Seasonality in bioaccumulation of organochlorines in lower trophic level arctic marine biota

Organochlorine (OC) pesticides in ice algae, phytoplankton, and microzoopla nkton during summer months and in meso- and macrozooplankton throughout 199 3 in the Canadian archipelago (Barrow Strait) were compared with seasonal c hanges in seawater (upper 50 m) concentrations. alpha-HCH, HCB, Sigma CHL, dieldrin, gamma-HCH, Sigma PCB; and Sigma DDT (<100 ng g(-1) lipid, <10 ng g(-1) wet weight) were quantified. Meso- and macrozooplankton had higher le vels of toxaphene (CHBs) (>100 ng g(-1) lipid, >10 ng g(-1) wet weight) tha n ice algae and phytoplankton. Highest OC concentrations occurred in macroz ooplankton during the winter-spring period of ice cover. Concentrations for all compounds except HCHs decreased during the open water period when bioa ccumulation factors (BAFs) (tissue: water concentrations) were maximum (10( 6)-10(7) lipid weight basis) for CHBs and Sigma DDT and minimum (10(3)-10(4 )) for HCHs. BAFs on a wet weight basis mirrored lipid-based values but wer e approximately 10-fold lower. Meso- and macrozooplankton had minimal BAFs in July and August when lipid levels were low (<3% wet weight) and suspende d particulate matter concentrations were at their seasonal maximum. Slopes for regressions of log octanol-water partition coefficients for nine OCs an d log BAF decreased from >0.9 during ice cover to <0.6 in the open water pe riod. Deviations from physical-chemical equilibrium could reflect more cont inuous input, zooplankton growth with nonequilibrium partitioning, selectiv e metabolism, and higher suspended particulate matter concentrations during the open water period.