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Author
Obura, D.Date
2008
Métadonnées
Afficher la notice complèteAbstract
Scleractinian coral species surveys were conducted at 10 sites in the western Indian Ocean, between 2002 and 2006. Each site varied from approximately 50-200 km in extent and was sampled with from 7 to 27 dives. Accumulation curves based on successive samples at each site were used to construct logarithmic regression curves, which provide estimated species numbers at each site at an arbitrary value of 30 samples per site, assumed to reflect the total number of species. The highest diversity of corals was found in southern Tanzania to northern Mozambique (from Mafia Island to Pemba town), with 280-320 species estimated per site. Species diversity was lower in the central Indian Ocean islands (140-240 species) and declined steadily to a minimum in northern Kenya (150 species). These patterns are consistent with the central coast (around 10oS in Tanzania/Mozambique) accumulating and retaining species due to the South Equatorial Current (SEC) and mixing/reversing currents locally, respectively. The islands may have restricted diversity due to low area but nevertheless be stepping stones to the East African mainland coast. Lower diversity northwards into Kenya may reflect distance and low dispersal from the center of diversity at 10oS, and poorer conditions due to the Somali Current influence in the north. Observer effects and unclear taxonomy of scleractinian corals may significantly affect the dataset, as may faunal changes due to bleaching or other impacts at individual sites during the course of the study. Finally, it is likely that the diversity gradient northwards into Kenya is replicated southwards into southern Mozambique and South Africa, providing a means to test latitudinal changes in diversity and species distributions.Page Range
pp.139-148Title of Parent Book or Report
Ten years after bleaching - facing the consequences of climate change in the Indian Ocean. CORDIO Status Report 2008. Coastal Oceans Research and Development in the Indian Ocean.Publisher or University
Sida-SARECCollections