Community structure of abyssal macrobenthos of the South and equatorial Atlantic Ocean - Identifying patterns and environmental controls

The DIVA (Latitudinal Gradients of Deep-sea BiodDIVersity in the Atlantic) expeditions studied benthic biodiversity of the abyssal Equatorial and South Atlantic as part of the Census of the Diversity of Abyssal Marine Life (CeDAMar), the abyssal component of the ten-year programme Census of Marine Life (2000-2010). Three expeditions were carried out from RV Meteor between 2000 and 2009. Samples were taken along a latitudinal gradient spanning the Cape, Angola, and Guinea basins in the SE Atlantic and the Argentine and Brazilian basins in the SW Atlantic. The objectives of this study were to analyse patterns of epi- and suprabenthic macrofaunal density and composition at higher taxon level from epibenthic sledge (EBS) taken during the DIVA sampling campaigns and how they relate to differences in environmental conditions. In particular, the different oceanic basins are characterized by variation in surface primary productivity, sedimentary properties, and depth. We expected this difference to be reflected in the structure of the abyssal benthic communities. Consistent with this hypothesis, we found significant differences in macrofauna density between different deep-sea basins, mainly related to food availability. However, only subtle differences in community composition were observed. We found that stations in close proximity to one another showed great variability in both macrofaunal density and composition. We conclude that smaller spatial scale sampling should be paired with higher taxonomic resolution analyses of macrofaunal samples to better understand the factors contributing to variations of macrobenthic communities in the deep sea.