EFFECTS OF COPPER EXPOSURE ON THE SCOPE FOR GROWTH OF THE CLAM RUDITAPES DECUSSATUS FROM SOUTHERN PORTUGAL

The clam Ruditapes decussatus L. was collected from Ria Formosa, Fare, southern Portugal, and exposed to a sublethal copper concentration of 0.01 mg l(-1) for 20 days, Physiological measurements, respiration ra tes, clearance rates and absorption efficiency, were undertaken initia lly and after 2, 5, 9, 14 and 20 days and used to calculate Scope for Growth, Copper accumulation rate was calculated through the analysis o f copper in the tissues at the same sampling times, The experiment sho wed two phases, Initially, copper was rapidly accumulated (1.95 mu g C u g(-1) dw day(-1) in the first 48 h), clearance rates declined marked ly (lowest value 13.5% of control) and respiration rates increased (11 6% of control), resulting in a rapid decline of Scope for Growth, whic h showed a negative value after 5 days, In the second phase, (from day 9 on), the rate of copper uptake declined to 0.55 mu g Cu g(-1) day(- 1) and g physiological responses were more stable, After 20 days, copp er concentration in the tissues was 38.4 mu g Cu g(-1) dw (bioconcentr ation factor 3840), Clearance rates were 50% of control rates and resp iration rates were still high, 145% of control rates, Therefore, Scope for Growth and performance of the clams was still greatly affected (c a. 23% of the control values), indicating that though animals partiall y recovered through detoxifying mechanisms, excess copper caused susta ined impairment of physiological functions, This experiment confirms t hat the physiological energetics approach and the integrated Scope for Growth measurement is a sensitive methodology to detect deviations fr om normal performance and assess stress at environmental realistic cop per concentrations, (C) 1997 Elsevier Science Ltd. All rights reserved .