Characterization of the benthic megafauna of coldwater coral mounds off Angola’s coast, and an initial exploration of their spatial distribution patterns.
Supervisor: Patricia Puerta Covadonga Orejas (IEO)
Cold-water coral (CWC) reefs provide habitat for multiple deep-sea species, including commercial ones, creating valuable and unique ecosystems in the deep-sea realm. CWC reefs and their associated fauna have been widely studied in several locations in the North Atlantic Ocean and Mediterranean Sea, but very scarce information is currently available on these deep-sea communities in the South Atlantic. A recent expedition to the continental margin off Angola’s coast in 2016 (R/V METEOR expedition M122) discovered a benthic biodiversity hot-spot area, which is characterized by the presence of CWC reefs dominated by Lophelia pertusa thriving under extreme hypoxic conditions, with dissolved oxygen concentrations as low as 0.5 mL· L-1. The aim of the present study was to characterize in detail the megafauna assemblages associated with these CWC reefs. For this purpose, video footage recorded by a Remotely Operated Vehicle (ROV SQUID) was used to obtain quantitative standardized data for occurrences and abundance. The results included the identification of 89 mega-faunal morphospecies along four video transects. The composition of deep-sea benthic communities was described in relation to environmental and terrain variables, observing some general spatial patterns. The results indicated that deep-sea biodiversity in the area of study seems to be lower if compared with other North Atlantic counterpart sites, although this biodiversity and population densities in several morphospecies was remarkably high despite the hypoxic conditions. This work contributes to characterizing deep-sea Vulnerable Marine Ecosystems (VME) and allows us to better understand their communities associated, thriving under limiting oxygen conditions. Therefore, it highlights the importance of the study area in terms of biodiversity and the adaptation capability of deep-sea vulnerable

taxa to face the future scenarios of climate change.

Keywords: Cold-water coral reefs, benthic megafauna communities, Remotely Operated Vehicle, Lophelia pertusa, coral mounds, South Atlantic Ocean, Angolan margin.