Environ. Sci. Technol. 2000, 34, 980-987
Seasonality in Bioaccumulation of Organochlorines in Lower Trophic Level Arctic Marine Biota B A R R Y T . H A R G R A V E , * ,† GEORGINA A. PHILLIPS,† W. PETER VASS,† PHILIP BRUECKER,‡ HAROLD E. WELCH,§ AND TIMOTHY D. SIFERD# Marine Environmental Sciences, Fisheries and Oceans Canada, Bedford Institute of Oceanography, Dartmouth, Nova Scotia B2Y 4A2, Canada, 343 East 11th Street, North Vancouver, British Columbia V7L 2H1, Canada, 31 Brentlawn Boulevard, Winnipeg, Manitoba R3T 4X9, Canada, and Fisheries and Oceans Canada, Central and Arctic Region, Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba R3T 2N6, Canada
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. R-HCH, HCB, ΣCHL, dieldrin, γ-HCH, ΣPCB, and ΣDDT (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 lipidbased values but were approximately 10-fold lower. Mesoand macrozooplankton had minimal BAFs in July and August when lipid levels were low (0.9 during ice cover to 1 g wet weight. Duplicate subsamples were removed to separate three size classes (microplankton: 25-125 µm, predominantly phytoplankton (only available in sufficient biomass for analysis during July); mesozooplankton: 125-509 µm; macrozooplankton: >500 µm) (5). Samples (1-5 g wet weight) were stored frozen in baked, solvent-cleaned, and preweighed vials. Sample Analysis. Details of tissue extraction, cleanup, fractionation, and analysis for lipids and OCs were reported previously (5). Sample extracts were spiked with a solution containing 13C-labeled surrogate standards (hexachlorobenzene, γ-HCH, p,p′-DDT, PCB 101, 180, and 209). PCB congeners were determined by high-resolution gas chromatography (HRGC/LRMS) using a Finnigan INCOS 50 mass spectrometer with a Varian 3400 GC operated in the MID mode acquiring two characteristic ions for each target analyte and surrogate standard. All toxaphene (CHBs) analyses were conducted using the Finnigan INCO 50 system in the electron capture negative ion (ECNI) mode with summation of 19 peaks in each chromatogram. Chromatographic separation of pesticides and PCB congeners was carried out using a 60 m DB-5 column (detection limits 1 ng g-1 for samples > 1 g wet weight). When levels were below this limit concentrations were reported as less than the actual value. All data were corrected for blanks and recovery efficiency of 13Clabeled internal standards (70-100% for various compounds in all sample types). Concentrations were expressed on both
FIGURE 1. (A) Suspended particulate organic carbon in Barrow Strait, Canadian Arctic Archipelago during 1993 integrated to 50 and 100 m; (B) chlorophyll a over the same depth layers; (C) the ratio of carbon:chlorophyll a in suspended matter; (D) percent of zooplankton wet weight as lipid for meso- (125-500 µm) and macrozooplankton (>500 µm) size fractions (mean values from duplicate samples). A positive correlation between POC (g m-2) and CHL (mg m-2) (0-50 m layer, n ) 24) was described by a nonlinear regression (CHL ) -4.29 + 0.64POC2, r 2 ) 0.93, p ) 0.003). Percent lipid content (PLC) in zooplankton was negatively correlated with POC (PLC ) 7.04 - 0.40POC, r 2 ) 0.27, p ) 0.009) and CHL (PLC ) 5.84 - 0.04CHL, r 2 ) 0.27, p ) 0.003). Dominant mesozooplankton species included copepodites of several copepod species (Oncaea borealis, Oithona similis, Microcalanaus sp.), juvenile stages (
