Spatial trends and bioaccumulation of organochlorine pollutants in marine zooplankton from the Alaskan and Canadian Arctic

Abstract

Planktonic copepods (Calanus glacialis and C. hyperboreus; n = 37) and water (n = 19) were collected to examine the spatial distribution and bioaccumulation of organochlorine contaminants (OCs) in the Alaskan and Canadian Arctic. The rank order of total OC (sigma OC) group concentrations in Calanus samples was toxaphene > or = sigma polychlorinated biphenyls (PCBs) > sigma hexachlorcyclohexane (HCH) > sigma DDT > sigma chlordane-related compounds (CHLOR) > sigma chlorobenzenes (ClBz). The dominant analyte was alpha-HCH in all water and zooplankton samples. The most abundant toxaphene congener in water and zooplankton samples was the hexachlorobornane B6-923. Organochlorine contaminant group concentrations in Alaskan zooplankton and water samples were lower than those in samples collected from sites in the eastern Canadian Arctic. Comparison of PCB and toxaphene congener profiles in zooplankton and water samples suggests that biotransformation by cytochrome P-4502B isozymes is low in Calanus, and limited phase I metabolism may occur. The log relationship of bioaccumulation factor (log BAF) versus octanol-water partition coefficient (log Kow) relationship was near 1:1 for OCs within the log Kow range of 3 to 6. A curvilinear model provided a better relationship between these two variables when OC compounds with log Kow > 6 were included. These results suggest that hydrophobic OCs (log Kow 3-6) in Calanus species are at equilibrium with the water concentrations and that physical partitioning, rather than biotransformation, is the major factor governing OC profiles in marine zooplankton.

Bioaccumulation Factors for PCBs Revisited

“…In the reviewed studies, lower seawater dissolved PCB concentrations (fg‚L -1 range) were reported when 200-400 L was extracted using XAD-2 resins (9), and when more than 400 L was extracted using PUFs (23,24) (Table 1). Higher seawater dissolved PCB concentrations (pg‚L -1 range) were reported when less than, or close to, 100 L was extracted using XAD-2 resins (14,15). Thus, it appears that extraction by XAD-2 and PUFs yields different measurements of dissolved PCBs, and/or that extraction of low water volume may result in greater interference from background PCB contamination.…”

“…The lack of correlation between marine BAF and zooplankton PCB concentrations indicates that the PCBs in zooplankton were determined in a similar and comparable way among studies. Most of the marine zooplankton samples were comparable in that they were largely dominated by large calanoid copepods (14,15,19,25). The quality of zooplankton PCB data is usually not considered problematic as lipids are relatively easy to separate and extract.…”

“…Several field studies with plankton have demonstrated a curvilinear relationship between log BAF and log KOW (e.g., 14,15,44). Higher BAFs than predicted by KOW, and a curvilinear relationship between log BAF and log KOW, suggest that PCB concentrations in zooplankton are not in equilibrium with water (2,14,25,37).…”

“…Of the elimination pathways, metabolism is often considered negligible in invertebrates (15,17), whereas growth rates vary considerably (e.g., 57) and may greatly influence the bioaccumulation in the animal (e.g., 53). Elimination Table 1 for water data and Table 2 for zooplankton data.…”

“…Unfortunately, relatively few field studies include PCB measurements in both zooplankton and the operational dissolved phase in water. We selected studies which report both water and zooplankton PCB concentrations (9,(14)(15)(16)(17)(18)(19)(20)(21)(22) as well as other work in which water and zooplankton were collected in the same region or lake but analyzed by separate groups (23)(24)(25)(26)(27)(28)(29) (Tables 1 and 2). All water samples were filtered to separate particle-bound and dissolved PCBs in all studies, except Oliver and Niimi (16) and Morrison et al (17) which were centrifuged (removing particles larger than 0.2 µm) (30).…”