Metallothioneins in Arctic bivalves

In the framework of an International Association for the Promotion of Cooperation with Scientists from the Independent States of the Former Soviet Union (INTAS) Project on biodiversity and adaptation strategies of Arctic coastal marine benthos, research was focused on the role of metallothioneins as a possible indicator of the effect on animals and availability of trace metals in the Arctic. Metallothioneins are low-molecular-weight, cysteine-rich proteins known to be induced by high environmental levels of trace metals. Specimens of Macoma balthica and Mytilus edulis were collected along several Arctic estuaries in the White and Pechora seas; whole tissues for M. balthica and the digestive gland and gills for M. edulis were dissected, frozen in liquid nitrogen, and lyophilized onboard. Metallothionein concentrations were determined by a polarographic assay. From the same stations organisms and sediments were also collected for metal analysis. The results revealed significant differences in metallothionein concentrations among the stations for M. balthica. Similar, although less marked, differences were also obtained in the organs of M. edulis. Data on metallothionein were compared with trace metal concentrations in both the organisms and sediments. Also, the relationship with abiotic factors (salinity) and biological variables (size of sampled organisms) was determined. In particular, biological variables seemed to influence metallothionein concentration in the organisms and their effect should be carefully considered for a correct assessment of differences between stations.