Macrozoobenthic communities in waters off Angola

Abstract

Macrozoobenthic biodiversity is described for waters off Angola, one of the poorest-known marine environments of the world. During research cruises in 2004 and 2011, the shelf region of Angola was investigated at 39 stations in water depths of between 19 and 340 m. Most of the stations were characterised by fine sediments, e.g. silt and sand. In all, 67 quantitative grab samples and 20 qualitative dredge samples were collected. The study area extended from c. 7° S to the Namibian border at c. 17° S. A total of 893 different taxa were collected, with polychaetes and crustaceans the most diverse groups and polychaetes the most abundant. Overall, molluscs had the greatest biomass. The diversity values (Shannon index) were >3.5 and in some cases even >4.5 for a large part of the shelf, but they did not show any latitudinal trend. A multivariate analysis revealed high variability in community composition between stations and without real grouping, except for a separate community in an oxygen-poor (≤1 ml l⁻¹) region near the Namibian border in southern Angola, where there was a limited number of species that are well adapted to such conditions. These species occurred at high abundance and biomass and included gastropods of the genus Nassarius and the bivalve Nuculana bicuspidata. There was also a marked presence of the polychaetes Cossura coasta, Diopatra neapolitana capensis and Galathowenia sp. in this region. The latter two species were also conspicuous in the better-oxygenated waters of the northern areas, however. Other taxa, such as the polychaete Prionospio as well as the amphipod Ampelisca, were strongly represented along the entire Angolan shelf.

Keywords:

• abundance
• biodiversity
• biomass
• macrozoobenthos