Evaluation of environmental levels and biological impact of TBT in Malta (central Mediterranean)

Chemical monitoring for butyltins in bulk seawater, surface microlayer and superficial sediments determined that the two main local sources of marine contamination by tributyltin (TBT) compounds in Malta are ship-repairing do ckyards and marinas. In bulk seawater, TBT values ranged from below the det ection limit of 5 ng Sn l(-1) to 300 ng Sn l(-1); in sediments derived from the most polluted areas, TBT concentrations as high as 1500 ng Sn g(-1) we re measured. At TBT levels found in local harbours, several sublethal biolo gical responses are possible and were observed, including a significant red uction in MFO enzyme system activities of fish; digestive cell atrophy in t he oyster Ostrea edulis; and induction of imposer in the snail Hexaplex tru nculus. The latter two responses are evident at TBT concentrations below th e environmental quality standard (20 ng TBT l(-1)). The ecological implicat ions of these results are discussed and it is concluded that exposure of ma rine organisms to TBT in local harbours may be expected to lead to a reduct ion in the long-term survival of a number of such organisms. For these reas ons, both the use of TBT-based antifouling paints for pleasure boats as wel l as drydock practices need to be controlled by appropriate regulations and their enforcement. (C) 2000 Elsevier Science B.V, All rights reserved.