Structural and functional aspects of the benthic communities in the deep Angola Basin

Abstract

During the RV 'Meteor' expedition 'DIVA I' the macro-and megafaunal communities were studied in 6 areas of the deep Angola Basin in July 2000. Water depths varied between 5162 and 5497 m. The macrofauna was dominated by polychaetes, peracarids and bivalves; the megafauna by ophiurids, bivalves and actiniarians. Abundance and biomass of macro-and megafauna were similar to other non-oligotrophic deep sea areas > 4000 m. Predatory polychaetes, peracarids and facultative surface deposit feeders or predatory sipunculids occurred in similar ratios in all areas. Facultative subsurface deposit-feeding or predatory nematodes and oligochaetes increased towards the northern Areas 4 to 6. The percentage of surface-deposit and interface-feeding organisms such as polychaetes and ophiurids, which dominated in Areas 2 and 3, decreased towards the north. For megafauna, the ratio of organisms feeding as suspension feeder or predator as well as surface-deposit feeder increased from south to north. In the northern Areas 4 to 6, high numbers of bivalves occurred, which feed as surface or subsurface deposit feeders. TOC and chlorophyll a contents in sediment, as well as macro-and megafaunal abundance and biomass, were lower in the southern Areas 1 to 3 than in the northern Areas 4 to 6. These differences seem to be connected to the different water masses north and south of the Angola-Benguela Front, which cross the transect of our 6 study sites. In the north, the Angola Basin is a highly productive region fed by the South Equatorial Counter Current and water masses from the Zaire (Congo) River, whereas in the south, the cold Benguela Oceanic Current is less productive. The structure and function of the benthic fauna in connection with sediment data give evidence for differences in food supply north and south of the front.

Angola Biodiversity of Bathyal Sea Bottoms

“…Their high richness and biodiversity were consistent with the scarce previous observations of such bathyal environments, as were their low productivity (low abundance and biomass). The increase of biodiversity from deep Block 17 sites to the ultra-deep Block 32 area also confirmed previous observations about the gradient of increasing biodiversity with depth in the deep Angola Basin (Kröncke and Türkay 2003).…”

Distribution patterns and biodiversity in polychaete communities of the Weddell Sea and Antarctic Peninsula area (Southern Ocean)

“…Additional sampling e¡orts in similar areas may alter the impressions derived from this study, and larger-scale deep-sea studies currently underway, such as DIVA (Kro« ncke & Tu« rkay, 2003) in the Angola Basin and ANDEEP (Fu« tterer et al, 2003;Brandt & Hilbig, 2004) in the Weddell and Scotia Seas may shed some more light on the diversity in the deep sea. However, comparisons with samples of a similar size (0.1m 2 ) taken o¡ the Farallon Islands (Hilbig & Blake, 2006) show that at depths less than 1000 m, diversity (H') is much higher in the Southern Ocean than in the northeast Paci¢c.…”

Asphalt mounds and associated biota on the Angolan margin

“…The benthic biology of the deep waters off Angola has received increasing attention (Arbizu and Schminke, 2005;Bianchi, 1992;Kroncke and Turkay, 2003;Sibuet et al, 1989;Van Gaever et al, 2009;Vinogradova et al, 1990) and has been the focus for a number of large international programmes with biological components including DIVA (Arbizu and Schminke, 2005), ZaiAngo and BioZaire Vangriesheim et al, 2009). These studies have mostly focussed on chemosynthetic systems in the deep bathyal (Sibuet and OluLeRoy, 2002;Sibuet and Vangriesheim, 2009) or deep-water coral reefs at the shelf-edge (Le Guilloux et al, 2009).…”