The comparative roles of iron and manganese in internal phosphorus loading were examined in a managed lake. Sediments and the water column of Irondequoit Bay, an embayment along Lake Ontario's southern shore, were sampled monthly during summer thermal stratification. Total phosphorus, total iron, and total manganese concentrations in the sediment averaged 1.389 ± 0.150 g/kg dry wt, 24.415 ± 0.760 g/kg dry wt, and 1.727 ± 0.053 g/kg dry wt, respectively. Elevated total phosphorus (maximum = 0.915 mg P/L) and soluble reactive phosphorus (maximum = 0.749 mg P/L) concentrations were observed in the hypolimnion. Sequential extraction of phosphorus fractions from the top 25 cm of deep-water sediment revealed that approximately 25% of phosphorus was stored in a redox-sensitive form, most likely associated with iron and manganese oxyhydroxides. Typically, phosphorus released from sediments is associated with iron, not manganese. However, iron and manganese profiles from the water column indicated that manganese from the sediment was cycling with phosphorus into the overlying waters, while iron did not demonstrate evidence of cycling. Although reductive dissolution of iron likely occurs in the sediment, iron was retained in the sediment and kept out of the water column by the maintenance of low concentrations of dissolved oxygen in the hypolimnion.

Nutritional status of Lake Michigan Chinook salmon (Oncorhynchus tshawytscha) is inadequately documented. An investigation was conducted to determine muscle and liver thiamine content and whole body fatty acid composition in small, medium and large Chinook salmon. Muscle and liver thiamine concentrations were highest in small salmon, and tended to decrease with increasing fish size. Muscle thiamine was higher in fall than spring in large salmon. The high percentage of Chinook salmon (24–32% in fall and 58–71% in spring) with muscle thiamine concentration below 500 pmol/g, which has been associated with loss of equilibrium and death in other Great Lake salmonines, suggest that Chinook appear to rely less on thiamine than other Great Lakes species for which such low concentrations would be associated with thiamine deficiency (Brown et al. 2005b). A positive correlation was observed between liver total thiamine and percent liver lipids (r = 0.53, P < 0.0001, n = 119). In medium and large salmon, liver lipids were observed to be low in fish with less than 4,000 pmol/g liver total thiamine. In individuals with greater than 4,000 pmol/g liver thiamine, liver lipid increased with thiamine concentration. Individual fatty acids declined between fall and spring. Essential omega-3 fatty acids appear to be conserved as lipid content declined. Arachidonic acid (C20:4n6), an essential omega-6 fatty acid was not different between fall and spring, although the sum of omega-6 (Sw6) fatty acids declined over winter. Elevated concentrations of saturated fatty acids (sum) were observed in whole body tissue lipid. In summary, thiamine, a dietary essential vitamin, and individual fatty acids were found to vary in Lake Michigan Chinook salmon by fish size and season of the year.

Diel feeding periodicity, daily ration, and diet composition of wild and hatchery subyearling Chinook salmon Oncorhynchus tshawytscha were examined in Lake Ontario and the Salmon River, New York. The diet of wild riverine salmon was composed mainly of aquatic invertebrates (63.4%), mostly ephemeropterans (25.8%), chiromomids (15.8%), and trichopterans (8.3%). The diet of riverine Chinook was more closely associated with the composition of drift samples rather than bottom samples, suggesting mid-water feeding. In Lake Ontario terrestrial invertebrates were more important in the diet of hatchery Chinook (49.0%) than wild salmon (30.5%) and diet overlap between hatchery and wild salmon was low (0.46%). The diet of both hatchery and wild Chinook salmon was more closely associated with the composition of mid-water invertebrate samples rather than benthic core samples, indicating mid-water and surface feeding. Hatchery Chinook salmon consumed significantly less food (P < 0.05) than wild Chinook salmon in the lake and in the river, and wild salmon from Lake Ontario consumed more food than wild salmon in the Salmon River. Peak feeding of wild Chinook salmon occurred between 1200–1600 hours in Lake Ontario and between 1600–2000 hours in the Salmon River; there was no discernable feeding peak for the hatchery Chinook in Lake Ontario. Hatchery Chinook salmon also had the least diverse diet over the 24-hour sample period. These results suggest that at 7 days post-stocking hatchery Chinook salmon had not yet fully adapted to their new environment.

We evaluated the potential of vegetation and sediment habitats in wetlands of the St. Lawrence River for developing a macroinvertebrate bioassessment program with reference conditions. During September 2004, we collected macroinvertebrates in emergent vegetation and sediment in both fluvial sites (reference) and tributary-plume sites (impacted) in waters of the north and south shores of Lake Saint-Pierre (St. Lawrence River). In each habitat, we compared taxa richness, abundance, and community structure of macroinvertebrates between reference and impacted sites, and used multivariate models to relate macroinvertebrate community to environmental conditions. Each habitat was suitable for discriminating reference fluvial sites from impacted tributary-plume sites based on macroinvertebrate communities. In emergent vegetation, macroinvertebrates were dominated by epibenthic fauna such as crustaceans (Gammaridae, Asellidae) and molluscs (Valvatidae) at fluvial sites, and insect larvae (Chironomidae, Caenidae) at tributary-plume sites. In sediment, macroinvertebrates comprised a greater proportion of endobenthic fauna such as Oligochaeta and Sphaeridae. Crustaceans and molluscs were still dominant at fluvial sites and Oligocheata and Chironomidae at tributary-plume sites. No strong difference was depicted in macroinvertebrate composition between north and south shore water masses. Environmental variables explained a higher proportion of variance in macroinvertebrate community composition in emergent vegetation than in sediment (68% versus 44%). Macroinvertebrate composition in sediment was more related to metal contamination, whereas macroinvertebrate composition in emergent vegetation was related primarily to vegetation type and water quality. Relevance of the study for bioassessment of macroinvertebrates in the St. Lawrence River using the reference condition approach is discussed.

Changes in water levels and development of shorelines are expected to negatively affect coastal marshes. The small-bodied fish assemblage was sampled in the inner marsh vegetation zone in five Les Cheneaux bays with differing levels of development. Observations were made from 1996 to 2004 during which time summer water levels varied from 177.2 m to 176.0 m (chart datum = 176.0 m). Each marsh was sampled for 10 consecutive days in July and August using gangs of five baited commercial minnow traps. Assemblage composition was assayed by species richness, the number of native minnow species, the percentage of selected tolerant fishes (bowfin, Amia calva, mudminnow, Umbra limi, common carp, Cyprinus carpio, and brown bullhead, Ameiurus nebulosus), and catch-per-unit-effort (CPUE). There were no consistent relationships between fish assemblage measures and year, water level, annual change in water level, exposure, and water temperature. Fish assemblage measures except CPUE were impacted by the density of building along the shoreline, a measure of development. Impervious surface area was < 4.5% and was not consistently related to fish assemblage measures.

This study estimates the economic benefits of remediation in the Buffalo River, NY Area of Concern (AOC) using two distinct empirical methods. One method analyzes the effects of proximity to the AOC on prices in the residential property market. The second uses a choice survey of recent home purchasers concerning the characteristics of homes and the river. After controlling for numerous structural, community, and spatial effects, the market analysis shows that single-family residential property prices south of the river are depressed due to their proximity to the AOC by $118 million (5.4% of total market value). The impacts are greater for properties closer to the AOC. Prices to the north of the AOC do not appear to be affected. Recovery of $118 million in property value losses could produce approximately $4.7 million/year in new property tax revenues. Considering only the area for which the market study shows price discounts, the survey-based estimates reveal a willingness to pay (WTP) for full cleanup of the AOC of approximately $250 million (14% of median-based market value). The reasons for discrepancies between the results of the two methods is a matter for further research.

This study estimates the economic benefits of remediation in the Sheboygan River, WI Area of Concern (AOC) using two distinct empirical methods. The methodology parallels that described by Braden et al. (2008). The results are mixed. Using hedonic analysis of property sales, for owner-occupied homes within a 5-mile radius of the Sheboygan River AOC, the overall estimated loss of value is $158 million (8% of market value). Of this total, only $49 million in losses for homes closest to the upper river segment has strong statistical support. The impacts are greatest proportionally for properties closest to the AOC. A survey-based method yields a mean estimate of $218 million (10% of property value) in willingness to pay for full cleanup of the AOC. If remediation were to induce recovery of property values, then the local communities could benefit through increased property tax revenues.

Observations from September 1994 and 1997 collections of hatchery-origin, mature female lake trout (Salvelinus namaycush) from Lake Ontario indicated that egg mass decreased with age, fueling the notion that stocked fish experienced premature reproductive senescence. Supplemental collections during September 2002 and November 2002–2004 were combined with the 1994 and 1997 samples to examine whether sample date or maternal age, body mass, condition (K), egg count, or strain were related to egg mass or energy content (percentage dry mass [%DM]). Body mass was correlated with egg mass for age ≥ 8 lake trout sampled in September, and egg count was correlated with egg mass for September age-6 lake trout only. Within each month, egg mass was not related to K or egg %DM, however, egg %DM was 1.52% greater (P ≤ 0.0247) in November than in September which is equivalent to a 110 cal/g difference. Samples were grouped for the three most abundant strains (Seneca, Superior, and Ontario) after finding no strain or year effects from our 1994 and 1997 samples and based on life history data from the literature and our assessment sampling. Further analysis indicated that September egg masses were greater for fish ages ≤ 6 than for fish ages ≥ 8. The age effect disappeared in November when mean egg mass across all ages (0.078 g) was greater than September means (P < 0.0005) for ages-5 (0.054 g), -6 (0.057 g) and ≥ 8 (0.041 g). Our results indicate that the decrease in egg mass with female age in September was not due to senescence, but to oogenesis being closer to completion in young age-5 and -6 fish than in older individuals.

Round gobies have had significant impacts on benthic fish and invertebrate communities in nearshore habitats of the Great Lakes. As round gobies have become more abundant in lake habitats, there has been an expansion of their populations into tributary streams and rivers. We compared stream invertebrate and fish communities in New York tributaries to Lake Erie with round gobies present and absent. Four of six benthic invertebrate metrics differed between streams with and without round gobies. Streams with round gobies present had reduced Shannon diversity, EPT richness, and EPT/chironomid ratios, and increased macroinvertebrate density relative to streams without round gobies, but there was no difference in non-Diptera density, or total taxa richness. None of the four fish metrics examined differed between streams with and without round gobies. However, darters occurred in all streams lacking round gobies, but did not occur in any streams with round gobies. Comparisons with historical fish and macroinvertebrate distributional data support our suspicion of goby-induced community changes. In these New York streams, round gobies seem to have had significant impacts on invertebrate communities via their consumptive behavior, whereas the impacts on fish communities are less evident. If round gobies continue to expand their distribution inland, the resultant alterations in macroinvertebrate communities may impact the suitability of tributary streams as spawning and nursery habitat for several sport fish species and for energy dynamics in tributary streams.

We show that the invasion of round gobies (Apollonia melanostoma) in Green Bay, Lake Michigan, has changed the benthic food web in fundamental ways related to their impact on invasive dreissenid mussels. Dreissenid mussels are of specific interest because they are one of the primary dietary items for round gobies. In this study, we collected rocks from each of 10 study sites along approximately 60 km of the eastern shoreline of Green Bay, Lake Michigan, to assess a temporal change in macroinvertebrate abundance related to the northward movement of the round goby invasion front from a point about midway along the shoreline in 2003 to the entire coast in 2006. The pattern of macroinvertebrate abundance in 2003 suggested that round gobies had already caused significant decreases in macroinvertebrate abundances south of the invasion front (interpretation of the data could have been compromised by confounding environmental gradients). In subsequent sampling in 2006 macroinvertebrates were picked off of sampled rocks in the field and underwater transects were videotaped to estimate round goby abundance at each site. Round gobies were collected for stomach analysis to assist in determining which invertebrates would likely be impacted by goby predation. Our results indicated that by 2006, round gobies had become abundant at those sites where they were absent in 2003 and zebra mussels (Dreissena polymorpha), quagga mussels (Dreissena bugensis), isopods, amphipods, trichopterans, and gastropods in the newly invaded sites had significantly decreased at the newly invaded sites.

The water quality standard setting process usually relies on mathematical models with strong mechanistic basis, as this provides assurance that the model will more realistically project the effects of alternative management schemes. From an operational standpoint, the interpretation of model results should be coupled with rigorous error analysis and explicit consideration of the predictive uncertainty and natural variability. In this study, our main objective is to attain effective model calibration and rigorous uncertainty assessment by integrating environmental mathematical modeling with Bayesian analysis. We use a complex aquatic biogeochemical model that simulates multiple elemental cycles (org. C, N, P, Si, O), multiple functional phytoplankton (diatoms, green algae and cyanobacteria) and zooplankton (copepods and cladocerans) groups. The Bayesian calibration framework is illustrated using three synthetic datasets that represent oligo-, meso- and eutrophic lake conditions. Scientific knowledge, expert judgment, and observational data were used to formulate prior probability distributions and characterize the uncertainty pertaining to a subset of the model parameters, i.e., a vector comprising the 35 most influential parameters based on an earlier sensitivity analysis of the model. Our study also underscores the lack of perfect simulators of natural system dynamics using a statistical formulation that explicitly accounts for the discrepancy between mathematical models and environmental systems. The model reproduces the key epilimnetic temporal patterns and provides realistic estimates of predictive uncertainty for water quality variables of environmental management interest. Our analysis also demonstrates how the Bayesian parameter estimation can be used for assessing the exceedance frequency and confidence of compliance of different water quality criteria. The proposed methodological framework can be very useful in the policy-making process and can facilitate environmental management decisions in the Laurentian Great Lakes region.

Understanding the hydrodynamics of Lake Champlain is a basic requirement for developing forecasting tools to address the lake's environmental issues. In 2003 through 2005, surface drifting buoys were used to help characterize the circulation of the main body and northeast region (Inland Sea) of the lake. Progressive vector diagrams of over-lake winds when compared to drifter trajectories suggest the presence of gyre-like circulation patterns. Drifter statistics suggest average current speeds of 10 cm s⁻¹ and were predominantly northward ( V) due to northerly-directed winds and lake geometry. Single-particle eddy diffusivities on the order of 10⁶ cm² s⁻¹ were calculated which is consistent with results from the Great Lakes and in some oceanic regions. However, the Lagrangian length and time scales, a measure of flow decorrelation scales, were in general smaller than seen in the Great Lakes, which is a natural consequence of the smaller basin size of Lake Champlain relative to the Great Lakes.

Three separate procedures were used to estimate the sediment oxygen demand (SOD) in the central basin of Lake Erie and were compared with other estimates determined previously and with historical data. First, whole core incubations involved sealing sediment cores at 12°C to ensure no interaction between the overlying water and the atmosphere and monitoring continuously to define the linear disappearance of oxygen. Second, sediment plugs were placed inside flow-through reactors and the influent and effluent concentrations were monitored to obtain steady-state reaction rates. Third, an extensive data set for the central basin of Lake Erie was compiled for input into the diagenetic BRNS model, and the SOD was calculated assuming all primary redox reactions, but no secondary reactions. All three procedures produced estimates of SOD that were in reasonable agreement with each other. Whole core incubations yield an average SOD of 7.40 × 10⁻¹² moles/cm²/sec, the flow-through experiments had an average SOD of 4.04 × 10⁻¹² moles/cm²/sec, and the BRNS model predicts an SOD of 7.87 × 10⁻¹² moles/cm²/sec over the top 10 cm of sediment and appears to be calibrated reasonably well to the conditions of the central basin of Lake Erie. These values compare reasonably well with the 8.29 × 10⁻¹² moles/cm²/sec obtained from diffusion modeling of oxygen profiles (Matisoff and Neeson 2005). In contrast, values reported from the 1960s to 1980s ranged from 10.5–32.1 × 10⁻¹² moles/cm²/sec suggesting that the SOD of the central basin has decreased over the last 35 years, presumably, in response to the decrease in phosphorus loadings to Lake Erie. However, since hypoxia in the hypolimnion persists these results suggest that improvement in hypolimnetic oxygen concentrations may lag decreases in loadings or that the hypolimnion in the central basin of Lake Erie is simply too thin to avoid summer hypoxia during most years.

Previously described models for predicting the percent of Lake Ontario wetlands that would be occupied by sedge/grass-dominated meadow marsh were used to test four proposed new plans for regulation of lake levels and to make comparisons with the current plan and unregulated conditions. The models for drowned river mouth, barrier beach, open embayment, and protected embayment wetlands assessed responses to lake levels that would be generated by each plan under net total supplies modified from those that occurred from1900 to 2000. In years when reduced supplies would allow meadow marsh regeneration, simulated unregulated lake levels produced the most meadow marsh in all wetland geomorphic types; current Plan 1958DD produced the least. Overall predicted percent meadow marsh under the test plans decreased in the order B , 2007, D , and A , and the latter three plans produced rather similar results in many cases. Lower percentages of meadow marsh under some plans were due to insufficient low lake levels that could allow soils to dry and restrict invasion by cattails, as well as lack of periodic high lake levels that could kill invading upland plants. An assessment of seasonal lake-level characteristics demonstrated that Plan 2007 would reduce mean winter lake levels by 13 cm or more than Plan B and springtime lake levels by more than 10 cm. These seasonal differences could result in less winter habitat for muskrats and reduced access to spring spawning habitats for fish such as northern pike. Our model results provide important information for use in the process of selecting a new regulation plan for Lake Ontario.

Early life stage survival often determines fish cohort strength and that survival is affected by habitat conditions. The structure and dynamics of ichthyoplankton assemblages can tell us much about biodiversity and fish population dynamics, but are poorly understood in nearshore areas of the Great Lakes, where most spawning and nursery habitats exist. Ichthyoplankton samples were collected with a neuston net in waters 2–13 m deep weekly or biweekly from mid-April through August, during 3 years (2000–2002) as part of a study of fish assemblages in west-central Lake Erie. A suite of abiotic variables was simultaneously measured to characterize habitat. Cluster and ordination analyses revealed several distinct ichthyoplankton assemblages that changed seasonally. A lake whitefish (Coregonus clupeaformis) dominated assemblage appeared first in April. In May, assemblages were dominated by several percid species. Summer assemblages were overwhelmingly dominated by emerald shiner (Notropis atherinoides), with large gizzard shad (Dorosoma cepedianum) and alewife (Alosa pseudoharengus) components. This seasonal trend in species assemblages was also associated with increasing temperature and water clarity. Water depth and drift processes may also play a role in structuring these assemblages. The most common and widely distributed assemblages were not associated with substratum type, which we characterized as either hard or soft. The timing of hatch and larval growth separated the major groups in time and may have adaptive significance for the members of each major assemblage. The quality and locations (with reference to lake circulation) of spawning and nursery grounds may determine larval success and affect year class strength.

The zebra mussel Dreissena polymorpha was first detected in the western basin of Lake Erie, Ontario, Canada, on natural gas wellheads and well markers between April and November 1986. It was found again in 1987 on the north shore of Lake Erie in a water treatment plant, and in vessel fouling. The population increased in Lake Erie in 1988. Dreissena may have spread from Lake Erie to Lake St. Clair, where it was then discovered on 1 June 1988.

To determine types of fungi in the water and associated with the benthic amphipod Diporeia spp., samples were collected at various depths in Lake Michigan in an area where the Diporeia population was in a severe state of decline. No fungi were found associated with living, freshly-dead, or dried Diporeia cultured separately from Lake Michigan water. When dead Diporeia and other organic substrates (snake skin and hemp seeds) were used to grow fungi in Lake Michigan water, a rich and diverse fungal and water mold community was revealed. A total of 31 species were found, with the most common genera being Achlya, Aphanomyces, Myzocytium, and Pythium. In general, species were homogeneously distributed in the water; that is, few differences were found in species richness between nearshore (10–15 m) and offshore (60–80 m) waters, and between near-surface (1 m) and near-bottom waters (1 m off bottom). Sampling occurred during the unstratified period (April and October) to maximize the number of species collected, which may have contributed to the uniform spatial pattern observed. While conclusions must be placed in context with our methods of detection, we found no evidence that a fungal infestation was associated with Diporeia in this region of the lake.