Macrozoobenthic biodiversity patterns in the northern province of the Benguela upwelling system

Abstract

This paper describes macrozoobenthos diversity in the vicinity of the Angola–Benguela Frontal Zone between 15° and 23° S in offshore waters of the Namib biogeographic province in a comprehensive zoogeographical context. At 38 selected stations, about 500 different macrozoobenthic taxa could be identified, including 209 bivalve, gastropod and peracarid species. These 209 taxa were reduced to 85 species by statistical procedures, to ensure the database was reliable in terms of statistics and taxonomy for community analysis. The evaluation of macrobenthic distribution patterns revealed three distinct biodiversity clusters, which are probably the result of different adaptation strategies to the diverse environmental conditions within the Benguela upwelling ecosystem. The dominating driver for benthic diversity is the extent of the oxygen minimum zone (OMZ). Temporal and spatial stability of the OMZ is, however, not fixed. Therefore, only the particular spatial pattern in total community structure during the cruises can be described in this study. Perennial temporal variability in the extent of OMZs can, however, be assessed by the distribution of longer-living molluscs’ shells. The assignment of macrofauna communities to recent patterns of frontal systems, upwelling cores and oxygen supply makes the hard-shell fraction of the communities a potential indicator of historic changes in these external conditions.