Search

Isotopic and chemical analyses were performed on crustaceans, forage fish, top predator fish, and sediment cores from Lake Ontario and two boreal forest lakes to investigate fractionation of the stable isotopes of Hg in aquatic ecosystems. Multicollector inductively coupled mass spectrometry was used to determine Hg isotope abundances. The Hg isotope data for all three lakes showed mass-independent variation in the organisms but only mass-dependent variation in the sediments. The mass-independent isotope effect was characterised by (1) selective enrichment in isotopes of odd mass number ( 199 Hg and 201 Hg), (2) enrichment in 201 Hg relative to 199 Hg, (3) an inverse relationship between isotopes of odd and even mass number in fish, and (4) a positive correlation with methylHg (CH 3 Hg + ) concentration, and hence with trophic level (although lake whitefish were consistently anomalous, possibly owing to biochemical demethylation). Isotope signatures of species at the same trophic level varied with habitat and diet, differentiating between planktonic and benthic crustaceans and their predators, and between fish that frequent deep, cold water and fish of similar diet that prefer warmer, shallower water, because of corresponding differences in CH 3 Hg + and inorganic Hg content. Isotopic analysis of CH 3 Hg + and inorganic Hg extracted from lake trout proved that the mass-independent isotope effect was due to anomalously high abundances of 199 Hg and 201 Hg in CH 3 Hg + , as implied by the data for whole organisms, suggesting mass-independent fractionation during microbial methylation of Hg. The purely mass-dependent variation in the sediments is attributable to the fact that Hg in sediments is mostly inorganic. The mass-independent fractionation of Hg isotopes can be explained by effects of nuclear spin or nuclear field shift, or both, and penetration of the inner electron shells of Hg by valence electrons of Hg-binding ligands. The results of the research demonstrate that isotopic analysis of Hg could yield valuable information about the biogeochemical cycling of Hg.

The extent of bioaccumulation of the syn- and anti-isomers of Dechlorane Plus (DP) is assessed in archived food web samples from Lake Winnipeg and Lake Ontario. Concentrations of the isomers were determined using purified analytical solutions of individual isomers as opposed to the technical mixture. The syn-isomer was consistently detected in all samples from both lakes; the anti-isomer was detected in all Lake Ontario samples, but only 45% of the samples from Lake Winnipeg. The pattern of bioaccumulation was different for the isomers in Lake Winnipeg. The anti-isomer was dominant in higher trophic level (TL) organisms like walleye [arithmetic mean +/- 1 x standard error: 730 +/- 120 pg/g, lipid weight (1w)] and goldeye (760 +/- 170 pg/g, Iw) while the syn-isomer dominated the lower TL organisms like zooplankton (550 +/- 40 pg/g, Iw) and mussels (430 +/- 140 pg/g, Iw). In Lake Ontario, the extent of bioaccumulation of the isomers and concentrations was greatest in the lower TL benthic organism, Diporeia (syn, 1307 +/- 554; and anti, 3108 +/- 898 pg/g Iw) and also high in zooplankton (syn, 719; and anti, 1332 pg/g Iw). This suggests that the isomers are bioavailable in sediment and that, despite their molecular size, diffusion from the water column into zooplankton can occur. Differences in the mean fractional abundance of the anti-isomer (mean fanti = mean concentration of the anti-isomer divided by sum of mean syn- and anti-concentrations) were pronounced in sediments between lakes (Lake Winnipeg mean fanti = 0.610, Lake Ontario mean fanti = 0.860) and the extent of enrichment (anti-) and depletion (syn-) of the isomers were more marked in Lake Winnipeg biota. There were also differences in the biomagnification potentials, as measured bythe trophic magnification factor (TMF), between the isomers in the Lake Winnipeg food web; no statistically significant TMFs for either isomer were found for the

The bioaccumulation and biotransformation of toxaphene was examined in the food webs of Lake Superior and Siskiwit Lake (Isle Royale) using congener specific analysis as well as stable isotope ratios of carbon and nitrogen to characterize food webs. Toxaphene concentrations (calculated using technical toxaphene) in lake trout (Salvelinus namaycush) from the western basin of Lake Superior (N = 95) averaged (±SD) 889 ± 896 ng/g wet wt and 60 ± 34 ng/g wet wt in Siskiwit Lake. Major congeners in lake trout were B8-789 (P38), B8-2226 (P44), B9-1679 (P50), and B9-1025 (P62). Toxaphene concentrations were found to vary seasonally, especially in lower food web organisms in Lake Superior and to a lesser extent in Siskiwit Lake. Toxaphene concentrations declined significantly in lake herring (Coregonus artedii), rainbow smelt (Omerus mordax), and slimy sculpin (Cottus cognatus) as well as in zooplankton (> 102 μm) and Mysis (Mysis relicta) between May and October. The seasonal variation may reflect seasonal shifts in the species abundance within the zooplankton community. Trophic magnification factors (TMF) derived from regressions of toxaphene congener concentrations versus δ15N were > 1 for most octa- and nonachlorobornanes in Lake Superior except B8-1413 (P26) and B9-715. Log bioaccumulation factors (BAFs) for toxaphene congeners in lake trout (ng/g lipid/ng/L dissolved) ranged from 4.54 to 9.7 and were significantly correlated with log octanol-water partition coefficients. TMFs observed for total toxaphene and congener B9-1679 in Lake Superior were similar to those in Arctic lakes, as well as to previous studies in the Great Lakes, which suggests that the bioaccumulation behavior of toxaphene is similar in pelagic food webs of large, cold water systems. However, toxaphene concentrations were lower in lake trout from Siskiwit Lake and lakes in northwestern Ontario than in Lake Superior possibly because of shorter food chains and greater reliance on zooplankton or other pelagic invertebrates.

The enantiomeric composition of seven chiral PCB congeners was measured in the Lake Superior aquatic food web sampled in 1998, to determine the extent of enantioselective biotransformation in aquatic biota. All chiral PCB congeners studied (CBs 91, 95, 136, 149, 174, 176, and 183) biomagnified in the Lake Superior aquatic food web, based on biomagnification and food web magnification factors greater than unity. PCB atropisomers were racemic in phytoplankton and zooplankton, suggesting no biotransformation potential toward PCBs for these low trophic level organisms. However, Diporeia and mysids had significantly nonracemic residues for most chiral congeners studied. This observation suggests that these macrozooplankton can stereoselectively metabolize chiral congeners. Alternatively, macrozooplankton obtained nonracemic residues from feeding on organic-rich suspended particles and sediments, which would imply that stereoselective microbial PCB biotransformation may be occurring in Lake Superior sediments at PCB concentrations far lower than that previously associated with such activity. Widely nonracemic PCB residues in forage fish (lake herring, rainbow smelt, and slimy sculpin) and lake trout suggest a combination of both in vivo biotransformation and uptake of nonracemic residues from prey for these species. Minimum biotransformation rates, calculated from enantiomer mass balances between predators and prey, suggest metabolic half-lives on the order of 8 yr for CB 136 in lake trout and 2.6 yr for CB 95 in sculpins. This result suggests that significant biotransformation may occur for metabolizable PCB congeners over the lifespan of these biota. This study highlights the potential of chiral analysis to study biotransformation processes in food webs.

The Great Lakes Water Quality Agreement stipulates that the Governments of Canada and the United States are responsible for restoring and maintaining the chemical, physical and biological integrity of the waters of the Great Lakes Basin Ecosystem. Due to varying mandates and areas of expertise, monitoring to assess progress towards this objective is conducted by a multitude of Canadian and U.S. federal and provincial/state agencies, in cooperation with academia and regional authorities. This paper highlights selected long-term monitoring programs and discusses a number of documented ecological changes that indicate the present state of the open and nearshore waters of the Great Lakes.

SigmaPCB and p,p'-DDE levels within and among walleye (Stizostedion vitreum) populations were examined to determine how the method of data analysis could influence the interpretation of (i) gender differences and (ii) geographic variation. In the lower Great Lakes (Huron, Erie, and Ontario) whole-body burdens of both contaminants tended to increase with body mass at a faster rate in males than in females. Thus, males generally had higher burdens than females at large body sizes but not at small body sizes. This result was not strongly influenced by the method of expressing contaminant level (burden, wet mass concentration, or lipid mass concentration) but was influenced by the choice of covariate (body mass, body length, or age) in some cases. Mean sigmaPCB and p,p'-DDE concentrations of walleye muscle declined along a gradient from the lower Great Lakes to the Northwest Territories. Analyses using means adjusted for age yielded a stronger contrast between Great Lakes and non-Great Lakes populations than analyses using means adjusted for body length. The gender composition of fish samples and the type and level of covariate used in statistical analyses should be considered in studies of spatiotemporal variation in organochlorine bioaccumulation in fish.

A food web bioaccumulation model was used to compare transport and fate of polychorinated biphenyls (PCB) congeners in three food webs in the Laurentian Great Lakes of North America. The model was used to quantify the contribution of sediment-derived and freely dissolved PCBs to the body burden of aquatic biota. In eastern Lake Erie (OH, USA), almost 100% of the chemical body burden of biota originates from sediment. In western Lake Erie, benthic invertebrates accumulated slightly more than half of their PCB body burden from sediment while fish accumulated less than half of their chemical body burden from sediment. Fish from Lake Ontario, Canada, accumulated less than 30% of their body burden of PCB congeners with log Kow or = 6.4 from sediment. Field data and the model were also used to determine the effects of declining concentrations of PCBs in water and sediment on concentrations of PCBs in aquatic biota. Results indicate that, as concentrations of PCB congeners in the ecosystem decline, the role of sediment as the source of contaminant to aquatic biota increases. Furthermore, as sediment becomes the predominant source of contaminant to aquatic biota. the concentration of PCB congeners in biota tends to equilibrium with bottom sediment.

PCB congener concentrations were measured in aquatic biota and sediment from the western basin of Lake Erie during 1993–1994 and 1996–1997. Between these time periods the round goby (Neogobius melanostomus) invaded and proliferated in the basin and mean annual particulate organic carbon (POC), dissolved organic carbon (DOC) and PCB congener concentrations in sediment changed. The objectives of this study were to use a food web bioaccumulation model and field data to quantify the relative importance of the round goby, POC, DOC and chemical concentration in sediment, to PCB congener levels in aquatic biota prior to (1993–1994) and since (1996–1997) the invasion of the basin by round gobies. The predicted effects of round gobies on PCB congener transfer, mediated through alterations in food web structure, were small increases (range 2–6%) in PCB burdens of pelagic fish species such as alewife and walleye. Larger increases (range 8–19%) in PCB burdens were predicted for benthic feeding sport fish species such as yellow perch and largemouth bass. Small decreases (range 1–5%) in PCB congener concentrations in fish were predicted to result from decreases in bioavailable concentrations of PCBs in water. Bioavailable concentrations of PCBs in water were predicted to decrease as a result of observed changes in POC and DOC concentrations. However, in all cases predicted changes in PCB concentrations in fish, resulting from changes in food web structure and POC and DOC, were smaller than those predicted from measured increases in PCB congener concentrations in sediment between 1993 and 1994 and 1996–1997. Increased concentrations of PCBs in sediment were attributed to exposure of older and more heavily contaminanted sediments from turbulence caused by higher wind speeds in 1996–1997 compared to 1993–1994.

Adult sea lamprey (Petromyzon marinus) were collected during their spawning migration in streams entering each of the Great Lakes, except Lake Michigan. Skinless muscle tissue samples were analyzed for a range of organochlorine contaminants including p,p’-DDE, total PCB, toxaphene, and mercury. Concentrations of p,p’-DDE and PCBs were above the detection limit of 0.002 μg/g in all samples. Levels of total toxaphene in some individuals from Lake Superior were above recent Health Canada consumption advisory limits of 0.2 μg/g for fish. PCBs and ΣDDT concentrations in some lamprey tissue samples from the Lake Ontario basin exceeded limits for unrestricted human consumption. Mercury concentrations were highest in lamprey from the Lake Superior basin. Mercury levels were above the 0.5 μg/g Canada Health Protection Guideline for consumption in 75% of all the lamprey muscle tissue samples analyzed. Comparison of organic contaminant levels for lamprey muscle tissue samples and whole lake trout (Salvelinus namaycush) collected from the same lakes showed patterns of contaminant accumulation that were similar within each lake for both species. Mercury concentrations were up to 10 times higher in lamprey muscle tissue samples than whole lake trout sampled from the same lake. Lamprey display a differential ability to accumulate mercury versus organochlorines. By understanding these relationships for different classes of contaminants, it may be possible to utilize lamprey as a future alternate to lake trout as an indicator species to track spatial and temporal contaminant trends in the Great Lakes.

A previously developed benthic/pelagic food web bioaccumulation model was parameterized to predict concentrations of nine nonmetabolized polychlorinated biphenyl (PCB) congeners in invertebrates and fish from Lake Ontario. Predicted concentrations were compared with field-measured concentrations to verify the predictability of the model. Overall, 86% of model predictions were within a factor of 2 and 100% of predictions were within a factor of 10 of field-measured concentrations. The parameterized model was used to estimate chemical metabolic rates for 15 PCB, polychlorinated dibenzo-p-dioxin (PCDD), and polychlorinated dibenzo-p-furan (PCDF) congeners that are potentially metabolized. Estimated chemical metabolic rates ranged from 7.5 × 10-3 to 1.0 × 10-7·day-1 and were in general agreement with qualitative studies describing rates of metabolism of these chemicals by aquatic biota. The calibrated model was used to predict concentrations of all 24 PCB, PCDD, and PCDF congeners in invertebrates and fish commonly found in Lake Ontario but for which no field-measured data exist. These concentrations were expressed as the logarithm of the bioaccumulation factor (log BAF). The log BAF's in benthic invertebrates and salmonids ranged from 4.2 to 10.2 and from 5.1 to 11.6, respectively, and were consistent with field-measured BAF's.

A food web bioaccumulation model was used to hindcast PCB congener concentrations in aquatic biota from western Lake Erie in the years prior to the zebra mussel invasion, and these results were compared to post-mussel predicted concentrations that had been verified previously against measured data to estimate the effects of mussels on the trophodynamics of PCB congeners in western Lake Erie. Two hindcasting scenarios were compared to a third, previously verified, scenario to determine the changes in PCB congener concentrations in biota in response to (i) modifications to food web structure, before and after the introduction of mussels, and (ii) modifications to food web structure combined with a decline in particulate organic carbon (POC) concentrations resulting from removal of seston from the water column by mussel filtering activities. The reduction in the concentration of POC, attributed to the prodigious filter-feeding of large zebra mussel populations, was predicted to have caused increases in the f...

Concentrations of 21 organochlorine contaminants (OCs) and 61 polychlorinated biphenyl (PCB) congeners were determined in archived samples of whole lake trout ( Salvelinus namaycush ), age 4 years, collected yearly from eastern Lake Ontario between 1977 and 1993. Temporal trend data show decreases in all parameters analyzed in samples collected from 1977 to 1993. OC levels declined between 60 and 90% from 1977 to 1993. Trends of total PCB and PCB congeners concentrations were variable, but overall levels declined 80% between 1977 and 1993, from 9,060 ng/g in 1,977 to 1,720 ng/g in 1993. Reanalyzed total PCB levels vary randomly from the historical total PCB levels, but overall exhibit a much smoother trend. The means of the two sample sets were not significantly different at a probability of 0.05. Lake trout aged from 3 to 9 years old, collected in 1988, were analyzed to determine changes in contaminant concentrations with age. OC levels on average increased three-fold from 3-year-old lake trout up to 9-year-old lake trout. Total PCB levels increased from 2,760 ng/g in 3-year-old lake trout to 8,000 ng/g in 9-year-old lake trout, and PCB congener concentrations showed similar increases over the same age range. Lipid content declined 30% between 1977 and 1993, but lipid normalizing the data did not change the observed trends.

Stable isotopes of nitrogen (δ15N) and carbon (δ13C) were used to describe the trophic status and interactions of biota characteristic of a Lake Ontario pelagic food web. Stable isotopes of nitrogen were further used to characterize the relationship between an organism's trophic position and the biomagnification of specific hydrophobic contaminants through this food web. The δ15N defines the relative trophic status as (i) the top predator, lake trout (Saivelinus namaycush); (ii) prey species, alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), and slimy sculpin (Cottus cognatus); (iii) macroinvertebrates, mysids (Mysis relicta), and amphipods (Diporeia hoyi); (iv) net zooplankton, dominated by cyclopoids (Diacyclops thomasi) and cladocerans (Bosmina longirostris); and (v) net phytoplankton, dominated by diatoms (Melosira spp.). The separation of the four fish species, lake trout and associated prey items (alewife, rainbow smelt, and slimy sculpin), on the basis of their mean δ13C signatures complements what is known about the preferred diet of these fishes. The enrichment of15N through this food web indicates that there is a strong correlation between the biomagnification of persistent lipophilic contaminants (p,p′-DDE, mirex, and PCB) and the relative trophic status of an organism as described by stable isotopes of nitrogen.

We determined total mercury (Hg) concentrations in 50 female lake trout (Salvelinus namaycush) and 69 male lake trout from Lake Ontario (Ontario, Canada and New York, United States). Results showed that, on average, males were 8% higher in Hg concentration than females in Lake Ontario. We also used bioenergetics modeling to determine whether a sexual difference in gross growth efficiency (GGE) could explain the observed sexual difference in Hg concentrations. According to the bioenergetics modeling results, male GGE was about 3% higher than female GGE, on average. Although the bioenergetics modeling could not explain the higher Hg concentrations exhibited by the males, a sexual difference in GGE remained a plausible explanation for the sexual difference in Hg concentrations of the lake trout. In an earlier study, male lake trout from Lake Ontario were found to be 22% higher in polychlorinated biphenyl (PCB) concentration than females from Lake Ontario. Thus, although males were higher in both Hg and PCB concentrations, the degree of the sexual difference in concentration varied between the two contaminants. Further research on sexual differences in Hg excretion rates and Hg direct uptake rates may be needed to resolve the disparity in results between the two contaminants.

Tissue levels of chlorinated dioxins and furans and the physiological and biochemical responses of fish were measured upstream and downstream of a bleached kraft mill in the St. Maurice River, Quebec. Relative to fish 10 km upstream of the source, white suckers (Catostomus commersoni) downstream showed evidence of chemical exposure, chemical metabolism, stress, and altered energy use. Levels of 2,3,7,8–tetrachlorodibenzo-p-dioxin and tetrachlorodibenzofuran in gutted whole fish averaged 23 and 260 pg/g immediately downstream of the plant and declined to 18 and 112 pg/g at 95 km downstream. The activity of hepatic aryl hydrocarbon hydroxylase (AHH) was 10X higher immediately downstream and 5X higher 95 km downstream. There were corresponding increases in relative liver size, hematocrit, serum glucose, serum protein, and fin-ray asymmetries, with a pattern of response that matched enzyme induction. These responses pointed to a strong effluent effect and followed the patterns of tissue contamination by dioxins and furans and of water contamination by chlorinated phenolics and guaiacols. There were strong correlations between AHH induction and tissue contamination. Whereas lipid levels increased at all downstream sites, condition factor decreased at 95 km from the source, indicating that there may be disturbances in energy metabolism. Effects on sexual maturation, as shown by levels of serum hormones and gonad somatic index, were inconclusive.

Whole body concentrations of DDE and total PCB in Lake Ontario smelt, and PCB concentrations in Lake Ontario sculpin, displayed no significant time trend from 1977 to 1988. Conversely, DDE concentrations in sculpin have decreased. Mercury concentrations in both smelt and sculpin whole fish samples decreased with a half life of about 10 years, similar to the rate of decrease in lake trout. The ratios of DDE and PCB concentrations in lake trout to those in smelt have decreased. This decrease correlates with a drop in lake trout lipid concentrations suggesting that food intake by trout may have decreased, and growth efficiency increased. DDE and PCB concentrations in both smelt and alewives were higher in the western end of Lake Ontario than in the eastern end, similar to the spatial trend observed for lake trout.

We determined polychlorinated biphenyl (PCB) concentrations in 61 female lake trout (Salvelinus namaycush) and 71 male lake trout from Lake Ontario (Ontario, Canada and New York, United States). To estimate the expected change in PCB concentration due to spawning, PCB concentrations in gonads and in somatic tissue of lake trout were also determined. In addition, bioenergetics modeling was applied to investigate whether gross growth efficiency (GGE) differed between the sexes. Results showed that, on average, males were 22% higher in PCB concentration than females in Lake Ontario. Results from the PCB determinations of the gonads and somatic tissues revealed that shedding of the gametes led to 3% and 14% increases in PCB concentration for males and females, respectively. Therefore, shedding of the gametes could not explain the higher PCB concentration in male lake trout. According to the bioenergetics modeling results, GGE of males was about 2% higher than adult female GGE, on average. Thus, bioenergetics modeling could not explain the higher PCB concentrations exhibited by the males. Nevertheless, a sexual difference in GGE remained a plausible explanation for the sexual difference in PCB concentrations of the lake trout.

A regression model was used to determine the trend in time and the effects of sampling site, age, and weight on DDE, PCB, mirex, dieldrin, chlordane, and mercury concentrations in lake trout from Lake Ontario from 1977 to 1988. The model allows the use of the entire data set collected by the Canadian Federal Department of Fisheries and Oceans monitoring program for lake trout in this lake up to 1988, and provides estimates of logarithmic mean concentrations in each age group independent of the overall (across all ages) contaminant: body size relationship. Mercury concentrations decreased steadily during the study period with a half life of 11 years. DDE concentrations decreased rapidly from 1977 to 1980 but then remained relatively constant. Mirex concentrations generally decreased, but with much year-to-year variation. Dieldrin concentrations decreased from 1978 to 1988, but chlordane concentrations remained relatively constant. PCB concentrations decreased from 1977 to 1981, increased in 1982 until 1984, and decreased again in 1985. The overall trend in PCB concentrations was a gradual decline with a half life of roughly 10 years. Deviations about this trend were closely related to the rate of growth of the alewife population, a principal food of lake trout, suggesting that food web interactions play an important role in regulating PCB concentrations in lake trout. Lipid concentrations in lake trout also decreased from 1977 to 1988, complicating interpretation of the time trends in the lipid soluble organic contaminants. PCB, DDE, and mirex concentrations in trout increased from east to west in Lake Ontario. All contaminant concentrations increased with increasing age and body size, but the body size effect was less within an age class than across age classes.

Chlorinated paraffins (CPs) are complex mixtures of chlorinated alkanes used in a myriad of industrial applications as flame retardant plasticizers and additives. In this study, the distribution and bioaccumulation/biomagnification of short-chain CPs (C10-C13, SCCPs) and medium-chain CPs (C14-C17, MCCPs) were investigated in samples collected between 1999 and 2004 from Lake Ontario and northern Lake Michigan. Total (sigma) SCCPs and sigmaMCCPs concentrations in water from Lake Ontario were 1190 pg/L and 0.9 pg/L (data from 2004 only), respectively. CPs were also detected in invertebrates and fish from both lakes. SCCP predominated in organisms from Lake Michigan with the highest mean concentrations found in lake trout [Salvelinus namaycush, 123 +/- 35 ng/g wet weight (ww)]. In Lake Ontario, MCCPs predominated in most species with the highest levels detected in slimy sculpin (Cottus cognatus, 108 ng/g ww) and rainbow smelt (Osmerus mordax, 109 ng/g ww). Bioaccumulation and biomagnification of CPs was evaluated on an isomer basis (i.e., C10H17Cl5, C10H16Cl6, etc). Log bioaccumulation factors for lake trout (lipid based) ranged from 4.1 to 7.0 for SCCPs and 6.3 to 6.8 for MCCPs. SCCPs and MCCPs were found to biomagnify between prey and predators from both lakes with highest values observed for Diporeia-sculpin (Lake Ontario, C15Cl9 = 43; Lake Michigan, C10Cl5 = 26). Trophic magnification factors for the invertebrates-forage fish-lake trout food webs ranged from 0.41 to 2.4 for SCCPs and from 0.06 to 0.36 for MCCPs. Given the prominence of CPs, particularly in lake waters and in lower food web organisms, further investigation is needed to evaluate the magnitude of their distribution and accumulation/magnification in the Great Lakes environment.

Biota and surface sediments collected from Lake Ontario were analyzed for polychlorinated naphthalenes (PCNs) and non- and mono-ortho-substituted polychlorinated biphenyls (n/m-o-PCBs) to compare bioaccumulation behavior of these classes of dioxin-like chemicals in a food web from the Great Lakes. Mean ΣPCN concentrations (tri-octaCN) ranged from 14 ± 9 pg/g in plankton to 3500 ± 3200 pg/g (wet weight) in lake trout, while sediments contained from 21 to 38 ng/g (dry weight). Principal components analysis of PCN congener patterns indicated that chlorine substitution determined which congeners favored accumulation (e.g., CN-42, -52, -60, -66, -67, and -73), while others may be subject to metabolism. The bioaccumulative congeners exhibited similar trophic magnification factors (TMFs; 1.23-1.42) and biomagnification factors (BMFs; 5.5-8.6) to the n/m-o-PCBs for the trout/weighted diet relation, although BMFs for a benthic feeding relationship (slimy sculpin/Diporeia) indicated that the n/m-o-PCBs were more bioavailable through the benthic pathway. PCNs contribute significantly to the burden of dioxin-like compounds in Lake Ontario biota, contributing between 12 and 22% of total PCN + PCB TEQ in lake trout and up to 69% in benthic organisms. © 2008 American Chemical Society.

Individual whole body homogenates of 4 year old lake trout (Salvelinus namaycush) samples collected in 2001 from each of the Great Lakes were extracted using a novel fluorophilicity cleanup step and analyzed for perfluoroalkyl compounds (PFCs). Standard addition and internal standardization were used for quantification. Results were reported (+/- SE) for perfluorinated carboxylates (PFCAs), perfluorinated sulfonates (PFSAs), and unsaturated fluorotelomer carboxylates (8:2 and 10:2 FTUCA). The lowest average concentration of sigmaPFC was found in samples from Lake Superior (13+/-1 ng g(-1)), while the highest average concentration was found in samples from Lake Erie (152+/-14 ng g(-1)). Samples from Lake Ontario (60+/-5 ng g(-1)) and Lake Huron (58 +/-10 ng g(-1)) showed similar average sigmaPFC concentrations, although the perfluorinated sulfonate/carboxylate ratios were different. The major perfluoroalkyl contaminant observed was perfluorooctane sulfonate (PFOS) with the highest concentration found in samples from Lake Erie (121+/-14 ng g(-1)), followed by samples from Lake Ontario (46+/-5 ng g(-1)), Lake Huron (39 +/-10 ng g(-1)), Lake Michigan (16+/-3 ng g(-1)), and Lake Superior (5+/-1 ng g(-1)). Perfluorodecane sulfonate (PFDS) was detected in 89% of the samples, with the highest concentration in Lake Erie samples (9.8+/-1.6 ng g(-1)), and lowest concentration in samples from Lake Superior (0.7 +/- 0.1 ng g(-1)). Statistically significant correlations were observed between PFOS and PFDS concentrations, and PFOS concentration and body weight, respectively. The PFCAs were detected in all samples, with the highest total average concentration in samples from Lake Erie (19 ng g(-1)), followed by samples from Lake Huron (16 ng g(-1)), Lake Ontario (10 ng g(-1)), Lake Michigan (9 ng g(-1)) and Lake Superior (7 ng g(-1)). The compounds with significant contributions to the sigmaPFCA concentrations were PFOA and C9-C13-PFCAs. The 8:2 FTUCA was detected at concentrations ranging between 0.1 and 0.2 ng g-1, with the highest level in samples showing also elevated concentrations of PFOA (4.4 ng g(-1) for Lake Michigan vs 1.5 ng g(-1) for all other samples). The 10:2 FTUCA was detected only in 9% of all samples (nd, 45 pg g(-1)). For those PFCs where we determined lake water concentrations, the highest log BAFs were calculated for PFOS (4.1), PFDA (3.9), and PFOSA (3.8).

We compared total mercury concentrations ([Hg]) among 6 forage fish species in 25 central Canadian lakes and related [Hg] to adjusted-delta15N (an index of trophic position), delta13C, growth rate, and a suite of environmental variables. Growth rates were also compared among species and related to environmental variables. We found that rainbow smelt (Osmerus mordax), a recent invader in many of these lakes, had intermediate [Hg] and growth rates relative to other species. Forage fish growth rates differed significantly among species and were related to latitude (inverse relationship) and lake conductivity (positive relationship). Mercury concentrations also differed significantly among species and the strongest predictors were growth rate and lake conductivity; [Hg] was significantly and negatively related to both. Adjusted-delta15N explained very little variation in [Hg] and was significant only when the analysis was restricted to biotic variables. These results indicate that biomagnification may not be observed at fine scales of trophic differentiation and that rainbow smelt are unlikely to cause post-invasion [Hg] increases in most predatory fish species.

Laboratory research has shown that female fish can pass toxic organochlorines (OCs) from their bodies to their eggs, killing their offspring if sufficient quantities are transferred. We conducted a controlled incubation study using gametes from a wild, OC-contaminated walleye (Sander vitreus) population (Bay of Quinte, Lake Ontario, Canada) in order to assess among-female variation in offspring early life survival in relation to ova concentrations of planar OCs (polychlorinated dibenzo-p-dioxins and furans and planar polychlorinated biphenyls) and a suite of other maternal and ova characteristics. Equal volumes of ova from each female were fertilized, pooled, and incubated together as an experimental cohort. Relative survival of each female's offspring was estimated as the proportion of surviving larvae (at approximately 5 d posthatch) that she contributed to the cohort as determined by microsatellite DNA parentage assignment. Total planar OC concentration (expressed as toxic equivalency of 2,3,7,8-tetrachlorodibenzo-p-dioxin) of ova was positively related to maternal age and size and to ova lipid content. However, early life survival did not decline with increasing ova planar OC concentrations. Similarly, we observed no significant relationships between early life survival and ova thiamine content, ova fatty acid composition, or maternal age or size. Early life survival was more strongly correlated with date of spawn collection, thyroid hormone status of the ova, and ovum size. Maternally transferred planar OCs do not appear to negatively influence female reproductive success in this walleye population.

We determined polychlorinated biphenyl (PCB) elimination patterns in lake trout (Salvelinus namaycush) from Lake Ontario using biomonitoring data collected from 1977 to 1993. The in situ elimination rates of these persis- tent pollutants were found to describe tissue turnover rates in lake trout. A model relating tissue turnover rates and en- dogenous energy conversion efficiencies revealed that chemical elimination in larger organisms is primarily regulated by food limitation and bioenergetic mechanisms rather than chemical kinetics. Lake trout approximately 2500 g and larger were observed to have higher PCB elimination rates than smaller fish as a result of increased lipid mobilization to supplement metabolic demands due to increased time spent foraging. This study concludes that the growth and pro- duction of large predators in Lake Ontario are regulated by the bioenergetic constraints of searching for prey in a food- limited environment. We also demonstrate that persistent organic pollutant kinetics can describe the proportion of en- dogenous energy required to support metabolism and production, thus providing important in situ measurements of bioenergetic processes. Resume : Des donnees de surveillance biologique de 1977 a 1993 nous ont servi a determiner les patrons d'elimination des biphenyls polychlores (BPC) chez le touladi (Salvelinus namaycush) au lac Ontario. Les taux d'elimination sur place des ces polluants persistants representent les taux de remplacement tissulaire chez le touladi. Un modele qui met en relation les taux de remplacement tissulaire et les efficacites endogenes de conversion energe- tique montre que l'elimination chimique chez les organismes de plus grande taille est principalement controlee par la limitation de nourriture et les mecanismes bioenergetiques que par la cinetique chimique. Les touladis d'environ 2500 g et de taille superieure ont des taux d'elimination de BPC plus eleves que les poissons plus petits a cause d'une mobili- sation plus forte des lipides pour assurer les besoins energetiques requis par un temps plus long passe a la recherche de nourriture. Notre etude conclut que la croissance et la production des grands predateurs dans le lac Ontario sont controlees par les contraintes bioenergetiques reliees a la recherche de proies dans un milieu ou la nourriture est li- mitee. Nous demontrons aussi que la cinetique des polluants organiques persistants peut decrire la proportion de l'energie endogene qui est requise pour supporter le metabolisme et la production, ce qui fournit des mesures in situ des processus bioenergetiques.

Perfluorooctane sulfonate (PFOS) is a persistent and bioaccumulative perfluorinated acid detectable in humans and wildlife worldwide that has alerted scientists to examine the environmental fate of other fluorinated organic contaminants. Recently a homologous series of perfluoroalkyl carboxylates (PFCAs) was detected in the Arctic, yet little is known about their sources, breadth of contamination, or environmental distribution. In this study we analyzed for PFOS, the homologous series of PFCAs ranging from 8 to 15 carbons in chain length, and the PFOS-precursor heptadecafluorooctane sulfonamide (FOSA) in various organisms from a food web of Lake Ontario. The sampled organisms included a top predator fish, lake trout (Salvelinus namaycush), three forage fish species including rainbow smelt (Osmerus mordax), slimy sculpin (Cottus cognatus), and alewife (Alosa pseudoharengus), and two invertebrates Diporeia (Diporeia hoyi) and Mysis (Mysis relicta). A striking finding was that the highest mean concentration for each fluorinated contaminantwas detected in the benthic macroinvertebrate Diporeia, which occupies the lowest trophic level of all organisms analyzed. Perfluorinated acid concentrations in Diporeia were often 10-fold higher than in Mysis, a predominantly pelagic feeder, suggesting that a major source of perfluoroalkyl contaminants to this food web was the sediment, not the water. PFOS was the dominant acid in all samples, but long-chain PFCAs, ranging in length from 8 to 15 carbons, were also detected in most samples between

The extent of bioaccumulation of hexabromocyclododecane (HBCD) isomers (alpha, beta, and gamma) was determined in the Lake Ontario pelagic food web using liquid chromatography tandem mass spectrometry (LC/MS/MS). Concentrations of the alpha-isomer were consistently higher than that of the gamma-isomer. The beta-isomer was below method detection limits in all samples. Whole body concentrations (ng/g, wet wt) of alpha- and gamma-HBCD were highest in the top predator lake trout samples ranging from 0.4 to 3.8 ng/g for the alpha-isomer and 0.1 to 0.8 ng/g for the gamma-isomer. For the prey fish species, the trends in alpha- and gamma-HBCD levels were slimy sculpin > smelt > alewife. Mean concentrations of total (sigma) HBCD (sum of alpha- and gamma-isomers) in the macrozooplankter Mysis relicta (0.14 +/- 0.02 ng/g wet wt) and in the benthic invertebrate Diporeia hoyi (0.16 +/- 0.02 ng/g, wet wt) were similar and approximately twice as high as in plankton (0.06 +/- 0.02 ng/g, wet wt). A strong positive linear relationship was found between sigmaHBCD concentrations (wet wt) and trophic level based on delta15N suggesting that HBCD biomagnifies in the Lake Ontario food web. The trophic magnification factor (TMF = 6.3) derived from the slope of the sigmaHBCD - trophic level relationship was slightly higher than TMFs for p,p'-DDE (6.1) and sigmaPCBs (5.7) found previously. Biomagnification factors (BMF, calculated as the ratio of lipid corrected concentration in predator/lipid corrected concentration in prey) were variable between feeding relationships and ranged from 0.4 to 10.8 for the alpha-isomer and from 0.2 to 10 for gamma-isomers.

The Great Lakes Water Quality Agreement stipulates that the Governments of Canada and the United States are responsible for restoring and maintaining the chemical, physical and biological integrity of the waters of the Great Lakes Basin Ecosystem. Due to varying mandates and areas of expertise, monitoring to assess progress towards this objective is conducted by a multitude of Canadian and U.S. federal and provincial/state agencies, in cooperation with academia and regional authorities. This paper highlights selected long-term monitoring programs and discusses a number of documented ecological changes that indicate the present state of the open and nearshore waters of the Great Lakes.

Concentrations of two types of brominated flame-retardants (BFRs); polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls (PBBs) were determined in a single age class of lake trout (Salvelinus namaycush) collected from the Laurentian Great Lakes in 1997. Mean concentrations of total PBDE were highest in samples from Lake Ontario at 95±22 ng / g wet weight (ww) or 434±100 ng / g lipid weight (lw) while the lowest concentrations were observed in Lake Erie lake trout (27±8.6 ng / g ww , 117±37 ng / g lw ) . In all samples, the predominant PBDE congeners were 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47), 2,2′,4,4′,5-pentabromodiphenyl ether (BDE-99), and 2,2′,4,4′,6-pentabromodiphenyl ether (BDE-100), which are the primary components of the commonly used penta-BDE formulation flame retardant. Lake trout collected from Lake Huron had the highest concentrations of PBBs (3.1±1.7 ng / g ww , 15±8.5 ng / g lw ) , while the lowest levels were detected in fish from Lake Superior (0.25±0.13 ng / g ww , 1.7±0.89 ng / g lw ) . In all lake trout samples, 2,2′,4,4′,5,5′-hexabromobiphenyl (BB-153), a major constituent of the flame-retardant FireMaster BP-6®, was the predominant PBB congener.

A food web bioaccumulation model was used to compare transport and fate of polychorinated biphenyls (PCB) congeners in three food webs in the Laurentian Great Lakes of North America. The model was used to quantify the contribution of sediment-derived and freely dissolved PCBs to the body burden of aquatic biota. In eastern Lake Erie (OH, USA), almost 100% of the chemical body burden of biota originates from sediment. In western Lake Erie, benthic invertebrates accumulated slightly more than half of their PCB body burden from sediment while fish accumulated less than half of their chemical body burden from sediment. Fish from Lake Ontario, Canada, accumulated less than 30% of their body burden of PCB congeners with log Kow6.4 from sediment and approximately half of their body burden of PCB congeners with log Kowor = 6.4 from sediment. Field data and the model were also used to determine the effects of declining concentrations of PCBs in water and sediment on concentrations of PCBs in aquatic biota. Results indicate that, as concentrations of PCB congeners in the ecosystem decline, the role of sediment as the source of contaminant to aquatic biota increases. Furthermore, as sediment becomes the predominant source of contaminant to aquatic biota. the concentration of PCB congeners in biota tends to equilibrium with bottom sediment.

Concentrations of polychlorinated naphthalenes (PCNs) were determined in archived lake trout (Salvelinus namaycush) from Lake Ontario, North America, collected between 1979 and 2004 to evaluate their temporal trends and the factors influencing their trends. Concentrations of PCNs, as well as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and non- and mono-ortho-substituted polychlorinated biphenyls (DL-PCBs), which were measured for comparative purposes, declined by eight-, seven-, and fivefold, respectively, between 1979 and 2004. Apparent elimination rate constants (k2) were calculated as the slopes of the regression lines of concentration versus time for PCN, DL-PCB, and PCDD/F congeners to compare the rate of decrease among congeners within and between compound classes. The k2 values for PCNs that had two pairs or three adjacent carbons unsubstituted with chlorine (congeners that can be biotransformed by vertebrates) were not significantly different from zero, indicating no decline in fish. For PCN congeners having no adjacent carbons unsubstituted with chlorine, the k2 values generally increased with hydrophobicity and degree of chlorination. This pattern differed from that of PCDD/Fs and DL-PCBs and from previous findings for non-DL-PCBs, for which the rate of contaminant decline decreased with hydrophobicity, and the pattern also differed from expectations based on thermodynamics. Differences in the rate of decline of PCN congeners may be caused by changes in source or mixture formulations over time and/or metabolic dechlorination of the less stable, higher-chlorinated PCNs 73, 74, and 75 to lower-chlorinated congeners. Based on suggested dioxin toxic equivalency factors, PCN concentrations in these whole lake trout may be sufficient to trigger consumption restrictions in Ontario, Canada, and our results suggest that PCNs merit incorporation into monitoring and assessment programs.

Concentrations of non-polybrominated diphenyl ether (PBDE) brominated (hexabromocyclododecane [HBCD], 1,2-bis[2,4,6-tribromophenoxy]ethane [BTBPE], and pentabromoethylbenzene [PEB]) and chlorinated (Dechlorane Plus [DP] as well as short- and medium-chain chlorinated paraffins [SCCP and MCCP, respectively]) flame retardants were evaluated in archived Lake Ontario, Canada, lake trout (Salvelinus namaycush) samples collected between 1979 and 2004. Polybrominated diphenyl ethers also were analyzed to provide a point of reference for comparison to previous studies. Concentrations of the dominant PBDE congeners (BDEs 28, 47, 99, 100, 153, and 154) increased significantly from 1979 until the mid-1990s, then either leveled off or decreased significantly between 1998 and 2004, a result that corresponds to those of previous studies. In contrast, BDE 209 increased approximately fourfold between 1998 and 2004. The temporal trends of the non-PBDE flame retardants varied, with sum (sigma) HBCD and DP showing significant overall decreases; BTBPE, sigmaSCCP, and sigmaMCCP showing parabolic trends; and PEB showing no overall change during the study period. Because many of the non-PBDE chemicals may be used as replacements for penta- and octa-BDE mixtures, these results will provide a baseline to evaluate future usage patterns. Possible changes in food-web structure, evaluated through stable nitrogen isotopes (delta15N), may be influencing our interpretations of contaminant trends in lake trout and are hypothesized to be partially responsible for the observed decrease in concentrations of BDEs 28, 47, 99, 100, 153, and 154 between 1998 and 2004. Retrospective analyses evaluating temporal trends in stable isotope values at the base of the food web, however, are recommended to test this hypothesis further.

The biomagnification of polychlorinated biphenyls (PCBs) and major organochlorine pesticides (OCPs) was studied using lake trout (Salvelinus namaycush) and other food web organisms collected from 17 lakes in Canada and the northeastern United States between 1998 and 2001. Whole lake trout (n = 357) concentrations of the sum (Sigma) of 57 PCB congeners ranged between 1.67 and 2,890 ng/g wet weight (median 61.5 ng/g wet wt). Slimy sculpin had the highest mean concentrations of SigmaPCB of all forage fish (32-73 ng/g wet wt). Positive relationships between log (lipid wt) concentrations of PCB congener 153, PCB congener 52, p,p'-dichlorodiphenyldichloroethylene, hexachlorobenzene, cis-chlordane, trans-nonachlor, or dieldrin and trophic level (determined using stable nitrogen isotope ratios) were found for most of the 17 food webs, indicating biomagnification of these PCBs and OCPs. The p,p'-dichlorodiphenyldichloroethylene had the highest trophic magnification factors (TMFs) of the 14 individual compounds studied, averaging 4.0 +/- 1.8 across the 17 lakes, followed by trans-nonachlor (3.6 +/- 1.5) and PCB congener 153 (3.4 +/- 1.2). Average TMFs for 14 individual PCBs or OCPs were significantly correlated with log octanol-water partition coefficient, implying that the rate of accumulation along the food web is dependent on hydrophobicity and recalcitrance. Significant correlations (p0.05) were found between TMFs of SigmaPCBs, hexachlorobenzene, alpha-hexachlorocyclohexane, and lindane and lake area, latitude, and longitude, but not for 11 other PCBs or OCPs. Overall, the results of the present study show that biomagnification of PCBs and most OCPs, as measured by TMFs, is only weakly influenced by such factors as latitude and longitude. Exceptions are hexachlorocyclohexane isomers and hexachlorobenzene, which had generally greater TMFs in northern lakes, possibly due to lower rates of elimination and biotransformation in the food web.

Levels of selected non-, mono-, and di-ortho-substituted polychlorinated biphenyl (PCB) congeners, polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) were determined in 4-year-old lake trout from the eastern basin of Lake Ontario, collected from 1977 to 1993. Results confirm that overall levels of contaminants have decreased steadily in lake trout since 1977, and that coplanar PCB levels do not appear to be increasing over time in relation to levels of other PCBs. Contaminant levels in lake trout from 3 to 9 years old, collected in 1988 from the western end of Lake Ontario, show the body burden of contaminants increases with age. Relative levels of coplanar PCBs to other PCBs for the age study samples showed no change, except for PCB 77, which exhibited a slight decrease in relation to total PCB levels. Toxic equivalents (TEQs) were calculated from fish contaminant concentrations measured for the time study using toxic equivalence factors (TEFs) from both mammalian and teleost studies. The relative contributions of PCBs, PCDDs, and PCDFs to total TEQs were examined. When TEFs used for risk assessment are applied to temporal trend data, 15 to 20% of the total TEQs were due to mono-ortho-substituted PCBs; 40 to 50% to non-ortho coplanar PCBs; and 20 to 30% to 2,3,7,8-substituted PCDD and PCDFs. The TEQs determined from lake trout extracts by an H4IIE cell bioassay technique are compared to those determined by chemical analyses, using a variety of TEFs.

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were measured in white sucker liver samples from seven pulp and paper mill sites, and three reference sites in Ontario. The mills included five bleached-kraft mills, with and without secondary treatment, and two sulfite-mechanical mills. 2,3,7,8-T[sub 4]CDD and 2,3,7,8-T[sub 4]CDF were the dominant congeners detected in both liver and fillet samples at all of the pulp and paper mill sites, with mean 2,3,7,8-T[sub 4]CDD toxic equivalent concentrations (TEQs) as high as 124 pg g[sup [minus]1] in liver tissue. concentrations of PCDDs/PCDFs in liver tissues were severalfold higher than in fillet tissue, but this difference can be accounted for by lipid normalization. Biological information, including liver weight, gonad weight, MFO activity (ethoxyresorufin-O-deethylase, EROD), and plasma sex steroids, was measured on individual fish. There was no relationship between TEQs and condition factor, gonadosomatic index, liver somatic index, or circulating plasma 11-ketotestosterone. A weak negative correlation was observed between circulating plasma testosterone and TEQs. Although there was a positive correlation between MFO activity (EROD) and TEQ, one site with very low chlorine used and low TEQs and EROD activity similar to levels observed at more contaminated sites. This finding, along with recent observations that MFO activity ismore » rapidly cleared in pulp-mill-exposed fish, casts doubt on an exclusive causal relationship between MFO activity and PCDDs/PCDFs in these sites.« less