HEAVY-METALS IN SURFACE SEDIMENT AND EPIBENTHIC MACROINVERTEBRATES FROM THE COASTAL ZONE AND CONTINENTAL-SLOPE OF KENYA

In surface sediments, a statistically significant increase was measure d in the concentration of copper and cadmium along all transects, and of zinc along only the most southern (Gazi) transect, radiating into t he Indian Ocean perpendicular to the Kenyan coast, Mean copper and cad mium increased from 5 to 30 mu g g(-1) dry wt and from 0.01 to 0.34 mu g g(-1) dry wt in shallow coastal (+/-20 m depth) to deep-sea station s (+/-2000 m depth), respectively. These gradients were found both dur ing the south-east monsoon and north-east monsoon period, The shallow estuarine zone of the Sabaki river mouth showed significantly enhanced levels of total organic carbon and nitrogen and all metals analysed, except cadmium. In crustaceans, the concentration of copper and partic ularly cadmium was significantly above baseline levels, varying from 4 5 to 90 mu g g(-1) dry wt and 1.0 to 8.5 mu g g(-1) dry wt, respective ly. Zinc levels (49-102 mu g g(-1) dry wt) were at about baseline leve ls or a little elevated. On the contrary, lead showed very low concent rations, varying from 0.1 to 0.6 mu g g(-1) dry wt. Other species gene rally showed the same pattern.