| Summary: | The Zanzibar Archipelago is the largest reef system in eastern Africa and represents the transition from the high-diversity region of the Asian Indo-Pacific to the cold-water areas of southern Africa. It is among the most productive and biologically rich ecosystems along eastern Africa and provides valuable benefits to coastal people. The Zanzibar Archipelago consists of the three major islands Zanzibar, Pemba and Mafia Island. These islands face an intensifying array of threats, including impacts from growing tourism, coastal development, overfishing, anthropogenic runoff, and consequences from global climate change (ocean acidification, temperature stress, bleaching). The combination of global and local stressors makes reefs increasingly susceptible to disturbance and ultimately reduces their capabilities to maintain their physical structure. Despite widespread recognition that the reefs along eastern Africa are seriously endangered, information on foraminifera, a prominent group of reefal carbonate producers, is limited. In this project the spatial distribution, composition, diversity and environmental significance of foraminiferal faunal assemblages in shallow-water reefal ecosystems were studied. For the first time in this area, a catalog of 167 species belonging to 98 genera, all illustrated by scanning electron microscopy, was established. The structure of the foraminiferal fauna was analyzed in different habitats that have been identified using statistical analyses, including observations made in the field. Quantitative faunal analyses of sediment samples show the presence of seven macro-habitats around the three islands of the Zanzibar Archipelago, characterized by specific indicator taxa: 1.) the nearshore habitat in the vicinity of mangrove forests, dominated by opportunistic species able to withstand eutrophic conditions, 2.) the shallow lagoon habitat, characterized by smaller porcelaneous foraminifera, 3.) the shallow and extremely warm reef flats, dominated by a single species adapted to extreme ...
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