BIOACCUMULATION OF POLYCHLORINATED-BIPHENYLS (PCBS) IN THE MARINE PELAGIC FOOD-WEB, BASED ON A SEASONAL STUDY IN THE SOUTHERN GULF OF ST-LAWRENCE, 1976-1977

Polychlorinated biphenyls (PCBs) were quantified in bulk seawater (3.1 +/- 1.0 ng l(-1), N = 3) in 1976, in plankton (2.9 +/- 3.3 ng g(-1) w et weight, N = 176) in 1976 and 1977 and in fish (155 +/- 194 ng g(-1) wet weight, N = 135) in 1977 collected from St. Georges Bay in the so uthern Gulf of St. Lawrence. PCB concentrations in the plankton of the entire water column varied seasonally by ten times, with the highest values occurring in spring, lowest during summer and variable levels i n late fall. The lower PCB levels in the total summer community coinci de with a reduced biomass in certain size fractions in the Bay rather than a decrease in PCB concentration of the plankton. PCBs were concen trated in the middle-sized fractions of the planktonic community and t his is attributed to the greater biomass present in these categories, PCB concentrations in plankton were most highly correlated with their lipid content at the time of sampling. Seasonal reductions of lipid in the plankton per m(3) resulted in a higher concentration of PCB per u nit lipid in the remaining community. Planktonic PCB concentrations, e xpressed on a lipid basis, are found to be correlated with cumulative rainfall 21 d before sampling for both years combined. Adult fish were more contaminated by PCBs than either their egg or juvenile stages. M ature gaspereau, herring and smelt had higher concentrations of PCB co ntamination than mackerel, capelin, white bake and silversides. No dif ference was found between PCB contamination of the sexes of fish speci es analyzed. PCBs were transferred from mother to offspring in fish, b ut at lower levels than the level present in the parent; and the maxim um accumulation from the environment occurred between immature and adu lt fish. The best predictors of PCB contamination in fish in St. Georg es Bay are lipid content followed by size and age.