Impacts of climate variability on coral reefs in mafia: a case of Chole and Jibondo Marine Islands

Climate change and variability extremes have been observed and recorded worldwide, and are mainly attributed to the increase in average global temperature that causes global warming. The increase in temperature has led into warming up of the ocean. Warming up of the ocean affects the health of coral reefs which are vulnerable to temperature rise above their optimal temperature (27oC to 28oC), has impacts on percentage live coral cover and fishery. In Mafia Island live coral cover was expected to increase up to 70% by 2015 but, have decreased regardless of management strategies put forward by Mafia Island Marine Park Authority. This research used ocean temperature dataset, LIT survey on coral health, secondary data on fish catch and coral health from Mafia Island Marine Park (MIMP). The data were analyzed by using Mann-Kendall trend test, Pearson Correlation analysis, Content analysis method and estimation methods. This study discovered that, sea surface temperature (SST) in Mafia has increased by 0.003oC since 2001 up to May 2016. This increase has moderate impacts on coral bleaching since; the rate of coral bleaching was low to that of recovery favoring coral reef recovery by 70% up to April 2015. However, from February to April 2016, sea surface temperature increased up to 31oC due to global warming coupled with El Nino incidence observed in November 2015. This incidence caused severe bleaching in Mafia Island, and almost 50% of live corals were bleached in Mafia Island by May 2016.This incidence degraded almost 50% of live coral cover health and is expected to cause a decrease in fish catch by 40% since; fish are expected to migrate to other reefs zone with low bleaching incidences.