Lake Erie

Larval fish were collected from nearshore sites in the west-central basin of Lake Erie from 2000 through 2002. More than 20 species of fish were identified from collections made mid-April through August. Overall fish densities were highest in 2000 and lowest in 2002. Emerald shiners were the most abundant species each year. Gizzard shad, rainbow smelt, white perch, and yellow perch were also abundant. Relative abundance of some species changed with year; rainbow smelt were most numerous in 2000 whereas clupeids were most numerous in 2000 and 2002. Thus far, water temperature and dissolved oxygen appear to follow similar trends among sites and years. However, turbidity changed drastically with year and site. Benthic invertebrate assemblages in soft substrate were primarily composed of oligochaetes, chironomids, nematodes, and clams at all sites throughout the study. Dreissenid mussels were the most abundant taxonomic group of invertebrates over hard substrate. Zooplankton differed wi...

Although the reproductive behavior of yellow perch Perca flavescens has been well documented in small systems, relatively little is known about the spawning preferences of yellow perch in large systems, such as the Laurentian Great Lakes. During 2006 and 2007, we compared the presence and abundance adult yellow perch during the spring spawning season with environmental variables in the western basin of Lake Erie. We also estimated the timing of yellow perch spawning by comparing the relative abundance of gravid and spent females collected in our trawls and then comparing the proportion of gravid females with environmental conditions at our sampling sites. Overall, the probability of catching adult yellow perch and the catch per unit effort increased with increasing bottom temperatures in the spring, whereas the probability of catching gravid females increased with increasing Secchi depth. However, the relationships between our catch metrics and environmental variables were not consistent across years, possibly as a result of the very strong 2003 year-class, which became first-year spawners in 2006. We also documented that yellow perch spawning occurred when bottom temperatures were between 11 • C and 15 • C in the western basin; these temperatures were reached on different dates in different parts of the basin and in different years. Thus, we suggest that management agencies consider basing the start of the commercial fishing season on prevailing bottom temperatures rather than using a set date across years and sites. The reproductive behaviors of yellow perch Perca flavescens and the closely related Eurasian perch P. fluviatilis have been intensively studied. In North America, yellow perch spawning occurs annually during the spring or early summer as water temperatures approach 8-10 • C (Keast 1968; Forney 1971), but considerable variation in peak spawning temperatures and spawning duration exists across the geographical range of this

Although the reproductive behavior of yellow perch Perca flavescens has been well documented in small systems, relatively little is known about the spawning preferences of yellow perch in large systems, such as the Laurentian Great Lakes. During 2006 and 2007, we compared the presence and abundance adult yellow perch during the spring spawning season with environmental variables in the western basin of Lake Erie. We also estimated the timing of yellow perch spawning by comparing the relative abundance of gravid and spent females collected in our trawls and then comparing the proportion of gravid females with environmental conditions at our sampling sites. Overall, the probability of catching adult yellow perch and the catch per unit effort increased with increasing bottom temperatures in the spring, whereas the probability of catching gravid females increased with increasing Secchi depth. However, the relationships between our catch metrics and environmental variables were not consi...

A method for projecting the water levels of the Laurentian Great Lakes under scenarios of human-caused climate change, used almost to the exclusion of other methods in the past, relies very heavily on the large basin runoff model (LBRM) as a component for determining the water budget for the lake system. This model uses near-surface air temperature as a primary predictor of evapotranspiration (ET); as in previous published work, it is shown here that the model’s very high sensitivity to temperature causes it to overestimate ET in a way that is greatly at variance with the fundamental principle of conservation of energy at the land surface. The traditional formulation is characterized here as being equivalent to having several suns in the virtual sky created by LBRM. More physically based methods show, relative to the traditional method, often astoundingly less potential ET and less ET, more runoff from the land and net basin supply for the lake basins, and higher lake water levels i...

The Coupled Hydrosphere-Atmosphere Research Model (CHARM) was developed by coupling the Regional Atmospheric Modeling System (RAMS) to models of the land hydrology of the Great Lakes basin and of the evaporation and thermodynamics of the Great Lakes. It is intended for running coupled atmosphere-surface climate scenarios for the Great Lakes basin, to gain a perspective that has been missed by running hydrologic models in off-line mode, driven by the output of global general circulation models. This paper presents validation of this model using historical atmospheric data to drive the regional embedded CHARM model. The current version of CHARM simulates the nearsurface air temperature in the region quite well, with some positive bias during the winter and negative bias during the summer. Biases in the temperature averaged over 1 month and over the portion of the domain that is not directly forced by observations are less than or approximately 2 K. The annual precipitation has a positive bias of 6.6% and does well at placing the lake-effect precipitation areas, but may have too strong a west-east gradient. Simulation of annually averaged runoff meets well with expectations, but additional empirical fitting may be required to replicate the seasonal cycle. Aspects of the model that remain troublesome are the tendency for unrealistically low pressure at mean sea level and for persistent heavy low stratus clouds.

I examined the forage base of Henderson Lake, Ontario following collapse of its walleye stock due to overexploitation, and an inexplicable decline of the ninespine stickleback population. In response to these events a very large yellow perch year class was produced. Subsequently, adult perch density increased while growth, mortality, size at maturity and fecundity decreased. Continued stunting in young yellow perch could not be attributed to direct interspecific competition with abundant shiners. As northern pike activity increased shiner activity declined but yellow perch remained active and available as prey. Thus, small perch occurred much more frequently in the diets of northern pike than did shiners. The large numbers of stunted yellow perch may provide excellent forage for enhancing the recovery of the walleye population

Preserving avian flyway connectivity has long been challenged by our capacity to meaningfully quantify continental habitat dynamics and bird movements at temporal and spatial scales underlying long‐distance migrations. Waterbirds migrating hundreds or thousands of kilometers depend on networks of wetland stopover sites to rest and refuel. Entire populations may rely on discrete wetland habitats, particularly in arid landscapes where the loss of limited stopover options can have disproportionately high impacts on migratory cost. Here, we examine flyway connectivity in water‐limited ecosystems of western North America using 108 GPS tagged greater sandhill cranes. Bird movements were used to reconstruct wetland stopover networks across three geographically unique sub‐populations spanning 12 U.S.–Mexican states and Canadian provinces. Networks were monitored with remote sensing to identify long‐term (1988–2019) trends in wetland and agricultural resources supporting migration and evalua...

In semi‐arid ecosystems, timing and availability of water is a key uncertainty associated with conservation planning for wetland‐dependent wildlife. Wetlands compose only 1–3% of these landscapes; however, large populations of migratory waterbirds rely on these wetlands to support energetically demanding life history events such as breeding and migration. Migration is considered a crucial period for birds associated with individual survival and reproductive success, yet our understanding of migration ecology remains limited. To better inform conservation planning supportive of these demands, we quantified synchrony of wetland flooding and waterbird migration by reconstructing bi‐monthly surface water patterns from 1984 to 2015 across 11.4 million ha of the semi‐arid Great Basin, USA. Results were then linked to seasonal migration chronologies for seven dabbling ducks species. Seasonal patterns were used in landscape planning simulations to assess efficiency in conservation strategie...

Lake Erie is the fourth largest, in surface area, of the Great Lakes. Seiching events in the lake have in the past led to breaches of the flood wall in Buffalo (at the eastern end of the lake), causing loss of life, and significant loss to properties. Here, we analyze the potential of Lake Erie for generating electricity from its storm surge, seiching, and wave energy resources. We find that there is significant potential energy in the lake that may be suitable for generating meaningful levels of electricity from seiches and storm surge; for instance, by developing an artificial 'lagoon'. It is shown that an extreme surge event similar to that of January 30, 2008 which generated a surge of approximately +3 m at the eastern end and a corresponding set-down of nearly -2.7 m at the western end of Lake Erie, could contain a total theoretical potential energy of approximately 5×10 7 kWh. If such energy could, practically, be harnessed using a surge lagoon with a surface area of 2 km 2 near Buffalo, the potential energy would be 2.3×10 4 kWh, enough energy to power the equivalent of 40 homes for an entire month. The cost of such a lagoon could be partially offset by the potential of such a structure, and the operation of such a lagoon, to help alleviate flooding during extreme events. Furthermore, as an example, the analysis of the lake-wide wave data for 2011 shows that the monthly mean wave power is greater in the central and eastern basins of Lake Erie. Wave power was highest in October and November when the monthly mean wave power reached 10 kW/m. In contrast to most oceanographic environments, the wave power resource is reduced in winter, mostly due to the presence of surface ice in the lake. The surface ice appears to significantly reduce wave height and power during winter months, resulting in a relatively low annual mean wave power. However, the monthly mean wave power was the lowest in late spring and during summer when the monthly mean wave power was around 2.5 kW/m. Although this study represents the first attempt to assess the marine renewable energy of Lake Erie, further research is necessary to examine the feasibility of energy extraction in the lake.

Lake Erie is the fourth largest, in surface area, of the Great Lakes. Seiching events in the lake have in the past led to breaches of the flood wall in Buffalo (at the eastern end of the lake), causing loss of life, and significant loss to properties. Here, we analyze the potential of Lake Erie for generating electricity from its storm surge, seiching, and wave energy resources. We find that there is significant potential energy in the lake that may be suitable for generating meaningful levels of electricity from seiches and storm surge; for instance, by developing an artificial 'lagoon'. It is shown that an extreme surge event similar to that of January 30, 2008 which generated a surge of approximately +3 m at the eastern end and a corresponding set-down of nearly -2.7 m at the western end of Lake Erie, could contain a total theoretical potential energy of approximately 5×10 7 kWh. If such energy could, practically, be harnessed using a surge lagoon with a surface area of 2 km 2 near Buffalo, the potential energy would be 2.3×10 4 kWh, enough energy to power the equivalent of 40 homes for an entire month. The cost of such a lagoon could be partially offset by the potential of such a structure, and the operation of such a lagoon, to help alleviate flooding during extreme events. Furthermore, as an example, the analysis of the lake-wide wave data for 2011 shows that the monthly mean wave power is greater in the central and eastern basins of Lake Erie. Wave power was highest in October and November when the monthly mean wave power reached 10 kW/m. In contrast to most oceanographic environments, the wave power resource is reduced in winter, mostly due to the presence of surface ice in the lake. The surface ice appears to significantly reduce wave height and power during winter months, resulting in a relatively low annual mean wave power. However, the monthly mean wave power was the lowest in late spring and during summer when the monthly mean wave power was around 2.5 kW/m. Although this study represents the first attempt to assess the marine renewable energy of Lake Erie, further research is necessary to examine the feasibility of energy extraction in the lake.

The emerging microbial source tracking (MST) methodologies aim to identify fecal contamination originating from domestic and wild animals, and from humans. Avian MST is especially challenging, primarily because the Aves class includes both domesticated and wild species with highly diverse habitats and dietary characteristics. The quest for specific fecal bacterial MST markers can be difficult with respect to attaining sufficient assay sensitivity and specificity. The present study utilizes high throughput sequencing (HTS) to screen bacterial 16S rRNA genes from fecal samples collected from both domestic and wild avian species. Operational taxonomic unit (OTU) analysis was then performed, from which sequences were retained for downstream quantitative polymerase chain reaction (qPCR) marker development. Identification of unique avian host DNA sequences, absent in non-avian hosts, was then carried out using a dedicated database of bacterial 16S rRNA gene taken from the Ribosomal Database Project. Six qPCR assays were developed targeting the 16S rRNA gene of Lactobacillus, Gallibacterium, Firmicutes, Fusobacteriaceae, and other bacteria. Two assays (Av4143 and Av163) identified most of the avian fecal samples and demonstrated sensitivity values of 91 and 70%, respectively. The Av43 assay only identified droppings from battery hens and poultry, whereas each of the other three assays (Av24, Av13, and Av216) identified waterfowl species with lower sensitivities values. The development of an MST assay-panel, which includes both domestic and wild avian species, expands the currently known MST analysis capabilities for decoding fecal contamination.

Information concerning turtle bycatch and its possible ramifications during biological sampling in freshwater systems is limited. Having such information will enable fisheries researchers and managers to modify fish sampling procedures to potentially minimize any impacts on turtle populations. Therefore, our objective was to utilize reflex response to characterize stress and mortality of western painted turtles (Chrysemys picta bellii) captured as bycatch in modified fyke nets during fish population assessments. Reflex-response-based condition classification (i.e. good, poor, unresponsive) data were collected from May to September during fish population assessments in 38 lakes and seven impoundments in northeast South Dakota from 2012 to 2014. We evaluated the relationship between observed condition and water temperature during two time periods, by turtle gender and size. Turtle bycatch mortality was assessed from June to September during fish population assessments in 14 lakes and three impoundments during 2013 and 2014. Delayed (i.e. overnight) mortality was determined for poor and unresponsive condition classifications and the relationship between observed mortality and water temperature for two time periods, by turtle gender and size was evaluated. Turtle condition decreased as water temperature increased. Condition was poorer during the May and June time period than August and September. Female turtles were in significantly worse condition than males. Condition was not related to turtle size. We observed varying mortality rates across condition classifications and the total estimated delayed mortality rate of known sex turtles was 36.4%. Mortality increased as temperature increased. Delayed mortality rates varied between the two sampling periods with higher mortality rates during the May and June time period. Female turtles had higher mortality rates than males. Delayed mortality did not vary by turtle size. Understanding the negative effects on bycatch during biological sampling is important to provide justification for the development and implementation of measures to protect non-target species.

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One of the most threatened remaining populations of lake sturgeon in the Great Lakes is found in the connecting channels between Lake Huron and Lake Erie. Only two spawning grounds are presently known to be active in this region, and both are in the St. Clair River. The spawning reef in the St. Clair River delta has been recently colonized by round gobies (Neogobius melanostomus) in densities up to 25/m 2 , raising concerns regarding predation on the benthic-oriented eggs and larvae of the sturgeon. Investigations in 1998Investigations in -1999 showed that while round goby predation does occur, a number of other factors may be equally affecting sturgeon spawning success, including few spawning adults (< 60), suspected poaching pressure, low retention rate of eggs on the reef, low hatch rate (~0.5%), the presence of organic contaminants, and predation from native and exotic invertebrates and fish. Overall, we estimate that less than 1% of the eggs deposited during a spawning run survive to hatch. We were able to increase the egg hatch rate to 16% by placing eggs in predator-exclusion chambers on the reef. The fate of the larvae is uncertain. Two weeks after hatching, no larvae were found on the reef. We were unable to find them anywhere else in the river, nor was predation on larvae noted in either year. There were factors other than predation affecting larval survival in 1999. There was a higher silt load on the reef than in 1998 and large numbers of dead larvae were found. Recruitment success from this site could be improved by utilizing techniques to increase the number of eggs on the reef, such as reducing the illegal take of adult fish and by placing eggs in predator-exclusion chambers to increase hatch rate.

Levels of chlorinated organic contaminants in predator fish have been monitored annually in each of the Great Lakes since the 1970s. This article updates earlier reports with data from 1991 to 1998 for lake trout (Salvelinus namaycush) and (Lake Erie only) walleye (Sander vitreus) to provide a record that now extends nearly 30 years. Whole fish were analyzed for a number of industrial contaminants and pesticides, including polychlorinated biphenyls (PCBs), dichloro-diphenyl-trichloroethane (DDT), dieldrin, toxaphene, and mirex, and contaminant trends were quantified using multicompartment models. As in the past, fish from Lakes Michigan, Ontario, and Huron have the highest levels of PCBs, DDT, and dieldrin; Superior has the highest levels of toxaphene; and Ontario has the highest levels of mirex. In the period after curtailment of chemical use, concentrations rapidly decreased, represented by relatively short half-lives from approximately 1 to 9 years. Although trends depend on both the contaminant and the lake, in many cases the rate of decline has been decreasing, and concentrations are gradually approaching an irreducible concentration. For dioxin-like PCBs, levels have not been decreasing during the most recent 5-year period (1994 to 1998). In some cases, the year-to-year variation in contaminant levels is large, mainly because of food-web dynamics. Although this variation sometimes obscures long-term trends, the general pattern of a rapid decrease followed by slowing or leveling-off of the downward trend seems consistent across the Great Lakes, and future improvements of the magnitude seen in the 1970s and early 1980s likely will take much longer.

Together, lake ecosystems and local human activity form complex social-ecological systems (SESs) characterized by feedback loops and discontinuous change. Researchers in diverse fields have suggested that complex systems do not have single stable equilibria in the long term because of inevitable perturbation. During this study, we sought to address the general question of whether or not stable socialecological equilibria exist in highly stressed and managed lacustrine systems. Using an integrated humanbiophysical model, we investigated the impacts of a species invasion and ecosystem restoration on SES equilibrium, defined here as a compromise in phosphorus management among opposing stakeholders, in western Lake Erie. Our integrated model is composed of a calibrated ecological submodel representing Sandusky Bay, and a phosphorus management submodel that reflects the societal benefits and costs of phosphorus regulation. These two submodels together form a dynamic feedback loop that includes freshwater ecology, ecosystem services, and phosphorus management. We found that the invasion of dreissenid mussels decreased ecosystem resistance to eutrophication, necessitating increased phosphorus management to preserve ecosystem services and thus creating the potential for a shift in social-ecological equilibrium. Additionally, our results suggest that net benefits in the region following the invasion of dreissenids may never again reach the pre-invasion level if on-site phosphorus control is the sole management lever. Further demonstrating transient system stability, large-scale wetland restoration shifted points of management compromise to states characterized by less on-site phosphorus management and higher environmental quality, resulting in a significant increase in net benefits in the region. We conclude that lacustrine SESs are open and dynamic, and we recommend that future models of these systems emphasize site-specific perturbation over equilibrium, thereby aiding the development of management plans for building system resistance to undesirable change that are both flexible and sustainable in an unknowable future.

In response to degraded water quality, federal policy makers in the US and Canada called for a 40% reduction in phosphorus (P) loads to Lake Erie, and state and provincial policy makers in the Great Lakes region set a load‐reduction target for the year 2025. Here, we configured five separate SWAT (US Department of Agriculture&#39;s Soil and Water Assessment Tool) models to assess load reduction strategies for the agriculturally dominated Maumee River watershed, the largest P source contributing to toxic algal blooms in Lake Erie. Although several potential pathways may achieve the target loads, our results show that any successful pathway will require large‐scale implementation of multiple practices. For example, one successful pathway involved targeting 50% of row cropland that has the highest P loss in the watershed with a combination of three practices: subsurface application of P fertilizers, planting cereal rye as a winter cover crop, and installing buffer strips. Achieving the...

Military lands and waters may be particularly valuable for migrating birds requiring stopover habitat to rest and refuel en route to very distant seasonal ranges. Recent developments in radar technology have provided powerful tools for investigating on a broad scale migrant use of military installations; thus providing an opportunity to improve both conservation and flight safety measures. In this study, spring and fall migrant use of 40 military installations across the United States were qualitatively investigated. These times of year were selected since they are the periods when BASH is of most concern. Migratory patterns on three installations (Eglin Air Force Base, FL; Ft. Polk, LA; and Yuma Proving Ground, AZ) were then closely examined and migration forecast models for those locations were developed with the goal of providing a tool for reducing the probability of collisions between birds and military aircraft. A comparison was also made between radar estimates of migrant densities aloft during exodus events and more traditional ground-based surveys to evaluate the effectiveness of estimating migrant abundance in stopover habitat with radar data. At Fort Polk, movement ecology and migrant-habitat relations of the Red-eyed Vireo were investigated during migratory stopover. Lastly, migrant use of diverse riparian habitats was compared along water courses near the Yuma Proving Ground. Results indicated that approximately half of the installations examined with radar data contained migrant stopover "hotspots," reaffirming the fact that military installations are important to migrating birds. Interestingly, migrant abundances, and species turnover as estimated by ground-based surveys, were found to poorly reflect migrant densities estimated with radar data. Migrant abundance, species richness, and community composition were all also found to be influenced by riparian vegetation composition. This information collectively suggested that radar data can be used to identify migratory hotspots on military installations and improve flight safety on installations with an aviation mission. However, radar data may not be sufficient to distinguish fine-scale differences in habitat use by migrants within an installation's boundaries. The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.

eDNA appears well positioned to play a significant role in the future of biomonitoring, and the need to assess the efficacy of eDNA-based surveys in a variety of habitats is increasing. We conducted an eDNA metabarcoding-based survey of fish communities in the Great Smoky Mountains National Park (GSMNP), located in eastern Tennessee and western North Carolina. The GSMNP, widely recognized as a biodiversity hotspot, encompasses 211,419 hectares of the Southern Appalachian Mountains with elevations up to 2205 meters and is home to approximately 73 species of fish, including 12 families and three species classified as endangered or threatened. We collected 50 water samples in first to sixth order streams at elevations of 336 to 1462 meters, including all major watersheds found in the park. eDNA was amplified utilizing two primer sets which each target differing regions of the 12S mitochondrial gene and generate amplicons of varying size (97 and 225 bp, respectively), and sequencing was conducted to an expected read depth of 400,000 reads per sample per marker. We detected a total of 40 fish species; of these, 36 were detected with the primer set which produces a 97 bp amplicon, and 12 of these 36 were detected only by this primer set. Species assemblages varied between stream orders, and species richness decreased with increasing elevation and increased with increasing stream order. Significant correlations were observed between biomass data from electrofishing monitoring (1984-2023) and eDNA metabarcoding read counts in five of seven species examined, including all salmonids. eDNA metabarcoding was demonstrated to be effective in assessing fish communities in high-elevation lotic systems in the Southern Appalachians, and our results suggest that primers targeting shorter amplicons may exhibit greater efficacy in these ecosystems.

One of the most distinctive aspects of the Connecticut College Arboretum has been our focus on the importance of long-term ecological research. Detailed studies of natural vegetation and bird communities began shortly after the establishment of the Bolleswood Natural Area in 1952. Since that time teams of faculty and students have documented the changes in these natural communities, and have shared the information generated from their studies in both technical and popular publications. The Arboretum Bulletin series has often served as a vehicle for disseminating Connecticut College original research to the general public, and the present edition is an excellent example of how to make scientific information accessible to a broad audience. The Arboretum map that is located in the center of this bulletin is the most accurate version we have ever produced. Generated in the College's Geographic Information Systems Lab, it details the wetlands, watercourses, topography, trails and stone walls with great clarity. This map was customized for this publication, and other digital and printable versions are available on the Arboretum website.

Burrowing mayflies (Hexagenia limbata and H. rigida) recolonized sediments of the western basin of Lake Erie in the 1990s following decades of pollution abatement. We predicted that Hexagenia would also disperse eastward or expand from existing localized populations and colonize large regions of the other basins. We sampled zoobenthos in parts of the western and central basins yearly from 1997-2005, along the north shore of the eastern basin in 2001-2002, and throughout the lake in 2004. In the island area of the western basin, Hexagenia was present at densities ≤ 1,278 nymphs/m 2 and exhibited higher densities in odd years than even years. By contrast, Hexagenia became more widespread in the central basin from 1997-2000 at densities ≤ 48 nymphs/m 2 but was mostly absent from 2001-2005. Nymphs were found along an eastern basin transect at densities ≤ 382/m 2 in 2001 and 2002. During the 2004 lake-wide survey, Hexagenia was found at 63 of 89 stations situated throughout the western basin (≤ 1,636 nymphs/m 2 , mean = 195 nymphs/m 2 , SE = 32, N = 89) but at only 7 of 112 central basin stations, all near the western edge of the basin (≤ 708 nymphs/m 2 ), and was not found in the eastern basin. Hexagenia was found at 2 of 62 stations (≤ 91 nymphs/m 2 ) in harbors, marinas, and tributaries along the south shore of the central basin in 2005. Oxygen depletion at the sediment-water interface and cool temperatures in the hypolimnion are probably the primary factors preventing successful establishment throughout much of the central basin. Hexagenia can be a useful indicator of lake quality where its distribution and abundance are limited by anthropogenic causes.

There are some locations in Lake Erie where, despite the presence of suitable habitat, mayfly (Hexagenia) nymphal density is low or absent, and midge (Chironomidae) larval density is high. We conducted laboratory experiments to determine if biotic interactions account for this spatial distribution. In the first experiment, we measured the effect of Hexagenia (0, 256, 512, 768, 1,024 nymphs m -2 ) and Chironomus (5,120, 2,560, 1,280, 640, 0 larvae m -2 ) density on survivorship and increase in body length of newly-hatched and large Hexagenia nymphs. Results did not suggest competition for space. Since the outcome of competition may be influenced by order of establishment, we tested temporal overlap by adding Chironomus larvae to containers with Hexagenia nymphs at different stages in their development and vice versa (experiment 2). Newly-hatched mayflies showed the smallest increase in body length after being exposed to midges after 0 and 10 days, but exhibited no significant difference from the control after 20, 40, and 60 days of exposure to midges. In experiment 3, we tested if Hexagenia or Chironomus larvae ate mayfly eggs. Chironomus larvae significantly reduced the number of Hexagenia eggs at densities examined and we speculate that the reduction occurred because of egg consumption. In contrast, the number of eggs remaining in the presence of a Hexagenia nymph did not differ significantly from the control. We confirmed that midges were present in Lake Erie sediments when Hexagenia oviposit. These findings suggest that tube-dwelling Chironomus larvae may contribute to the inability of Hexagenia to become established in certain locations in western Lake Erie.

Burrowing and ventilation activities of benthic invertebrates can influence water column turbidity, nutrient concentrations, and possibly oxygen balance of lakewide ecosystems. In laboratory experiments, we determined rates of bioturbation-induced suspension of fine Lake Erie sediments caused by the burrowing mayfly Hexagenia of various sizes (lengths 13-28 mm) and multiple densities (70-1,111 larvae/m 2 ) and water temperatures (10-25°C). Larvae were inoculated into 2-L jars containing Lake Erie sediment and water. Bioturbation and sediment settling rates were independently estimated from sediment concentrations in water, measured twice daily for 14-18 d. Nonlinear regression was used to estimate sediment suspension rate for each jar (flux, mg/L/h). Logarithmic transformations of size, density, and temperature best described sediment flux. Separate experiments demonstrated that flux was unaffected by sediment depth, but did vary by sediment type, which was related to location from which Lake Erie sediment had been collected. Sediment suspension rates increased as food became depleted. Sediment suspension by pre-emergent (25 mm long) larvae at densities and water temperature typical for late spring in western Lake Erie (400 larvae/m 2 at 22°C) averaged 12 g/m 2 /h. Although this level of bioturbation by Hexagenia larvae in western Lake Erie likely contributes only a small fraction of the basinwide annual sediment load, sediment suspension is possibly an important epibenthic source of nutrients and sediment-associated contaminants during spring. Such concentrations would exceed the clearance capacity of dreissenid mussels and may partially explain why dreissenids have not become abundant in soft sediments of the western basin.

Identification and Distribution of Various Species of Adult Odonata at Brookhaven National Laboratory. MEGAN C. DYER (University of Rhode Island, Kingston, RI, 02881) DR. TIMOTHY M. GREEN (Brookhaven National Laboratory, Upton, NY 11973). There are about 5,500 odonate species (dragonflies and damselflies) in the world, 164 of which can be found in the New York area. The purpose of this project was to identify and catalog the various species of dragonflies and damselflies inhabiting the wetland habitats of Brookhaven National Laboratory in Upton, New York. Specimens were collected in the field using a 15” white mesh insect net, a digital camera, chest waders, zip-lock bags, and a cooler full of ice. Specimens were identified in the lab using taxonomic keys, 20x field microscope, dissecting forceps, a refrigerator, and the Internet. There were a total of 25 species of odonates found to inhabit the ponds of the Lab, 18 dragonfly species and 7 species of damselfly. The data collected wi...

An illustrated taxonomic key is presented using structures of the chela and carapace to identify the 4 species and 2 subspecies of Cambarus, and one species of Fallicambarus known to occur in Ohio. Those forms broadly distributed throughout the state are C. (Lacunicambarus) diogenes diogenes Girard, a primary or secondary burrower; and C. (Cambarus) bartonii cavatus Hay, a secondary or tertiary burrower; the latter crayfish has not been previously recorded from the state. Species with restricted distributions are C. (C.) ortmanni Williamson, a primary or secondary burrower confined to the Ordovician region of southwestern Ohio; C. (C.) sciotensis Rhoades, a stream dweller occurring in the Scioto River, Little Scioto River, and tributaries of the Ohio River in Scioto and Lawrence counties; C. (C.) b, carinirostris Hay, a secondary or tertiary burrower frequenting streams of the Flushing Escarpment, Mahoning River, and Grand River drainages in eastern and northeastern Ohio; C. (Puncticambarus) robustus Girard, a stream inhabitant occupying primarily tributaries to Lake Erie and central and northern tributaries to the Ohio River, and F. (Creaserinus) fodiens (Cottle), a primary burrower occurring chiefly in the glaciated regions of northern Ohio. Species with broad distributions generally have a larger number of species as associates than those with restricted distributions.

The wave propagation within coastal areas is strongly influenced by the coastal morphology with its islands, bars, shoals and channels. Predominant processes in this zone are shoaling, bottom friction, breaking, refraction, wind generation and to some extent diffraction of waves. The numerical formulation of these processes in standard wave models, like HISWA (HIndcast Shallow Water WAves, TU Delft), SWAN (Simulation WAves Nearshore, TU Delft) and MIKE 21 EMS (Elliptic Mild Slope, Danish Hydraulic Institute) were tested by comparing the simulation results with measurements in a wave tank and on site measurements at the North Frisian Coast of Germany. The numerical and experimental data measured in the wave flume are in very good agreement for all applied wave models proving the numerical formulation quality of bottom friction, shoaling and breaking. A comparison of numerical simulations results with SWAN and field data shows also a quite good agreement but revealed in some cases larger differences which may be contributed to the interaction of tidal currents and waves.

Under a Canadian Foundation for Climate and Atmospheric Sciences (CFCAS) project, targeted to study the feasibility to link regional climate models with lake models, one of the tasks was to consider such a coupling in large lakes. The objective is to provide detailed information on temperature and circulation distributions of the lake to take into account the spatial variability for temperature and the heat exchange through the water's surface. The major contribution of this work is focused on realistic representation of the heat fluxes and temperature distributions to and from lakes especially during the thermally stratified ice-free periods. This paper presents the detailed 3-D ELCOM model applied in Lake Erie in order to produce, at the surface layer of the lake, the spatial distribution of temperature and heat exchanges that eventually can be coupled with a regional climate model (CRCM). Preliminary results will be presented on how this lake model may improve the regional climate models, which currently do not consider such large lake circulation effects.

Lake Erie has experienced dramatic changes in water quality over the past several decades requiring extensive monitoring to assess effectiveness of adaptive management strategies. Remote sensing offers a unique potential to provide synoptic monitoring at daily time scales complementing in-situ sampling activities occurring in Lake Erie. Bio-optical remote sensing algorithms require knowledge about the inherent optical properties (IOPs) of the water for parameterization to produce robust water quality products. This study reports new IOP and apparent optical property (AOP) datasets for western Lake Erie that encapsulate the May-October period for 2015 and 2016 at weekly sampling intervals. Previously reported IOP and AOP observations have been temporally limited and have not assessed statistical differences between IOPs over spatial and temporal gradients. The objective of this study is to assess trends in IOPs over variable spatial and temporal scales. Large spatio-temporal variability in IOPs was observed between 2015 and 2016 likely due to the difference in the extent and duration of mid-summer cyanobacteria blooms. Differences in the seasonal trends of the specific phytoplankton absorption coefficient between 2015 and 2016 suggest differing algal assemblages between the years. Other IOP variables, including chromophoric, dissolved organic matter (CDOM) and beam attenuation spectral slopes, suggest variability is influenced by river discharge and sediment re-suspension. The datasets presented in this study show how these IOPs and AOPs change over a season and between years, and are useful in advancing the applicability and robustness of remote sensing methods to retrieve water quality information in western Lake Erie.

Microplastic pollution is becoming a fast growing problem in our environment. Our society is highly dependent on plastic products; from large industrial goods to the smallest plastic bags one gets from the stores, can all be potential hazards to the environment if they are not disposed properly. These products are not being recycled properly and they are polluting different water bodies and also other natural environments. Microplastic pollution can be highly catastrophic to the aquatic organisms because of the known potential to adsorb persistent organic pollutants, POPs, which can affect the human race. The problem is not being emphasized as it should be compared to its disastrous impact. The objective of this research is to provide an assessment of the pollution caused by microplastic debris in the Great Lakes waters by adsorption of toxic compounds. The preliminary results presented are from 44 samples from surface water (33 samples) and sediments (11 samples) collected from May to August, 2014. The plastic debris collected was classified by color, size, and chemical composition of the synthetic polymer.

Lake Erie is a classic case of development, recovery from, and return to eutrophication, hypoxia, and harmful algal blooms. Forecast models are used annually to predict bloom intensity for the whole Western Lake Erie Basin, but do not necessarily reflect nearshore conditions or regional variations, which are important for local stakeholders. In this study we: 1) developed relationships between observed whole basin and nearshore bloom sizes, and 2) updated and extended a Bayesian seasonal bloom forecast model to provide new regional predictions. The western basin was subdivided into 5 km near-shore regions, and bloom start date, size, and intensity were quantified with MODIS-derived images of chlorophyll concentrations for July-October 2002-2016 for each subdivision and for the entire basin. While bloom severity within each subdivision is temporally and spatially unique, it increased over the study period in each subdivision. The models for the 5 km subdivisions explained between 83 and 95% of variability between regional sizes and whole bloom size for US subdivisions and 51% for the Canadian subdivision. By linking predictive basin-wide models to regional regression estimates, we are now able to better predict potential bloom impacts at scales and in specific areas that are vital to the economic well-being of the region and allow for better management responses.

Implementation Strategies on Phosphorus Reduction. One of the major sources of water quality degradation is the excessive use of nutrients in agriculture, which could lead to eutrophication of freshwater resources. Meanwhile, implementation of wetlands has been proven as an effective approach for mitigating the impacts of excessive nutrients. However, to have an efficient water quality management at the watershed scale, site selection for wetland implementation is a key factor. In this study, three conventional and two pseudo-random targeting scenarios are investigated. The Soil and Water Assessment Tool (SWAT), a watershed model is coupled with Urban Stormwater Treatment and Analysis Integration (SUSTAIN) to study the impacts of wetland implementation scenarios on the Saginaw River watershed, located in Michigan. The results showed that the similarity between these targeting scenarios increases with the implementation area. The conventional method that is based on phosphorus load generated per unit area at the subwatershed scale, on average, performed better. However, considering the total area of the implemented wetlands, another conventional method based on the long-term impacts of the wetland had better performance. In all cases, the climate impact was the major factor affecting the wetland performance.

Hepatic butyltin concentrations were determined in 63 cetaceans belonging to 14 species and four pinnipeds belonging to two species collected from North Pacific and Asian coastal waters. Butyltin compounds (BTs) including tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) were detected in almost all the liver samples suggestive of its worldwide distribution. The elevated residues detected in coastal species and low concentrations found in off-shore species indicate a high degree of butyltin contamination in coastal waters than in the open sea. Mammals inhabiting waters of developed nations were found to contain higher BT concentrations compared with those collected from the waters proximal to developing countries. These observations strongly suggest serious BT contamination in the waters of developed countries than in developing nations at present. Among the samples collected off Japanese coastal waters, lower BT concentrations were found in pinnipeds compared with the cetaceans, suggestive of a possible difference in degradation capacities and excretory moulting between these two groups of animals. The estimated concentration ratio of BT in the liver of killer whale fetus to its pregnant mother was relatively low (0.015), indicative that transplacental transfer of BTs from the mother to her fetus is a deal less. Among the BT breakdown products, DBT was predominant in most of the liver samples analyzed, followed by TBT and MBT.

Brown bullheads (Ameiurus nebulosus) are known to hybridize naturally with closely related black (Ameiurus melas) and yellow bullhead (Ameiurus natalis) species. The presence of hybrid specimens may obscure accurate ecological and toxicological studies, which may in turn influence evaluations of aquatic ecosystem health. Thus, there is a need for a reliable method to detect introgression in bullheads from tissue samples collected in the field. Specimens from each bullhead species were identified using taxonomic keys and descriptions of morphological characteristics. The morphological identifications were compared with molecular characters from a 431 bp of mtDNA control region sequences. The results identified a single possible A. melas × A. nebulosus hybrid individual out of 11 fish identified as having A. nebulosus morphology from Presque Isle Bay, Erie, PA. Four additional fish revealed possible gene introgression from A. melas to A. nebulosus. We suggest that future studies making toxicological and ecological comparisons examine possible introgression within the bioindicator population.

Fish and Wildlife Service U.S. Department of the Interior ^Sf^ÜTIÖ¥^TATEjgNT_Ä Approved for public release; . Distribution Unlimited Als Js.oiißaOf. the;fiijst reports to be published in* the new "Biological ^p|r|"||eQ^"5.;ifils gtechnical .report selves, published by the Research and Development branch of"the U.S. Fish and Wildlife Service, replaces the "FWS/OBS" series publfshecj, from 1976 to September 1984. The Bio^o §* ical Report series is designed for the rapid publication of reports with an application orientation, and it continues the focus of the FWS/OBS series on resource management issues and fish and wildlife needs. • Habitat models are designed for a wide variety of planning applications where habitat information is an important consideration in the decision process. However, it is impossible to develop a model that performs equally well in all situations. Assistance from users and researchers is an important part of the model improvement process. Each model is published individually to facilitate updating and reprinting as new information becomes available. User feedback on model performance will assist in improving habitat models for future applications. Please complete this form following application or review of the model. Feel free to include additional information that may be of use to either a model developer or model user. We also would appreciate information on model testing, modification, and application, as well as copies of modified models or test results.

Freshwater bivalves of the family Sphaeriidae (fingernail, pea, and pill clams) are difficult to survey and identify due to their small size and overlapping morphological traits. Environmental DNA (eDNA) metabarcoding offers a cost-effective method for assessing species richness and distributional patterns at large scales. We evaluated sphaeriid species richness and distribution at 15 sites in the Maumee River, Ohio, USA, based on two eDNA metabarcoding assays (broad and targeted), and we compared our results with those from a traditional benthic macroinvertebrate survey. We detected seven molecular operational taxonomic units (MOTUs) in the Maumee River, including Sphaerium transversum, five MOTUs representing Euglesa spp., and one MOTU representing Odhneripisidum sp. Sphaerium transversum was widely distributed, occurring at 10 sites, but Euglesa and Odhneripisidum were restricted to one to four sites in the upper river. Distributional patterns were broadly similar between both metabarcoding assays and benthic surveys. However, eDNA metabarcoding provided species-level identifications, resulting in higher species richness. Environmental DNA sampling augments and enhances traditional benthic surveys, but greater eDNA sample replication is needed to improve detection, and additional sphaeriid reference sequences are needed to improve species-level identification.

We examined territorial behaviors and interactions between two species of benthic clingers, nonindigenous round gobies (Neogobius melanostomus) and native mottled sculpins (Cottus bairdi). Interactions were observed for 24 h using infrared video photography in the laboratory. Trials were conducted using either a round goby or mottled sculpin resident in a shelter. An intruder (either a round goby or mottled sculpin) was added at random. Fish (fasted for 24 h before each trial) were used only once. Food (Gammarus, amphipods), maintained below satiation levels (estimated from functional feeding experiments), was used to enhance interactions. Over 24 h, amount of time spent in a refuge by a resident round goby did not change when intruders were present (round gobies or mottled sculpins). Time spent in a refuge over 24 h by a resident mottled sculpin was significantly reduced in the presence of a round goby intruder, but not in the presence of a mottled sculpin intruder. Both round gobies and mottled sculpins spent more time outside a refuge during the night than during the day. Resident round gobies and mottled sculpins spent more time in a refuge at night when a conspecific was present and even more time in the refuge when a fish of another species was introduced. The mean number of approaches, chases, and bites by resident round gobies was significantly greater than those of intruders. Mottled sculpin intruders never exhibited any aggressive behaviors (approaches, chases, bites). In cases where mottled sculpins were resident, a round goby intruder exhibited a greater number of acts (approaches, chases, bites) that were more aggressive compared to the resident sculpin (approaches). In nature, the aggressive habits of round gobies will likely result in the demise of mottled sculpins.

Lead concentrations in blood of 45 specimens of mute swan from the molting area of the Isonzo River Mouth Nature Reserve (Italy) were determined in two consecutive years (2006)(2007), some birds were neck ringed to identify their homing behavior. The second sampling included whole body X-ray radiography and Cu and Zn plasma analyses to investigate the health impact of putative Pb exposure. X-ray images of all investigated specimens did not show any radiopacity due to the ingestion of metal bodies. Lead levels (0.08-0.44 µg/ml) were in the range of those reported for swans living in unpolluted or slightly polluted environments and excluded acute intoxication, as confirmed by clinical investigation. Zinc concentrations ranged between 2.93 and 7.59 µg/ml and were one order of magnitude higher than Cu concentrations (0.21-0.42 µg/ml). The negative correlation between Pb and Zn concentrations could be indicative of adverse health effects caused by chronic lead exposure. To our knowledge this is the first study reporting Pb, Zn and Cu blood levels, X-ray radiographies and data on the origin of swan populations.

The time‐dependent flow and dispersion of suspended sediments in the western basin of Lake Erie are being studied by means of numerical models utilizing data from remote‐sensing studies and flume experiments. Mechanisms of sediment dispersion included in the models are convection and turbulent diffusion, river loading, gravitational settling, and physical resuspension and deposition at the sediment‐water interface. The time‐dependent currents are computed by means of a free surface hydrodynamic model. A wave‐hindcasting model is used to compute the wave parameters needed for estimation of shear stress generated at the sediment‐water interface under given wind conditions. The rate of sediment resuspension as a function of bottom shear stress and sediment properties is based on data from flume experiments using lake sediments. A series of numerical calculations with the models were performed on a two‐dimensional lake with a variable bottom representing a transverse cross section of La...

Recreational boating can have significant impacts on freshwater turtle individuals and populations through a variety of mechanisms, including direct injuries due to propeller strikes. We monitored the incidence of propeller wounds in four species of freshwater turtles in Dewart Lake in northern Indiana, USA, nearly annually from 1979-2014. Overall, Chrysemys picta (18.4%) had the highest frequency of propeller wounds, followed by Graptemys geographica (10.7%), and Trachemys scripta elegans (5.3%), and Chelydra serpentina (4.4%). We found little evidence for any changes in the proportion of turtles with propeller wounds over the entire study period for any of the species we examined. However, previous analyses showed an increase in propeller wounds in C. picta from 1993-2003, and our new analyses show that this was followed by a strong decrease in the proportion of C. picta with propeller injuries between the years 2002-2010 (i.e., the years after the terrorist attacks in the U.S. in 2001 and the global recession of 2008). In conclusion, our observations suggest that the frequency of propeller injuries can vary among species, with species-specific behaviors (e.g., basking, water column use) potentially driving the differences and vary over time, perhaps with economic factors that influence recreational use of lakes.

Small wetlands, despite their ecological significance, are often overlooked in biodiversity conservation. This study investigates the role of Typha angustifolia-dominated wetlands in supporting avian diversity in semi-urban landscapes. This year-long study (January-December 2024) investigated bird population in small wetland dominated by Typha angustifolia at the Biodiversity Lab of Sant Guru Ghasidas Government Post Graduate College, Kurud, Chhattisgarh, India. A total of 52 bird species from 12 orders and 30 families were recorded, with a Shannon

The concentrations of DDE, PCBs (1:1 mix of Aroclor 1254:1260), mirex, HCB, QCB, and tetrachlorobenzenes in eggs of herring gulls are presented for nine colonies in Lake Huron in 1980, as part of intensive investigations of herring gull numbers, biology, and contaminant burdens in that year. Additional data are given for seven other organochlorine contaminants at two colonies. These data are analyzed in relation to eggshell thickness, clutch size and reproductive output, and population trends at sample colonies. Levels of all contaminants measured were markedly lower than during the 1970s, and eggshells were only 6% thinner on average than during the pre-DDT era. Levels ofmost organochlorine (OC) residues were highest in eggs from Saginaw Bay, which remains one of the most heavily contaminated sites on the Great Lakes. Discriminant function analyses provided reasonably good regional, but not colony-specific, separation of eggs based on suites of OCs. Reproductive output was relatively high, and we found little evidence of impaired reproduction attributable to OC contamination or burden in 1980. Lake-wide, herring gull numbers were increasing slightly, but decreasing at colonies on the main body of Lake Huron.

Archaeological investigations of Apple Island in Orchard Lake, Oakland County, Michigan, were casually begun in the early decades of the 20th century when the owners of the centrally located Campbell family farm plowed up and then reinterred a Native American burial accompanied by a pewter bowl filled with white shell beads. 2000 and 2003 discontinuous shallow excavations conducted by local middle school students under the direction of Michael Stafford of the Cranbrook Institute of Science, yielded quantities of animal bone and a scattering of European trade goods. Stafford assigned these to a “Fur Trade” site but never fully reported on the site or its contents. In 2008 excavations supported by the Greater West Bloomfield Historical Society and the University of Detroit - Mercy, were conducted by West Bloomfield School science teachers, directed by David S. Brose. Careful stratigraphic and geomorphological analyses documented the extent of the 18th century occupation and revealed a...

Nuisance growth of the alga Cladophora, reported from Lake Ontario since the 1930s, abated in the decades following implementation of phosphorus control measures in the 1970s. Our examination of beach fouling records and historical observations of algal biomass has confirmed literature reports that a resurgence in nuisance growth of Cladophora has occurred since invasion of Great Lakes waters by dreissenids. Our findings indicate that the growth rate of Cladophora (specific rate of net photosynthesis) has decreased by 44% since 1972 in response to phosphorus controls. However, improved transparency, a response to mussel activity, has increased the maximum depth colonizable by Cladophora by a factor of 5 over that same interval. The net result is a sixfold increase in production potential since the late 1980s (the Post-P Management II Period) and a threefold increase since the 1970s (the Pre-P Management Period). Although the Cladophora resurgence has been driven by dreissenid modification of the light environment, phosphorus management remains the only alternative for reversing and ameliorating nuisance conditions. Elucidation of the nature of the Cladophora resurgence will aid decision-makers in maintaining a focus on phosphorus management as the appropriate means of remediating nuisance growth of the alga. Résumé : La nuisible prolifération de Cladophora repérée sur le Lac Ontario au moins depuis les années 1930 a visiblement diminué après la mise en place de mesures de contrôle du phosphore a `la fin des années 1970. Notre analyse des données historiques sur les plages souillées et sur la biomasse historique des algues a confirmé qu'il y a eu une résurgence de la nuisible prolifération de Cladophora sur la période qui a suivi l'invasion des Grands Lacs par les dreissenidés. Notre découverte indique que le taux net de photosynthèse en Cladophora a diminué de 44 % depuis 1972, en réponse aux réductions de concentration de phosphore. Pourtant, la meilleure transparence, une réponse aux activités des dreissenidés, a augmenté la profondeur maximum disponible pour la colonisation par Cladophora par un facteur de 5 durant le même intervalle. En résulte quasiment une augmentation de six fois du potentiel de croissance pendant les années 1980s (l'ère Post-P Management II) et une augmentation de trois fois depuis les années 1970s (l'ère Pre-P Management). Bien que cette augmentation ait été poussée par la modification de l'environnement de lumière par les dreissenidés, la gestion du phosphore demeure la seule alternative pour inverser et améliorer ces conditions nuisibles. L'élucidation de la nature de la résurgence de Cladophora aidera les décideurs en maintenant l'accent sur la gestion du phosphore comme le moyen approprié pour corriger la nuisible prolifération de cette algue.

Submerged aquatic vegetation (SAV) in clearwater systems simultaneously provides habitat for invertebrate prey and acts as refugia for small fishes. Many fishes in Lake Erie rely on shallow, heavily vegetated bays as spawning grounds, the loss or absence of which is known to reduce recruitment in other systems. The Maumee River and Maumee Bay, once with abundant macrophyte beds, have experienced a decline of SAV and increase in suspended solids (turbidity) over the last century due to numerous causes. To compare fish communities in open water (turbid) and SAV (clearer water) habitats in this Area of Concern, and suggest community changes that could occur with expansion of SAV habitat, we sampled a 300-hectare sector of northern Maumee Bay containing both habitats. Using towed neuston nets through patches of each habitat, we determined that areas of SAV contained more species and a different species complex (Jaccard Index and Wetland Fish Index, WFI PA ), than the open water habitat (averaging 8.6 vs. 5 species per net trawl). SAV was dominated by centrarchids, including Largemouth Bass (Micropterus salmoides), Bluegill (Lepomis macrochirus) and Black Crappie (Pomoxis nigromaculatus). Open water was dominated by Spottail Shiner (Notropis hudsonius), Gizzard Shad (Dorosoma cepedianum), and invasive White Perch (Morone americana). These results suggest that restoration efforts aimed at decreasing turbidity and increasing the distribution of SAV could cause substantive shifts in the fish community and address important metrics for assessing the Beneficial Use Impairments (BUI) in this US. EPA designated Area of Concern.

Pseudomonas aeruginosa is a metabolically flexible member of the Gammaproteobacteria. Under anaerobic conditions and the presence of nitrate, P. aeruginosa can perform (complete) denitrification, a respiratory process of dissimilatory nitrate reduction to nitrogen gas via nitrite (NO 2 ), nitric oxide (NO) and nitrous oxide (N 2 O). This study focuses on understanding the influence of environmental conditions on bacterial denitrification performance, using a mathematical model of a metabolic network in P. aeruginosa. To our knowledge, this is the first mathematical model of denitrification for this bacterium. Analysis of the longterm behavior of the network under changing concentration levels of oxygen (O 2 ), nitrate (NO 3 ), and phosphate (PO 4 ) suggests that PO 4 concentration strongly affects denitrification performance. The model provides three predictions on denitrification activity of P. aeruginosa under various environmental conditions, and these predictions are either experimentally validated or supported by pertinent biological literature. One motivation for this study is to capture the effect of PO 4 on a denitrification metabolic network of P. aeruginosa in order to shed light on mechanisms for greenhouse gas N 2 O accumulation during seasonal oxygen depletion in aquatic environments such as Lake Erie (Laurentian Great Lakes, USA). Simulating the microbial production of greenhouse gases in anaerobic aquatic systems such as Lake Erie allows a deeper understanding of the contributing environmental effects that will inform studies on, and remediation strategies for, other hypoxic sites worldwide.