HYDROCARBON CONTENT OF AN ANTARCTIC INFAUNAL BIVALVE - HISTORICAL RECORD OR LIFE-CYCLE CHANGES

The Antarctic bivalve Yoldia eightsi (Couthouy) has been assessed as a monitor species in the vicinity of a research station at Signy Island. For animals of comparable age n-alkane loading was highest at the site closest to the station. The character of the n-alkane pool of Yoldia varied with distance from the station and also differed from that of the sediment. The polycyclic aromatic hydrocarbon (PAH) loading was highest 250 m from the station. Loading of n-alkanes and PAH varied through the year; the lowest levels of n-alkanes were in October and the highest in April. The maximum for PAH was in October. Hydrocarbons increased with age for animals from five to 50 years old; 10-2000 ng animal(-1) for n-alkanes and 1-21 ng animal(-1) for PAH. Tissue concentrations decreased with age; 6000-500 mu g kg(-1) for n-alkanes and 25-5 mu g kg(-1) for PAH. Several biogenic branched chain alkenes were also present; one C-25:3 isomer was predominant at concentrations up to 290 mu g kg(-1) in mature animals (40% of the aliphatic fraction). Accumulation was not constant with age and concentrations reflected both anthropogenic and biogenic hydrocarbons in the marine environment. Seasonal variation in PAH load suggested the major proportion of accumulation over the year was only temporary. Yoldia eightsi were not suitable to monitor low level contamination such as that at Signy Island and past incidents were not resolved from the background input.