Different organochlorine contaminant profiles in groups of flounders (Platichthys flesus) from sampling locations around Denmark

Flounders ( Platichthys flesus ) from the waters around Denmark were analysed for their organochlorine (OC) profile to study whether fish from the same genetic population could be separated into characteristic subpopulations, based on their feeding grounds. The chemical analysis of fish liver provided a data set of 16 OC compounds in 94 samples from 2004 to 2006. Except for hexachlorocyclohexane, OC compounds were intercorrelated, indicating similar environmental fate and bioaccumulation. OC profiles are less affected than absolute concentrations by potentially confounding biological factors and thus more suitable for studies of intrapopulation differences in relation to feeding grounds. Principal component analysis grouped the samples according to locations. All but three of the 94 samples could be reclassified. Samples from the same and additional locations collected in 2003 provided validation, with only few misclassifications. This statistical separation likely reflects location-specific pollutant patterns in sediments and biota, even on the relatively small scale of this study. Thus, despite the lack of genetic differences, characteristic subpopulations of flounders could be identified with separate feeding grounds. OC profiles have been used increasingly to distinguish stocks.

A Comparison of Organochlorine Contaminant Levels, on a Lipid Basis, in Sea Lamprey Larvae from Mad River, Lake Huron Basin and Michipicoten River, Lake Superior Basin (1960-1976)

Organochlorine concentrations, on a lipid basis, were determined for formalin-preserved sea lamprey larvae, collected between 1960 and 1976 in the Mad River, Lake Huron basin, and compared with previously published data from Michipicoten River, Lake Superior basin. Although the ages of the lamprey specimens between the two lake basins were different, their lipid content, expressed as a percentage of dry body weight, was comparable. Despite the fact that the samples came from areas separated by about 550 km and with different land use (heavily forested area with mining activities but little agriculture for Lake Superior versus poultry farming, agricultural, urban and military uses for Lake Huron), no statistically significant differences were found for most organochlorine residue concentrations (Σaldrin, ΣCB, Σchlordane, ΣDDT, Σendosulfan and ΣPCB) between the two lake basins. The exception was ΣHCH, which was significantly lower in Lake Huron due to the absence of a high-level period observed in 1970 to 1975 in Lake Superior samples. Additionally, no differences were found between the relative concentrations of the various DDT metabolites between the two basins, but significantly higher relative concentrations of higher chlorinated PCBs (hexa to decachloro congeners) were found in Lake Huron samples. This study demonstrates the usefulness of formalin-preserved museum material to conduct retrospective contaminant analyses. However, given that certain amounts of contaminants were also found in the preservative solution, consideration of these levels is important to properly interpret the results.

A Comparison of Organochlorine Contaminant Levels in the Zebra Mussel, Dreissena polymorpha, versus its Unionid Attachment, Elliptio complanata, in the Rideau River, Ontario

Organochlorine contaminant levels were compared between the native unionid Elliptio complanata and the exotic zebra mussel, Dreissena polymorpha, at four sites along the Rideau River near Ottawa in 1995. Overall, the two taxa exhibited similar bioaccumulation patterns. PCB congeners, treated individually or as classes, showed strong positive and significant correlations between the two taxa. Additionally, the ratios DDD/ΣDDT, DDE/ΣDDT and DDT/ΣDDT were not significantly different between the two taxa. Mean concentrations of ΣPCB, ΣDDT, and Σchlordane were 65.8, 14.0, 1.2 and 227.9, 10.6, 1.8 ng/g soft tissue dry weight in E. complanata and D. polymorpha, respectively. These three organochlorine groupings accounted for 98.2 and 98.7% of the organochlorine soft tissue dry weight burden in E. complanata and D. polymorpha, respectively. However, while the bioaccumulation patterns were similar in E. complanata and D. polymorpha, the ΣPCB concentration was significantly higher in D. polymorpha. The organochlorine dry weight burden was 2.0 to 5.6 times greater in D. polymorpha compared to that in E. complanata and this was mostly attributable to differences in ΣPCB. This difference may be explained in part by the relative lipid content in D. polymorpha being 1.8 times greater on average than in E. complanata. We conclude that D. polymorpha is a good alternative freshwater biomonitor for E. complanata.