Influence of coral bleaching on the fauna of Tutia Reef, Tanzania

In 1998, coral reefs of Tanzania were severely affected by bleaching. The coral mortality that followed caused a concern for coral reef degradation and overall resource depletion. In this study, we investigated coral bleaching effects on the coral reef fauna at Tutia Reef in Mafia Island Marine Park, Tanzania. Corals from adjacent reef patches of the species Acropora formosa were transplanted into plots, and reef structure and associated fish assemblages were examined before and after the bleaching event. Following the coral bleaching, 88% of all corals died. A year after the event, a large proportion of the dead corals was still standing. As surviving and dead corals were from different clones, results suggested that genetic variation might influence bleaching tolerance. After the bleaching event, a change in fish community composition, with an increase in fish abundance, could be seen. Species diversity, however, was less affected. There was a correlation between structural complexity and fish densities after disturbance. This indicates that the reef may uphold an abundant fish population as long as the architectural structure is intact. The impact that the coral beaching event may have on fisheries is difficult to anticipate. The Tutia Reef supports a multi-species fishery and a variety of techniques are used. As a broad range of species are targeted, including smaller fishes, catches may not be reduced as long as the reef structure is sustained. If reef degradation follows, however, fish abundance is likely to decrease