Seasonality in Bioaccumulation of Organochlorines in Lower Trophic Level Arctic Marine Biota

Abstract

Organochlorine (OC) pesticides in ice algae, phytoplankton, and microzooplankton during summer months and in meso- and macrozooplankton throughout 1993 in the Canadian archipelago (Barrow Strait) were compared with seasonal changes in seawater (upper 50 m) concentrations. α-HCH, HCB, ΣCHL, dieldrin, γ-HCH, ΣPCB, and ΣDDT (<100 ng g-1 lipid, <10 ng g-1 wet weight) were quantified. Meso- and macrozooplankton had higher levels of toxaphene (CHBs) (>100 ng g-1 lipid, >10 ng g-1 wet weight) than ice algae and phytoplankton. Highest OC concentrations occurred in macrozooplankton during the winter−spring period of ice cover. Concentrations for all compounds except HCHs decreased during the open water period when bioaccumulation factors (BAFs) (tissue:water concentrations) were maximum (106−107 lipid weight basis) for CHBs and ΣDDT and minimum (103−104) for HCHs. BAFs on a wet weight basis mirrored lipid-based values but were approximately 10-fold lower. Meso- and macrozooplankton had minimal BAFs in July and August when lipid levels were low (<3% wet weight) and suspended particulate matter concentrations were at their seasonal maximum. Slopes for regressions of log octanol−water partition coefficients for nine OCs and log BAF decreased from >0.9 during ice cover to <0.6 in the open water period. Deviations from physical-chemical equilibrium could reflect more continuous input, zooplankton growth with nonequilibrium partitioning, selective metabolism, and higher suspended particulate matter concentrations during the open water period.