EFFECTS OF TRIBUTYLTIN AND DIBUTYLTIN ON THE PHYSIOLOGICAL ENERGETICS OF THE MUSSEL, MYTILUS-EDULIS

Sublethal physiological responses (clearance rate, oxygen up-take, absorption efficiency and scope for growth) of mussels (Mytilus edulis) were measured following exposure to tributyltin (TBT) and dibutyltin (DBT). Effects were related to the concentration of TBT and DBT in the mussel tissues. Rate of oxygen uptake increased two-fold with increasing TBT concentration from 0.5 to 10 mug TBT g-1 (dry weight). Clearance (=feeding) rate was significantly reduced above a threshold concentration of 3 to 4 mug TBT g-1. Absorption efficiency was unaffected at concentrations below 10 mug TBT g-1. The overall effect, in terms of scope for growth, indicated a severe inhibition of growth above 4 mug TBT g-1. DBT was shown to be an order of magnitude less toxic than TBT, when expressed in terms of the tissue concentration inducing toxic effects. The threshold concentrations causing a reduction in the rates of feeding and oxygen uptake were 23 and 36 mug DBT g-1, respectively. These sublethal effects are discussed in relation to mechanisms of toxicity. previous alkyltin studies and environmental concentrations.