Physiological energetics of the brown mussel Perna perna (L.) transplanted in the Itajaí-Açu river mouth, Southern Brazil

Groups of the mussel Perna perna were transplanted to two points and at three different depths in the coastal region close to the Itajaí-Açu River mouth, an impacted river in the south of Brazil. With the objective of evaluating the physiology changes in the organisms in relation to the control area (origin of the organisms), the clearance, respiration and excretion rates, absorption efficiency and growth were estimated. The levels of metals in the organism tissue were determined in an attempt to explain the physiological changes occurring in the study area. Organisms from Point 2 placed near the bottom showed physiological changes in comparison to the control and the transplanted organisms from Point 1. Point 2 showed greater sediment resuspension and availability of trace metals to the organisms closer to the bed. The increase in Cr concentration in the tissues of the organisms (up to 0.21 mg kg⁻¹ ww) was not sufficient to explain the decrease in the inhibition of clearance (28.8%) and in the absorption efficiency (15.7%), or the increased excretion rate (282.5%), which led to the organisms having a reduced scope for growth (48.6%). This indicates the possible presence of other contaminants, which were not measured, and which probably had synergistic action with the trace metals investigated.