Uptake and depuration of 63Ni by Mytilus edulis

The uptake and depuration of Ni (as radioisotope 63Ni) by Mytilus edulis (Mollusca: Bivalvia) has been investigated in a laboratory mesocosm. Nickel was reversibly held on low energy surface sites of estuarine suspended particulate matter (SPM), with a partition coefficient of the order 10(3) ml g-1, resulting in approximately 80% of radioisotopic Ni being in the dissolved phase. Mussels were fed a diet of radio-labelled estuarine SPM for 30 h in a flow-through exposure period and for a further 24 h in a static exposure period. Following exposure, the mussels were allowed to depurate in particle-free seawater. Pseudofaeces and faeces were collected throughout the experiment and tissues were dissected after 48 h of depuration. The 63Ni activity in the faeces was approximately 50% of that in the feedstock SPM, while the activity in the tissues was 2-29% of SPM activity. Tissue-specific accumulation occurred in the order viscera > byssus > mantle > adductor muscle > gill > foot. The results are discussed in the context of the bioavailability of Ni to mussels.