Huron Lake Research Articles

Evaluating the Performance of Seven Ongoing Satellite Altimetry Missions for Measuring Inland Water Levels of the Great Lakes.

Satellite altimetry can provide long-term water level time series for water bodies lacking hydrological stations. Few studies have evaluated the performance of HY-2C and Sentinel-6 satellites in inland water bodies, as they have operated for less than 1 and 2 years, respectively. This study evaluated the measured water level accuracy of CryoSat-2, HY-2B, HY-2C, ICESat-2, Jason-3, Sentinel-3A, and Sentinel-6 in the Great Lakes by in-situ data of 12 hydrological stations from 1 January 2021 to 1 April 2022. Jason-3 and Sentinel-6 have the lowest mean root-mean-square-error (RMSE) of measured water level, which is 0.07 m. The measured water level of Sentinel-6 satellite shows a high correlation at all passing stations, and the average value of all correlation coefficients (R) is also the highest among all satellites, reaching 0.94. The mean RMSE of ICESat-2 satellite is slightly lower than Jason-3 and Sentinel-6, which is 0.09 m. The stability of the average deviation (bias) of the ICESat-2 is the best, with the maximum bias only 0.07 m larger than the minimum bias. ICESat-2 satellite has an exceptionally high spatial resolution. It is the only satellite among the seven satellites that has retrieved water levels around twelve stations. HY-2C satellite has the highest temporal resolution, with a temporal resolution of 7.5 days at station 9075014 in Huron Lake and an average of 10 days in the Great Lakes region. The results show that the seven altimetry satellites currently in operation have their own advantages and disadvantages, Jason-3 and Sentinel-6 have the highest accuracy, ICESat-2 has higher accuracy and the highest spatial resolution, and HY-2C has the highest temporal resolution, although it is less accurate. In summary, with full consideration of accuracy and space-time resolution, the ICESat-2 satellite can be used as the benchmark to achieve the unification of multi-source data and establish water level time series.

Bioaccumulation of polyfluoroalkyl substances in the Lake Huron aquatic food web

Polyfluoroalkyl substances (PFAS) are a group of fluorinated organic chemicals that have been produced for industrial and commercial application since the 1950s. PFAS are highly persistent and ubiquitous in water, sediment, and biota. Toxic effects of PFAS on humans and the ecosystem have increased scientific and public concern. To better understand the distribution of PFAS in the Laurentian Great Lakes, carbon (12C and 13C) and nitrogen (14N and 15N) stable isotope enrichment, fatty acid profiles, and PFAS were measured in the Lake Huron (LH) aquatic food web. The trophic level of the organisms was estimated using δ15N and found to be a determinant of PFAS biomagnification. The δ13C and fatty acid profiles were used to assess the carbon/energy flow pathway and predator-prey relationships, respectively. The δ13C, δ15N, and fatty acids were used to elucidate the trophodynamics and understand the PFAS trophic transfer in the LH aquatic food web. Perfluorooctanesulfonic acid (PFOS) was the dominant PFAS observed, followed by C9 - C11 perfluorinated carboxylic acids (PFCA). The highest PFOS concentrations (45 ± 11 ng/g, wet weight (wwt)) were detected in lake trout (Salvelinus namaycush), while the highest total PFCA concentrations (sum of C4 – C16 PFCAs) were detected in deepwater sculpin (Myoxocephalus thompsonii). With the exception of perfluorooctanoic acid (PFOA), C8-C14 PFAS biomagnification factors (BMFs) were found to be generally greater than 1, suggesting PFAS biomagnification from prey to predator. Trophic magnification factors (TMFs) of C8-C14 PFCA were found to be independent of compound hydrophobicity.

Nutrient concentrations and loadings in the St. Clair River–Detroit River Great Lakes Interconnecting Channel

Abstract Long-term (2001–2015) water quality monitoring data for the St. Clair River are presented with data from studies in the Detroit River in 2014 and 2015 to provide the most complete information available about nutrient concentrations and loadings in the Lake Huron–Lake Erie interconnecting corridor. Concentrations of total phosphorus (TP) in the St. Clair River have reflected declines in Lake Huron. We demonstrate that St. Clair River TP concentrations are higher than offshore Lake Huron values. The recent average (2014 and 2015) incoming TP load from the upstream Great Lakes is measured here to be 980 metric tonnes per annum (MTA), which is roughly three times greater than previous estimates. Significant TP load increases are also indicated along the St. Clair River. We treat the lower Detroit River as three channels to sample water quality as part of a two year monitoring campaign that included winter sampling and SRP in the parameter suite. We found concentrations of many parameters are higher near the shorelines, with the main Mid-River channel resembling water quality upstream measured at the mouth of the St. Clair River. Comparison with past estimates indicates both concentrations and loadings of TP have dramatically declined since 2007 in the Trenton Channel, while those in the Mid-River and in the Amherstburg Channel have remained similar or have possibly increased. The data demonstrate that the TP load exiting the mouth of the Detroit River into Lake Erie is currently in the range of 3740 (in 2014) to 2610 (2015) MTA.

Movement patterns and spatial segregation of two populations of lake trout Salvelinus namaycush in Lake Huron

Abstract Movement ecology is an important component of life history and population dynamics, and consequently its understanding can inform successful fishery management decision-making. While lake trout populations in Lake Huron have shown signs of recovery from near extinction in recent years, knowledge of their movement behavior remains incomplete. We used acoustic telemetry to describe and compare movement patterns of two Lake Huron lake trout populations: Drummond Island and Thunder Bay. Both populations showed high spawning site fidelity, with no evidence of co-mingling during non-spawning season. Detections between spawning periods were mainly limited to receivers within 100 km of spawning locations, and suggested that the two populations likely remained segregated throughout the year. Drummond Island fish, which spawn inside the Drummond Island Refuge, primarily dispersed east into Canadian waters of Lake Huron, with 79–92% of fish being detected annually on receivers outside the refuge. In contrast, Thunder Bay fish tended to disperse south towards Saginaw Bay. Large proportions (i.e., > 80%) of both populations were available to fisheries outside the management zone containing their spawning location. Thunder Bay fish moved relatively quickly to overwinter habitat after spawning, and tended to repeat the same post-spawning movement behavior each year. The consistent, predictable movement of both populations across management zones highlights the importance of understanding population dynamics to effective management of Lake Huron lake trout.

Groundwater shapes sediment biogeochemistry and microbial diversity in a submerged Great Lake sinkhole.

For a large part of earth's history, cyanobacterial mats thrived in low-oxygen conditions, yet our understanding of their ecological functioning is limited. Extant cyanobacterial mats provide windows into the putative functioning of ancient ecosystems, and they continue to mediate biogeochemical transformations and nutrient transport across the sediment-water interface in modern ecosystems. The structure and function of benthic mats are shaped by biogeochemical processes in underlying sediments. A modern cyanobacterial mat system in a submerged sinkhole of Lake Huron (LH) provides a unique opportunity to explore such sediment-mat interactions. In the Middle Island Sinkhole (MIS), seeping groundwater establishes a low-oxygen, sulfidic environment in which a microbial mat dominated by Phormidium and Planktothrix that is capable of both anoxygenic and oxygenic photosynthesis, as well as chemosynthesis, thrives. We explored the coupled microbial community composition and biogeochemical functioning of organic-rich, sulfidic sediments underlying the surface mat. Microbial communities were diverse and vertically stratified to 12cm sediment depth. In contrast to previous studies, which used low-throughput or shotgun metagenomic approaches, our high-throughput 16S rRNA gene sequencing approach revealed extensive diversity. This diversity was present within microbial groups, including putative sulfate-reducing taxa of Deltaproteobacteria, some of which exhibited differential abundance patterns in the mats and with depth in the underlying sediments. The biological and geochemical conditions in the MIS were distinctly different from those in typical LH sediments of comparable depth. We found evidence for active cycling of sulfur, methane, and nutrients leading to high concentrations of sulfide, ammonium, and phosphorus in sediments underlying cyanobacterial mats. Indicators of nutrient availability were significantly related to MIS microbial community composition, while LH communities were also shaped by indicators of subsurface groundwater influence. These results show that interactions between the mats and sediments are crucial for sustaining this hot spot of biological diversity and biogeochemical cycling.

Contrasting PCB bioaccumulation patterns among Lake Huron lake trout reflect basin-specific ecology.

This study collected multiple age classes of lake trout from Lake Huron's Main Basin, Georgian Bay, and North Channel regions to compare and contrast top predator polychlorinated biphenyl (PCB) bioaccumulation patterns in separate compartments of the same ecosystem. Sum PCB concentrations were highest for Main Basin (260 ± 24.9 ng g(-1) wet wt) fish, followed by Georgian Bay (74.6 ± 16.2 ng g(-1) ) and North Channel (42.0 ± 3.3 ng g(-1)) fish. Discriminant functions analysis of lake trout PCB profiles and stable carbon (δ(13)C) and nitrogen (δ(15)N) isotope values clearly distinguished fish by location, indicating high degrees of basin fidelity throughout their lifetimes in addition to highly contrasting PCB bioaccumulation profiles. These unique profiles were not attributable to significant differences in lake trout lipid contents (p = 0.856) or trophic position (δ(15)N; p = 0.334), with rainbow smelt representing the primary prey across the basins. Furthermore, significant differences were observed among the basins for the relationships between PCB biomagnification factors and hydrophobicity. An empirical model for predicting PCB biomagnification in Lake Huron lake trout indicated that basin-specific population growth rates and prey abundances were significant for explaining these contrasting patterns of PCB bioaccumulation. The results of the present study are fundamental for understanding the role of ecology in legacy persistent organic pollutant (POP) bioaccumulation. Specifically, ecosystem characteristics such as prey abundances, foraging ecology, and ultimately consumer growth can regulate the variability of legacy POP bioaccumulation as observed within and among a wide range of freshwater ecosystems.

PCB Food Web Dynamics Quantify Nutrient and Energy Flow in Aquatic Ecosystems.

Measuring in situ nutrient and energy flows in spatially and temporally complex aquatic ecosystems represents a major ecological challenge. Food web structure, energy and nutrient budgets are difficult to measure, and it is becoming more important to quantify both energy and nutrient flow to determine how food web processes and structure are being modified by multiple stressors. We propose that polychlorinated biphenyl (PCB) congeners represent an ideal tracer to quantify in situ energy and nutrient flow between trophic levels. Here, we demonstrate how an understanding of PCB congener bioaccumulation dynamics provides multiple direct measurements of energy and nutrient flow in aquatic food webs. To demonstrate this novel approach, we quantified nitrogen (N), phosphorus (P) and caloric turnover rates for Lake Huron lake trout, and reveal how these processes are regulated by both growth rate and fish life history. Although minimal nutrient recycling was observed in young growing fish, slow growing, older lake trout (>5 yr) recycled an average of 482 Tonnes·yr(-1) of N, 45 Tonnes·yr(-1) of P and assimilated 22 TJ yr(-1) of energy. Compared to total P loading rates of 590 Tonnes·yr(-1), the recycling of primarily bioavailable nutrients by fish plays an important role regulating the nutrient states of oligotrophic lakes.

Trends in growth and recruitment of Lake Huron lake whitefish during a period of ecosystem change, 1985 to 2012

Abstract We use fishery-independent survey data to describe trends in growth and recruitment for lake whitefish ( Coregonus clupeaformis ) in the southern main basin of Lake Huron. We also used a model selection approach to evaluate the potential contribution of key variables (population biomass, temperature, dreissenid mussel establishment in 1993, and the regime shift in 2003) to trends in growth and recruitment. Overall, mean growth of juvenile whitefish (i.e. back-calculated growth occurring between ages 1 and 2 years) has been reduced to approximately half of what it was before dreissenids invaded. The number of recruits per kg spawner biomass averaged 36.1 before dreissenids were established, 2.48 between dreissenid establishment and the regime shift, and 4.61 thereafter. Accounting for the timing of dreissenid establishment and the regime shift greatly improved the ability of both density-dependent growth and stock-recruitment relationships to explain the variation in growth and relative recruitment over time, providing evidence that both of these relationships have been altered by recent ecosystem changes. Current rates of growth and recruitment are much lower than before dreissenids became established, likely reducing the productivity of these populations, and in turn affecting sustainable harvest levels.

Mercury biomagnification and contemporary food web dynamics in lakes Superior and Huron

Trophic structure is an integral part of understanding the flow of contaminants within an aquatic system. Persistent, bioacccumulative, and toxic substances and food web perturbations by invasive species are critical ecological issues with far-reaching consequences for the health of the Laurentian Great Lakes. The historically-different aquatic ecosystems of Lakes Superior and Huron were evaluated for mercury (Hg) biomagnification using stable carbon (δ 13C) and nitrogen (δ 15N) isotope ratios. The results showed that δ values vary significantly with sampling depth, particularly for the lower food web components, reflecting depth- and diet-specific patterns of δ values. The stable isotope assessment of the Lake Superior food webs was consistent with previous results, underscoring the temporal stability of this ecosystem. However, based on stable isotope data, the Lake Huron lake trout appear to be incorporating the exotic round goby in their diet, possibly compensating for the collapse of alewife populations, historically their principal food. Our results suggest that the well-documented perturbations in the Lake Huron ecosystem have likely contributed to increasing Hg concentrations in the lake trout. Similar Hg biomagnification rates were observed suggesting strong similarities in the contemporary contaminant flow in Lakes Superior and Huron.

Target Detection Method for Water Mapping Using Landsat 8 OLI/TIRS Imagery

Extracting surface water distribution with satellite imagery has been an important subject in remote sensing. Spectral indices of water only use information from a limited number of bands, thus they may have poor performance from pixels contaminated by ice/snow, clouds, etc. The detection algorithms using information from all spectral bands, such as constrained energy minimization (CEM), could avoid this problem to some extent. However, these are mostly designed for hyperspectral imagery, and may fail when applied to multispectral data. It has been proved that adding linearly irrelevant data to original data could improve the performance of CEM. In this study, two kinds of linearly irrelevant data are added for water extraction: the spectral indices and the spectral similarity metric data. CEM is designed for targets with low-probability distribution in an image, but water bodies do not always satisfy this condition. We thereby impose a sensible coefficient for each pixel to form the weighted autocorrelation matrix. In this study, the weight is based on the orthogonal subspace projection, so this new method is named Orthogonal subspace projection Weighted CEM (OWCEM). The newly launched Landsat 8 images over two lakes, the Hala Lake in China with ice/snow distributed in the north, and the Huron Lake in North America, a lake with a very large surface area, are selected to test the accuracy and robustness of our algorithm. The Kappa coefficient and the receiver operating characteristic (ROC) curve are calculated as an accuracy evaluation standard. For both lakes, our method can greatly suppress the background (including ice/snow and clouds) and extract the complete water surface with a high accuracy (Kappa coefficient > 0.96).

Toxaphene trends in the Great Lakes fish

As part of the U.S. Great Lakes Fish Monitoring and Surveillance Program (GLFMSP), more than 300 lake trout (Salvelinus namaycush) and walleye (Stizostedion vitreum vitreum) collected from the Laurentian Great Lakes each year from 2004 to 2009, have been analyzed for total toxaphene and eight selected congeners. The analytical results show fish toxaphene concentrations are quite different among lakes. Between 2004 and 2009, Lake Superior lake trout had the highest concentration (119 to 482ng/g) and Lake Erie walleye had the lowest concentration (18 to 47ng/g). Combining these results with the historical total toxaphene data (1977–2003), temporal changes were examined for each lake. Because of different analytical methods used in the previous studies, the historical data were adjusted using a factor of 0.56 based on a previous inter-method comparison in our laboratory. Trend analysis using an exponential decay regression showed that toxaphene in Great Lakes fish exhibited a significant decrease in all of the lakes with t1/2 (confidence interval) of 0.9 (0.8–1.1) years for Lake Erie walleye, 3.8 (3.5–4.1) years for Lake Huron lake trout, 5.6 (5.1–6.1) years for Lake Michigan lake trout, 7.5 (6.7–8.4) years for Lake Ontario lake trout and 10.1 (8.2–13.2) years for Lake Superior lake trout. Parlars 26, 50 and 62 were the dominant toxaphene congeners accounting for 0.53% to 41.7% of the total toxaphene concentration. Concentrations of these congeners generally also decreased over time.

9201 Tolerability profile of carfilzomib enables full-dose anti-tumor treatment for up to 12 months

Polyfluoroalkyl substances (PFAS) are a group of fluorinated organic chemicals that have been produced for industrial and commercial application since the 1950s. PFAS are highly persistent and ubiquitous in water, sediment, and biota. Toxic effects of PFAS on humans and the ecosystem have increased scientific and public concern. To better understand the distribution of PFAS in the Laurentian Great Lakes, carbon (12C and 13C) and nitrogen (14N and 15N) stable isotope enrichment, fatty acid profiles, and PFAS were measured in the Lake Huron (LH) aquatic food web. The trophic level of the organisms was estimated using δ15N and found to be a determinant of PFAS biomagnification. The δ13C and fatty acid profiles were used to assess the carbon/energy flow pathway and predator-prey relationships, respectively. The δ13C, δ15N, and fatty acids were used to elucidate the trophodynamics and understand the PFAS trophic transfer in the LH aquatic food web. Perfluorooctanesulfonic acid (PFOS) was the dominant PFAS observed, followed by C9 - C11 perfluorinated carboxylic acids (PFCA). The highest PFOS concentrations (45 ± 11 ng/g, wet weight (wwt)) were detected in lake trout (Salvelinus namaycush), while the highest total PFCA concentrations (sum of C4 – C16 PFCAs) were detected in deepwater sculpin (Myoxocephalus thompsonii). With the exception of perfluorooctanoic acid (PFOA), C8-C14 PFAS biomagnification factors (BMFs) were found to be generally greater than 1, suggesting PFAS biomagnification from prey to predator. Trophic magnification factors (TMFs) of C8-C14 PFCA were found to be independent of compound hydrophobicity.

Warmer and drier climates that make Lake Huron into a terminal lake

Paleo-hydrologists have adjusted for glacial isostatic uplift and compared the original elevations of paleo-water level indicators and basin outlets for Lake Huron, revealing that Huron lake levels fell tens of meters below its lowest possible outlet (becoming a terminal lake) about 7,900 14C years BP. This corresponds to when the upper Great Lakes stopped receiving glacial melt inflow and became dependent for water supply on precipitation alone, as at present. Since these researchers accounted for differential isostatic effects, they surmised that the upper Great Lakes were impacted by severe dry climate. To understand possible climate changes that led to the closure, the Great Lakes Environmental Research Laboratory applied their Advanced Hydrologic Prediction System to explore deviations from present climates that could force the upper Great Lakes to become terminal. GLERL modeled the steady-state water balance of the present upper Great Lakes with pre-development natural water flow conditions by employing lake outflow-depth rating curves (using estimated sill elevations) reasonable for a natural system and by using dynamic lake areas controlled by observed hypsometric relations for each lake. By using systematic shifts in precipitation and temperature relative to the present base climate, GLERL showed the temperature rises and precipitation drops required for a terminal lake; they may be less extreme if additional effects of past differences in wind speed and insolation are also considered.

Are PCB Levels in Fish from the Canadian Great Lakes Still Declining?

Long- and short-term levels and trends of polychlorinated biphenyls (PCBs) in lake trout ( Salvelinus namaycush) and walleye ( Sander vitreus) from the Canadian waters of the Great Lakes are examined using the bootstrap resampling method in light of the Great Lakes Strategy 2002 (GLS-2002) objective of decrease in concentrations by 25% during 2000–2007. This objective has been set as an indicator of progress toward the long-term goal of all Great Lakes fish being safe to eat without restriction. Lake Superior lake trout and walleye PCB concentrations were almost unchanged between 1990-2006, and the bootstrap analysis suggests that the probability of achieving the GLS-2002 objective is negligible (< 2%). The PCB levels in Lake Huron lake trout and walleye are decreasing; the declines between 2000–2007 are estimated to be 25–35% and 5–30%, respectively. In contrast, Lake Erie walleye concentrations will likely increase by 25–50% between 2000–2007. For Lake Ontario lake trout, achieving the 25% reduction target seems highly probable with a likely decrease of 45–55%; for Lake Ontario walleye, the probability of achieving such a reduction is only 8% with an expected change of −13 to +15%. Although the targeted reduction may not be achieved for walleye from Lakes Superior, Huron, and Ontario, their best projected 2007 PCB levels are below the unlimited fish consumption guideline of 105 ng/g wet weight used by the Ontario Ministry of the Environment. In contrast, although there are high probabilities of achieving the goal for lake trout from Lakes Huron and Ontario, their best projected 2007 PCB levels (160 and 370 ng/g ww, respectively) will continue to result in consumption restrictions. Lake Superior lake trout concentrations may remain unchanged at the current elevated level of 160 ng/g ww. For Lake Erie fish, the projected 2007 concentrations and the increasing trends are both worrisome. Additional measurements beyond 2007 are necessary to confirm these estimates because of the observed periodic oscillations in the concentrations.

Circulation and thermal structure in Lake Huron and Georgian Bay: Application of a nested-grid hydrodynamic model

A nested-grid hydrodynamic modelling system is used to study circulation and temperature distributions in Lake Huron (LH) and adjacent areas. This nested system is based on the three-dimensional, primitive-equation z-level ocean model. The nested system consists of two sub-components: a coarse-resolution outer model covering LH and Georgian Bay (GB) with a horizontal resolution of roughly 2.5 km, and the fine-resolution inner model covering eastern LH and northwestern GB with a horizontal resolution of roughly 900 m. Both the outer and inner models have 30 z-levels in the vertical. To assess the model performance, we simulate the three-dimensional circulation and temperature distributions of LH and GB in 1974–1975 and compare the model results with observations made in the lake. We demonstrate that outer model of the nested system simulates reasonably well the large-scale circulation and seasonal evolution of thermal stratifications in LH and GB, and the inner model produces reasonably well the three-dimensional flow and thermal structure over the coastal boundary layer close to the eastern shore of the lake.

Ballast-mediated animal introductions in the Laurentian Great Lakes: retrospective and prospective analyses

Since completion of the St. Lawrence Seaway in 1959, at least 43 nonindigenous species (NIS) of animals and protists have established in the Laurentian Great Lakes, of which ~67% were attributed to discharge of ballast water from commercial ships. Twenty-three NIS were first discovered in four "hotspot" areas with a high representation of NIS, most notably the Lake Huron – Lake Erie corridor. Despite implementation of the voluntary (1989, Canada) and mandatory (1993, U.S.A.) ballast water exchange (BWE) regulations, NIS were discovered at a higher rate during the 1990s than in the preceding three decades. Here we integrate knowledge of species' invasion histories, shipping traffic patterns, and physicochemical factors that constrain species' survivorship during ballast-mediated transfer to assess the risk of future introductions to the Great Lakes. Our risk-assessment model identified 26 high-risk species that are likely to survive intercontinental transfer in ballast tanks. Of these, 10 species have already invaded the Great Lakes. An additional 37 lower-risk species, of which six have already invaded, show some but not all attributes needed for successful introduction under current BWE management. Our model indicates that the Great Lakes remain vulnerable to ship-mediated NIS invasions.

The effects of presentation time on the localization accuracy of 3D sound through headphones

The present study deals with the relationship between sound presentation time and localization accuracy of 3D sound presented through headphones. Huron Lake CP4 system was used for sound presentation and Flock of birds tracking system was used to register movement of the head. There were 31 volunteers (15 females and 16 males) in this experiment. Six different types of sounds were presented with the duration of 0.5, 2, 4, and 6 s. They were dog bark (0–500 Hz), coin drop with three different bandwidths (0–1650 Hz, 1650–6500 Hz, and 0–8500 Hz), alarm (0–5500 Hz) and male speech voice (0–7000 Hz). The results showed that the accuracy of localizing the sound is significantly related to the duration of the sound presentation. The perceived azimuth difference for 0.5 s duration (45°±15° in average) is significantly higher compared with the longer presentation duration. The perceived azimuth difference for 2 s duration is also significantly higher than 4 and 6 s duration (21°±9° in average). There is not any significant difference between 4 and 6 s duration. There is not any significant difference between male and female subjects, but individual difference is significant.

Age and Growth of Round GobyNeogobius melanostomusin the Upper Detroit River

The round goby Neogobius melanostomus has quickly become one of the most abundant benthic fishes in the Lake Huron–Lake Erie corridor of the Laurentian Great Lakes since it was first discovered in the St. Clair River in 1990. We describe the age, growth, and size structure of the round goby population from samples collected in the upper Detroit River. Round gobies were collected using an otter trawl about every 3 weeks during spring, summer, and autumn 1996. Age-1 fish were found to be the most abundant group in the population, and fish size within a given age-group was highly variable. Both males and females were found to be maturing younger and at smaller sizes than in their native range. Marginal increment analysis of otoliths revealed that annulus formation occurred in late May–early June. Although mean size of fish differed significantly with sample date (P < 0.001), there was little increase in mean size from May to October. Age-1 fish had a larger growth than age-2 fish. Mean annual growth for age-1 males (37 mm) was greater than for females (33 mm), but size ranges overlapped. Early maturity and rapid growth are two factors that may ensure the continued expansion of the round goby throughout the Great Lakes.

PCB Congener Patterns in Rats Consuming Diets Containing Great Lakes Salmon: Analysis of Fish, Diets, and Adipose Tissue

As part of a multidisciplinary toxicological investigation into Great Lakes contaminants, chinook salmon were collected from Lake Huron (LH) and Lake Ontario (LO) and incorporated (as lyophilized fillets) into standard rat diets as 20 or 100% of the protein complement (5 or 20%, w/w diet—LH5, LH20, LO5, and LO20 diets). Final PCB concentrations in the experiment ranged from 3.15 ng/g in the control diet to 1080 ng/g in the high-dose (20%) LO diet, with maximal estimated daily consumption by the rats of 82μg PCBs/kg body wt in the LO20 dietary group. Seventeen PCB congeners, PCB 85, 99, 101, 105, 110, 118, 128, 129, 132, 138, 149, 153, 170, 177, 180, 187, and 199, occurred at ≥3.0% of the total PCBs in the fish with no major site differences. Cumulatively, these 17 congeners accounted for up to 75% of the total PCBs in the fish compared to 44 and 54% in two commercial Aroclors, 1254 and 1260, respectively. PCB 77 was the major “dioxin-like” congener in the fish, followed by PCB 126 and then PCB 169. All major dietary congeners bioaccumulated in the adipose tissue of the rats with the exception of PCB congeners 101, 110, 132, and 149. The group of 17 major congeners accounted for up to 71% of the total PCBs in adipose tissue samples collected from the rats following up to 19 weeks of diet ingestion. Of the coplanar PCB congeners, PCB 77 appeared to bioaccumulate to a lesser extent compared to PCBs 126 and 169. When comparing PCBs in the rat adipose tissue to PCB congeners in Canadian breast milk, PCBs 44, 49, 74, and 137 tended to occur in higher amounts in the human samples (contributing together 18.4 vs. 1.4% of the total PCB concentration), whereas PCB 129 occurred at higher levels in the rats (3.4 vs. 0.3% of the total PCB concentration, respectively). Although adipose tissue from the rats fed diets containing Great Lakes salmon had up to two orders of magnitude higher concentrations of PCBs compared to average human values, with the exception of some lower chlorinated congeners, similar major congeners tended to be present in both the rats in the present study and humans.

Effects of Great Lakes Fish Consumption on the Immune System of Sprague–Dawley Rats Investigated during a Two-Generation Reproductive Study: II. Quantitative and Functional Aspects

The effects of Great Lakes fish contaminants on several quantitative and functional aspects of the immune system were investigated in the first (F1) and second (F2) generations of Sprague–Dawley rats. The F0rats were fed either a control diet or diets containing 5 or 20% lyophilized chinook salmon from the Credit River of Lake Ontario (LO) and Owen Sound point of Lake Huron (LH). The F1and F2pups were exposed to fishin utero, through the dam's milk to 21 days old, and through the dam's respective diets to 13 weeks of age. The study included an F1-reversibility (F1-R) phase in which rats at 13 weeks of exposure to fish or control diets were switched to the control diet for 3 months. The most outstanding finding was a statistically significant increase in absolute spleen leukocytes and absolute and percentage lymphocytes in the F2male rats fed the LH fish diets compared to the control and to those fed the LO fish diets with the 20% fish diets having higher cell numbers compared to the LO-5% fish diets. A parallel increase in the T-helper/inducer T-lymphocyte subset numbers was observed. Increased but statistically insignificant plaque-forming cell (PFC) numbers were obtained in the F2male rats fed the LH fish diets compared to those fed the LO fish diets and in the F1-R female group of rats fed the LH fish diet compared to those fed the LO fish diets. Phagocytosis by resident peritoneal macrophages was significantly increased in the F1male and F2female rats fed the fish diets compared to the control. The phagocytic activity was significantly higher in the F2-generation male and female rats fed the LO diets compared to those fed the LH diets. Other parameters including lymphocyte transformation in response to mitogens, the number ofListeria monocytogenesbacteria surviving in the rat spleens, and the natural killer cell activity were not affected significantly by any of the treatments. Overall, the effects of diets containing chinook salmon from the LO and LH sources on the immune system of rats were minimal and were on quantitative rather than on functional aspects of the system. Further focused research would be required in order to establish conclusively that the immune system of cohorts who ingest Great Lakes fish frequently is at a greater risk for adverse effects.