Lake Erie

In this study passive air samplers (PAS) were deployed on a monthly basis at a number of sites along a south-north transect, extending 700 km north from Toronto, Ontario, characterizing an urban-agricultural-forested gradient, to investigate the spatial and temporal trends of current-use pesticides (CUPs), between spring 2003 and spring 2004. The most frequently detected CUPs were chlorpyrifos, dacthal, trifluralin, and a-endosulfan. Highest air concentrations of chlorpyrifos were observed in May, whereas a-endosulfan and dacthal peaked in July and August, reflecting differences in usage patterns. At the agricultural site, representing the source region of CUPs, chlorpyrifos air concentrations (pg m À3 ) varied from 2700 to 3.2 and a-endulsulfan from 1600 to 19. The most frequently detected legacy pesticides were the hexachlorocylcohexanes (a-HCH and g-HCH). For the forested sites, located on the Precambrian Shield, a region with limited agricultural activity, seasonal differences were less pronounced and air concentrations were observed to be much lower. For instance, air concentrations (pg m À3 ) of chlorpyrifos and a-endosulfan ranged from 7.6 to 0.3 and 50 to 2.0, respectively. By combining PAS data with trajectory air shed maps it is demonstrated that potential source-receptor relationships can be assessed. Air shed maps produced in this study indicate a potential of increased deposition of CUPs to Lake Erie and Lake Ontario.

In large lakes, temporal variability is compounded by strong spatial variability associated with mesoscale physical processes such as upwelling and basin-scale circulation. Here we explore the ability of a three dimensional model (ELCOM-CAEDYM) to capture temporal and spatial variability of phytoplankton and nutrients in Lake Erie. We emphasized the east basin of the lake, where an invasion by dreissenid mussels has given special importance to the question of spatial (particularly nearshore-offshore) variability and many comparative observations were available. We found that the model, which did not include any simulation of the mussels or of smaller diffuse nutrient sources, could capture the major features of the temperature, nutrient and phytoplankton variations. Within basin variability was large compared to among-basin variability, especially but not exclusively in the western regions. Consistent with observations in years prior to, but not after, the mussel invasion the model predicted generally higher phytoplankton concentrations in the nearshore than the offshore zones. The results suggest that the elevated phytoplankton abundance commonly observed in the nearshore of large lakes in the absence of dreissenid mussels does not have to depend on localized nutrient inputs but can be explained by the favourable light, temperature and nutrient environment in the shallower and energetic nearshore zone. The model is currently being extended to allow simulation of the effects of dreissenid mussels.

Cyanobacteria of genus Microcystis sp. have been commonly found in Lake Erie waters during recent summer seasons. In an effort to elucidate relationships between microcystin production, genotypic composition of Microcystis community and environmental parameters in a large lake ecosystem, we collected DNA samples and environmental data during a three-year (2003)(2004)(2005) survey within Lake Erie and used the data to perform a series of correlation analyses. Cyanobacteria and Microcystis genotypes were quantified using quantitative real-time PCR (qPCR). Our data show that Microcystis in Lake Erie forms up to 42% of all cyanobacteria, and that Microcystis exists as a mixed population of potentially toxic and (primarily) non-toxic genotypes. In the entire lake, the total abundance of Microcystis as well as the abundance of microcystin-producing Microcystis is strongly correlated with the abundance of cyanobacteria suggesting that Microcystis is a significant component of the cyanobacterial community in Lake Erie during summer seasons. The proportion of total Microcystis of all cyanobacteria was strongly linked to the microcystin concentrations, while the percentage of microcystin-producing genotypes within Microcystis population showed no correlation with microcystin concentrations. Correlation analysis indicated that increasing total phosphorus concentrations correlate strongly with increasing microcystin concentrations as well as with the total abundance of Microcystis and microcystin-producing Microcystis.

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-temperaturedepth 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 b3 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 lesshypoxic 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 food web interactions and fisheries management.

Although it is common knowledge that Pb concentrations have increased in lake sediments in the northeastern United States over the last 150 years, the processes responsible have been the subject of debate. In this study, differences in lead isotopic compositions and concentrations in sediment from large lakes (Lake Erie, Ontario, and Michigan) and small ones (Deep Lake and Lake Andrus) are used to infer temporal changes in the source(s) of anthropogenic Pb in the Great Lakes region. A natural (background) component of Pb is present in sediment deposited prior to 1860 in Lake Erie and the other lakes as indicated from low Pb concentrations and uniform lead isotopic compositions.

Recent expansion of Phragmites australis throughout many Great Lakes wetlands has caused concern among resource managers because it is thought to degrade waterfowl habitat and reduce biodiversity. Wetlands at Long Point, Lake Erie, have some of the most important habitats for staging waterfowl on the Great Lakes and anecdotal evidence suggests that Phragmites has been expanding rapidly in some of these wetlands. To make informed management decisions, a better understanding of historical changes in distribution and abundance of this species is needed, as well as the ability to identify which plant species/communities Phragmites is replacing. Long Point's wetland communities were digitally mapped from aerial photographs from 1945 to 1999. The aerial extent of Phragmites stands was measured by digitizing vegetation boundaries, ground-truthing, and analyzing the data using a GIS. A geometric growth formula was used to determine the intrinsic rate of change of Phragmites over time. its abundance increased exponentially between 1995 and 1999 (137 ha; intrinsic rate of growth in area = +0.50/yr). The species/communities that were most often replaced by Phragmites between 1995 and 1999 were Typha spp. (33.8%), marsh meadow (31%), sedge/grass hummock (10.8%), and other mixed emergents (9.6%). Of 31 stands analyzed within the study area, 28 (90%) were of a non-native strain of Phragmites australis (haplotype M) that has been rapidly expanding throughout the Atlantic region of the United States. We suggest that the recent rapid expansion of Phragmites at Long Point is the direct result of this exotic invasion, and that it has been facilitated by both declines in Great Lakes water levels and increases in ambient air temperatures; anthropogenic and natural disturbances have possibly also contributed. Given the invasive nature of the exotic genotype, combined with future global warming predictions, Phragmites probably will continue to rapidly expand throughout lower Great Lakes coastal wetlands.

This article offers a synopsis of recent research into the pre-contact fishery on the upper Niagara River, with a view towards the Middle Woodland period (ca. 2,100-1,000 B.P.) and subsequent modern environmental impacts. During the Middle Woodland, fishing was a major subsistence activity, and the climate and water levels were within their historically documented range. However, many details of the pre-contact upper Niagara River fishery have hitherto remained unclear. Archaeological data suggest that during the Middle Woodland period a diverse fish community was exploited, with spawning walleye as a major focus. Anecdotal historical accounts suggest that spawning walleye were captured with nets in the upper Niagara River. Interestingly, despite the presence of some favourable habitat conditions, there is no confirmed walleye spawning ground in the upper Niagara River today. It is likely that over the past two centuries a suite of anthropogenic factors contributed to the environmental degradation of such hypothesized spawning grounds. We hope the results of this study will be germane to future palaeo-environmental reconstruction and rehabilitation efforts.

The ratio of DDE to PCB (DDE:PCB) concentrations was examined in herring gull (Lams argentatus) eggs collected from thirteen sites on the Great Lakes from 1979 to 1996. This ratio has been shown to have had a number of biological interpretations in the past and the data in this study have been used to test the validity of these interpretations. The findings suggest that the consistency of DDE:PCB over many years reflects the relative availability of DDT and PCB in different geographical areas and provides an indication of a bird's general foraging ecology. The ratio can also be used as a reflection of the relative rates of increase or decrease of DDE and PCBs in food over time. A significant increase was found in the ratio in eggs sampled from sites on the upper Great Lakes and Lake Ontario during the study period. This is attributed to PCB levels decreasing faster than DDE levels at these sites. At Lake Erie and its two connecting channels, a significant increase was detected in the ratio but at a rate 56% or less than that found at other Great Lakes sites. This lower rate is attributed to DDE and PCB levels decreasing at high and equal rates. Similarities/differences in the fates of these contaminants among the Great Lakes would never have been realized upon an examination of individual contaminant levels alone. The ratio is valuable as a measure of the relative exposure of the two contaminants in nonmigratory birds such as herring gulls. The use of the ratio as an indication of contamination movement through the food chain could not be assessed; the ratio cannot be used as a reflection of the interspecific differences in the accumulation and metabolism of the two contaminants. Similarities in the patterns of these ratios shown by eggs collected from sites in close proximity or within the same lake reinforce the fact that herring gulls are important as monitors of regional contaminant conditions.

Northern Ohio is a tough place to be a caver. The Cleveland Grotto, in existence since 1945, usually travels out of state to take part in exploration and conservation activities due to a limited number of caves in the area. A grotto member’s visit to Green Island in 2006, and subsequent discussion with Dr. Horton Hobbs of the Ohio Cave
Survey, resulted in an upwelling of interest in the Lake Erie islands area and its cave potential. This interest soon developed into a survey project with the permission of the Ohio Department of Natural
Resources (ODNR), and with a grant from the Cleveland Grotto Science Fund, generously established by Bob and Bev Danielson.
On this trip, eight Cleveland Grotto members surveyed a total of five cave features on Green Island, and discovered several more features of interest that perhaps bear further investigation.  Two caves on Kelleys Island, where none had previously been documented, were also surveyed
for future analysis. Trip members included AJ Goslin, Curt Harler, Bill
Lendvay, Cynthia Norris, Gretchen Robertson, Mickey Skowronsky,
Chad Waffen, and Robert Ward.

Identifying species and population genetic compositions of biological invasions at early life stages and/or from environmental (e)DNA using targeted high‐throughput sequencing (HTS) metabarcode assays offers powerful and cost‐effective means for early detection, analysis of spread patterns, and evaluating population changes. The present study develops, tests, and applies this method with a targeted sequence assay designed to simultaneously identify and distinguish between the closely related
invasive Eurasian zebra and quagga mussels (Dreissena polymorpha and D. rostriformis) and their relatives and discern their respective population genetic patterns. Invasions of these dreissenid mussel species have markedly changed freshwater ecosystems throughout North America and Europe, exerting severe ecological and economic damage. Their planktonic early life stages (eggs and larvae) are morphologically indistinguishable, yet each species exerts differential ecological effects, with the quagga often outcompeting the zebra mussel as adults. Our targeted assay analyzes genetic variation from a diagnostic sequence region of the mitochondrial (mt)DNA cytochrome oxidase I (COI) gene, to assess temporal and spatial inter‐ and intra‐specific genetic variability. The assay facilitates analysis of environmental (e)DNA from water, early life stages from thousands of individuals, and simultaneous analysis of 50–100 tagged field‐collected samples. Experiments evaluated its accuracy and performance using: (a) mock laboratory communities containing known DNA quantities per taxon, (b) aquaria with mixed‐species/haplotype compositions of adults, and (c) field‐collected water and plankton versus traditional sampling of adult communities. Results delineated species compositions, relative abundances, and population‐level
diversity differences among ecosystems, habitats, time series, and life stages from two allopatric concurrent invasions in the Great Lakes (Lake Erie) and the Hudson River, which had separate founding histories. Findings demonstrate application of this targeted assay and our approach to accurately and simultaneously discern species‐ and population‐level differences across spatial and temporal scales, facilitating
early detection and ecological understanding of biological invasions.

The potential destruction of prehistoric archaeological sites in the Western Basin of Lake Erie as the result of urban development is of particular interest to Ohio archaeologists, due both to the significant number of archaeological sites in the area (OAI 2008), as well as with the fact that the Western Basin of Lake Erie has become a popular tourist destination during the summer months, encouraging a boom in residential and other construction activity in recent years (Waffen 2006).
Urban development (in addition to coastal erosion), in this region is known to have both destroyed (Stothers and Abel 2001) as well as uncovered (Redmond and Scanlan 2008) a number of prehistoric sites over the years.  The popularity of the area around the Sandusky Bay and the Lake Erie Islands in particular, has resulted in increased urban development activities for the construction of cottages for weekend vacationers, commercial establishments, infrastructure, and industry - all with the potential to disturb both known and unknown archaeological sites of value.  This is of some concern to archaeologists because of well-documented and significant use of these islands as seasonal hunting/fishing camps and later for habitation by prehistoric populations of the area (Stothers and Abel 2002), since the area around the Sandusky Bay (once the Great Black Swamp) and the nearby islands were fertile hunting and fishing grounds (Stothers, et al 1994).  In order to better understand the rate of urban development over the last 20 years in this area and its effects on the preservation of archaeological sites, Kelleys Island was chosen for study, in part because of its record of prehistoric occupation, increasing urban development, as well as because its limited land mass enables a focused case study on the rate of urban development and its potential effect on archaeological site destruction.  In addition, it was believed that such a study would also facilitate an understanding of the rate of development on the island itself in order to estimate the potential for future encroachment on sites – both known and unknown.  Thus, the objectives of this project were to:
1. Utilize satellite imagery to understand the rate of urban development on Kelleys Island over a 20 year period (1989–2009), through a comparison of ground cover
2. Use this satellite data and that of 48 documented prehistoric archaeological sites on the island, in order to quantify the rate of encroachment/destruction of known archaeological sites on the island over the same 20 year period
3. Draw conclusions on cause/effect, utility, bias, and future predictions regarding the issue of the effect that urban development has on prehistoric site encroachment/destruction, as well as the potential ability of satellite imagery to better understand this issue

The surface sediment concentrations of past-use persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated napthalenes (PCNs), and organochlorine pesticides (OCPs), and current-use chemicals such as the polybrominated diphenylethers (PBDEs) and perfluorinated chemicals (PFCs), were determined in sediments from 22 sites across Lake Simcoe. PFCs were also measured in surface waters. Maximum concentrations of historical POPs, which included PAHs (5400 ng/g), PCBs (36 ng/g) and PCNs (800 pg/g), occurred in Kempenfelt Bay, indicative of past inputs from sources in the Barrie area. This contrasted with the PFCs which had maximum sediment concentrations (2.0 ng/g perfluorooctane sulfonate (PFOS) and 1.4 ng/g perfluorooctanoic acid (PFOA)) in the Main Basin of Lake Simcoe. The distributions of many of the chemicals included in the study were relatively uniform across Lake Simcoe outside of Kempenfelt Bay, indicating contributions by atmospheric pathways from regional air masses that cover large urban and industrial areas. This is further supported by the similarity of sediment concentrations of PBDEs and PAHs and water concentrations of PFCs between Lake Simcoe and the lower Great Lakes, Lake Erie and Lake Ontario. PBDE concentrations were more variable within basins than the other compounds, and contributions from the urban Barrie area were apparent. A sediment core collected from Kempenfelt Bay showed increasing concentrations to current times for PBDEs and PFCs, while historical inputs of PCBs, PAHs, polychlorinated dibenzo-p-dioxins, and PCNs peaked in the 1950s (PAHs) and late 1960s (chlorinated contaminants), generally consistent with usage and emissions history.

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 (b 2 mg O 2 /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.

Unexpected habitat innovations among invading species are illustrated by the expansion of dreissenid mussels across sedimentary environments in shallow water unlike the hard substrates where they are conventionally known. In this note, records of population characteristics of invading zebra (Dreissena polymorpha) and quagga (Dreissena bugensis) mussels from 1994 through 1998 are reported from shallow (less than 20 m) sedimentary habitats in western Lake Erie. Haphazard SCUBA collections of these invading species indicated that combined densities of zebra and quagga mussels ranged from 0 to 32,500 individuals per square meter between 1994 and 1998, with D. polymorpha comprising 75-100% of the assemblages. These mixed mussel populations, which were attached by byssal threads to each other and underlying sand-grain sediments, had size-frequency distributions that were typical of colonizing populations on hard substrates. Moreover, the presence of two mussel cohorts within the 1994 samples indicated that these species began expanding onto soft substrates not later than 1992, within 4 years of their initial invasion in western Lake Erie. Such historical data provide baselines for interpreting adaptive innovations, ecological interactions and habitat shifts among the two invading dreissenid mussel species in North America.

Integrated, quantitative expressions of anthropogenic stress over large geographic regions can be valuable tools in environmental research and management. Despite the fundamental appeal of a regional approach, development of regional stress measures remains one of the most important current challenges in environmental science. Using publicly available, pre-existing spatial datasets, we developed a geographic information system database of 86 variables related to five classes of anthropogenic stress in the U.S. Great Lakes basin: agriculture, atmospheric deposition, human population, land cover, and point source pollution. The original variables were quantified by a variety of data types over a broad range of spatial and classification resolutions. We summarized the original data for 762 watershed-based units that comprise the U.S. portion of the basin and then used principal components analysis to develop overall stress measures within each stress category. We developed a cumulative stress index by combining the first principal component from each of the five stress categories. Maps of the stress measures illustrate strong spatial patterns across the basin, with the greatest amount of stress occurring on the western shore of Lake Michigan, southwest Lake Erie, and southeastern Lake Ontario. We found strong relationships between the stress measures and characteristics of bird communities, fish communities, and water chemistry measurements from the coastal region. The stress measures are taken to represent the major threats to coastal ecosystems in the U.S. Great Lakes. Such regional-scale efforts are critical for understanding relationships between human disturbance and ecosystem response, and can be used to guide environmental decision-making at both regional and local scales.

Cyanobacterial harmful algal bloom (CyanoHAB) proliferation is a global problem impacting ecosystem and human health. Western Lake Erie (WLE) typically endures two highly toxic CyanoHABs during summer: a Microcystis spp. bloom in Maumee Bay that extends throughout the western basin, and a Planktothrix spp. bloom in Sandusky Bay. Recently, the USA and Canada agreed to a 40% phosphorus (P) load reduction to lessen the severity of the WLE blooms. To investigate phosphorus and nitrogen (N) limitation of biomass and toxin production in WLE CyanoHABs, we conducted in situ nutrient addition and 40% dilution microcosm bioassays in June and August 2019. During the June Sandusky Bay bloom, biomass production as well as hepatotoxic microcystin and neurotoxic anatoxin production were N and P co-limited with microcystin production becoming nutrient deplete under 40% dilution. During August, the Maumee Bay bloom produced microcystin under nutrient repletion with slight induced P limitation under ...

Lake Erie walleye Sander vitreus exhibits significant interannual variability in year-class strength. Recent research revealed the importance of larval growth and survival rates in determining walleye year-class strength in western Lake Erie, indicating that spatial and temporal overlap of larvae with good habitat conditions (e.g., abundant prey, warm waters) promoted walleye growth and survival. To assess the spatial overlap between walleye larvae and habitat parameters (water depth, temperature, water clarity, prey density) in western Lake Erie, we evaluated the spatial distribution of walleye larvae and these habitat parameters with intensive sampling at 30 to 36 sites during spring 1994-1999. We analyzed spatial relationships among pelagic walleye larvae and various habitat attributes using a geographic information system and principal components analysis. Larval walleye density was consistently highest at nearshore sites during all years and showed a high degree of spatial overlap with high ichthyoplankton density, and warm water temperatures. Larval walleye density was negatively associated with water depth and water clarity. Two principal components represented 79.6% of the total variability in site attributes. Principle components analysis supported our spatial analysis by graphically separating sites into distinct groups based on larval walleye density and habitat attributes. These analyses indicated that similar relationships between larval distribution and habitat attributes occur each year, emphasizing the importance of nearshore coastal zones as nursery areas for walleye.

Analysis of diatom assemblages preserved in a 210 Pb-dated core from Lake Erie's central basin indicates rapid recent ecological change in the system. Sediments deposited after ca. 1972 contain increasing numbers of diatom populations associated with oligotrophic conditions, particularly Cyclotella species, which grow in the summer deep chlorophyll maximum in the Great Lakes. The nearest analogs of assemblages deposited after ca. 1986 are assemblages deposited around ca. 1900. However, the analogy is far from perfect. Many conspicuous indigenous species have not reestablished and may be extinct. Many species have increased recently that were not abundant in the Great Lakes flora prior to 1950. Several of them appear to be associated with relatively high nitrate concentrations. Most recently deposited diatom assemblages in Lake Erie are thus substantially different from any deposited during the past 200 years. The direction and timing of changes observed lead us to conclude that the most important factors forcing the changes observed are (i) institution of effective phosphorus loading controls in the early 1970s and (ii) invasion of zebra mussels (Dreissena polymorpha) in the mid-1980s.

Nuisance growth of the attached, green alga Cladophora was considered to have been abated by phosphorus management programs mandated under the Great Lakes Water Quality Agreement. The apparent resurgence of nuisance growth in Lakes Erie, Michigan and Ontario has been linked conceptually to ecosystem alterations engineered by invasive dreissenid mussels (Dreissena polymorpha and Dreissena bugensis). Here, we apply contemporary modeling tools and historical water quality data sets in quantifying the impact of long-term changes in phosphorus loading and dreissenid-mediated changes in water clarity on the distribution and production of Cladophora. It is concluded that reductions in phosphorus loading in the predreissenid period achieved the desired effect, as model simulations were consistent with the biomass declines reported from the early 1970s to the early 1980s. These declines were, however, largely offset by dreisseniddriven changes in water clarity that extended the depth of colonization by Cladophora, increasing total production. We were not able to isolate and quantify the significance of dreissenid mediation of phosphorus cycling using the historical database. Phosphorus management remains the appropriate mechanism for reducing nuisance levels of Cladophora growth. The development of action plans will require an improved understanding of nearshore phosphorus dynamics such as might be obtained through regular monitoring of soluble reactive phosphorus levels, internal phosphorus content and Cladophora biomass in impacted nearshore regions of the Great Lakes.

Steelhead (Onchorhynchus mykiss) have been stocked in Ohio tributaries to Lake Erie for over a decade yet little information on the value of this fishery exists. A steelhead angler intercept survey was conducted in fall, winter, and spring of 2002-2003. Almost 77% of the anglers surveyed (375) responded to a mail survey with useful information. Typical steelhead anglers were 46 years old, middle class, male, and had 9 years steelhead angling experience. Less than two-thirds of respondents fished with spinning tackle and one-third used fly tackle. On average, individuals traveled with 1.7 people in their group. They mostly took single day trips (94% of respondents), traveling approximately 84 kilometers round trip. Steelhead catch rates are positively related to number of trips taken, angler experience, number of streams visited per trip, number of hours fished per trip, and type of tackle used.

We evaluated the abundance patterns of Gammarus fasciatus and Echinogammarus ischnus in dreissenid and macrophyte areas in Hatchery Bay, Lake Erie before (1997) and after round goby (2001, 2002) invaded the area. Total amphipod abundance was higher before round goby invasion in both habitats. In mussel beds, E. ischnus abundance was similar or significantly higher than G. fasciatus. In macrophytes, G. fasciatus was significantly more abundant than E. ischnus. In laboratory experiments, we compared amphipod survivorship and growth when fed mussel feces and pseudofeces (F+P) or macrophytes with epiphytes (M+E). Gammarus fasciatus survivorship and growth were higher when fed F+P than M+E. Echinogammarus ischnus showed similar survivorship under both diets, but significantly higher growth when fed M+E than F+P. Therefore inter-habitat differences in food resources cannot explain the abundance patterns observed in the lake. We also estimated the relative vulnerability of G. fasciatus and E. ischnus to yellow perch (Perca flavescens) and round goby (Neogobius melanostomus) predation in laboratory feeding trials using mussel colonies or macrophyte beds as substrate. Both fish strongly preferred E. ischnus in macrophytes, but consumed relatively more G. fasciatus than E. ischnus in dreissenid habitats. Our results suggest that dreissenid establishment may have facilitated the invasion of E. ischnus. However, habitat-specific differences in vulnerability to fish predation may mediate the coexistence of G. fasciatus and E. ischnus by minimizing expansion of E. ischnus to macrophyte areas. Our results also suggest that round goby invasion can alter amphipod abundance patterns in Lake Erie.

Population genetic structure and systematic relationships were investigated for two exotic fishes introduced to the Great Lakes in 1990, the round goby Neogobius melanostomus and the tubenose goby Proterorhinus marmoratus, using DNA sequences from the left domain of the mitochondrial DNA control region. Samples of round gobies were compared from different sites in the Great Lakes, an introduced population from the Gulf of Gdansk in Poland, and a native population from the northern Black Sea. The round goby was characterized by relatively high genetic variability, and 17 haplotypes were identified from 64 individuals. Levels of genetic variation for the round goby were similar in the invasive and native sampling sites, suggesting relatively large founding populations and lack of bottlenecks. The northern Black Sea was eliminated as a probable founding source for both the Great Lakes and the exotic population in Poland. Substitutions in the left domain of the control region revealed significant differences among samples from the Great Lakes and Eurasia, and between Lakes Erie and St. Clair, suggesting non-random mating. No variation was detected in the tubenose goby population in the Great Lakes, which has been less successful in terms of spread and population growth. A molecular clock calibration suggested that the genera Neogobius and Proterorhinus diverged about 5.2 ± 1.0 million years ago, apparently separating from a common ancestor shared with Gobius during the isolation of the Paratethys basin from the Mediterranean Tethys Sea.

The round goby Neogobius melanostomus successfully invaded the Great Lakes perhaps, in part, because of its reproductive strategy, whereby females spawn many times over an extended reproductive season. Female round gobies were collected from the upper Detroit River (by trawling and angling) during spring, summer, and fall of 1996 in order to determine fecundity patterns and length of the reproductive season. Female round gobies were mature at 1 year of age, which is 1 year earlier than has been noted for gobies in Europe. Gravid females were present in May and declined at the end of July, which indicates that spawning occurs from spring until midsummer. Mean fecundity was 198 eggs, and variation in fecundity was correlated with standard length (r 2 ϭ 0.76, P Ͻ 0.0001) of females. Fecundity was lower than that observed for the same species in Europe, but it was generally higher than that of most native species with which gobies would compete. A field experiment showed that artificial nests contained fewer eggs but were used more often by more spawning females than were such nests in Europe. The relatively high fecundity (compared with that of native species), rapid maturation, aggressive behavior, and extended spawning season may favor the continued expansion of round gobies throughout the Great Lakes.

The odonate fauna of Bosanquet (North Lambton County, Ontario) is surveyed. Sixty-two species ofOdonata are recorded for Bosanquet, bringing the Lambton County odonate total to 66 species. Thirty-five species are added as new to Lambton County. Enal/agma /ravia/urn is new to Canada and the record of Enallagma basidens signifies that this species is continuing to expand its range northward. Pachydip/ax /ongipennis is discovered on the Lake Huron shoreline for the first time, away from its regular haunts along Lakes Erie and Ontario. Libellula quadrimaculala and Nanno/hemis bella were recorded in Lambton County by Walker and Corbet (1973) but were not discovered in our study. They are presumed to be extirpated.

As part of the BAQS-Met 2007 field campaign, Aerodyne time-of-flight aerosol mass spectrometers (ToF-AMS) were deployed at two sites in southwestern Ontario from 17 June to 11 July 2007. One instrument was located at Harrow, ON, a rural, agriculture-dominated area approximately 40 km southeast of the Detroit/Windsor/Windsor urban area and 5 km north of Lake Erie. The second instrument was located at Bear Creek, ON, a rural site approximately 70 km northeast of the Harrow site and 50 km east of Detroit/Windsor. Positive matrix factorization analysis of the combined organic mass spectral dataset yields factors related to secondary organic aerosol (SOA), direct emissions, and a factor tentatively attributed to the reactive uptake of isoprene and/or condensation of its early generation reaction products. This is the first application of PMF to simultaneous AMS measurements at different sites, an approach which allows for self-consistent, direct comparison of the datasets. Case studies are utilized to investigate processing of SOA from (1) fresh emissions from Detroit/Windsor and (2) regional aerosol during periods of inter-site flow. A strong correlation is observed between SOA/excess CO and photochemical age as represented by the NO x /NO y ratio for Detroit/Windsor outflow. Although this correlation is not evident for more aged air, measurements at the two sites during inter-site transport nevertheless show evidence of continued atmospheric processing by SOA production. However, the rate of SOA production decreases with airmass age from an Correspondence to: J. P. D. Abbatt (jabbatt@chem.utoronto.ca) initial value of ∼10.1 µg m −3 ppmv −1 CO h −1 for the first ∼10 h of plume processing to near-zero in an aged airmass (i.e. after several days). The initial SOA production rate is comparable to the observed rate in Mexico City over similar timescales.

In some lakes, first-year growth of walleyes Stizostedion vitreum has been identified as an important factor governing recruitment of juveniles to the adult population. We developed a regression model for walleye recruitment in western Lake Erie by considering factors such as first-year growth, size of the spawning stock, the rate at which the lake warmed during the spring, and abundance of gizzard shad Dorosoma cepedianum. Gizzard shad abundance during the fall prior to spring walleye spawning explained over 40% of the variation in walleye recruitment. Gizzard shad are relatively high in lipids and are preferred prey for walleyes in Lake Erie. Therefore, the high degree of correlation between shad abundance and subsequent walleye recruitment supported the contention that mature females needed adequate lipid reserves during the winter to spawn the following spring. According to the regression analysis, spring warming rate and size of the parental stock also influenced walleye recruitment. Our regression model explained 92% of the variation in recruitment of age-2 fish into the Lake Erie walleye population from 1981 to 1993. The regression model is potentially valuable as a management tool because it could be used to forecast walleye recruitment to the fishery 2 years in advance. First-year growth was poorly correlated with recruitment, which may reflect the unusually low incidence of walleye cannibalism in western Lake Erie. In contrast, first-year growth was strongly linked to age at maturity.

Over the last 12 600 years, lake levels in the eastern Lake Erie basin have fluctuated dramatically, causing major changes in drainage patterns, flooding and draining ephemeral Lake Wainfleet several times and widening and narrowing the Niagara Gorge as the erosive effects of Niagara Falls waxed and waned. The control sill for Lake Erie levels was at first the Fort Erie/Buffalo

Over the past several decades, reductions in phytoplankton stocks and increased water clarity in Lake Erie have resulted from phosphorus load abatement and the introduction of zebra ͑Dreissena polymorpha͒ and quagga mussels ͑D. bugensis͒. The relative impacts of these developments and their implications for lake management have remained difficult to delineate. To address this issue, we numerically model the complex biophysical interactions occurring in Lake Erie using a two-dimensional hydrodynamic and water quality model that is extended to include dreissenid mussel and zooplankton algorithms. The model reasonably simulates longitudinal trends in water quality as well as the dynamics of central basin hypoxia. Phosphorus is the limiting nutrient through the euphotic zone and its control decreases the algal growth rate and biomass ͑ϳ55-60% ͒. Filter feeding by dreissenid mussels also decreases algal biomass ͑ϳ25-30% ͒, simultaneously stimulating increased net algae growth through enhanced algal consumption and subsequent phosphorus recycling. Effective recycling implies that algae stocks are ultimately regulated by external phosphorus loads. Returning phosphorus loads to pre-abatement 1960s levels, in the presence of dreissenid mussels, results in a western basin algae concentration of ϳ0.7 mg dry weight L −1 with a potential for nuisance algae growth.

We constructed a complex ecological model of Lake Erie, EcoLE, based on a two-dimensional hydrodynamic and water quality model (CE-QUAL-W2). We used data from 1997 to calibrate the model, and data from 1998 and 1999 to verify it. The simulated surface and bottom water temperatures show good agreement with field observations. In spite of limitations of this 2D model and data availability, the simulated values of biological and nutrient state variables match well with field measurements. Although EcoLE's performance for the verification years is as good as that of the calibration year, the wide standard deviations of both field measurements and model simulations as well as the complexity of an ecosystem of this size make us consider our model more as a valid analytical tool rather than a predictive one at this moment. Nevertheless, we have constructed the first fine-scale dynamic ecological model of a large lake that couples hydrodynamics and detailed food web of lower trophic levels and is driven by real-time air temperature and wind conditions and the inputs from the atmosphere and tributaries. Using the model we investigate the impacts of zebra mussels (Dreissena polymorpha) and quagga mussels (D. bugensis) on phytoplankton of Lake Erie. The simulation results show that dreissenid grazing impacts on non-diatom edible algae (NDEA) are weakened by the boundary layer above the basin bottom. However, dreissenid grazing impacts on diatoms are less affected by the boundary layer due to the higher sinking rates of diatoms. Dreissenid mussels increase non-diatom inedible algae (NDIA) rapidly with increasing mussel population size, because the dreissenid population excretes a large amount of ammonia and phosphate. Our results indicate that dreissenid mussels have weak direct grazing impacts on algal biomass, while indirect effects of their nutrient excretion have a greater impact on the system. (H. Zhang). gitudes, and its long axis at about N70 • E. It is approximately 386 km (240 miles) long and more than 80 km (50 miles) wide at its midpoint . Its watershed's relatively warm weather and high productivity attract more people than the other Great 0304-3800/$ -see front matter

The objective of this study was to measure the in situ spectral reflectance of lake water that contains a bloom of Microcystis, a species of cyanobacteria. Reflectance spectra (350-2,500 nm) of lake water near a boat dock in Upper Klamath Lake, Oregon, were collected with a portable spectroradiometer on a cloud-free day with sunlight as a source of illumination between 0845 to 0915 hours, Pacific Daylight Time (PDT) on 17 August 2004, at a near-normal angle of observation. The averaged spectrum of the lake water containing the Microcystis bloom exhibits reflectance maxima from 550-590 nm and near 710 nm wavelengths and reflectance minima near 630 nm and 675 nm wavelengths. The reflectance gradually decreases from 810-1,000 nm and has very low reflectance in the 1,000-2,500 nm wavelength region. Our results show that the spectral reflectance of Microcystis at this stage of its bloom remains low for wavelengths longer than 1,000 nm in the near-infrared region of the spectrum. These spectral results have implications in selecting the spectral ratios and refining the algorithms that will be used to estimate phycocyanin content using satellite models. Microcystis is the predominant species of cyanobacteria blooms in Lake Erie, which makes these spectral data as important to the Great Lakes as it is to Upper Klamath Lake. Satellite algorithms have been published that have mapped phycocyanin, a pigment more uniquely associated with cyanobacteria than is chlorophyll a, in Lake Erie with data from LANDSAT TM bands 1, 3, 4, 5, and 7, and the reflectance spectra reported here are the first that cover the entire spectral range of all those LANDSAT TM spectral bands for a Microcystis bloom.

During the past decade, algae blooms, which include the toxic cyanobacterium Microcystis, have reoccurred in the Laurentian Great Lakes, most commonly in the western basin of Lake Erie. Whereas the western basin is the most impacted by toxic Microcystis in Lake Erie, there has historically been little effort focused on identifying the spatial distribution of Microcystis throughout this lake. To address this lack of knowledge, we have employed a polymerase-chain-reaction-based detection of genes required for synthesis of the toxin microcystin (mcyD and mcyB), as well as 16S rDNA fragments specific to either all Microcystis or all cyanobacteria. Using a multiplex approach, we tested 21 samples from 13 field stations and found that toxigenic Microcystis were present in the western and eastern basins in the summers of 1999, 2000, and 2002 and the central basin in 1999 and 2002. This is the most extensive distribution of Microcystis reported in Lake Erie. Clone libraries (16S rDNA) of these cyanobacterial communities were generated from 7 of the 13 field stations (representing all three basins) to partially characterize this microbial community. These libraries were shown to be dominated by sequences assigned to the Synechococcus and Cyanobium phylogenetic cluster, indicating the importance of picoplankton in this large lake system.

We compared results from analysis of split-beam and single-beam acoustic surveys using two data sets, one from the Baltic Sea (both systems at 70 kHz) and one from Lake Erie (70 kHz single beam, 70 and 120 kHz split beam). First, we show that there is a bias towards smaller targets associated with implementation of a commonly used algorithm for deconvolving target strength distributions from single beam data (modi®ed Craig±Forbes). This bias is 0.8 dB for a circular transducer. Differences in water column ®sh density estimates were not large although the single beam analysis consistently resulted in lower ®sh densities (85±95% of split beam densities). Target strength distributions obtained by split and single beam methods were very similar for the Baltic Sea data resulting in almost identical overall average TS. This was also true for epilimnetic targets strength distributions in Lake Erie. However, hypolimnetic target strength distributions still yielded smaller target strengths with single than with the two split beam units.

The trophic roles of key Ponto-Caspian invaders (quagga mussels Dreissena bugensis, amphipods Echinogammarus ischnus and round goby Apollonia melanostomus) within the littoral food web of eastern Lake Erie were quantified using stable isotopes (δ13C, δ15N). A dual stable isotope parameter search with a mass balance component was used to assess the isotopic importance of quagga mussels and amphipods as dietary items to two size classes of round goby. The utility of the mass balance simulation was also evaluated as a tool to approximate isotopic contributions of feasible prey and identify gaps incurred by “missing” prey items not included in the sampling. The mass balance dietary simulation, confirmed by stomach content data, indicated that isotopically important prey to small round goby (< 11.2 cm) were chironomids and Ponto-Caspian amphipods, while large round goby (≥ 11.2 cm) showed strong preference for quagga mussels. The dietary mass balance simulation output also supported the isotopic importance of round goby to the somatic growth of smallmouth bass, rock bass and freshwater drum. The isotopic mass balance output for yellow perch was more ambiguous, which may be in line with their known broadly omnivorous diet. The white bass output was in line with published data indicating increasing consumption of round goby for this species, while the brown trout output strongly favoured alewife isotopic contributions. However for white perch and walleye, the mass balance simulations were not in line with their known published diets in Lake Erie, probably due to a lack of key prey items in the sample set (e.g. zooplankton for white perch and shiner species for walleye). As expected, the Ponto-Caspian species have integrated themselves into the littoral food webs, and the “quagga mussel–round goby–smallmouth bass” food chain forms one of the key components within the trophodynamics of Lake Erie.

We compare the results of lakewide plankton studies conducted during 1996–2002 with data reported in the literature from previous years to evaluate the effectiveness of continued nutrient control, the relationship between external phosphorus loading and plankton abundance, and the many predicted outcomes of the dreissenid invasion. We found that although recent external annual phosphorus loading has not changed since reaching mandated target levels in the early- to mid-1980s, phytoplankton communities have. Total phytoplankton biomass, measured through enumeration and size-frequency distributions has increased since minima were observed in 1996 or 1997, with summer (July–September) biomasses generally greater than before the dreissenid establishment in the late 1980s. Cyanobacteria biomass also increased during summer in all basins after the dreissenid invasion. In contrast, chlorophyll a concentration has decreased in all basins during both spring and summer. However chlorophyll a concentration was poorly correlated with total phytoplankton biomass. Relative to the mid-1980s, crustacean zooplankton biomass during the years 1996–2002 increased in the western basin during spring and summer, increased in the central basin during spring but remained the same during summer, and decreased to low levels in the eastern basin. Several of these observations are consistent with predictions made by previous researchers on the effects of reduced total external phosphorus loading and the stimulatory or inhibitory effects of dreissenid mussels. However, several were not. Results from this study, particularly the inconsistencies with tested predictions, highlight the need for further research into the factors that regulate plankton community dynamics in Lake Erie.

Historic reports imply that the lower Detroit River was once a prolific spawning area for lake whitefish (Coregonus clupeaformis) prior to the construction of the Livingstone shipping channel in 1911. Large numbers of lake whitefish migrated into the river in fall where they spawned on expansive limestone bedrock and gravel bars. Lake whitefish were harvested in the river during this time by commercial fisheries and for fish culture operations. The last reported landing of lake whitefish from the Detroit River was in 1925. Loss of suitable spawning habitat during the construction of the shipping channels as well as the effects of over-fishing, sea lamprey (Petromyzon marinus) predation, loss of riparian wetlands, and other perturbations to riverine habitat are associated with the disappearance of lake whitefish spawning runs. Because lake whitefish are recovering in Lake Erie with substantial spawning occurring in the western basin, we suspected they may once again be using the Detroit River to spawn. We sampled in the Detroit River for lake whitefish adults and eggs in late fall of 2005 and for lake whitefish eggs and fish larvae in 2006 to assess the extent of reproduction in the river. A spawning-ready male lake whitefish was collected in gillnets and several dozen viable lake whitefish eggs were collected with a pump in the Detroit River in November and December 2005. No lake whitefish eggs were found at lower river sites in March of 2006, but viable lake whitefish eggs were found at Belle Isle in the upper river in early April. Several hundred lake whitefish larvae were collected in the river during March through early May 2006. Peak larval densities (30 fish/1,000 m 3 of water) were observed during the week of 3 April. Because high numbers of lake whitefish larvae were collected from mid-and downstream sample sites in the river, we believe that production of lake whitefish in the Detroit River may be a substantial contribution to the lake whitefish population in Lake Erie.

To evaluate levels of primary production and community metabolism in Lake Erie, we conducted incubations with 18 O-labelled water and determined the ratio of respiration to primary production (R:P) during the summer and early fall of 2002. The epilimnion of Lake Erie was characterized by δ 18 O values less than 0.7‰ at all times that reflects a strong contribution of O 2 from primary production. High δ 18 O values (maximum of 6.6‰) were common in the O 2 depleted waters of the hypolimnion as a consequence of isotope fractionation during respiration. Hypoxic conditions were evident in the central basin in August when the fractional abundance of O 2 reached a minimum value of 0.04. Rates of primary production varied from 0.23 to 1.76 mmol-O 2 . m -3. h -1 , decreased from west to east in August, and were at a minimum in the central basin in September. Ratios of respiration to photosynthesis (R:P) (determined from the abundance and isotopic composition of dissolved O 2 ) in the epilimnion as low as 0.45 in July were strong evidence of net autotrophy and preceded the development of hypoxia in August. Net heterotrophy prevailed in August and September. The absolute values of R:P ratios were not indicative of trophic state, however, the wide range of R:P ratios (0.45 to 20.40), fraction of O 2 saturation (0.04 to 1.36), and δ 18 O-O 2 (-6.0 to 7.5‰) values were all indicative of a eutrophic system. An average isotope fractionation factor for respiration of 7.9‰ was determined from samples in the hypolimnion in July and August. Based on unique fractionation factors for respiration in the water column (23.5‰) and in sediments (3‰) we calculate that 61% of hypolimnion O 2 respiration occurs within sediments and 39% occurs within the water column.

In this study we investigated the effect of the phosphonate herbicide glyphosate (N-(phosphonomethyl) glycine) on the phytoplankton community structure in Lake Erie using lake water incubations, laboratory growth experiments and phylogenetic analysis of phosphonate metabolism genes. In microcosms, addition of glyphosate to Sandusky Bay water resulted in a significant increase in phytoplankton abundance, specifically causing an increase in the abundance of Planktothrix spp. In microcosms using Maumee Bay water, glyphosate did not stimulate phytoplankton growth but caused a decrease in Microcystis spp. abundance. The difference in the ability of Planktothrix spp. and Microcystis spp. to grow in the presence of glyphosate was confirmed in laboratory growth experiments. Further, an examination of the molecular pathways involved in phosphonate metabolism demonstrated that heterotrophic bacteria may be critical in allowing this proliferation. The results indicate that glyphosate has both positive and negative influences on phytoplankton community structure, serving as a nutrient source to microbes able to tolerate the herbicidal effects of the compound while killing those less tolerant. Moreover, this work highlights that in natural environments microorganisms function as communities, and the metabolic abilities of individual species are often less important than the collective ability of the community.

We explored temporal trends of young-of-year (YOY) fishes caught in bottom trawl hauls at an established offshore monitoring site in Lake Erie in fall during 1961-2001. Sampling was conducted during morning, afternoon, and night in each year. Catches per hour (CPH) of alewife (Alosa pseudoharengus) YOY were relatively low and exhibited no temporal trend. This result was consistent with the species&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; intolerance to Lake Erie&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s adverse winter water temperatures. Gizzard shad (Dorosoma cepedianum) YOY decreased sharply after 1991, which was consistent with recent oligotrophication of the lake. Following the establishment in 1979 and rapid increase of white perch (Morone americana) YOY, white bass (Morone chrysops) and freshwater drum (Aplodinotus grunniens) YOY decreased. Trout-perch (Percopsis omiscomaycus) YOY decreased during 1986-1991, but recovered to previous levels during 1991-2001. The recovery coincided with the resurgence of mayflies (Ephemoptera) in the lake. CPH of spottail shiner (Notropis hudsonius) and emerald shiner (N. atherinoides) YOY exhibited no temporal trend between 1961 and the late 1970s to early 1980s. CPH of yellow perch (Perca flavescens) YOY decreased during 1961-1988, and walleye (Sander vitreum) YOY increased overall during the time series. These observations were consistent with published studies of adults in the region. CPH of 4 of the 10 species of YOY considered were greatest during night. CPH for walleye YOY was higher in the morning than in the afternoon, but there was no significant difference between night and morning abundances. The results suggest that (1) CPH of YOY fishes may be a useful monitoring tool for Lake Erie, and (2) offshore monitoring programs that do not include night sampling periods may underestimate recruitment for several common species.

Dioxins, furans, and polychlorinated biphenyls (PCBs) are toxic, persist in the environment, and bioaccumulate to concentrations that can be harmful to humans. Sport anglers may be exposed to these residues via consumption of contaminated Great Lakes (GL) fish. The Health Departments of five GL states, Wisconsin, Michigan, Ohio, Illinois, and Indiana, formed a consortium to study body burden levels of chemical residues in fish consumers of Lakes Michigan, Huron, and Erie. In Fall 1993, a telephone survey was administered to sport angler households to obtain fish consumption habits and demographics. A blood sample was obtained from a portion of the study subjects. One hundred serum samples were analyzed for 8 dioxin, 10 furan, and 4 coplanar PCB congeners. Multiple linear regression was conducted to assess the predictability of the following covariates: GL sport fish species, age, BMI, gender, years sport fish consumed, and lake. Of the 100 subjects, there were 58 men; 35 consumed sport fish from Lake Michigan, 29 from Lake Huron, and 36 from Lake Erie. The overall average number of GL sport fish meals consumed in the previous 12 months was 43. Lake Erie male and female consumers, on average, ate more GL sport fish, a mean of 57 and 42 meals, respectively, than men and women from the other two lake subgroups. Median total dioxin toxic equivalents (TEq), total furan TEq, and total coplanar PCB TEq were higher among all men than all women (P=0.0001). Lake trout, salmon, age, BMI, and gender were significant regression predictors of log(total coplanar PCBs). Lake trout, age, gender, and lake were significant regression predictors of log(total furans). Age was the only significant predictor of total dioxin levels.

Genetic variability and structure of nonindigenous vs native populations are compared for the Eurasian round goby Neogobius melanostomus and the tubenose goby Proterorhinus marmoratus, which both invaded Lake St. Clair of the North American Great Lakes about 1990. The round goby spread rapidly to all of the Great Lakes and the tubenose goby largely has been restricted to Lake St. Clair, with some recent range extension into western Lake Erie. Risk analyses may indicate whether genetic variability of colonizers is predictive of their relative invasive and establishment successes. The present investigation examined DNA sequence variation across the left domain of the mitochondrial DNA cytochrome b gene in round and tubenose gobies from Eurasian and Great Lakes locations. We also sequenced six additional Neogobius species (including the monkey N. fluviatilis, racer N. gymnotrachelus, and bighead N. kessleri gobies that have been 'on the move' in Europe) and the knout goby Mesogobius batrachocephalus from the Black Sea in order to develop diagnostic genetic characters to identify them in case of future and/or undetected invasions and to delineate their phylogenetic relationships. Results show that a diverse number of haplotypes characterize round and tubenose goby populations from both North America and Eurasian sites, fitting a risk analysis prediction of high genetic variability in their successful introductions. Phylogenetic results indicate that the current genus Neogobius is paraphyletic and that the subgenus Apollonia thus should be elevated to the level of genus, containing Apollonia (N.) melanostomus (the round goby) and A. (N.) fluviatilis (the monkey goby). In addition, there appear to be two separate species of Proterorhinus marmoratus, a marine P. marmoratus Pallas 1814 in the Black Sea (matching the original type locality), and a 'cryptic' freshwater species in the Danube and Dnieper Rivers and probably other Eurasian freshwater habitats, as well as invasive in the Great Lakes. We suggest resurrecting the name P. semilunaris Heckel 1837 for the freshwater species (a taxon that was originally described from rivers draining into the Aegean Sea and the Danube River, but was later placed in synonymy with P. marmoratus).

Many transoceanic vessels enter the Great Lakes carrying residual ballast water and sediment that harbours live animals and diapausing eggs. In this study, we examine the potential for sodium hypochlorite (NaOCl) to reduce the risk of species introductions from diapausing invertebrate eggs in residual ballast sediment. We collected sediment from three transoceanic vessels and from Lake Erie and exposed them to NaOCl concentrations between 0 and 10,000 mg/L for 24 h. Hatching success was reduced by >89% in all four experiments at 1000 mg/L relative to unexposed controls. Fewer species hatched at high than at low NaOCl concentrations. Based on an average residual ballast of 46.8 tonnes, the volume of NaOCl required to treat inbound vessels is 374 L. Impacts of NaOCl use could be minimized by neutralization of treated residuals with sodium bisulfite. Further research is needed, however, to evaluate the effect of NaOCl on ballast tank corrosion.