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In the present study, effects of the trematode eye fluke Diplostomum spathaceum infection and parasite-induced cataract on energetic costs and feeding of hatchery-bred one-summer-old Lake Saimaa Arctic charr Salvelinus alpinus were examined. The energetic effects (measured as oxygen uptake) of acute eye fluke infection on S. alpinus were negligible, but in the chronic infections mean oxygen consumption of infected fish was significantly higher than that of controls. Feeding capability of S. alpinus was studied in aquarium experiments, and uninfected healthy-eyed fish reacted to zooplankton more rapidly and caught zooplankton with better success compared to individuals with cataracts in the same school. The results suggested that to compensate energetic costs and impaired feeding capability caused by eye fluke, cataract-bearing fish spend more time foraging, which may result in increased predation risk.

The equilibrium sampling in silicone is increasingly applied to measure freely dissolved concentrations and chemical activities within bioaccumulation research of hydrophobic organic chemicals. Two equilibrium methods were applied to PCB-contaminated soil and sediment, and directly calibrated with respect to equilibrium partitioning concentrations in lipids (C(lipid,partitioning)): (i) Solid phase microextraction in the headspace above the sample (HS-SPME) required optimization for its application to PCBs, and it was calibrated above external partitioning standards in olive oil. (ii) Equilibrium sampling with internally coated glass jars with varying thicknesses of silicone (PDMS) resulted in proportionality between coating and analyte mass, which confirmed several validity criteria. C(lipid,partitioning) was here determined as product of PDMS concentration and PDMS to lipid partition ratio. The results of the two methods were in good agreement and thus validated each other. Finally, the coated glass jar method was applied to field sediment containing invertebrates, which lead to C(lipid,partitioning) that were about two times higher than measured lipid-normalized concentrations in the organisms. Temperature differences and animal lipid structure were discussed as possible reasons for this discrepancy. Both methods combine high analytical performance, reduced equilibration times and new calibration possibilities, which makes them suited for bioaccumulation research and environmental monitoring.

Knowledge on the internal distribution of halogenated organic chemicals (HOCs) would improve our understanding of dose-effect relationships and subsequently improve risk assessment of contaminated sites. Herein, we determine the concentrations of HOCs based on equilibrium partitioning in storage lipids, membrane lipids, and proteins in field-contaminated fish using equilibrium sampling devices. The study shows the importance of protein as a sorptive phase in lean fish. Our results provide a basis for using species-specific equilibrium partitioning coefficients between sorptive tissues and fish internal water as a substitute for K(ow) in, for example, upgrading models that simulate food-chain accumulation of the chemical.

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Equilibrium sampling devices can be applied to study and monitor the exposure and fate of hydrophobic organic chemicals on a thermodynamic basis. They can be used to determine freely dissolved concentrations and chemical activity ratios and to predict equilibrium partitioning concentrations of hydrophobic organic chemicals in biota lipids. The authors' aim was to assess the equilibrium status of polychlorinated biphenyls (PCBs) in a contaminated lake ecosystem and along its discharge course using equilibrium sampling devices for measurements in sediment and water and by also analyzing biota. The authors used equilibrium sampling devices (silicone rubber and polyethylene [PE]) to determine freely dissolved concentrations and chemical activities of PCBs in the water column and sediment porewater and calculated for both phases the corresponding equilibrium concentrations and chemical activities in model lipids. Overall, the studied ecosystem appeared to be in disequilibrium for the studied phases: sediment, water, and biota. Chemical activities of PCBs were higher in sediment than in water, which implies that the sediment functioned as a partitioning source of PCBs and that net diffusion occurred from the sediment to the water column. Measured lipid‐normalized PCB concentrations in biota were generally below equilibrium lipid concentrations relative to the sediment (CLip⇌Sed) or water (CLip⇌W), indicating that PCB levels in the organisms were below the maximum partitioning levels. The present study shows the application versatility of equilibrium sampling devices in the field and facilitates a thermodynamic understanding of exposure and fate of PCBs in a contaminated lake and its discharge course. Environ Toxicol Chem 2015;34:2463–2474. © 2015 SETAC

Ecology of the glacial relict macrocrustacean Gammaracanthus lacustris, a rare inhabitant of deep Fennoscandian lakes, is poorly understood. We studied the life cycle and trophic position of this cold‐stenothermic amphipod in Lake Paasivesi, eastern Finland. The study is based on intensive sampling and analyses of fatty acid composition as well as stable carbon (δ13C) and nitrogen (δ15N) isotope ratios. Both day and night, the G. lacustris population occurred at depths below 25 m at temperatures <8°C, and the density increased towards the bottom of the lake, where it was 0.4–0.6 individuals/m3. Gammaracanthus lacustris was observed to reach a length of >40 mm and live up to 4 years. The oldest and the largest individuals and females seemed to favour the deepest zones. In October, almost 100% of females with length at least 25 mm (i.e. females presumably at least 1‐year‐old) had an embryo sack with 20–200 eggs or embryos—the larger the female, the more young it had. The developing eggs of G. lacustris had a very high fatty acid content, indicating that the females invest heavily on provisioning their young. Furthermore, the fatty acid composition differed among life stages, and in particular the eggs had a higher proportion of eicosapentaenoic acid than juveniles or adults. The stable δ13C and δ15N isotope ratios and fatty acid biomarkers of the food web, together with visual observations, indicate that G. lacustris is a carnivore that feeds mainly on zooplankton and other relict macrocrustaceans. Due to its high content of essential polyunsaturated fatty acids, G. lacustris is a valuable prey for fish and other predators in the food web. However, as a glacial relict with strict habitat requirements the species is vulnerable to global warming and local environmental changes. These facts should be considered in the management of lakes and their catchments.