Sedimentation effects on shallow coral communities in Kenya
McClanahan, T. R.; Obura, D. (1997). Sedimentation effects on shallow coral communities in Kenya. J. Exp. Mar. Biol. Ecol. 209(1-2): 103-122. dx.doi.org/10.1016/S0022-0981(96)02663-9
In: Journal of Experimental Marine Biology and Ecology. Elsevier: New York. ISSN 0022-0981; e-ISSN 1879-1697, more
Since the early 1960s increased soil erosion due to changing land-use practices in the Sabaki River catchment basin, has increased river-sediment discharge into coastal waters around Malindi, Kenya. Line transect surveys of shallow (< 5 m at low tide) coral reef communities were conducted in 1985–1988 and 1992–1993 on a gradient of sediment influence in the Watamu (low influence) and Malindi (intermediate and high influence) National Marine Parks. Total algal cover increased between surveys only at the control (low sediment) reef, to levels comparable to the sediment influenced reefs. Within algal categories (turf, calcareous, fleshy and coralline) there were no consistent differences among treatment groups consistent with sediment influence. Soft coral and sponge cover were higher at increasing levels of sediment influence, though this trend is confounded by a parallel increase in water motion. Coral cover increased significantly over time at the intermediate reef, to levels comparable to the low and high-sediment influenced reefs. Generic richness, diversity and dominance of corals were broadly similar among all reefs except for higher dominance in the control reef. Positive correlation between differences in coral genus abundance and differences in mean coral colony sizes over time and among reefs suggests a suite of sediment-tolerant (Echinopora, Galaxea, Hydnophora, Millepora and Platygyra) and sedimentintolerant (Favia, Montipora andPocillopora) genera. Acropora, Astreopora, Favites and Porites were intermediate between these groups. Reefs exposed to high sediment influence were dominated by sediment tolerant and intermediate coral genera during both surveys, while reefs exposed to low sediment influence were dominated by sediment-intolerant and intermediate genera. Overall, although there were changes in some of the parameters listed above, and in coral genus abundance patterns, no evidence for decreased diversity and ecological health of sediment influenced reefs could be found for our set of community-level measurements of the shallow-water coral assemblage.
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