Benthic biodiversity of soft-sediment habitats of the western Indian Ocean
2025
Everett, Bernadine I | Fennessy, Sean T | Randrianalisoa, Avotramalala N. | Abdula, Sylvia | Fondo, Esther | Kishe, Mary | Silas, Matthew O
The biodiversity of the western Indian Ocean is known mostly from inshore habitats, but little is known from the most extensive habitat of the region, the soft, unconsolidated sediments. Demersal trawl data from Kenya, Tanzania, Mozambique, South Africa and Madagascar were analysed, using average taxonomic distinctness in association with various environmental factors, to determine the biodiversity, the dominant genera that characterise the community assemblages and the areas where biodiversity was highest. A decreasing trend in biodiversity was observed from Kenya to Mozambique, including Madagascar, but South Africa had the highest average biodiversity. The continental slope was more biodiverse than the shelf, and biodiversity increased with depth to approximately 500 m, whereafter it declined. Depth and turbidity were the factors that best accounted for differences in community assemblages. The deep-water fish genera, Chlorophthalmus and Chaunax, dominated the slope assemblages, while the shelf communities were dominated by the shallow-water shrimp genera, Penaeus and Metapenaeus. Areas that have higher diversity, in general, included off Durban, South Africa, the Delagoa Bight off Maputo, Mozambique, and most of the area off southern Kenya. The information presented has improved the knowledge of soft sediment habitats in the WIO, thereby supporting decision-makers when deciding on planning options.
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