the relative importance of different processes influencing pollution transport and inactivation, a finite-element model of surf-zone hydrodynamics (coupled with models for temperature, E. coli and enterococci) was used. Enterococci appear to survive longer than E. coli, which was described using an overall first-order inactivation coefficient in the range 0.5-2.0 per day. Our analysis suggests that the majority of fecal indicator bacteria variation can be explained based on loadings from the tributaries. Sunlight is a major contributor to inactivation in the surf-zone and the formulation based on sunlight, temperature and sedimentation is preferred over the first-order inactivation formulation.

LIU, P. C., K. R. MacHuchon, and C. H. Wu. Exploring rogue waves from observations in South Indian Ocean. In Rogue Waves 2004. M. Olagnon and M. Prevosto (Eds.). Ifremer, Brest, France, 1-10 (2004).

Amidst all the enticing advancements on rogue waves in recent years, the conspicuous scarcity of actual, in situ, rogue wave measurements still represents an inevitable hindrance shadowing over the horizon of rogue wave studies. In this paper we wish to present an exploratory observational study of rogue waves based on wave measurement made in South Indian Ocean. As there have been significant theoretical advancements in numerical simulation of rogue waves, the need for actual field observations of rogue waves should certainly be commensurably supplemented. We hope our efforts in this study can be ventured toward further understanding of rogue waves in reality.

LIU, P. C., and K. R. MacHutchon. Are there different kinds of rogue waves? Proceedings, 25th International Conference on Offshore Mechanics and Arctic Engineering, Hamburg, Germany, June 4-9, 2006. ASME, 6 pp. (2006).

Inasmuch as there is as yet still no universally accepted definition for rogue waves in the ocean, we think there might just be 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. 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 can not be readily answered by theoretical considerations alone and there is a crucial need for long-term wave time series measurements for studying rogue waves.

LUDSIN, S. A., B. J. Fryer, and J. E. Gagnon. Comparison of solution-based versus laser ablation inductively coupled plasma mass spectrometry for analysis of larval fish otolith microelemental composition. Transactions of the American Fisheries Society 135:218-231 (2006).

Otolith microchemistry has become a widely used tool for fisheries-based research in marine systems. However, its application to systems without well-defined juvenile nursery areas in which distinct otolith elemental signatures can develop (i.e., most freshwater systems) remains limited. In large part, this deficiency is due to unsuitable protocols for reliably processing and analyzing small otoliths of larvae. Herein, we evaluate the abilities of solution-based (SO) and laser ablation (LA) inductively coupled plasma mass spectrometry (ICPMS) to quantify the otolith elemental composition of larval yellow perch Perca flavescens captured in three distinct spawning locations in Lake Erie (USA–Canada). Analysis of otolith pairs by each technique demonstrated that both SO- and LA-ICPMS could be used to reliably quantify the more abundant elements, such as Sr and Ba. Magnesium and zinc, analyzed by use of both SO- and LA-ICPMS, also met the criteria for inclusion in our analyses (i.e., the coefficients of variation of standards were ,10.5%, and over 90% of samples were above detection limits at a single location). Upon closer inspection of the data, however, we found that estimates of Mg and Zn were only reliable for LA-ICPMS. Estimates of these two elements using SO-ICPMS were unrealistically high, probably owing to contamination during the otolith dissolution and handling phases. We also found that LA-ICPMS provided more precise estimates than did SO-ICPMS for nearly all elements explored, but LA-ICPMS was somewhat limited by high limits of detection for some elements. Despite these differences, both techniques could accurately discriminate among larvae produced in different Lake Erie spawning locations, primarily because of the significant variation in Sr among larval otoliths. Ultimately, although both methods are appropriate for analysis of otoliths from larvae, we recommend the use of LA-ICPMS in future otolith microchemical applications involving larvae.

Madenjian, C. P., D. V. O'Connor, S. A. POTHOVEN, P. J. Schneeberger, R. R. Rediske, J. P. O'Keefe, R. A. Bergstedt, R. L. Argyle, and S. B. BRANDT. Evaluation of a Lake Whitefish bioenergetics model. Transactions of the American Fisheries Society 135:61-75 (2006).

We evaluated the Wisconsin bioenergetics model for lake whitefish Coregonus clupeaformis in the laboratory and in the field. For the laboratory evaluation, lake whitefish were fed rainbow smelt Osmerus mordax in four laboratory tanks during a 133-d experiment. Based on a comparison of bioenergetics model predictions of lake whitefish food consumption and growth with observed consumption and growth, we concluded that the bioenergetics model furnished significantly biased estimates of both food consumption and growth. On average, the model overestimated consumption by 61% and underestimated growth by 16%. The source of the bias was probably an overestimation of the respiration rate. We therefore adjusted the respiration component of the bioenergetics model to obtain a good fit of the model to the observed consumption and growth in our laboratory tanks. Based on the adjusted model, predictions of food consumption over the 133-d period fell within 5% of observed consumption in three of the four tanks and within 9% of observed consumption in the remaining tank. We used polychlorinated biphenyls (PCBs) as a tracer to evaluate model performance in the field. Based on our laboratory experiment, the efficiency with which lake whitefish retained PCBs from their food (g) was estimated at 0.45. We applied the bioenergetics model to Lake Michigan lake whitefish and then used PCB determinations of both lake whitefish and their prey from Lake Michigan to estimate g in the field. Application of the original model to Lake Michigan lake whitefish yielded a field estimate of 0.28, implying that the original formulation of the model overestimated consumption in Lake Michigan by 61%. Application of the bioenergetics model with the adjusted respiration component resulted in a field g estimate of 0.56, implying that this revised model underestimated consumption by 20%.

Madenjian, C. P., S. A. POTHOVEN, J. M. Dettmers, and J. D. Holuszko. Changes in seasonal energy dynamics of alewife (Alosa pseudoharengus) in Lake Michigan after invasion of dreissenid mussels. Canadian Journal of Fisheries and Aquatic Sciences 63:891-902 (2006).

The dreissenid mussel invasion of Lake Michigan during the 1990s has been linked to a concomitant decrease in the abundance of the amphipod Diporeia. We tracked the seasonal energy dynamics of alewife (Alosa pseudoharengus) in Lake Michigan during 2002–2004 and compared our findings with previously published results for years 1979–1981. Adult alewife energy density exhibited a pronounced seasonal cycle during both the pre-invasion and post-invasion periods, with energy density in October or November nearly twice as high as that in early summer. However, on average, adult alewife energy density was 23% lower during the post-invasion period compared with the preinvasion period. This significant decline in energy density was attributable to decreased importance of Diporeia in adult alewife diet. In contrast, energy density of juvenile alewives did not significantly differ between the pre-invasion and post-invasion periods. To attain a weight of 8 kg by age 4, bioenergetics modeling indicated that a Chinook salmon (Oncorhynchus tshawytscha) in Lake Michigan would have to consume 22.1% more alewives during the post-invasion period compared with the pre-invasion period.

Mantha, P. S., J. B. Rose, and S. JOSEPH. Water pollution studies for the lower Grand River, MI. Michigan State University Dept. of Fisheries and Wildlife, E. Lansing, MI, 2 pp. (2006).

Researchers at Michigan State University and the NOAA Center for Excellence in Great Lakes and Human Health, in cooperation with Ottawa County, are conducting water quality investigations in the lower Grand River to better understand bacteria, parasite and virus pollution. In order to characterize and further our understanding of the sources of pollution and how the microorganisms are transported in the river, we are monitoring the beaches and locations within the river. The ultimate goals are to be able to predict impaired water quality events, to aid in decisions on pollution prevention and to further the protection of the public using the waterways and beaches

MASON, D. M., T. B. Johnson, C. J. Harvey, J. F. Kitchell, S. T. Schram, C. R. Bronte, M. H. Hoff, S. J. LOZANO, A. S. Trebitz, D. R. Schreiner, E. C. Lamon, and T. Hrabik. Hydroacoustic estimates of abundance and spatial distribution of pelagic prey fishes in western Lake Superior. Journal of Great Lakes Research 31:426-438 (2005).

Lake herring (Coregonus artedi) and rainbow smelt (Osmerus mordax) are a valuable prey resource for the recovering lake trout (Salvelinus namaycush) in Lake Superior. However, prey biomass may be insufficient to support the current predator demand. In August 1997, we assessed the abundance and spatial distribution of pelagic coregonines and rainbow smelt in western Lake Superior by combining a 120 kHz split beam acoustics system with midwater trawls. Coregonines comprised the majority of the midwater trawl catches and the length distributions for trawl caught fish coincided with estimated sizes of acoustic targets. Overall mean pelagic prey fish biomass was 15.56 kg ha–1 with the greatest fish biomass occurring in the Apostle Islands region (27.98 kg ha–1), followed by the Duluth Minnesota region (20.22 kg ha–1), and with the lowest biomass occurring in the open waters of western Lake Superior (9.46 kg ha–1). Biomass estimates from hydroacoustics were typically 2–134 times greater than estimates derived from spring bottom trawl surveys. Prey fish biomass for Lake Superior is about order of magnitude less than acoustic estimates for Lakes Michigan and Ontario. Discrepancies observed between bioenergetics-based estimates of predator consumption of coregonines and earlier coregonine biomass estimates may be accounted for by our hydroacoustic estimates.

McCORMICK, M. J., T. O. Manley, A. J. FOLEY III, J. C. Gascard, and G. L. FAHNENSTIEL. Lake Champlain Lagrangian experiment. Verh. Internat. Verein. Limnol. 29:1683-1687 (2006).

Lake Champlain is a mesotrophic lake bordering the states of New York and Vermont and the Canadian province Quebec. The lake lies between the Adirondack Mountains in the west and the Green Mountains of Vermont to the east. Its orientation is predominantly north and south spanning a length of 193 km, and it is relatively narrow with its widest part extending 19 km. The surface area of the lake is 1127 kin' and mean depth is 19.5m, with a maximum depth of 122m. Large amplitude internal seiches and bores have recently been observed (Hunkins et al. 1998), and an extensive field program is being conducted to study the lake's circulation and mixing. Part of the observation strategy involves Lagrangian experiments, which began in summer 2003. Both surface tracking buoys and subsurface buoyancy-controlled (RAFOS) buoys, were used to track the baroclinic circulation. This marks the first time that we are aware of that RAFOS technology has been used in a freshwater environment.

Millie, D. F., G. R. Weckman, H. W. Paerl, J. L. Pinckney, B. J. Bendis, R. J. Pigg, and G. L. FAHNENSTIEL. Neural net modeling of estuarine indicators: Hindcasting phytoplankton biomass and net ecosystem production in the Neuse (North Carolina) and Trout (Florida) rivers, USA. Ecological Indicators 6(3):589-608 (2006).

Phytoplankton biomass, as chlorophyll (Chl) a, and net ecosystem production (NEP), were modeled using artificial neural networks (ANNs). Chl a varied seasonally and along a saline gradient throughout the Neuse River (North Carolina). NEP was extremely dynamic in the Trout River (Florida), with phototrophic or heterotrophic conditions occurring over short-term intervals. Physical and chemical variables, arising from meteorological and hydrological conditions, created spatial and/or temporal gradients in both systems and served as interacting predictors for the trends/patterns of Chl a and NEP. ANNs outperformed comparable linear regression models and reliably modeled Chl a concentrations less than 20 µg L-1 and NEP values, denoting the apparent non-linear interactions among abiotic and indicator variables. ANNs underestimated Chl a concentrations greater than 20 µg L-1, likely due to the periodicity of data acquisition not being sufficient to generalize system variability, the designated ‘lag’ effect for variables not being adequate to portray estuarine flow dynamics, the exclusion of (one or more) variables that would have improved prediction, and/or an unrealistic expectation of network performance. Variables indicative of meteorological and hydrological forcing and/or proxy measurements of phytoplankton had the greatest relative impact on prediction of Chl a and NEP. Except for their predictive capability, ANNs might appear to be of limited value for ecological applications and problem solving; interpreting the absolute impact of and/or interacting relationships among network variables is intrinsically difficult. Statistical methods or ‘rule extraction’ algorithms that convey comprehensible network interpretation are needed prior to the routine use of ANNs in programs assessing and/or forecasting the response of biotic indicators to perturbation or for a means to discern estuarine function

Millie, D. F., G. R. Weckman, R. J. Pigg, P. A. Tester, J. DYBLE, R. W. Litaker, H. J. Carrick, and G. L. FAHNENSTIEL. Modeling phytoplankton abundance in Saginaw Bay, Lake Huron: Using artificial neural networks to discern functional influence of environmental variables and relevance to a Great Lakes observing system. Journal of Phycology 42:336-349 (2006).

Phytoplankton abundance, as chl a, in Saginaw Bay, Lake Huron was modeled using artificial neural networks. Suites of abiotic variables served as predictors for the trends/patterns in chl a concentrations. Spatial and temporal gradients of sampling stations throughout the bay were evident, with physical/chemical differences arising from hydrological/ meteorological forcing and zebra mussel recruitment. Chlorophyll a concentrations displayed corresponding disparities; concentrations differed between the inner and outer bays and varied intra- and inter-annually. Trained networks reproduced the intrinsic variance and magnitude of chl a dynamics. Modeled-measured concentrations best approximated a 1:1 relationship in a hybrid network incorporating both supervised and unsupervised training whereas concentrations greater than 15 lg/L were underestimated in networks utilizing only supervised training, likely because of inadequate training data. Variables indicative of phytoplankton nutrition, acting as proxy measurements of algal biomass, and/or corresponding to descriptors of hydrological and meteorological forcing had the greatest influence upon modeled concentrations. A conjunctive decision tree and a novel sensitivity analysis provided rule-based information and comprehensible interpretation of relationships among multiple predictor variables. From this, the ‘‘knowledge’’ embedded in trained networks proved extractable and usable for ecological theory generation and/or decision making within water-quality problem solving. Forecasting initiatives within the developing Great Lakes Observing System may be best served by embedding neural networks in mechanistic models to quantitatively initialize variables, qualitatively delineate conditions for projecting ecological structure, and/or estimate deviations from predictability within mechanistic simulations

NALEPA, T. F., D. L. FANSLOW, A. J. FOLEY III, G. A. LANG, B. J. EADIE, and M. A. QUIGLEY. Continued disappearance of the benthic amphipod Diporeia spp. in Lake Michigan: Is there evidence of food limitation? Canadian Journal of Fisheries and Aquatic Sciences 63:872-890 (2006).

Benthic surveys were conducted in the southern basin of Lake Michigan and throughout the lake to assess trends in benthic populations, emphasizing recent changes in densities of the benthic amphipod Diporeia spp. and dreissenid mussels. In the southern basin, Diporeia populations declined 89%, 91%, and 45% between 1993 and 2002 at sites <30, 31–50, and 51–90 m, respectively. Lakewide, the population declined 65% between 1994–1995 and 2000. Over the same time period, dreissenid densities, particularly Dreissena bugensis, increased. Intensive studies at 45 m sites in the southeastern region examined changes in lipid content, age structure, and benthic food inputs relative to the hypothesis that food limitation was a factor in Diporeia’s disappearance. As Diporeia densities declined to zero, length–weight remained unchanged, and lipid content generally increased. Recruitment still occurred, but the young did not survive to become adults. Based on organic carbon, biogenic silica, and chlorophyll collected in sediment traps and found in the upper sediments, pelagic inputs to the benthic region still occurred. Our field observations and laboratory experiments did not disprove the hypothesis that food limitation from dreissenid filtering activities was the cause of the decline, but direct relationships between the loss of Diporeia and indicators of food availability were difficult to establish

NALEPA, T. F., D. L. FANSLOW, A. J. FOLEY III, G. A. LANG, B. J. EADIE, and M. A. QUIGLEY. Continued disappearance of the benthic amphipod Diporeia spp. in Lake Michigan: Is there evidence for food limitation? Aquatic Invaders 17(3):1-12 (2006).

The increased spread of aquatic invasive species has led to the growing realization that these invaders, either individually or in concert, can change ecosystems at many levels of organization (Simon and Townsend 2003). A striking example is the Great Lakes ecosystem where, over the past 10-15 years, species invasions have led to the loss of native species, altered pathways of energy and nutrient flux through food webs, and redefined fundamental understanding of ecosystem function (Nalepa et al. 1996; Vanderploeg et al. 2002; Hecky et al. 2004). When considering imposed changes within the Great Lakes, perhaps the most large-scale, and certainly the most equivocal, has been the disappearance of the deepwater amphipod Diporeia spp. Declines in Diporeia populations have recently been documented in all the lakes except Lake Superior, and large areas in southeastern Lake Michigan (Nalepa et al. 1998), outer Saginaw Bay, Lake Huron (Nalepa et al. 2003), eastern Lake Erie (Dermott and Kerec 1997), and Lake Ontario (Dermott 2001; Lozano et al. 2001) are now mostly devoid of this organism

NALEPA, T. F., D. C. Rockwell, and D. W. Schloesser. Disappearance of the amphipod Diporeia spp. in the Great Lakes: Workshop summary, discussion, and recommendations. NOAA Technical Memorandum GLERL-136. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 20 pp. (2006).

A workshop was held in October, 2006 to discuss population status and causes of the disappearance of the benthic amphipod Diporeia spp. in the Great Lakes, and to provide recommendations for future research. Recent surveys indicate that Diporeia continues to decline in Lakes Michigan, Huron, and Ontario, but surveys in Lake Superior are conflicting. One data set shows that the population in Lake Superior is declining in offshore regions (> 90 m) but not in nearshore regions (< 90 m). Other data sets show that the population is stable throughout the lake. Reasons for this discrepancy were not resolved. In the other lakes, Diporeia are now rare or completely gone at depths < 90 m, and are declining at depths > 90 m. Latter declines are preceding the expansion of Dreissena bugensis (quagga mussel) from shallow to deeper regions. While there is a strong negative relationship between Diporeia and Dreissena in the Great Lakes, Diporeia remains abundant in the Finger Lakes, New York, despite the long-term presence of Dreissena. There are areas in the Great Lakes where Diporeia seemed to persist but are now declining, indicating that environmental conditions do play a mitigating role to some extent. While there was agreement that Dreissena was the cause of the disappearance of Diporeia in the Great Lakes, a survey of workshop participants indicated no clear consensus on potential mechanisms for the negative response. The most popular theories were food limitation directly or indirectly related to dreissenid filtering activities, a toxic by-product associated with dreissenid biodeposits, and an introduced pathogen/disease. Based on previous field surveys and laboratory experiments, there are inconsistencies in each of these theories, which may imply a multitude of causative factors whose relative importance may vary depending on specific environmental conditions. Given the potential for multi-stressors, techniques that provide genomic or protein profiles offer promise in defining a specific cause. Included among the recommendations for future research are continued monitoring of Diporeia in the Finger Lakes along with an assessment of conditions that allow it to persist, experiments to further define a dreissenid by-product that negatively impacts Diporeia, the development of genomic and protein expressions specific for Diporeia, a better definition of taxonomic status, and further efforts to characterize/resolve conflicting trends in offshore populations in Lake Superior.

Osgood, K., N. Cyr, O. C. T., J. Polovina, D. J. SCHWAB, and P. Stabeno. Ecosystem responses for climate variability. White Paper #1. In Ecosystem Science Capabilities Required to Support NOAA's Mission in the Year 2020. NOAA Technical Memorandum NMFS-F/SPO-74. S.A. Murawski and G.C. Matlock (Eds.). NOAA, National Marine Fisheries Service, Silver Spring, MD, 6-14 (2006).

Variations in the world’s climate have significant implications for the productivity and structure of marine and coastal (including Great Lakes) ecosystems ranging from the tropics to the poles. Climate-driven variability of environmental conditions is manifest on many time and space scales, including year-to-year variation, multi-year (e.g., El Niño-Southern Oscillation [ENSO]), and decadal scales (e.g., Pacific Decadal Oscillation, North Atlantic Oscillation, and Arctic Oscillation). In addition to this shorter-term variability, the Earth’s climate system has demonstrably warmed on both global and regional scales since the pre-industrial era impacting ice extent (IPCC, 2001). As a consequence of global warming and subsidence, sea levels continue to rise and the rate of rise is projected to accelerate. Precipitation and resulting rates of runoff are predicted to change significantly over the next century. These variations and changes in environmental conditions have profound implications for ecosystems and the human activities that are dependent on them by changing the distributions and productivity of living resources.

PANGLE, K. L., and S. D. PEACOR. Non-lethal effect of the invasive predator Bythotrephes longimanus on Daphnia mendotae. Freshwater Biology 51:1070-1078 (2006).

1. We evaluated the antipredator behaviour of Daphnia mendotae to the invasive invertebrate predator, Bythotrephes longimanus, and the consequent effect of the predator on prey growth rate (referred to as a non-lethal effect of the predator)

2. In a laboratory experiment, Daphnia in the absence of Bythotrephes kairomones remained in the top, warmer regions of experimental columns, whereas in the presence of Bythotrephes kairomones, Daphnia migrated vertically, occupying a middle region by night and a low, cold region during the day. Over a 4-day experiment, the vertical migration induced by Bythotrephes caused a 36% reduction in the somatic growth rate of Daphnia, a level that is sufficient to have an effect on prey population growth rate

3. A second laboratory experiment indicated that concentrations of Bythotrephes kairomones in water taken directly from the field (Lake Michigan) were high enough to induce behavioural shifts that led to these large reductions in somatic growth rate.

4. Our results identify a means by which Bythotrephes has substantial effects on native prey populations other than through direct consumption.

PEACOR, S. D., and C. A. Pfister. Experimental and model analyses of the effects of competition on individual size variation in wood frog (Rana sylvatica) tadpoles. Journal of Animal Ecology 75:990-999 (2006).

1. Size variation is a ubiquitous feature of animal populations and is predicted to strongly influence species abundance and dynamics; however, the factors that determine size variation are not well understood.

2. In a mesocosm experiment, we found that the relationship between mean and variation in wood frog (Rana sylvatica) tadpole size is qualitatively different at different levels of competition created by manipulating resource supply rates or tadpole density. At low competition, relative size variation (as measured by the coefficient of variation) decreased as a function of mean size, while at high competition, relative size variation increased. Therefore, increased competition magnified differences in individual performance as measured by growth rate.

3. model was developed to estimate the contribution of size-dependent factors (i.e. based on size alone) and size-independent factors (i.e. resulting from persistent inherent phenotypic differences other than size that affect growth) on the empirical patterns.

4. Model analysis of the low competition treatment indicated that size-dependent factors alone can describe the relationship between mean size and size variation. To fit the data, the size scaling exponent that describes the dependence of growth rate on size was determined. The estimated value, 0·83, is in the range of that derived from physiological studies.

5. At high competition, the model analysis indicated that individual differences in foraging ability, either size-based or due to inherent phenotypic differences (size-independent factors), were much more pronounced than at low competition. The model was used to quantify the changes in size-dependent or size-independent factors that underlie the effect of competition on size-variation. In contrast to results at low competition, parameters derived from physiological studies could not be used to describe the observed relationships.

6. Our experimental and model results elucidate the role of size-dependent and size independent factors in the development of size variation, and highlight and quantify the context dependence of individual (intrapopulation) differences in competitive abilities.

Plattner, S., D. M. MASON, G. A. LESHKEVICH, D. J. SCHWAB, and E. S. Rutherford. Classifying and forecasting coastal upwellings in Lake Michigan using satellite derived temperature images and buoy data. Journal of Great Lakes Research 32:63-76 (2006).

Coastal upwellings are common in the Great Lakes but have lacked enumeration and systematic classification of spatial extent, frequency, duration, and magnitude. Near real-time sea surface temperature (SST) images derived from the Advanced Very High Resolution Radiometer (AVHRR) provide indices of upwelling events, but visual inspection of daily images can be tedious. Moreover, the definition of what constitutes an upwelling from AVHRR data is subjective. We developed a semi-automated method to classify upwellings during the period of thermal stratification using daily, cloud-free surface temperature charts from AVHRR SST data. Then we statistically evaluated the location, frequency, magnitude, extent, and duration of upwelling events in Lake Michigan from 1992–2000. Further, we analyzed meteorological data from the National Data Buoy Center buoys in an attempt to improve the reliability of the classification and to provide a means for future forecast of coastal upwelling. Although variable, upwelling events along the western shoreline were preceded by 4 days of southerly and west-to-northwesterly winds, while upwelling events occurring along the eastern shore were preceded by 4 days of northerly winds. Probability of an upwelling event occurring was a function of the direction-weighted wind speed, reaching a 100% probability at direction weighted wind speeds of 11 m s–1 for the western shore. Probability of an upwelling occurrence along the east coast reached 73% at 11 m s–1 and 100% at 13 m s–1. Continuous measurements of wind data with a sufficient temporal resolution are required during the entire upwelling season to improve the predictability of upwellings

POTHOVEN, S. A., and T. F. NALEPA. Feeding ecology of lake whitefish in Lake Huron. Journal of Great Lakes Research 32:489-501 (2006).

We determined diet composition, feeding strategy, prey size, and effects of prey type on food weight and energy in stomachs for lake whitefish Coregonus clupeaformis in Lake Huron during 2002–04. Age-0 lake whitefish (73–149 mm TL) ate mainly large-bodied cladoceran zooplankton in the summer (July–mid September). Medium lake whitefish (≤ 350 mm TL excluding age-0) generally ate softbodied macroinvertebrates, especially Chironomidae larvae and pupae, in the spring (mid May-June). Zooplankton, if eaten, were generally most important in the summer. Molluscs were generally a minor part of medium lake whitefish diets. Large lake whitefish (> 350 mm) mainly ate molluscs, particularly quagga mussels (Dreissena bugensis), despite geographic differences in mussel abundance. Large-bodied crustaceans (Diporeia spp., Mysis relicta, Isopoda) were a minor part of large lake whitefish diets. Lake whitefish demonstrated a flexible feeding strategy, with individual specialization on some prey and generalized feeding on others. The size of benthic prey (Diporeia spp., Chironomidae, and Dreissena spp.) eaten increased with fish size and influenced the energetic value of prey for medium and large lake whitefish. The type of prey eaten affected the food and energy intake differently for each size class of lake whitefish. Age-0 lake whitefish that ate mainly zooplankton had more food and energy in stomachs than fish eating shelled prey or other macroinvertebrates. On the other hand, food weight in stomachs did not differ across prey groups for medium fish, but energy in stomachs was lowest for fish that ate shelled prey. For large lake whitefish, there was no difference in food weight or energy in stomachs for different prey groups

POTHOVEN, S. A., T. F. NALEPA, C. P. Madenjian, R. R. Rediske, P. J. Schneeberger, and J. X. He. Energy density of lake whitefish Coregonus clupeaformis in Lakes Huron and Michigan. Environmental Biology of Fishes 76:151-158 (2006).

We collected lake whitefish Coregonus clupeaformis off Alpena and Tawas City, Michigan, USA in Lake Huron and off Muskegon, Michigan USA in Lake Michigan during 2002–2004. We determined energy density and percent dry weight for lake whitefish from both lakes and lipid content for Lake Michigan fish. Energy density increased with increasing fish weight up to 800 g, and then remained relatively constant with further increases in fish weight. Energy density, adjusted for weight, was lower in Lake Huron than in Lake Michigan for both small (≤800 g) and large fish (>800 g). Energy density did not differ seasonally for small or large lake whitefish or between adult male and female fish. Energy density was strongly correlated with percent dry weight and percent lipid content. Based on data from commercially caught lake whitefish, body condition was lower in Lake Huron than Lake Michigan during 1981–2003, indicating that the dissimilarity in body condition between the lakes could be long standing. Energy density and lipid content in 2002–2004 in Lake Michigan were lower than data for comparable sized fish collected in 1969–1971. Differences in energy density between lakes were attributed to variation in diet and prey energy content as well as factors that affect feeding rates such as lake whitefish density and prey abundance.

QUINN, F. H., and C. E. SELLINGER. A reconstruction of Lake Michigan-Huron water levels derived from tree ring chronologies for the period 1600-1961. Journal of Great Lakes Research 32:29-39 (2006).

A dendrochronolgy of annual precipitation and air temperatures from six Great Lakes locations was used to reconstruct Lake Michigan-Huron water levels from 1600–1961 representing the present St. Clair River channel conditions and basin land cover. The reconstructions are based upon a multi-linear regression model relating multi-year annual precipitation and air temperature to annual water levels. An increased frequency of low lake levels was found to occur prior to the twentieth century, accompanied by a major extreme in water levels, greater than that experienced in the historical record, in the early 1600s. The comparison of simulated and measured water levels also indicates that the impact of some of the channel changes in the St. Clair River may be underestimated and that the major drop in lake level in the 1880s may be due to erosion as well as to decreased precipitation. The occurrence of extreme levels around 1640, in 1838, and in 1986 suggests a return interval of 150–190 years for extreme lake levels. The analysis also suggests that the variability of lake levels has greatly decreased over the last century when comparing tree-ring-derived level variability. Thus climatic periods used for the development of the current regulation plans may not be representative of the longer-term climate and lake levels.

RAIKOW, D. F., D. F. REID, E. E. MAYNARD, and P. F. LANDRUM. Sensitivity of aquatic invertebrate resting eggs to SeaKleen (Menadione): A test of potential ballast tank treatment options. Environmental Toxicology and Chemistry 25(2):552-559 (2006).

The introduction of aquatic species in resting life stages by the release of ballast water is a less well-known but potentially important invasive species vector. Best-management practices designed to minimize transport of ballast water cannot eliminate this threat, because residual water and sediment are retained in ballast tanks after draining. To evaluate the potential efficacy of chemical treatment of residual material in ship ballast tanks, the present study examined the acute toxicity of the proposed biocide SeaKleen® (menadione; Garnett, Watkinsville, GA. USA) on resting eggs of Brachionus plicatilis (a marine rotifer), a freshwater copepod, Daphnia mendotae (a freshwater cladoceran), and Artemia sp. (a marine brine shrimp). SeaKleen was toxic to resting eggs of all taxa. Daphnia mendotae resting eggs encased in protective ephippia were the least sensitive, as indicated by a 24-h lethal concentration of toxicant to 90% of organisms of 8.7 mg/L (95% confidence interval, ± 0.1 mg/L). SeaKleen induced teratogenic effects in D. mendotae and Artemia sp. Exposure to sunlight quickly degraded SeaKleen, which lost all toxicity after 72 h outdoors. SeaKleen increased in toxicity slightly after 72 h in darkness. Burial of D. mendotae ephippia in natural lake sediment reduced SeaKleen toxicity by a factor of 20. Reduced toxicity in the presence of sediment raises serious doubts as to the potential for this, or any, chemical biocide to kill aquatic invertebrate resting stages buried in sediment retained in ship ballast tanks.

Reavie, E. D., J. A. ROBBINS, E. F. Stoermer, M. S. V. Douglas, G. E. Emmert, N. R. MOREHEAD, and A. Mudroch. Paleolimnology of a fluvial lake downstream of Lake Superior and the industrialized region of Sault Saint Marie. Canadian Journal of Fisheries and Aquatic Sciences 62:2586-2608 (2005).

A paleolimnological study was undertaken to describe the past environment of the St. Mary’s River downstream of Lake Superior. Two sediment cores were obtained from the deepest part of Lake George, a fluvial lake in the river system. Rigorous analyses of radionuclides (210Pb, 226Ra, and 137Cs) and chemical properties provided an accurate sediment chronology. More than 450 diatom species from 47 genera were identified. Diatom and geochemical data indicated gradual environmental change in response to anthropogenic activities, including logging, hydrologic manipulation, and steel, leather, and paper industries. A decline in water quality occurred gradually from the late 1800s through the 20th century in response to human activities, as was apparent from an increase in eutrophic–planktonic diatom taxa. A decline in benthic taxa and an increase in contaminant metals were also contemporaneous with impacts during the 20th century. Subfossil diatoms were similar to those recorded in paleolimnological investigations from the Great Lakes. However, diatom profiles indicate that the algal supply from upstream Lake Superior has been minimal and that the cores mainly reflect environmental characteristics of the near-upstream environment. Despite stochastic sedimentary regimes and complex habitats in the lotic system, this study reinforces the value of river paleolimnology at carefully selected sites.

SANO, L. L., S. M. Bartell, and P. F. LANDRUM. Decay model for biocide treatment of unballasted vessels: Application for the Laurentian Great Lakes. Marine Pollution Bulletin 20:1050-1060 (2005).

A biocide decay model was developed to assess the potential efficacy and environmental impacts associated with using glutaraldehyde to treat unballasted overseas vessels trading on the Laurentian Great Lakes. The results of Monte Carlo simulations indicate that effective glutaraldehyde concentrations can be maintained for the duration of a vessel s oceanic transit (approximately 9–12 days): During this transit, glutaraldehyde concentrations were predicted to decrease by approximately 10% from initial treatment levels (e.g., 500 mg L 1). In terms of environmental impacts, mean glutaraldehyde concentrations released at Duluth-Superior Harbor, MN were predicted to be 100-fold lower than initial treatment concentrations, and ranged from 3.2 mg L 1 (2 SD: 2.74) in April to 0.7 mg L 1 (2 SD: 1.28) in August. Sensitivity analyses indicated that the reballasting dilution factor was the major variable governing final glutaraldehyde concentrations; however, lake surface temperatures became increasingly important during the warmer summer months.

Schiesari, L., S. D. PEACOR, and E. E. Werner. The growth-mortality tradeoff: Evidence from Anuran larvae and consequences for species distribution. Oecologia 149:194-202 (2006).

A tradeoff affecting the ability to grow under high versus low resource levels has been commonly hypothesized to influence species distributions across resource gradients in a wide variety of taxa. This influence is dependent on individual growth being proportional to traits that affect demographic processes such as mortality. However, data on how individual growth scales with demographic performance are rare. We conducted a mesocosm experiment, and reanalyzed data from a similarly designed Weld experiment, to examine the relationship between growth and mortality in two tadpole species that segregate across a resource gradient. Overall, environmental conditions leading to faster growth also lead to lower mortality rates. However, species differed in this relationship. Leopard frogs achieved faster growth than wood frogs, but their absolute mortality was greater and increased steeply as growth decreased. Conversely, absolute mortality of wood frogs was lower and less strongly dependent on growth. These interspecies differences suggest a second tradeoff, that between maximizing growth rates or minimizing mortality, with potentially important demographic consequences. Leopard frogs grow faster than wood frogs in productive ponds, but are excluded from unproductive ponds dominated by wood frogs due to accelerating mortality rates with declining realized growth. A review of the literature suggests that in diverse taxa, including plants, microcrustaceans and drosophilids, patterns in mortality are consistent with this tradeoff indicating that the mechanism we demonstrate could be a link between individual performance and demographic rates influencing species distributions in other systems.

Schuler, L. J., P. F. LANDRUM, and M. J. Lydy. Comparative toxicity of fluoranthene and pentachlorobenzene to three freshwater invertebrates. Environmental Toxicology and Chemistry 25(4):985-994 (2006).

This study examined the temporal component of pentachlorobenzene lethal body residues among three freshwater invertebrates. Also, using previous fluoranthene data allowed a more detailed examination of the role of biotransformation in lethal body residues and comparisons of lethal residues across chemical classes. Time-dependent toxicity of fluoranthene and pentachlorobenzene were compared among Hyalella azteca, Chironomus tentans, and Diporeia spp. Lethal body residues required for 50% mortality (LR50) were not constant and decreased with exposure time for all species. Fluoranthene was most toxic to C. tentans with LR5O values of 0.38 mmol.g-1 at 2 d to 0.15 mmol.g-1 at 10 d and least toxic to Diporeia spp. with values of 9.97 mmol.g-1 at 10 d to 3.67 mmol.g-1 at 28 d. The LR5O values for H. azteca were intermediate and ranged from 2.25 mmol.g-1 at 5 d to 0.56 mmol.g-1 at 28 d. Pentachlorobenzene LR5O values were less variable among species and ranged from 1.20 mmol.g-1 at 4 d to 0.81 mmol.g-1 at 10 d for C. tentans, 5.0 mmol.g-1 at 20 d and 2.75 mmol.g-1 at 28 d for Diporeia spp., and 1.51 mmol.g-1 at 4 d and 0.71 mmol.g-1 at 28 d for H. azteca. When LR50 values for fluoranthene and pentachlorobenzene were compared at steady state, the lethal residues for the amphipod species were within the range expected for nonpolar narcotic chemicals (anesthetics); however, C. tentans was more sensitive to fluoranthene than pentachlorobenzene, confirming our previous hypothesis that biotransformation of fluoranthene likely produces a metabolite(s) acting by some specific mechanism of action. The information collected from this study allows a greater understanding of residue-response relationships, specifically relative species sensitivities.

SCHWAB, D. J., B. J. EADIE, R. A. ASSEL, and P. J. Roebber. Climatology of large sediment resuspension events in southern Lake Michigan. Journal of Great Lakes Research 32:50-62 (2006).

Lake Michigan, particularly the southern basin, is subject to recurrent episodes of massive sediment resuspension by storm-induced waves and currents. The purpose of this paper is to investigate the climatology of these events for Lake Michigan, including an analysis of associated meteorological conditions. This paper begins by examining turbidity records from two water treatment plants (Chicago, IL and St. Joseph, MI) for which long-term records are available. The turbidity records from the two plants show significant differences indicating that turbidity measurements from a single location would probably not be representative of a basin-wide climatology. A one-dimensional sediment resuspension and deposition model for fine-grained sediments is then developed and calibrated with data from the water treatment plants. The one-dimensional model is applied at 15 points around the southern basin for a 45-year period for which Lake Michigan wave climatology is available and the results are averaged to obtain a basin-wide turbidity index (Southern Lake Michigan Turbidity Index, SLMTI). A frequency distribution of the turbidity index is presented and meteorological conditions associated with the largest events are examined. Our analysis indicates that significant resuspension events in southern Lake Michigan are usually caused by a strong cyclone passing to the east of the lake. The most likely time of the year for this to occur is October to April. There is an average of 1 event per year with SLMTI above 25 mg/L and each event typically lasts about 3 days. Our analysis indicates that events have occurred more frequently since the late 1980s as the number of winter storms has increased and ice cover has decreased.

Stroud, J., B. M. Lesht, D. J. SCHWAB, D. BELETSKY, and M. L. Stein. Tracking suspended sediment motion in Lake Michigan by combining satellite images with a numerical model. Technical Report No. 38. The University of Chicago, Center for Integrating Statistical and Environmental Science, Chicago, IL, 36 pp. (2006).

Because satellite observations are synoptic, collected frequently, and highly resolved on geophysical scales, they can be a valuable source of information for development and application of numerical models. Data derived from satellite sensors may be used in model evaluation studies, as well as for operational and prognostic updating of both model state and forcing variables. Although satellite data are used routinely with many types of operational atmospheric models, little work has been done to integrate satellite data with models of aquatic systems. In this paper, we develop and examine schemes for combining daily images obtained by the Sea-viewing Wide Field Spectrometer (SeaWiFS) with a two-dimensional sediment transport model representing southern Lake Michigan. We perform a forecasting study focused on two-month period in spring 1998 when a large storm caused substantial amounts of sediment resuspension and horizontal sediment transport in the lake. We find that data assimilation schemes improve forecast root-mean-square-error (RMSE) by 40% over purely model-based approaches and by 20% over purely data-based approaches.

Tirelli, V., D. Borme, F. Tulli, M. Cigar, S. Fonda Umani, and S. B. BRANDT. Energy density of anchovy, Engraulis encrasicolus L. in the Adriatic Sea. Journal of Fish Biology 68:982-989 (2006).

European anchovy Engraulis encrasicolus, with total lengths ranging from 40 -0 to 132-5 mm, were sampled during October 2002 and May 2003 in the northern Adriatic Sea in order to estimate their energy densities (ED). A highly significant (P < 0-001) relationship between ED (y) (J g-1wet mass) and per cent dry mass (x) was found: y =321x - 3316-9 (n = 161, r2 = 0 - 82).

VANDERPLOEG, H. A., and M. R. Roman. Introduction to special section on analysis of zooplankton distributions using the optical plankton counter. Journal of Geophysical Research 111(C05S01):doi:10.1029/2006JC003598 (2006).

We briefly introduce the optical plankton counters (OPCs) currently in use and summarize major themes and conclusions of papers from this special section. These collected papers demonstrate that the OPC and the new laser OPC (LOPC) are useful tools for mapping fine-scale distributions of zooplankton over broad expanses of space and for examining patterns in the size structure of zooplankton communities, which give insights into the top-down and bottom-up forces affecting them. The LOPC or OPC are particularly valuable sensors when used in conjunction with an array of other sensors on a tow body so that investigators can synoptically measure physical and biotic variables. Caution must be exercised in using the OPC or LOPC because there are times when nonzooplankton particles comprise a significant portion of the particles counted. The contribution of nonzooplankton particles to the total seston varies with system and conditions

Werner, E. E., and S. D. PEACOR. Lethal and non-lethal predator effects on an herbivore guild mediated by system productivity. Ecology 87(2):347-361 (2006).

Indirect effects propagated through intervening species in a food web have important effects on community properties. Traditionally, these indirect effects have been conceptualized as mediated through density changes of the intervening species, but it is becoming increasingly apparent that those mediated through trait (phenotypic) responses also can be very important. Because density- and trait-mediated indirect effects have different properties, it is critical that we understand the mechanisms of transmission in order to predict how they will interact, and when or where they will be important. In this study, we examined the mechanisms and consequences of the lethal (density mediated) and nonlethal (trait-mediated) effects of a larval odonate predator on a guild of four herbivore species (a larval anuran and three species of snails) and their resources. We also manipulated system productivity in order to explore the effects of environmental context on the transmission of these two types of indirect effects. We show that trait mediated effects arising from the predator can be very strong relative to density-mediated effects on both the competing herbivores and the species composition and production of their resources. A number of these indirect effects are shown to be contingent on productivity of the system. We further present evidence that trait- and density-mediated indirect effects originating from a predator may be transmitted independently through different routes in a food web, particularly when spatial responses of the transmitting prey are involved. Finally, effects on prey growth due to trait responses to the predator varied from negative to positive in predictable ways as a function of time and indirect effects on the larger food web. These results indicate the important role that trait-mediated indirect effects can play in trophic cascades and keystone predator interactions, and we discuss how the mechanisms involved can be incorporated in theory.

Zhulidov, A. V., T. F. NALEPA, A. V. Kozhara, D. A. Zhulidov, and T. Y. Gurtovaya. Recent trends in relative abundance of two dreissenid species, Dreissena polymorpha and Dreissena bugensis in the lower Don River System, Russia. Archives fur Hydrobiologie 165(2):209-220 (2006).

We sampled sites in the lower Don River system, Russia between 1977 and 2004 (5 sites) or between 1999 and 2004 (10 sites) to determine relative trends in two dreissenid species, Dreissena bugensis and Dreissena polymorpha. The sites were located in the main river, in connecting reservoirs, and in a major tributary, the Manych River. For sites sampled beginning in 1977, D. bugensis was first found in the lower river in 1980 and then more upstream in 1991. The relative proportion of D. bugensis increased to reach a maximum of 30–50% of the dreissenid population by 1999. After 1999, this species decreased at 14 of the 15 sites. At sites in the Don River, the proportion that D. bugensis comprised of the total dreissenid population after 1999 declined from 25–50% to 10–18%, whereas at sites in the Manych River the proportion declined from 65–75% to 33–43%. The decline of D. bugensis relative to D. polymorpha is unique; in most other water bodies D. bugensis displaces D. polymorpha over time because of its superior physiological attributes. Reasons for the relative decline of D. bugensis are unclear, but we speculate that selective predation by fish may be a potential factor.



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