SABAKI RIVER SEDIMENT LOAD AND CORAL STRESS - CORRELATION BETWEEN SEDIMENTS AND CONDITION OF THE MALINDI-WATAMU REEFS IN KENYA (INDIAN-OCEAN)

Sediment discharges from rivers have a negative impact on coral reef e cosystems. Indicators of coral decline measured in the present study w ere: (1) injury to living stony corals; (2) soft coral cover; and (3) bare rocky substrate suitable for colonization by corals. The relation ship between these indicators and the distribution of terrigenous sedi ment was studied for the Malindi-Watamu fringing reef complex along th e Kenyan coast off East Africa during 1982 and 1983. Decline of this r eef had been repeatedly noted during the preceding decade. The influen ce of terrigenous sediment from the Sabaki River appears to be stronge st in the Watamu area in the south and in the northern-most part of th e Malindi reef area. Correlations, between each of the above three cor al stress response indicators, on the one hand, and quantitative indic ators of sediment loading, on the other hand, were not clear. However, a combined coral stress indicator involving all three factors was sho wn to have a clear relationship with terrigenous sediment loading and provided a rapid means of field evaluation of the effects of sediment stress on stony corals. Values for the combined coral stress indicator were found to increase in proportion to increasing values of terrigen ous sediment loads in both study areas. A higher coral stress indicato r value means a high proportion of injured or algae infested corals, a nd/or a high soft coral cover, and/or a high proportion of rocky subst rate suitable for, but unoccupied by, living corals.