Variation in the bioaccumulation of a sediment-sorbed hydrophobic compound by benthic macroinvertebrates: patterns...

Aquatic ecological risk assessment is primarily focused on aqueous exposure, but many hydrophobic contaminants bind to particulate material and accumulate in sediments. The risk posed by such contaminants is partially dependent on the importance of dietary exposure. Here, we describe the bioaccumulation of a highly hydrophobic compound (dioctadecyl-dimethyl ammonium chloride (DODMAC)) to four freshwater macroinvertebrates (i.e., Asellus aquaticus, Chironomus riparius, Gammarus pulex, Lumbriculus variegatus) and investigate the mechanistic basis for observed interspecific variation in bioaccumulation. Although more than 99.99% of DODMAC was sediment-bound, it was bioavailable to all four species via dietary exposure. Interspecific variation in bioaccumulation was apparent despite the lack of selective feeding and biotransformation potential and after normalization for body size and lipid content. Chironomus riparius had the highest lipid-normalized DODMAC concentration and L. variegatus had the lowest. Study species differed in factors affecting uptake (i.e., feeding rate) and absorption efficiency (i.e., gut passage time and gut surfactancy). Feeding rate did not explain interspecific variation in bioaccumulation, but bioaccumulation was enhanced by either high surfactancy and short gut passage time (e.g., G. pulex) or low surfactancy and long gut passage time (e.g., C. riparius). Risk assessment of hydrophobic contaminants should consider dietary exposure and the potential food chain effects of interspecific variation in bioaccumulation.