GLERL Publications with Abstracts

January 2009 - December 2009

Basu, N., J.A.HEAD, A.M. Scheuhammer, S.J. Bursian, K. Rouvinen-Watt, and H.M. Chan. The mink is still a reliable sentinel species in environmental health. Environmental Research 109:940-941 (2009).

We thank Bowman andSchulte-Hostedd e(2009) for their useful commentary.As outlined in our paper, mink have several characteristics that support their value as a sentinel species (Basu et al. ,2007). Key characteristics of a sentinel species in the field of environmental health are provided in Table 1 of our paper and these were adapted from extensive reviews conducted by academic scientists and government panels (Beeby, 2001; Fox, 2001; LeBlanc and Bain,1997; National Research Council,1991; Van derSchalie et al., 1999). As there are few mammalian species that can effectively meet such criteria (Golden and Rattner, 2003), it is no surprise that mink have been recognized as an excellent sentinel by many agencies worldwide. The main assertion by Bowman and Schulte-Hostedde (2009) is that because of the high frequency of ranch escapees, mink are not‘‘ a continuous resident of the environment under evaluation’’ (criteria adapted from a ‘‘critique’’  paper written by Landres et al.,1988), and that this precludes their value as sentinel species. While we agree that the presence of ranched mink in the wild population is a confounding factor for some ecotoxicological studies and should be taken into account when designing environmental research or monitoring studies using mink, we disagree with the conclusion that ‘‘the mink is not a  reliable sentinel species’’.

Biddanda, B.A., S.C. Nold, S.A. RUBERG, S.T. Kendall, T.G. Sanders, and J.J. Gray. Great Lakes sinkholes: A microbiogeochemical frontier. EOS Transactions 90(8):61-62 (2009).

Recent underwater explorations have revealed unique hot spots of biogeochemical activity at several submerged groundwater vents in Lake Huron, the third largest of the Laurentian Great Lakes. Fueled by venting groundwater containing high sulfate and low dissolved oxygen, these underwater ecosystems are characterized by sharp physical and chemical gradients and spectacularly colorful benthic mats that overlie carbon-rich sediments. Here, typical lake inhabitants such as fish and phytoplankton are replaced by communities dominated by microorganisms: bacteria and archaea that perform unique ecosystem functions. Shallow, sunlit sinkholes are dominated by photosynthetic microorganisms and processes, while food webs in deep aphotic sinkholes are supported primarily by chemosynthesis.

Boss, E., L. Taylor, S. Gilbert, K. Gundersen, N. HAWLEY, C. Janzen, T.H. JOHENGEN, H. Percell, C. Robertson, D. Schar, G.J. Smith, and M.N. Tamburri. Comparison of inherent optical properties as a surrogate for particulate matter concentration in coastal waters. Limnology and Oceanography: Methods 7:803-811 (2009).

Particulate matter concentration (PM, often referred to as total suspended solids [TSS]) is an important parameter in the evaluation of water quality. Several optical measurements used to provide an estimate of water turbidity have also been used to estimate PM, among them light transmission, backscattering, and side-scattering. Here we analyze such measurements performed by the Alliance for Coastal Technologies (ACT) at various coastal locations to establish whether a given optical method performs better than others for the estimation of PM. All the technologies were found to perform well, predicting PM within less than 55% relative difference for 95% of samples (n = 85, four locations). Backscattering performed best as a predictor of PM, predicting PM with less than 37% relative difference for 95% of samples. The correlation coefficient (R) was between 0.96 and 0.98 for all methods with PM data ranging between 1.2 to 82.4 g m�3. In addition, co-located measurements of backscattering and attenuation improves PM prediction and provides compositional information about the suspended particles; when their ratio is high, the bulk particulate matter is dominated by inorganic material while when low, dominated by organic material.

Chang, P.A., W. Wilson, J. Carneal, P. Atsavapranee, S. Verosto, D.F. REID, and P.T. Jenkins. Final Report: Computational modeling of ballast water tanks to improve understanding and maximize effectiveness of management practices and treatment mechanisms. Phase II: Extension of Laboratory Study. NOAA Technical Memorandum GLERL-148. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 78 pp. (2009).

Mid-ocean ballast water exchange (BWE) is presently the primary management practice with widespread acceptance for reducing or preventing the spread of nonindigenous aquatic species via ballast water. Attempts to determine the efficiency of BWE via on-board experiments have generally produced inconsistent and unreliable results. Such experiments are labor intensive and difficult to run, so reproducibility is difficult to demonstrate for the same ship and tank structure. In addition, on-board experiments involving flow-through exchange generally relied on measurements taken at the overflow outlet of the tank, which may not represent the actual volume mixture that remains in the ballast tank. Given the complex structural nature of ballast tanks and the difficulty of obtaining direct experimental verification from inside ballast tanks, development of a computer-based model of the flow and mixing dynamics in ballast tanks during flow-through exchange can provide several advantages over on-board experimental approaches, and can also help interpret such experimental results. The NOAA Ballast Water Technology Demonstration Program provided funding for GLERL and NSWCCD to design and build a 1/3-scale model BWE facility and to develop a computational model for predicting BWE efficacy. In Phase I of this effort, documented in Wilson et al. a 1/3-scale physical model facility was built at NSWCCD. In this report the (physical) scale-model experimental setup and measurement techniques used in Phases I and II of this project are described. Then, the results and the two-fluid physics that were observed during the entire 3-TVE are shown. In the CFD section the methodology is described followed by comparisons of the CFD predictions with the measured quantities from the physical scale-model experiments. Additionally, full-scale simulations are documented and an Appendix shows the uncertainty analysis.

Chatterjee, A., C. DeMARCHI, and A.M. Michalak. Estimating over-lake precipitation in the Great Lakes by combining radar and rain gages. Seventh International Symposium on Ecohydraulics and Eighth International Conference on Hydroinformatics, Concepcion, Chile, January 12-16, 2009. 10 pp. (2009).

Over-lake precipitation is a key component of the Great Lakes’ water balance. Its estimation is, therefore, vital for planning and operational purposes. Yet, reliable over-lake precipitation estimates are difficult to obtain because the lack of gages on the lakes themselves and the scarcity of gages in parts of the draining basins. Traditionally, over-lake precipitation is estimated by distance-weighted interpolation methods. In spite of their wide acceptance, these methods suffer from intrinsic limitations as they fail to take into account the spatial variability of rainfall. Recently, multisensor products combining radar-based precipitation estimates and rain gage data (MPE) have provided a suitable alternative to estimates based on the sparse gage data. However, biases in the MPE data have raised serious concerns about their accuracy. A promising approach for overcoming the limitations of either of these methodologies for estimating monthly-averaged over-lake precipitation is to spatially integrate the MPE data with the gage observations in a geostatistical framework based on universal kriging. In this work, the estimates from these techniques are compared to (i) more traditional methods based on the weighted interpolation gage data only, and (ii) the available MPE data. Results for Lake Erie reveal that the universal kriging setup outperforms the estimation methods based only on one of the two data types, by providing estimates with significantly lower root mean square error and lower overall bias. Overall, the results demonstrate the robustness of the proposed approach in assimilating two different information sources for providing more accurate and reliable estimates of over-lake precipitation.

DeMARCHI, C., T.E. CROLEY II, T.S. HUNTER, and C. He. Application of a distributed watershed hydrology and water quality model in the Great Lakes basin. Seventh International Symposium on Ecohydraulics and Eighth International Conference on Hydroinformatics, Concepcion, Chile, January 12-16, 2009. 10 pp. (2009).

The NOAA Great Lakes Environmental Research Laboratory, Western Michigan University, and the University of Michigan are jointly developing a Distributed Large Basin Runoff Model (DLBRM), a physically based, spatially-distributed hydrology and water quality model, to simulate spatial and temporal point and nonpoint source material distributions in Great Lakes watersheds. We automatically calibrated the DLBRM hydrology to reproduce the 1950-1964 and the 1999-2006 watershed outflows in 18 watersheds throughout the Great Lakes region with excellent results; we are extending it to an additional 16 watersheds. In this paper, we analyze the performance of the DLBRM hydrology components in space and time and its further development.

FAHNENSTIEL, G.L., Y. Hong, D.F. Millie, M. Doblin, T.F. JOHENGEN, and D.F. REID. Marine dinoflagellate cysts in the ballast tank sediments of ships entering the Laurentian Great Lakes. Verh. Internat. Verein. Limnol. 30(7):1035-1038 (2009).

One of the greatest threats to the ecological health of the Laurentian Great Lakes is the introduction of non-indigenous species (Mills et al. 1993). The Laurentian Great Lakes have a long history of non-indigenous introductions with significant ecological and economic consequences. Since the opening of the St. Lawrence Seaway in 1959, approximately 65% of all non-indigenous species introductions into the Great Lakes have been attributed to ballast water release (Ricciardi 2006). Because of the concern of ballast water and its potential for introduction of non-indigenous species, the U.S. Coast Guard promulgated regulations in 1993, requiring ships with ballast water inbound to the Great Lakes to exchange ballast water with open ocean water. Despite these new regulations, the discovery rate of non-indigenous species increased after mandatory controls were implemented (Holek et al. 2004). Unfortunately, most of the ships entering the Great Lakes are exempt from the 1993 regulations. The majority of ships entering the Great Lakes since 1993 are loaded with cargo and are declared as ‘no ballast water on board’ (NOBOB) ships. These NOBOB ships carry residual water and sediments in their ballast tanks. Once in the Great Lakes these NOBOB ships discharge their residual water and sediment into the Great Lakes during the off-loading of inbound cargo and the loading of outbound cargo. These NOBOB ships represent a greater risk for introductions into the Great Lakes than ballasted ships (Duggan et al. 2005).

FAHNENSTIEL, G.L., M.J. McCORMICK, and R. Artz. Proceedings of NOAA Lake Champlain Program Review - October 29-30, 2008. NOAA Technical Memorandum GLERL-146. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 50 pp. (2009).

On October 29-30 2008, a formal review of NOAA’s Lake Champlain Research Program was held in Burlington, Vermont. Despite being in existence for 18 years, this was the first external review of the program. The first day of the review consisted of project presentations and open discussions of existing research and future directions (see Appendix 1). Principal investigators from all four funded projects were asked to make formal presentations as well as provide a summary (1-2 pages with supplementary materials as needed). The summaries and supplementary materials were made available to the public (see Appendix 2). Five external experts (two in hydrodynamics research, two in atmospheric/mercury research, and one oceanographer/ecologist) were invited to review the research activities with special attention to the quality and quantity of existing research and future direction. The first day of the review was open to the public, approximately 35 people attended. On the second day, NOAA program managers met with the review panel to discuss the program in a closed session. This technical report summarizes the review meeting.

Fishman, D.B., S.A. Alderstein, H.A. VANDERPLOEG, G.L. FAHNENSTIEL, and D. Scavia. Causes of phytoplankton changes in Saginaw Bay, Lake Huron during the zebra mussel invasion. Journal of Great Lakes Research 35:482-495 (2009).

Colonization of the Laurentian Great Lakes by the invasive mussel Dreissena polymorpha was a significant ecological disturbance. The invasion reached Saginaw Bay, Lake Huron, in 1991 and initially cleared the waters and lowered algal biomass. However, an unexpected result occurred 3 years after the initial invasion with the return of nuisance summer blooms of cyanobacteria, a problem that had been successfully addressed with the implementation of phosphorus controls in the late 1970s. A multi-class phytoplankton model was developed and tested against field observations and then used to explore the causes of these temporal changes. Model scenarios suggest that changes in the phytoplankton community can be linked to three zebra mussel-mediated effects: (1) removal of particles resulting in clearer water, (2) increased recycle of available phosphorus throughout the summer, and (3) selective rejection of certain Microcystis strains. Light inhibition of certain phytoplankton assemblages and the subsequent alteration of competitive dynamics is a novel result of this model. These results enhance our understanding of the significant role of zebra mussels in altering lower trophic level dynamics of Saginaw Bay and suggest that their physical reengineering of the aquatic environment was the major force driving changes in the phytoplankton community composition.

Freeman, A.M., E.C. Lamon, and C.A. STOW. Nutrient criteria for lakes, ponds, and reservoirs: A Bayesian TREED model approach. Ecological Modelling 220:630-639 (2009).

We develop regional-scale eutrophication models for lakes, ponds, and reservoirs to investigate the link between nutrients and chlorophyll-a. The Bayesian TREED (BTREED) model approach allows association of multiple environmental stressors with biological responses, and quantification of uncertainty sources in the empirical water quality model. Nutrient data for lakes, ponds, and reservoirs across the United States were obtained from the Environmental Protection Agency (EPA) National Nutrient Criteria Database. The nutrient data consist of measurements for both stressor variables (such as total nitrogen and total phosphorus), and response variables (such as chlorophyll-a), used in the BTREED model. Markov chain Monte Carlo (McMC) posterior exploration guides a stochastic search through a rich suite of candidate trees toward models that better fit the data. The Bayes factor provides a goodness of fit criterion for comparison of resultant models. We randomly split the data into training and test sets; the training data were used in model estimation, and the test data were used to evaluate out-of-sample predictive performance of the model. An average relative efficiency of 1.02 between the training and test data for the four highest log-likelihood models suggests good out-of-sample predictive performance. Reduced model uncertainty relative to over-parameterized alternative models makes the BTREED models useful for nutrient criteria development, providing the link between nutrient stressors and meaningful eutrophication response.

HAWLEY, N., C.K. Harris, B.M. Lesht, and A.H. CLITES. Sensitivity of a Lake Michigan sediment transport model for Lake Michigan. Journal of Great Lakes Research 35:560-576 (2009).

A two-dimensional (vertical and cross-shore) sediment transport model was applied to several transects in southern Lake Michigan using observations of waves and currents recorded during the spring of 2000. Conditions during this period included several storms that are among the largest observed in the lake. The observations were used to examine the sensitivity of the model to variations in the input parameters (waves, currents, initial bottom sediment size distribution, settling velocity, and bottom stress required for erosion). The results show that changing the physical forcing (waves and currents) or the initial bottom sediment size distribution affected the results more than varying the particle properties (settling velocity and critical shear stress) or the size classes used to describe the size distribution. This indicates that for this model specification of input parameters are of first order importance and should be specified with some confidence before adding additional complexity by including processes such as flocculation and bed consolidation.

He, C., and C. DeMARCHI. Modeling spatial distributions of point and nonpoint source pollution loadings in the Great Lakes watersheds. World Academy of Science, Engineering, and Technology 54:795-801 (2009).

A physically based, spatially-distributed water quality model is being developed to simulate spatial and temporal distributions of material transport in the Great Lakes Watersheds of the U.S. Multiple databases of meteorology, land use, topography, hydrography, soils, agricultural statistics, and water quality 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. Comparison of these estimates to the monitored total phosphorous load indicates that both point and nonpoint sources are major contributors to the total nutrient loads in the study watersheds, with nonpoint sources being the largest contributor, particularly in the rural watersheds. 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 in support of water management programs.

He, C., C. DeMARCHI, T.E. CROLEY II, Q. Feng, and T.S. HUNTER. Hydrologic modeling of the Heihe wateshed by DLBRM in Northwest China. Journal of Glaciology and Geocryology 31(3):411-421 (2009).

Water shortage is a chronic problem in arid Northwest China. The increasing poulation growth and expanding urbanization as well as potential climate change impacts are likely to worsen the situation, threatening domestic, irrigation, and industrial supplies and even the survivial of the ecosystems in Northwest China. This paper describes the preliminary work of adapting the Distributed Large Basin Runoff Model (DLBRM) to the Heihe watershed (the second largest inland river in arid Northwestern China, with a drainage area of 128,000 km2) for understanding distribution of glacial/snow melt, groundwater, surface runoff, and evapotranspiration, and for assessing hydrological impacts of climate change and glacial recession on water supply in the middle and lower reaches of the watershed. Preliminary simulation results show that Qilian Mountain in the upper reach area produces most runoff in the Heihe watershed. The simulated daily river flows of the 1990-2000 indicate that the Heihe River discharges about 1 billion m3 of water from the middle reach (at Zhengyixia station) to lower reach, with surface runoff and interflow contributing 51 and 49 percent respectively. The sandy lower soil zone in the middle reach has the highest evapotranspiration rate and also contributed nearly half of the river flow. Work underway focuses on the DLBRM model improvement and incorporation of the climate chanage and management scnarios to the hydrological simualtions in the watershed.

HÖÖK, T.O., and S.A. POTHOVEN. Energy content of young alewives in eastern Lake Michigan and Muskegon Lake, a connected drowned river mouth lake. North American Journal of Fisheries Management 29(2):378-387 (2009).

Energy content is an important determinant of an individual fish’s condition and a key input variable for bioenergetics applications. Energy content of young fish can change rapidly during ontogeny; given the numerical abundance and high mass-specific metabolic rates of young fish, it is particularly important to obtain detailed information on their energy content. To this end, we quantified the total body energy content and energy density of economically and ecologically important young (age-0–1) nonnative alewives Alosa pseudoharengus collected during 1998–2003 in eastern Lake Michigan and Muskegon Lake, a connected drowned river mouth lake. Our analysis demonstrates that energy content of young alewives varies across years, seasons, lakes, and ontogeny. Consistent with previous observations of size-dependent overwinter mortality, young alewives deplete a large amount of body energy between late fall and late spring (i.e., declines in length-specific energy content and energy density occur overwinter). Interestingly, unlike several past studies of young fish in their native range, size-specific energy content of young alewives does not appear to increase over the summer and fall (there is no evidence of increased energy storage in preparation for the resource-scarce winter period). Finally, our measured values are similar to the few previously published energy density values for age-0 alewives. The high degree of variation in the energy content of young fish emphasizes the necessity of using appropriate energy measures for bioenergetics applications to inform fisheries management.

Jaeger Miehls, A.L., D.M. MASON, K.A. Frank, A.E. Krause, S.D. PEACOR, and W.W. Taylor. Invasive species impacts on ecosystem structure and function: A comparison of Oneida Lake, New York, USA, before and after zebra mussel invasion. Ecological Modelling 220:3194-3209 (doi:10.1016/j.ecolmodel.2009.07.020) (2009).

Exotic species invasion is widely considered to affect ecosystem structure and function. Yet, few contemporary approaches can assess the effects of exotic species invasion at such an inclusive level. Our research presents one of the first attempts to examine the effects of an exotic species at the ecosystem level in a quantifiable manner. We used ecological network analysis (ENA) and a social network analysis (SNA) method called cohesion analysis to examine the effect of zebra mussel (Dreissena polymorpha) invasion on the Oneida Lake, New York, USA, food web. We used ENA to quantify ecosystem function through an analysis of food web carbon transfer that explicitly incorporated flow over all food web paths (direct and indirect). The cohesion analysis assessed ecosystem structure through an organization of food web members into subgroups of strongly interacting predators and prey. Our analysis detected effects of zebra mussel invasion throughout the entire Oneida Lake food web, including changes in trophic flow efficiency (i.e., carbon flow among trophic levels) and alterations of food web organization (i.e., paths of carbon flow) and ecosystem activity (i.e., total carbon flow). ENA indicated that zebra mussels altered food web function by shunting carbon from pelagic to benthic pathways, increasing dissipative flow loss, and decreasing ecosystem activity. SNA revealed the strength of zebra mussel perturbation as evidenced by a reorganization of food web subgroup structure, with a decrease in importance of pelagic pathways, a concomitant rise of benthic pathways, and a reorganization of interactions between top predator fish. Together, these analyses allowed for a holistic understanding of the effects of zebra mussel invasion on the Oneida Lake food web.

Jaeger Miehls, A.L., D.M. MASON, K.A. Frank, A.E. Krause, S.D. PEACOR, and W.W. Taylor. Invasive species impacts on ecosystem structure and function: A comparison of the Bay of Quinte, Canada, and Oneida Lake, USA before and after zebra mussel invasion. Ecological Modelling 220:3182-3193 (doi:10.1016/j.ecolmodel.2009.07.013) (2009).

As invasion rates of exotic species increase, an ecosystem level understanding of their impacts is imperative for predicting future spread and consequences.We have previously shown that network analyses are powerful tools for understanding the effects of exotic species perturbation on ecosystems. We now use the network analysis approach to compare how the same perturbation affects another ecosystem of similar trophic status.We compared food web characteristics of the Bay of Quinte, Lake Ontario (Canada), to previous research on Oneida Lake, New York (USA) before and after zebra mussel (Dreissena polymorpha) invasion. We used ecological network analysis (ENA) to rigorously quantify ecosystem function through an analysis of direct and indirect foodweb transfers.We used a social network analysis method, cohesion analysis (CA), to assess ecosystem structure by organizing food web members into subgroups of strongly interacting predators and prey. Together, ENA and CA allowed us to understand how food web structure and function respond simultaneously to perturbation. In general, zebra mussel effects on the Bay of Quinte, when compared to Oneida Lake,were similar in direction, but greater in magnitude. Both systems underwent functional changes involving focused flow through a small number of taxa and increased use of benthic sources of production; additionally, both systems structurally changed with subgroup membership changing considerably (33% in Oneida Lake) or being disrupted entirely (in the Bay of Quinte). However, the response of total ecosystem activity (as measured by carbon flow) differed between both systems, with increasing activity in the Bay of Quinte, and decreasing activity in Oneida Lake. Thus, these analyses revealed parallel effects of zebra mussel invasion in ecosystems of similar trophic status, yet they also suggested that important differences may exist. As exotic species continue to disrupt the structure and function of our native ecosystems, food web network analyses will be useful for understanding their far-reaching effects.

Jin, M., C. Deal, J. WANG, and C.P. McRoy. Response of lower trophic level production to long-term climate change in the southeastern Bering Sea. Journal of Geophysical Research 114(C04010, doi:10.1029/2008JC005105):10 pp. (2009).

[1] The Bering Sea ecosystem has undergone profound changes in response to climate regime shifts in the past decades. Here, lower trophic level production is assessed with a vertically one-dimensional (1-D) coupled ice-ocean ecosystem model, which was applied to data collected by a National Oceanic and Atmospheric Administration (NOAA)/Pacific Marine Environmental Laboratory (PMEL) mooring from 1995 to 2005. The physical model is forced by sea surface winds, heat and salt fluxes, tides, and sea ice. The biological model includes coupled pelagic and ice algae components. Model results are validated with daily mooring temperature, fluorometer, and daily Sea-viewing Wide Field-of-view Sensor (SeaWiFS) chlorophyll data. Two distinct ocean conditions and phytoplankton bloom patterns are related to the Pacific Decadal Oscillation (PDO) Index regimes: warmer temperature and later warm-water phytoplankton species bloom in PDO > 1 year; colder temperature and earlier cold-water phytoplankton species bloom in PDO < - 1 year. Productivity of different phytoplankton species changed dramatically after the 1976 climate shift, but the total annual net primary production (NPP) remained flat over the past four decades under similar nutrient regulation. Climate shift also affected the vertical distribution of lower trophic level production and energy flow to the upper ocean pelagic ecosystem or the benthic community. A long-term PDO regime shift occurred in 1976, and a short-term PDO reversal occurred in 1998. Phytoplankton biomass responded promptly to both short- and long-term climate changes. Zooplankton biomass responded more to the long-term than to the short-term climate shift. The model results captured observed trends of zooplankton abundance changes from the 1990s to 2004.

JOSEPH, S.T., L.A. CHAIMOWITZ, M.A. QUIGLEY, R.A. STURTEVANT, D.M. MASON, C.E. SELLINGER, J. WANG, C. DeMARCHI, and S.B. BRANDT. Impact of climate change on the Great Lakes ecosystem: A NOAA science needs assessment workshop to meet emerging challenges - summary report. NOAA Technical Memorandum GLERL-147. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, Ann Arbor, MI, 48 pp. (2009).

From July 29 to 31, 2008, NOAA’s Great Lakes Environmental Research Laboratory (GLERL) co-hosted the workshop – Impact of Climate Change on the Great Lakes Ecosystem – A NOAA Science Needs Assessment to Meet Emerging Challenges. The workshop was held at the School of Natural Resources and Environment, University of Michigan Central Campus, Ann Arbor, Michigan. Workshop co-hosts were the Cooperative Institute for Limnology and Ecosystems Research (CILER), the Great Lakes Sea Grant Network, and the NOAA Great Lakes Regional Team. Event co-sponsors included: GLERL, CILER, and the Pennsylvania, Ohio, Wisconsin, Illinois/Indiana, Minnesota, and Michigan Sea Grant Programs. The purpose of the workshop was to take the first step in developing a NOAA research strategy that addresses the impact of climate change on Great Lakes coastal ecosystems that is driven by user needs. The workshop was unique because of its focus on identifying and prioritizing research needs and future plans toward understanding the impact of climate change on the physical, chemical, and biological processes in Great Lakes coastal waters and connecting channels. Previous workshops, conferences, and reports that address climate change impacts in the Great Lake region are listed in Appendix I.

JOSEPH, S.T. Harmful algal blooms and muck: What's the difference? Fact Sheet. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (2009).

Harmful algal blooms and muck, otherwise known as Cladophora, can be mistaken for each other simply because people may associate an algal bloom with either type. However, both represent significantly different species. Unlike green algae such as Cladophora, blue-green algae is technically not an algae, but is a bacteria known as cyanobacteria that photosynthesizes like algae do. Blue-green harmful algal blooms (HABs) and green algae blooms can be found in similar locations. However, the two species differ in appearance and in factors that influence their growth and movement in the Great Lakes.

JOSEPH, S.T. Harmful algal blooms in the Great Lakes. Fact Sheet. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (2009).

There are many species of single-celled organisms living in the Great Lakes, including algae. When certain conditions are present, such as high nutrient or light levels, these organisms can reproduce rapidly. This dense population of algae is called a bloom. Some of these blooms are harmless, but when the blooming organisms contain toxins, other noxious chemicals, or pathogens, it is known as a harmful algal bloom, or HAB. HABs can cause the death of nearby fish and foul up nearby coastlines, and produce harmful conditions to marine life as well as humans.

Kidwell, D.M., A.J. Lewitus, E.B. Jewett, S.B. BRANDT, and D.M. MASON. Ecological impacts of hypoxia on living resources. Journal of Experimental Marine Biology and Ecology 381:51-53 (2009).

Hypoxia (typically defined as dissolved oxygen levels <2mgL−1) is a common symptom of degraded water quality that often results from anthropogenic activities (e.g., nutrient pollution). Recognized as a threat to ecosystems worldwide, the occurrence of hypoxia in coastal waters has increased steadily over the past 50 years (Diaz and Rosenberg, 2008). The formation of hypoxia is typically the result of interactions among water column stratification, biologic processes, nutrient inputs, and other factors (e.g., Rabalais et al., 2007). Although hypoxia is an inherent feature in many ecosystems, increased anthropogenic nutrient inputs and other environmental perturbations have increased both the frequency of occurrence and intensity of naturally occurring hypoxia and has induced its occurrence in ecosystems where it had not been previously documented (Hagy et al., 2004; Rabalais et al., 2007; Diaz and Rosenberg, 2008). In the United States, hypoxia has been found in over 300 ecosystems (see Diaz and Rosenberg, 2008) and often forms seasonally. Although the primary factors causing hypoxia are fundamentally understood in many ecosystems, the impacts of hypoxia on living resources and food webs are far less known.

Lee, J.-H., C.A. STOW, and P.F. LANDRUM. Bayesian multilevel discrete interval hazard analysis to predict DDE mortality in Hyalella azteca based on body residues. Environmental Toxicology and Chemistry 28:2458 (2009).

We exposed Hyalella azteca to p,p'-dichlorodiphenyldichloroethylene for intervals of 1 to 4 d and followed mortality out to 10 d. Mortality was determined as the cessation of heartbeat; dead organism body residue was determined daily. To model mortality probability, body residues of the living organisms were estimated using published kinetic data with concentration-dependent rate constants. The estimated residues compared favorably with measured residues in the dead organisms (predicted body residue = 1.302 ± 0.142 measured body residue + 10.351 ± 15.766, r2 = 0.64, n = 50). The response data were collected at discrete intervals; thus, it was not possible to determine the exact time of death for organisms. Consequently, we analyzed the mortality data using discrete interval analysis, in a Bayesian hierarchical framework, with body residue as the dose metric. The predicted body residues to produce mortality were similar across the duration of exposure when postexposure mortality was considered. The concentration for 50% mortality was 0.47 μmol/g (148.6 μg/g, range 0.32–0.66 μmol/g), and predictions of response indicted 95% (range 73–99.9%) mortality at 0.79 μmol/g (250 μg/g) and 4% (range 1.2–9.6%) mortality at 0.16 μmol/g (50 μg/g). The lethal residue for 50% mortality based on interval analysis for short-term exposures with postexposure mortality resulted in values similar to long-term continuous exposures for exposure durations of more than 600 h.

Lekki, J., R. Anderson, Q.V. Nguyen, J. Demers, G.A. LESHKEVICH, J. Flatico, and J. Kojima. Development of hyperspectral remote sensing capability for the early detection and monitoring of Harmful Algal Blooms (HABs) in the Great Lakes. AIAA Infotech Aerospace Conference, Seattle, WA, April 6-9, 2009. American Institute of Aeronautics and Astronautics, 14 pp. (2009).

Hyperspectral imagers have significant capability for detecting and classifying waterborne constituents. One particularly appropriate application of such instruments in the Great Lakes is to detect and monitor the development of potentially Harmful Algal Blooms (HABs). Two generations of small hyperspectral imagers have been built and tested for aircraft based monitoring of harmful algal blooms. In this paper a discussion of the two instruments as well as field studies conducted using these instruments will be presented. During the second field study, in situ reflectance data was obtained from the Research Vessel Lake Guardian in conjunction with reflectance data obtained with the hyperspectral imager from overflights of the same locations. A comparison of these two data sets shows that the airborne hyperspectral imager closely matches measurements obtained from instruments on the lake surface and thus positively supports its utilization for detecting and monitoring HABs.

LESHKEVICH, G.A., and S.V. Nghiem. Using satellite radar data to map and monitor variations in Great Lakes ice cover. 2009 IEEE Radar Conference, Pasadena, CA, May 4-8, 2009. IEEE, 3 pp. (2009).

Satellite-borne radars, including synthetic aperture radar (SAR) and scatterometer data, are used to classify and map Great Lakes ice cover and to derive freeze-up date, breakup date, and ice cover duration. These are important indicators of regional climatic conditions.

LIU, P.C., H.S. Chen, D.J. Doong, C.C. Kao, and Y.J.G. Hsu. Freaque waves during Typhoon Krosa. Annales Goephysicae 27:2633-2642 (2009).

This paper presents a subjective search for North Sea Draupner-like freaque waves from wave measurement data available in the northeastern coastal waters of Taiwan during Typhoon Krosa, October 2007. Not knowing what to expect, we found rather astonishingly that there were more Draupner-like freaque wave types during the build-up of the storm than we ever anticipated. As the conventional approach of defining freaque waves as Hmax/Hs > 2 is ineffective to discern all the conspicuous cases we found, we also tentatively proposed two new indices based on different empirical wave grouping approaches which hopefully can be used for further development of effective indexing toward identifying freaque waves objectively.

LIU, P.C., C.H. Wu, K.R. MacHutchon, and D.J. SCHWAB. An analysis of measurement from a 3D oceanic wave field. WIT Transactions on Ecology and the Environment 126:15-26 (doi:10.2495/CP090021) (2009).

We present here a preliminary examination and analysis of a small suite of 3D wave data to explore what new insight or inference we can garner – particularly toward the realm where conventional approaches have not yet been. While we caught a few glimpses that might indicate a need for new conceptualizations, it by no means negates the vast positive contributions that the conventional approaches have allowed us to make in the past century. We feel it is timely to encourage further 3D ocean wave measurement and thereby facilitate fresh new states of study and to enhance our understanding of ocean waves.

Liu, Z., S.H.Choudhury, M. XIA, J. Holt, C.M. Wallen, S. Yuk, and S.C. Sanborn. Water quality assessment of coastal Caloosahatchee Eiver watershed,Florida. Journal of Environmental Science and Health Part A 44 (DOI: 10.1080/10934520902996872):972-984 (2009).

Caloosahatchee River watershed and estuary has experienced a general decline in the water quality over the last several decades due to agriculture practices, development, and other human activities. The objective of this study is to assess the water quality condition in coastal Caloosahatchee River watershed by analyzing the data collected by South Florida Water Management District and Lee County. Results indicated that during 1995 to 2006, averaged annually, Lake Okeechobee released 1124 million m3 of freshwater into the Caloosahatchee River, whereas the average annual freshwater discharge out of the Caloosahatchee River was approximately 2277 million m3. Lake Okeechobee might have more impacts on the water quality condition of Caloosahatchee River in dry season than wet season. The loads ratios of Lake Okeechobee to those out of Caloosahatchee River were much higher in dry season than wet season for flow (72% to 36%), total phosphorus (63% to 20%), total nitrogen (72% to 41%), organic nitrogen (85% to 47%), and NH3 (78% to 39%). In the coastal watershed area where the urban area is concentrated, of the total 5453 water samples, 74% of them have dissolved oxygen concentration less than 5 mg L−1, the United States Environmental Protection Agency and Florida Department of Environmental Protection water quality standard. Only in January is the average monthly dissolved oxygen concentration higher than 5 mg L−1.

Ludsin, S.A., X. Zhang, S.B. Brandt, M.R. Roman, W.C. Boicourt, D.M. MASON, and M. Costantini. Hypoxia-avoidance by planktivorous fish in Chesapeake Bay: implications for food web interactions and fish recruitment. Journal of Experimental Marine Biology and Ecology 381:S121-131 (2009).

Chesapeake Bay has been experiencing severe eutrophication-driven bottom hypoxia for several decades, yet the effects of hypoxia on its food webs, especially its pelagic components, remain largely enigmatic. To better understand how hypoxia influences the interaction and spatial overlap between planktivorous fishes (e.g., bay anchovy Anchoa mitchilli) and their mesozooplankton prey (e.g., Acartia tonsa), we contrasted the spatial distributions of these food-web components along the Bay's entire north–south axis during spring, summer, and fall 1996, 1997, and 2000, and along several cross-Bay transects during summer of these same years. Pelagic fish biomass was estimated with a surface-towed split-beam echosounder. Dissolved oxygen and mesozooplankton biomass were simultaneously quantified using a towed, undulating ScanFish sensor package. Results indicate that hypoxia can disrupt the diel vertical migration behavior of planktivorous fishes in Chesapeake Bay during summer by reducing access to bottom waters and forcing fish to reside in well oxygenated surface or nearshore waters. In turn, reduced access to bottom waters reduces spatial overlap with mesozooplankton prey, which appear to use the hypoxic zone as a refuge. Ultimately, we discuss how these hypoxia-driven changes in behavior and spatial overlap may influence food web interactions and bay anchovy recruitment in Chesapeake Bay.

MacHutchon, K.R., W.J. Wessels, C.H. Wu, and P.C. LIU. The use of streamed digital video data and Binocular Stereoscopic Image System (BISIS) processing methods to analyse ocean wave field kinematics. Proceedings of the ASME 2009 28th International Conference on Ocean, Offshore, and Arctic Engineering OMAE2009, Honolulu, HI, May 31-June 5, 2009. American Society of Mechanical Engineers, 7 pp. (2009).

The kinematics of short crested steep and breaking waves in the ocean is a subject that is best studied spatially, in the time domain, to obtain a good understanding of the multi-directional spreading of energy, which is dependant on strongly non-linear wave interactions in the system. The paper will cover the collection, recording and processing of streamed sea surface image data, obtained simultaneously from multiple digital video cameras, for analysis using stereoscopic image processing methods to provide information on the kinematics of ocean wave fields. The data streaming architecture, which will be reviewed, incorporates an advanced laptop computer and two to three stand-alone digital video cameras which are all linked through a gigabit ethernet network connection with sufficient bandwidth to simultaneously transfer the image data from the cameras to hard drive storage. The modifications to the laptop computer comprise the provision of increased processing capacity to enable it to accept and process large IP frames simultaneously. The system has the capacity to continuously record images, at a rate of up to 60 frames per second, for periods of up to one hour. It includes an external triggering mechanism, which is synchronised to a micro-second, to ensure that stereo pairs of images are captured simultaneously. Calibration of the cameras, and their stereoscopic configuration, is a critical part of the overall process, and we will discuss how ill-conditioned and singular matrices, which can prevent the determination of required intrinsic and extrinsic parameters, can be avoided. The paper will include examples of wave field image data which has been collected using streamed digital video data and Binocular Stereoscopic Image System (BiSIS) processing methods. It will also give examples digital video images and dimensional wave field data which has been collected and processed using the Automated Trinocular Stereoscopic Imaging Systems (ATSIS) methods. Both of these systems provide a valuable means of analysing irregular, non-linear, short crested waves, which leads to an improved understanding of ocean wave kinematics.

Millie, D.F., G.L. FAHNENSTIEL, J. DYBLE BRESSIE, R.J. Pigg, R.R. Rediske, D.M. Klarer, P.A. Tester, and R.W. Litaker. Late-summer phytoplankton in western Lake Erie (Laurentian Great Lakes): bloom distributions, toxicity, and environmental influences. Aquatic Ecology DOI 10.1007/s10452-009-9238-7:20 pp. (2009).

Phytoplankton abundance and composition and the cyanotoxin, microcystin, were examined relative to environmental parameters in western Lake Erie during late-summer (2003–2005). Spatially explicit distributions of phytoplankton occurred on an annual basis, with the greatest chlorophyll (Chl) a concentrations occurring in waters impacted by Maumee River inflows and in Sandusky Bay. Chlorophytes, bacillariophytes, and cyanobacteria contributed the majority of phylogenetic-group Chl a basin-wide in 2003, 2004, and 2005, respectively. Water clarity, pH, and specific conductance delineated patterns of group Chl a, signifying that water mass movements and mixing were primary determinants of phytoplankton accumulations and distributions. Water temperature, irradiance, and phosphorus availability delineated patterns of cyanobacterial biovolumes, suggesting that biotic processes (most likely, resource-based competition) controlled cyanobacterial abundance and composition. Intracellular microcystin concentrations corresponded to Microcystis abundance and environmental parameters indicative of conditions coincident with biomass accumulations. It appears that environmental parameters regulate microcystin indirectly, via control of cyanobacterial abundance and distribution.

NALEPA, T.F., D.L. FANSLOW, and G.A. LANG. Transformation of the offshore benthic community in Lake Michigan: Recent shift from the native amphipod Diporeia spp. to the invasive mussel Dreissena rostriformis bugensis. Freshwater Biology 54(3):466-479 (2009).

1. The native amphipod Diporeia spp. was once the dominant benthic organism in Lake Michigan and served as an important pathway of energy flow from lower to upper trophic levels. Lake-wide surveys were conducted in 1994 ⁄1995, 2000 and 2005, and abundances of Diporeia and the invasive bivalves Dreissena polymorpha (zebra mussel) and Dreissena rostriformis bugensis (quagga mussel) were assessed. In addition, more frequent surveys were conducted in the southern region of the lake between 1980 and 2007 to augment trend interpretation.
2. Between 1994/1995 and 2005, lake-wide density of Diporeia declined from 5365 to 329 m-2, and biomass (dry weight, DW) declined from 3.9 to 0.4 g DW m-2. The percentage of all sites with no Diporeia increased over time: 1.1% in 1994/1995, 21.7% in 2000 and 66.9% in 2005. On the other hand, total dreissenid density increased from 173 to 8816 m-2, and total biomass increased from 0.4 to 28.6 g DW m-2. Over this 10-year time period, D. r. bugensis displaced D. polymorpha as the dominant dreissenid, comprising 97.7% of the total population in 2005. In 2007, Diporeia was rarely found at depths shallower than 90 m and continued to decline at greater depths, whereas densities of D. r. bugensis continued to increase at depths greater than 50 m.
3. The decline in Diporeia occurred progressively from shallow to deep regions, and was temporally coincident with the expansion of D. polymorpha in nearshore waters followed by the expansion of D. r. bugensis in offshore waters. In addition, Diporeia density was negatively related to dreissenid density within and across depth intervals; the latter result indicated that dreissenids in shallow waters remotely influenced Diporeia in deep waters.
4. With the loss of Diporeia and increase in D. r. bugensis, the benthic community has become a major energy sink rather thana pathway to upper trophic levels. With this replacement of dominant taxa, we estimate that the relative benthic energy pool increased from 17 to 109 kcal m-2 between 1994/1995 and 2005, and to 342 kcal m-2 by 2007. We project that previously observed impacts on fish populations will continue and become more pronounced as the D. r. bugensis population continues to expand in deeper waters.

NALEPA, T.F., S.A. POTHOVEN, and D.L. FANSLOW. Recent changes in benthic macroinvertebrate populations in Lake Huron and impact on the diet of lake whitefish (Coregonus clupeaformus). Aquatic Ecosystem Health and Management 12(1):2-10 (2009).

Surveys of the benthic macroinvertebrate community were conducted in the main basin of Lake Huron in 2000 and 2003, and corresponding studies of lake whitefish diets were conducted in 2002-2004. Populations of three major benthic taxa, Diporeia spp., Sphaeriidae, and Chironomidae, declined dramatically between 2000 and 2003, with densities declining 57%, 74%, and 75% over this 3-year period. By 2003, Diporeia, an important food source for lake whitefish, was gone or rare at depths <50 m except in the far northeastern portion of the lake. In contrast, densities of the Dreissena bugensis (quagga mussel) increased between 2000 and 2003, particularly at the 31-50 m depth interval, while densities of the zebra mussel Dreissena polymorpha remained stable. As expected, the diet of lake whitefish varied with fish size. Age-0 lake whitefish fed mainly on zooplankton, most of which were Daphnia (98%). Medium lake whitefish (<350 mm excluding age-0 fish) fed mainly on zooplankton, Chironomidae, and Dreissena bugensis, and large lake whitefish (350 to 688 mm) fed mainly on D. bugensis and Gastropoda. The diet of medium and large lake whitefish reflected the changing nature of the benthic community; that is, Diporeia was rarely found in the diet while D. bugensis played a prominent role. Since Diporeia has a much higher energy content than D. bugensis, contrasting density trends in the two organisms will have long term consequences to the relative health of lake whitefish populations in the lake.

Pichlova-Ptacníkova, R., and H.A. VANDERPLOEG. The invasive cladoceran Cerocopagis pengoi is a generalist predator capable of feeding on a variety of prey species of different sizes and escape abilities. Fundamental and Applied Limnology 173(4):267-279 (2009).

We carried out a comprehensive exploration of predation by the invasive predatory cladoceran Cercopagis pengoi in the laboratory. A range of potential prey was offered to the predator, including all major summer nearshore zooplankton taxa in Lake Michigan; we used prey in different concentrations from 5 to 100 ind. L–1. We found that Cercopagis is a generalist capable to consume a variety of prey species, including small and large prey, and slowly and rapidly swimming prey. Consumption rates increased with concentration in several species, but did not saturate even at the highest concentration tested (40 or 100 ind. L–1). Cladocerans were consumed at a higher rate than copepods. Cercopagis was able to catch and handle prey of nearly its own body size to prey about seventeen times smaller; however, it did not show any clear size preference within this range. In contrast to most indigenous Great Lakes zooplankton,  Cercopagis can efficiently feed on veligers of the zebra mussel, another invader from the Ponto-Caspian region.

Piehler, M.F., J. DYBLE, P.H. Moisander, A.D. Chapman, J. Hendrickson, and H.W. Paerl. Interactions between nitrogen dynamics and the phytoplankton community in Lake George, Florida, USA. Lake and Reservoir Management 25(1):1-14 (2009).

Nutrient addition bioassays were conducted to examine the relationship between inorganic nutrient enrichment and phytoplankton community structure and function in Lake George in the St. Johns River System, Florida, USA. Additionally, a nitrogen budget for the lake was developed and included data from the period of this study. We identified the factors that affected cyanobacterial productivity, prevalence, and nitrogen (N2) fixation. The importance of N2 fixation to the nitrogen (N) budget of the system was also assessed. We hypothesized that N2 fixation significantly contributed to the Lake George N budget and that changing the nutrient conditions in manipulative experiments would affect rates of N2 fixation and composition of the phytoplankton, particularly the N2-fixing community. Phytoplankton primary productivity in Lake George was stimulated by the addition of both N and phosphorus (P). Phytoplankton biomass accumulation was most often enhanced by the combined addition of N and P; however, N alone was also often stimulatory. When detected, N2 fixation was always stimulated by P additions. Short-term changes in phytoplankton community composition included taxonomic shifts in response to nutrient manipulations. Fixation of N2 appeared to be a significant contributor to the N load to the lake. Human impacts that change the loading of N, P, or both N and P to Lake George may affect phytoplankton community structure (composition and biomass) and function (primary productivity and N2 fixation). These changes could have consequences for biogeochemical cycling in Lake George and potentially through the freshwater-marine continuum. Continuing nutrient management efforts in this and other similar systems must account for the activity of N2-fixing cyanobacteria, as products (carbon fixation) and drivers (sources of new nitrogen) of eutrophication.

POTHOVEN, S.A., H.A. VANDERPLOEG, S.A. Ludsin, T.O. HÖÖK, and S.B. BRANDT. Feeding ecology of emerald shiners and rainbow smelt in Lake Erie. Journal of Great Lakes Research 35:190-198 (2009).

To better understand the feeding ecology of two important Laurentian Great Lakes prey species, rainbow smelt Osmerus mordax and emerald shiners Notropis atherinoides, we quantified the diet composition, selectivity, daily ration, and diet overlap of both species in offshore central Lake Erie during May through October 2005, which spanned a period of severe hypolimnetic hypoxia (<2 mg O2/L). Rainbow smelt fed upon a variety of prey taxa, including zooplankton, chironomid pupae and larvae, and fish, whereas emerald shiners primarily consumed cladocerans, if available. In turn, diet overlap between rainbow smelt and emerald shiners was low except during September when hypolimnetic hypoxia reduced rainbow smelt access to benthic prey. Rainbow smelt most frequently selected chironomid pupae, while emerald shiners generally selected pupae or large predatory cladocerans (Leptodora or Bythotrephes). Daily ration and individual consumption by rainbow smelt were 54–68% less during hypoxia than at the same site during stratified pre-hypoxic or mixed post-hypoxic conditions. Although emerald shiner daily ration and individual consumption decreased between pre-hypoxic and hypoxic periods, it continued to decrease during the posthypoxic period, suggesting that reduced consumption may not have been linked to hypoxic conditions. Ultimately, our findings suggest that emerald shiners are as important regulator of zooplankton abundance in the Great Lakes as rainbow smelt, given their potentially high mass-specific consumption rates, selectivity and diet patterns, and current high abundance.

REID, D.F., and R. STURTEVANT. Ballast water and aquatic nuisance species introductions in the Great Lakes. Fact Sheet. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (2009).

Over the last two centuries the Great Lakes have been invaded by aquatic nonindigenous species (ANS) moving via a broad array of vectors, including transoceanic shipping. Ships are believed to be responsible for ANS additions starting in the 1860’s through disposal of solid ballast. The opening of the St. Lawrence Seaway in 1959 resulted in a substantial increase in the importance of ballast water as a vector for the introduction of nonindigenous species. Ballast water is used to supply stability on ships that have no load. It is loaded on before departure and often carries stowaways in the form of tiny organisms. Ship discharge of ballast water is considered the most likely source for the majority of ANS additions in the Great Lakes since 1959. Due to the invasion of zebra mussels in the late-1980s, mandatory ballast water management regulations were established in 1993 for all ships entering the Great Lakes with pumpable ballast water. Under these regulations, ships are required to replace ballast water with saltwater from the middle of the ocean in a process known as ballast water exchange (BWE).

ROBERTS, J.J., T.O. Hook, S.A. Ludsin, S.A. POTHOVEN, H.A. VANDERPLOEG, and S.B. Brandt. Effects of hypolimnetic hypoxia on foraging and distributions of Lake Erie yellow perch. Journal of Experimental Marine Biology and Ecology 381:S132-S142 (2009).

Bottom hypoxia (< 2 mg O2 L−1) is a widespread phenomenon in marine and freshwater systems, yet the ecological consequences of hypoxia are generally unknown, especially for mobile organisms such as fish. Herein, we explore how a large area of hypolimnetic (i.e., sub-thermocline) hypoxia that develops seasonally in Lake Erie's central basin influences yellow perch (Perca flavescens), a demersal species of both ecological and economic importance. We hypothesized that hypolimnetic hypoxia would negatively affect yellow perch by limiting access to benthic prey and preferred (cool) temperatures. To explore how hypoxia influences yellow perch foraging and migration patterns in central Lake Erie, we collected a suite of biological (i.e., fish with bottom and mid-water trawls, benthic macroinvertebrates using Ponar grabs, and zooplankton via depth-specific pumping) and physical (i.e., temperature and dissolved oxygen) data monthly during June through October 2005. Our results indicate that yellow perch avoid hypoxic bottom waters by either moving horizontally away from the hypoxic zone or migrating above the oxycline. We also found evidence to suggest that individuals that moved above the hypoxic hypolimnetic layer continue to “dive” into the hypoxic layer to feed on benthic invertebrates. Even so, during the height of hypoxia, both the amount and proportion of benthic macroinvertebrates consumed decreased, whereas consumption of zooplankton increased. While hypoxia-induced changes in yellow perch distributions and foraging likely affect individual condition and growth in the short-term, the long-term effects on population production remain equivocal.

Rose, K.A., A.T. ADAMACK, C.A. Murphy, S.E. Sable, S.E. Kolesar, J.K. Craig, D.L. Breitburg, P. Thomas, M.H. Brouwer, C.F. Cerco, and S. Diamond. Does hypoxia have population-level effects on coastal fish? Musing from the virtual world. Journal of Experimental Marine Biology and Ecology 381:S188-S203 (2009).

Hypoxia is often associated with increasing nutrient loadings and has clear mortality effects on sessile organisms, but its population effects on mobile organisms in coastal environments are uncertain. The evidence for hypoxia having population level effects is laboratory experiments, many examples of localized effects in nature, a few population-level examples, fish kills, and intuition. Despite the perception by many people, none of these provide conclusive evidence of widespread population responses to hypoxia.We synthesize the results from seven ecological simulation models that examined how low dissolved oxygen (DO) affected fish at the individual, population, and community levels. These models represent a variety of species, simulate the dynamics at a range of temporal scales and spatial scales, and impose a variety of subsets of possible DO effects. Several patterns emerged from the accumulated results. First, predicted responses were large in simpler models, and small to large in more complex models. Second, while the main effects of increased hypoxia were generally small to moderate, there were instances of relatively large indirect effects and interaction effects. Indirect effects involved growth and mortality responses due to altered spatial distribution (rather than due directly to DO) and food web interactions. Interaction effects were larger responses to hypoxia when other factors were at certain levels (e.g., responses at low versus high fish densities). Interactions also occurred when the predicted responses were larger than would be expected by the sum of the separate effects. Third, accurate information on exposure and degree of avoidance of low DO were critical unknowns. Our interpretations should be viewed as suggestive rather than definitive. The patterns described were based on a collection of modeling results that were not designed to be compared to each other. A quick look at other models seems to confirm our patterns, or at minimum, does not contradict our patterns. Quantifying the effects of hypoxia on fish populations, whether large or small, is critical for effective management of coastal ecosystems and for costeffective and efficient design of remediation actions. The potential for interaction and indirect effects complicates field study and management. Improving our predictions of the effects of hypoxia on fish populations and communities has moved from a computational issue to a biological issue. We seem to be making progress on monitoring and modeling movement behavior, but progress is slower in food web theory and empirical research and in quantifying interspecific interactions and habitat quality in terms of process rates that relate to population dynamics.

RUBERG, S.A., S.T. Kendall, B.A. Biddanda, T. Black, S.C. Nold, W.R. Lusardi, R. Green, T. Casserley, E. Smith, T.G. Sanders, G.A. LANG, and S.A. CONSTANT. Observations of the Middle Island sinkhole in Lake Huron: A unique hydrogeologic and glacial creation of 400 million years. Marine Technology Society Journal 42(4):12-21 (2009).

In the northern Great Lakes region, limestone sediments deposited some 400 million ybp during the Devonian era have experienced erosion, creating karst features such as caves and sinkholes. The groundwater chemical constituents of the shallow seas that produced these rock formations now contribute to the formation of a unique physical (sharp density gradients), chemical (dissolved oxygen-depleted, sulfate-rich), and biological (microbe-dominated) environment in a submerged sinkhole near Middle Island in freshwater Lake Huron. A variety of methods including aerial photography, physico-chemical mapping, time series measurements, remotely operated vehicle (ROV) survey, diver observations, and bathymetric mapping were employed to obtain a preliminary understanding of sinkhole features and to observe physical interactions of the system’s groundwater with Lake Huron. High conductivity ground water of relatively constant temperature hugs the sinkhole floor creating a distinct sub-ecosystem within this Great Lakes ecosystem. Extensive photosynthetic purple cyanobacterial benthic mats that characterize the benthos of this shallow sinkhole were strictly limited to the zone of ground water influence.

Ruetz, D.R., D.L. Strouse, and S.A. POTHOVEN. Energy density of introduced round goby compared with four native fishes in a Lake Michigan tributary. Transactions of the American Fisheries Society 138:938-947 (2009).

The round goby Neogobius melanostomus is an invasive species that has changed Great Lakes food webs and become an important prey for many predators. We tested whether the round goby from a Lake Michigan tributary was energetically equivalent to four native fishes: mottled sculpin Cottus bairdii, johnny darter Etheostoma nigrum, bluntnose minnow Pimephales notatus, and rock bass Ambloplites rupestris. We found positive linear relationships between energy density and the percent dry weight of a fish for each species. We also found evidence of temporal and spatial variation in round goby energy density. Energy density was lower in spring and summer than in fall. The spatial variation in energy density may be linked to the inclusion of the low quality prey, dreissenid mussels, in the diets of larger round goby. For a given size, the johnny darter and bluntnose minnow had the highest energy density while mottled sculpin had the lowest. Our results show that the energy density of the round goby is intermediate to those of the four native fishes, suggesting that the round goby is an energetically average prey in a Lake Michigan tributary.

Santagata, S., K. Bacela, D.F. REID, K.A. McLean, J.S. Cohen, J.R. Cordell, C.W. Brown, T.H. JOHENGEN, and G.M. Ruiz. Concentrated sodium chloride brine solutions as an additional treatment for preventing the introduction of nonindigenous species in the ballast tanks of ships declaring no ballast on board. Environmental Toxicology and Chemistry 28(2):346-353 (2009).

Currently, seawater flushing is the only management strategy for reducing the number of viable organisms in residual sediments and water of ballast tanks of vessels declaring no ballast on board (NOBOB) that traffic ports of the eastern United States. Previously, we identified several species of freshwater and brackish-water peracarid crustaceans able to survive the osmotic shock that occurs during open-ocean ballast water exchange and, potentially, to disperse over long distances via ballasted ships and NOBOB vessels. We tested the efficacy of concentrated sodium chloride brine solutions as an additional treatment for eradicating the halotolerant taxa often present in the ballast tanks of NOBOB ships. The lowest brine treatments (30 ppt for 1 h) caused 100% mortality in several species of cladocerans and copepods collected from oligohaline habitats. Several brackish-water peracarid crustaceans, however, including some that can survive in freshwater as well, required higher brine concentrations and longer exposure durations (45–60 ppt for 3–24 h). The most resilient animals were widely introduced peracarid crustaceans that generally prefer mesohaline habitats but do not tolerate freshwater (required brine treatments of 60–110 ppt for 3–24 h). Brine treatments (30 ppt) also required less time to cause 100% mortality for eight taxa compared with treatments using 34 ppt seawater. Based on these experiments and published data, we present treatment strategies for the ballast tank biota often associated with NOBOB vessels entering the Great Lakes region. We estimate the lethal dosage of brine for 95% of the species in our experiments to be 110 ppt (95% confidence interval, 85–192 ppt) when the exposure time is 1 h and 60 ppt (95% confidence interval, 48–98 ppt) when the exposure duration is 6 h or longer.

SCHWAB, D.J., D. BELETSKY, J. DePinto, and D.M. Dolan. A hydrodynamic approach to modeling phosphorus distribution in Lake Erie. Journal of Great Lakes Research 35:50-60 (2009).

The purpose of this paper is to show how a high-resolution numerical circulation model of Lake Erie can be used to gain insight into the spatial and temporal variability of phosphorus (and by inference, other components of the lower food web) in the lake. The computer model simulates the detailed spatial and temporal distribution of total phosphorus in Lake Erie during 1994 based on tributary and atmospheric loading, hydrodynamic transport, and basin-dependent net apparent settling. Phosphorus loads to the lake in 1994 were relatively low, about 30% lower than the average loads for the past 30 years. Results of the model simulations are presented in terms of maps of 1) annually averaged phosphorus concentration, 2) temporal variability of phosphorus concentration, and 3) relative contribution of annual phosphorus load from specific tributaries. Model results illustrate that significant nearshore to offshore gradients occur in the vicinity of tributary mouths and their along-shore plumes. For instance, the annually-averaged phosphorus concentration can vary by a factor of 10 from one end of the lake to the other. Phosphorus levels at some points in the lake can change by a factor of 10 in a matter of hours. Variance in phosphorus levels is up to 100 times higher near major tributary mouths than it is in offshore waters. The model is also used to estimate the spatial distribution of phosphorus variability and to produce maps of the relative contribution of individual tributaries to the annual average concentration at each point in the lake.

STOW, C.A., J. Jolliff, D.J. McGillicuddy, S.C. Doney, J.I. Allen, M.A.M. Friedrichs, K.A. Rose, and P. Wallhead. Skill assessment for coupled biological/physical models of marine systems. Journal of Marine Systems 76:4-15 (2009).

Coupled biological/physical models of marine systems serve many purposes including the synthesis of information, hypothesis generation, and as a tool for numerical experimentation. However, marine system models are increasingly used for prediction to support high-stakes decision-making. In such applications it is imperative that a rigorous model skill assessment is conducted so that the model's capabilities are tested and understood. Herein, we review several metrics and approaches useful to evaluate model skill. The definition of skill and the determination of the skill level necessary for a given application is context specific and no single metric is likely to reveal all aspects of model skill. Thus, we recommend the use of several metrics, in concert, to provide a more thorough appraisal. The routine application and presentation of rigorous skill assessment metrics will also serve the broader interests of the modeling community, ultimately resulting in improved forecasting abilities as well as helping us recognize our limitations.

STOW, C.A., E.C. Lamon, S.S. Qian, P.A. Soranno, and K.H. Reckhow. Bayesian hierarchical/multilevel models for inference and prediction using cross-system lake data. In Real World Ecology: Large Scale and Long-Term Case Studies and Methods. S. Carstenn S. Miao, and M. Nungesser (Eds.). Springer Science and Business Media, New York, NY, 111-136 (2009).

Cross-system studies are commonly used for large-scale ecological inference (Cole et al. 1991). Many processes change slowly within a particular ecosystem, thus long time periods can be required to measure how changes in one process may influence changes in another. By using data from many systems, researchers essentially substitute space for time, assuming commonanlity among the systems being compared. Comparing characteristics among systems helps researchers identify patterns that provide clues for understanding ecosystem function, generate testable hypotheses, and isolate cause-effect relationships.

STOW, C.A., and D. Scavia. Modeling hypoxia in the Chesapeake Bay: Ensemble estimation using a Bayesian hierarchical model. Journal of Marine Systems 76:244-250 (2009).

Quantifying parameter and prediction uncertainty in a rigorous framework can be an important component of model skill assessment. Generally, models with lower uncertainty will be more useful for prediction and inference than models with higher uncertainty. Ensemble estimation, an idea with deep roots in the Bayesian literature, can be useful to reduce model uncertainty. It is based on the idea that simultaneously estimating common or similar parameters among models can result in more precise estimates. We demonstrate this approach using the Streeter–Phelps dissolved oxygen sag model fit to 29 years of data from Chesapeake Bay. Chesapeake Bay has a long history of bottom water hypoxia and several models are being used to assist management decision-making in this system. The Bayesian framework is particularly useful in a decision context because it can combine both expert-judgment and rigorous parameter estimation to yield model forecasts and a probabilistic estimate of the forecast uncertainty.

Stroud, J.R., B.M. Lesht, D.J. SCHWAB, D. BELETSKY, and M.L. Stein. Assimilation of satellite images into a sediment transport model of Lake Michigan. Water Resources Research 45(W02419, doi:10.1029/2007WR006747):16 pp (2009).

In this paper we develop and examine several schemes for combining daily images obtained from the Sea-viewing Wide Field Spectrometer (SeaWiFS) with a two dimensional sediment transport model of Lake Michigan. We consider two data assimilation methods, direct insertion and a kriging-based approach, and perform a forecasting study focused on a 2-month period in spring 1998 when a large storm caused substantial amounts of sediment resuspension and horizontal sediment transport in the lake. By beginning with the simplest possible forecast method and sequentially adding complexity we are able to assess the improvements offered by combining the satellite data with the numerical model. In our application, we find that data assimilation schemes that include both the data and the lake dynamics improve forecast root mean square error by 40% over purely model-based approaches and by 20% over purely data-based approaches.

STURTEVANT, R., and A. MARSHALL. Educator House Call: On-line data for educators' needs assessment - summary report. NOAA Technical Memorandum GLERL-149. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 9 pp. (2009).

The overreaching purpose of this focus group was to advise NOAA and NOAA partners on the best ways to make NOAA data available to educators with a focus on online delivery. There was also an emphasis on inquiry-based education.

STURTEVANT, R.A., L. Ge, R. Nagy, and R. Patel. Lake Michigan Food Web. Fact Sheet. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (2009).

Pictorial presentation of the food web of Lake Michigan.

STURTEVANT, R.A., L. Ge, R. Nagy, and R. Patel. Lake Erie Food Web. Fact Sheet. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (2009).

Pictorial presentation of the food web of Lake Erie.

STURTEVANT, R.A., L. Ge, R. Nagy, and R. Patel. Lake Huron Food Web. Fact Sheet. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (2009).

Pictorial presentation of the food web of Lake Huron.

STURTEVANT, R.A., L. Ge, R. Nagy, and R. Patel. Lake St. Clair Food Web. Fact Sheet. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (2009).

Pictorial presentation of the food web of Lake St. Clair.

STURTEVANT, R.A., L. Ge, R. Nagy, and R. Patel. Lake Ontario Food Web. Fact Sheet. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (2009).

Pictorial presentation of the food web of Lake Ontario.

STURTEVANT, R.A., L. Ge, R. Nagy, and R. Patel. Lake Superior Food Web. Fact Sheet. NOAA Great Lakes Environmental Research Laborataory, Ann Arbor, MI, 2 pp. (2009).

Pictorial presentation of the food web of Lake Superior.

VANDERPLOEG, H.A., T.H. JOHENGEN, and J.R. LIEBIG. Feedback between zebra mussel selective feeding and algal composition affects mussel condition: did the regime changer pay a price for its success? Freshwater Biology 54:47-63 (2009).

1. We investigated the role of algal composition on pumping, clearance, assimilation, pseudofaeces and faeces production, feeding time budgets, and condition of zebra mussels from spring to autumn at two sites in Saginaw Bay (Lake Huron) and one site in western Lake Erie. Size-fractioned chlorophyll was used to distinguish between feeding on small (<53 μm) and large (>53 μm) size fractions, and mussel feeding behaviour was quantified by video observations. 2. Mussel pumping, clearance and assimilation rates varied among sites, particularly during summer, when phytoplankton composition varied considerably among sites. Lowest values were seen at the inner-bay site of Saginaw Bay, low to moderate values at the outer-bay site of Saginaw Bay, and high values at the Lake Erie site. Clearance, pumping and assimilation rates were all highly positively correlated (R2 = 0.76) with percent contribution of flagellates to total algal biomass and negatively correlated with percent of Microcystis aeruginosa (R2 = 0.63). The negative effects on pumping rate (as determined by clearance rate on the <53 μm fraction) of Microcystis, which occurred in the >53 μm fraction, could be mitigated by the presence of flagellates in the <53 μm fraction. 3. Visual observations of mussel feeding showed evidence for poor seston quality during summer negatively affecting feeding rates. High faeces production during times of low assimilation rate was suggestive of poor assimilation efficiency and⁄or viable gut passage of grazing resistant algae. Long periods of time not filtering by the mussels during some Microcystis blooms and lack of production of a filtering current during one experiment were suggestive of intoxication from microcystin or other secondary compounds. 4. Clearance and feeding rates of the mussels in Saginaw Bay were high during spring and autumn and very low in summer, particularly at the inner-bay site. Condition of the mussels (mass : length ratio) was highest in spring and lowest during summer. This seasonal variation probably reflected high food assimilation rate during autumn and spring and low assimilation rate and reproduction during summer. The condition of mussels throughout the year was higher at the outer-bay than the inner-bay site, reflecting better feeding conditions at the former. Mussel selective feeding may have been responsible for the poor quality of food at the inner bay site; therefore, we postulate that a regime shift in phytoplankton composition promoted by the mussels fed back into lowered condition of the mussels.

VANDERPLOEG, H.A., S.A. Ludsin, J.F. CAVALETTO, T.O. Hook, S.A. POTHOVEN, S.B. Brandt, J.R. LIEBIG, and G.A. LANG. Hypoxic zones as habitat for zooplankton in Lake Erie: Refuges from predation or exclusion zones? Journal of Experimental Marine Biology and Ecology 381:S108-S120 (2009).

Bottom hypoxia has reemerged as a prominent feature of Lake Erie's central basin during late summer. Similar to coastal marine systems, the impacts of hypoxia on pelagic organisms in Lake Erie remain largely enigmatic. During summer 2005 and 2007, we used pump sampling for mesozooplankton and fish acoustics to test the hypothesis that mesozooplankton use hypoxia as a refuge from predation. We explored species-specific diel vertical migration (DVM) of mesozooplankton and spatial overlap with planktivorous fishes at several offshore stations in the central basin of Lake Erie with similar thermal structure, but varying hypolimnetic dissolved oxygen (DO) concentrations (range: 0.3 to 4.6 mg l−1). The tendency of a zooplankter to use the hypolimnion under normoxic conditions and its sensitivity to DO defined its DVM and overlap with fish, which were generally more sensitive to hypoxia than mesozooplankton. The diaptomids (calanoid copepods) and the predatory cladoceran Leptodora kindtii were largely unaffected by hypoxia, using the epilimnion during both day and night. Daphnia mendotae and the predatory cladoceran Bythotrephes longimanus, both of which migrated from the metalimnion and epilimnion to the hypolimnion during the day under normoxic conditions, avoided the hypolimnion at DO levels ≤ 2.0 mg l−1. Dissolved oxygen levels between 1.0 and 1.2 mg l−1 were critical avoidance thresholds for most other mesozooplankton species, with the copepod Mesocyclops edax, a migrator between the epilimnion and hypolimnion, avoiding DO ≤ 1.2 mg l−1. By contrast the cool water, hypolimnetic copepod Diacyclops thomasi and Daphnia longiremis continued to use the hypolimnion during the day until DO became ≤ 1.0 mg l−1. These species aggregated in the metalimnion (primarily) and epilimnion (secondarily) at night. Only Bosmina was found in abundance in the hypolimnion at DO levels equal to 0.3 mg l−1. Hypoxia intolerant species (e.g., D. mendotae, B. longimanus) that were compressed into the thin metalimnion during day likely faced high predation pressure from visual-feeding planktivorous fishes (e.g., rainbow smelt Osmerus mordax, emerald shiners Notropis atherinoides) as well as the predatory cladoceran, B. longimanus. By contrast, hypoxia-tolerant species (e.g., D. thomasi, D. longiremis, and B. longirostris) that remained in the hypolimnion may have found refuge in hypoxic areas with DO N1.0 mg l−1, although fish were occasionally observed making feeding excursions into hypoxic waters.

VANDERPLOEG, H.A., S.A. Ludsin, S.A. RUBERG, T.O. Hook, S.A. POTHOVEN, S.B. Brandt, G.A. LANG, J.R. LIEBIG, and J.F. CAVALETTO. Hypoxia affects spatial distributions and overlap of pelagic fish, zooplankton, and phytoplankton in Lake Erie. Journal of Experimental Marine Biology and Ecology 381:S92-S107 (2009).

Bottom hypoxia has reemerged as a prominent feature of Lake Erie's central basin during late summer. Similar to coastal and marine systems, the influence of hypoxia on pelagic organisms remains largely enigmatic in Lake Erie. During 2005, we used a plankton survey system (a sensor package consisting of an optical plankton counter, fluorometer, dissolved oxygen sensor, light sensor, and conductivity–temperature–depth sensor), coupled with a fish hydroacoustics system, to explore how the distribution of phytoplankton (chlorophyll), mesozooplankton, and fish varied vertically and horizontally in relation to oxygen concentrations. To do so, we conducted surveys of the entire water column on a continuous basis during mild (August) and severe (September) hypoxia. Our surveys included two sampling designs: 1) basin-wide transects sampled during day and night to define broad-scale patterns of spatial overlap among pelagic organisms; and 2) shorter (5 km) transects sampled every 4 h over a 24-h period to explore how diel vertical migration and hypoxia interact to affect time-specific spatial overlap among fishes, mesozooplankton, and phytoplankton. Our findings indicated that fish avoided regions of the hypolimnion with dissolved oxygen concentrations > 3 mg l−1 by 1) moving horizontally into areas with higher oxygen, or 2) moving vertically into the metalimnion, where a sharp thermocline and oxycline existed. A portion of the mesozooplankton continued to use the hypoxic hypolimnion as a refuge from fish predation during daytime at oxygen concentrations between 1 and 3 mg l−1; however, there was usually a mesozooplankton maximum in the metalimnion, even when fish were compressed into this region. Prior to development of hypoxia, the metalimnion in some areas may have served as thermal refuge from predation from the epilimnetic planktivore, the emerald shiner, and the hypolimnetic planktivore–benthivore, the rainbow smelt. Overall, the horizontal compression of fish into less hypoxic regions in the deep area of the central basin followed by vertical compression into the metalimnion as hypoxia developed further may have led to local reduction of mesozooplankton prey in these regions. Herein, we discuss the potential implications of these hypoxia-induced impacts for understanding foodweb interactions and fisheries management.

WANG, H.-Y., and T.O. HÖÖK. Eco-genetic model to explore fishing-induced ecological and evolutionary effects on growth and maturation schedules. Evolutionary Applications 438-455 (2009).

Eco-genetic individual-based models involve tracking the ecological dynamics of simulated individual organisms that are in part characterized by heritable parameters. We developed an eco-genetic individual-based model to explore ecological and evolutionary interactions of fish growth and maturation schedules. Our model is flexible and allows for exploration of the effects of heritable growth rates (based on von Bertalanffy and biphasic growth patterns), heritable maturation schedules (based on maturation reaction norm concepts), or both on individual- and population-level traits. In baseline simulations with rather simple ecological trade-offs and over a relatively short time period (<200 simulation years), simulated male and female fish evolve differential genetic growth and maturation. Further, resulting patterns of genetically determined growth and maturation are influenced by mortality rate and density-dependent processes, and maturation and growth parameters interact to mediate the evolution of one another. Subsequent to baseline simulations, we conducted experimental simulations to mimic fisheries harvest with two size-limits (targeting large or small fish), an array of fishing mortality rates, and assuming a deterministic or stochastic environment. Our results suggest that fishing with either size-limit may induce considerable changes in life-history trait expression (maturation schedules and growth rates), recruitment, and population abundance and structure. However, targeting large fish would cause more adverse genetic effects and may lead to a population less resilient to environmental stochasticity.

WANG, H.-Y., H.A. Cook, D.W. Einhouse, D.G. Fielder, K.A Kayle, L.G. Rudstam, and T.O. Hook. Maturation schedules of walleye populations in the Great Lakes region: Comparison of maturation indices and evaluation of sampling-induced biases. North American Journal of Fisheries Management 29:1540-1554 (2009).

Maturation schedules, key determinants of fish stocks’ harvest potential and population dynamics, are influenced by both plastic and adaptive processes. Various indices are used to describe maturation schedules, and these have differential advantages for discriminating between plastic and adaptive processes. However, potential sampling-related biases associated with different maturation indices have not been fully evaluated. We analyzed three maturation indices for walleyes Sander vitreus in Lake Erie; Saginaw Bay, Lake Huron; and Oneida Lake, New York: age and length at 50% maturity, midpoint of age-specific maturity ogives (age-specific length at which probability of maturity ¼ 0.50), and midpoints of probabilistic maturation reaction norms (PMRNs; age-specific length at which probability of maturing in the following year ¼ 0.50). We then compared estimated maturation indices to evaluate sensitivity of different maturation indices to sampling-induced biases and to assess the relative importance of plastic versus adaptive processes in structuring interstock and temporal variation in maturation schedules. Our findings suggest that although small changes in sampling month, gear, and agency-related effects can bias estimates of age and length at 50% maturity and midpoints of maturity ogives, PMRN estimates appear to be robust to these biases. Furthermore, PMRN estimates are suggestive of potential adaptive variation in maturation schedules among walleye stocks and over time. For instance, Oneida Lake walleyes (which had relatively slow growth and low mortality rates) matured at a smaller size for a given age (smaller midpoints of PMRNs) than the other stocks. Temporally, walleyes in the western basin of Lake Erie matured at a larger size in recent years, as evidenced by increasing midpoints of PMRNs (1978–1989 versus 1990–2006 for Ohio Department of Natural Resources data and 1990–1996 versus 1997–2006 for Ontario Ministry of Natural Resources data). Our study highlights the necessity of monitoring maturation schedules via multiple maturation indices and the need to account for sampling-induced biases when comparing maturation schedules.

WANG, J., H. HU, K. Mizobata, and S. Saitoh. Seasonal variations of sea ice and ocean circulation in the Bering Sea: A model-data fusion study. Journal of Geophysical Research 114(C02011, doi:10.1029/2008JC004727):24 pp. (2009).

A 9-km coupled ice-ocean model (CIOM) was implemented in the entire Bering Sea to investigate seasonal cycles of sea ice and ocean circulation under atmospheric forcing. Sea ice cover with a maximum of 0.6 x 106 km2 in February to late March was reasonably reproduced by the Bering-CIOM and validated by Special Sensor Microwave/Imager (SSM/I) measurements. The model also captures some important spatial variability and downscaling processes such as polynyas and ridging, which the SSM/I measurements cannot reproduce because of their coarse (25 km) resolution. There are two distinct surface ocean circulation patterns in winter and summer on the Bering shelves because of the dominant winds, which are northeasterly in winter and southwesterly in summer. Summer low-temperature, high-salinity water mass (<3 oC) on the Bering shelf is formed locally during winter because of strong vertical convection caused by salt injection when ice forms, wind, and wind-wave mixing on the shelf. The northward volume transport across the 62.5 oN line, with an annual mean of 0.8 ± 0.33 Sv (1 Sv = 106 m3 s-1) that is consistent with the measurements in the Bering Strait, has barotropic structure, which transports heat flux (with an annual mean of 7.74 TW; 1 TW = 1012 W) northward. The Anadyr Current advects warmer, saltier water northward during summer; nevertheless, it reverses its direction to southward during winter because of predominant northeasterly and northerly wind forcing. Therefore, the Anadyr Current advects cold, salty water southward. The volume transport on the broad midshelf is northward year round, advecting heat (3.3 ± 2.4 TW) and freshwater (- 8 ± 10  x 104 practical salinity unit (psu) m3 s-1) northward. One important finding is that the Anadyr Current and the midshelf current are out of phase in volume and heat transports. The Alaskan Coastal Current also transports heat and freshwater northward on an annual basis. The Bering-CIOM also captures the winter dense water formation along the Siberian coast, which is promoted by the downwelling favorable northeasterly wind, and the summer upwelling due to the basin-scale upwelling favorable southwesterly wind, which brings up the cold, salty, and nutrient-rich water from the subsurface to the surface within a narrow strip along the west coast. This upwelling found in the model was also confirmed by satellite measurements in this study.

WANG, J., J. Zhang, E. Watanabe, M. Ikeda, K. Mizobata, J.E. Walsh, X. BAI, and B. Wu. Is the dipole anomaly a major driver to record lows in Arctic summer sea ice extent? Geophysical Research Letters 36(L05706, doi:10.1029/2008GL036706):5 pp. (2009).

Recent record lows of Arctic summer sea ice extent are found to be triggered by the Arctic atmospheric Dipole Anomaly (DA) pattern. This local, second–leading mode of sea–level pressure (SLP) anomaly in the Arctic produced a strong meridional wind anomaly that drove more sea ice out of the Arctic Ocean from the western to the eastern Arctic into the northern Atlantic during the summers of 1995, 1999, 2002, 2005, and 2007. In the 2007 summer, the DA also enhanced anomalous oceanic heat flux into the Arctic Ocean via Bering Strait, which accelerated bottom and lateral melting of sea ice and amplified the ice–albedo feedback. A coupled ice–ocean model was used to confirm the historical record lows of summer sea ice extent.

ZHANG, H., S.A. Ludsin, D.M. MASON, A.T. ADAMACK, S.B. Brandt, X. Zhang, D.G. Kimmel, M.R. Roman, and W.C. Boicourt. Hypoxia driven changes in the behavior and spatial distribution of pelagic fish and mesozooplankton in the northern Gulf of Mexico. Journal of Experimental Marine Biology and Ecology 381:S80-S91 (2009).

Hypoxia (<2 mg O2 l−1) is a major global water quality and fisheries management issue in coastal ecosystems. Although the impact of hypoxia on benthic communities has been intensively studied, less is known about hypoxia's effect on pelagic communities. Herein, we explored how hypoxia can influence the horizontal and vertical distribution of pelagic fish, as well as their overlap with mesozooplankton prey in the northern Gulf of Mexico, an area with extensive seasonal hypoxia. Using an undulating Scanfish sensor package (with CTD and optical plankton counter) towed in parallel with a split-beam acoustics system, we simultaneously collected water temperature, dissolved oxygen, salinity, mesozooplankton biomass, and relative fish biomass density data along transects (day and night) during 2003, 2004, and 2006. We used spatial analytical techniques to account for intercorrelation and spatial autocorrelation in data and to discern patterns in the distribution of pelagic organisms. We observed low fish biomass in hypoxic waters, with fish aggregating horizontally at the edges of hypoxic areas. Fish also aggregated immediately above hypoxic bottom waters, but only during years of severe hypoxia. Spatial overlap between fish biomass and mesozooplankton biomass was high during mild hypoxia, but reduced during years of severe hypoxia. Consistent with other coastal systems such as Chesapeake Bay and the Neuse River Estuary, our findings ultimately suggest that hypoxia can reduce the availability of quality habitat for zooplanktivorous fish in the northern Gulf of Mexico by reducing access to bottom habitat and mesozooplankton prey

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