Abstract

Many studies in various parts of the world have investigated the levels of pollutants in seawater, sediments and marine organisms. Such studies have been used either to describe the environmental behaviour of pollutants or to monitor the levels of contamination in those constituents of the coastal marine environment. This work relates to the levels of some trace metals in the coastal marine environment of Mauritius. Concentrations of Cadmium, Chromium, Copper, Lead, Tin and Zinc were measured in samples of seawater, sediment and biota from 20 sites around the island during 1998-2000. The main objectives were to identify potential bio -indicators for heavy metal contamination and pollution hot spots around the coastline and also to assess whether trace metal levels in commercial fish species represent a health hazard to the community. The data generated indicate that the western coastline would be more vulnerable than elsewhere because of its accessability and more sheltered condition. However, elevated contamination of both seawater and sediment was localised at certain sites, the 'hot spots' normally corresponding to the sites of waste water discharge or underground seepage in the lagoons. The most contaminated zone would be Port Louis and the surrounding areas, which anyway are highly degraded due to discharge of untreated industrial and domestic wastewater. Installation islandwide of a sewerage network and wastewater treatment facilities would be the only solution to improve the environmental health of the coastal environment in Mauritius. Comparison with levels cited in literature indicates that contamination by any of the metals investigated in this study would not be higher than elswhere in the world. The levels recorded in samples of marine biota as well as in the commercial fish species were well below the recommended limits for consumption. This work should be considered only as preliminary. The organisms which have been indentified as potential bio-indicators need to be studied much more rigorously for extended periods of time so that some of them can actually serve as real sentinels for coastal marine pollution in Mauritius.