Influence of local environmental conditions and bleaching histories on the diversity and distribution of <i>Symbiodinium</i> in reef-building corals in Tanzania

<p>Pollution, turbidity and coral bleaching history, as well as coral diversity, vary along the Tanzanian coastline. Prior to this study, it was not known whether exposure to such environmental variation might have influenced the diversity and distribution of <i>Symbiodinium</i> along this coastline. Such information can provide insight into whether Tanzanian reef-building corals develop adaptation to current trends of climate change. Here, 10 reef-building coral samples were collected from different reefs along the Tanzanian coast with different micro-environments and bleaching histories. The ITS-2 region of ribosomal DNA was employed in the characterisation of <i>Symbiodinium</i> harboured by reef-building corals. DGGE fingerprints and DNA sequences showed that most coral species host a single <i>Symbiodinium</i> type, which is maintained throughout the coast regardless of local environmental differences. We present polymorphic symbioses in <i>Acropora</i> spp., <i>Millepora</i> sp. and <i>Galaxea fascicularis</i> in mainly turbid and warm environments as a sign of adaptation to harsh conditions. However, such adaptation may not provide marked resistance to bleaching because <i>Acropora</i> is a bleaching-susceptible genus.</p