Ecological and physiological aspects of contaminant accumulation and transport by the filter-feeding mussel, Mytilus edulis

Abstract: This thesis examines the influence of food availability on the bioaccumulation kinetics and the transport of hydrophobic organic contaminants (HOCs) by the Baltic Sea blue mussel, Mytilus edulis. In laboratory studies, food availability was found to significantly modify the rate of physiological processes involved in filter-feeding. This also influenced the rate of exposure to HOCs as determined by the amount of HOCs associated with the flux of water and food. The uptake rate of HOCs by the mussels was found to be positively related to the exposure rate, whereas HOC elimination appeared to be unaffected by differences in food availability. However, the amount of HOCs assimilated declined with increases in the exposure rate, and the largest increase in HOC tissue concentrations was found at an intermediate food availability.The role of the blue mussel in the cycling of carbon and HOCs was also investigated in the field and by a modelling approach. As filter-feeders the mussels consume near-bed suspended particulate organic matter that, in contaminated areas, contains high concentrations of HOCs. Filter-feeding activity and the subsequent release of faecal matter by the mussels increased the vertical flux of HOCs from the water column to the benthic community by at least 50% in the study area. Other significant routes of HOC transport by mussels in the coastal zone of the Baltic proper include transfer to predators, elimination of dissolved HOC, and elimination via spawning and transfer to zooplanktivores, as indicated in the established annual budget models.It is concluded that the filter-feeding activity of the mussels have a significant influence on HOC fluxes within both the organism and the ecosystem. The findings presented here emphasise the role of animal physiology in contaminant kinetics and have important implications for the experimental design and interpretation of laboratory bioaccumulation and toxicity studies, as well as field sampling and marine monitoring programmes.