This study examined the distribution and abundance of corallimorpharians (Cnidaria, Anthozoa) in Tanzania in relation to different aspects of the coral reef environment. Five reefs under varying degrees of human disturbance were investigated using the line intercept transect and point technique. Corallimorpharian growth and the composition of the substratum were quantified in different habitats within reefs: the inner and middle reef flat, the reef crest, and at the 2 and 4 m depths on the reef slope. Corallimorpharians occurred on all the reefs and 5 species were identified: Rhodactis rhodostoma, R. mussoides, Ricordea yuma, Actinodiscus unguja and A. nummiforme. R. rhodostoma was the dominant corallimorpharian at all sites. Within reefs, they had the highest densities in the shallow habitats. While R. rhodostoma occurred in all habitats, the other corallimorpharian species showed uneven distributions. Corallimorpharians ranked second, after scleractinian coral, in percent living cover. Results from this study suggested that corallimorpharians benefited from disturbance compared with other sessile organisms. They preferred inhabiting areas with dead coral, rock and rubble whilst live coral was avoided. There was a positive relationship between percent cover of corallimorpharians and water turbidity and they dominated the more disturbed reefs, Le. reefs that were affected by higher nutrient loads and fishing.poridae and Poritidae (13, 27). As corallimorpharians are able to withstand various disturbances that influence the reef environment, human disturbances could work in their favor. Since 1996, the abundance of corallimorpharians appears to have increased on coral reefs in Tanzania ( 28). This could be the result of increased human disturbances from, e.g. sewage loads and fishing activities. The 1998 coral bleaching event in the region (29-32) further disturbed reefs as it resulted in massive coral mortality, possibly favorable to the distribution of corallimorpharians. Not only did it open up space, but corallimorpharians may also be more resistant to increased temperatures (24), which was the primary cause of the coral bleaching event 1998 (31). The aim of this study was to examine how the distribution and abundance of corallimorpharians in Tanzania is influenced by habitat characteristics and environmental disturbance.
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