Carbon and nitrogen stable isotopes of benthic megafauna on the Angolan cold-water coral reefs (SE Atlantic)

We used carbon and nitrogen stable isotope (δ13C and δ15N) analyses to investigate the trophic network of the CWC reef habitat off Angola (SE Atlantic Ocean). Samples were collected in January 2016 during the M122 (“ANNA”) expedition on board R/V Meteor. In total, 18 reef sites, including seven CWC mound settings over a bathymetric range of 250 to 530 m water depth, were sampled for stable isotope analyses. Samples of organisms belonging to the taxa Porifera, Cnidaria, Arthropoda, Annelida, Echinodermata and Chordata were collected by means of a box corer, a Van-Veen grab sampler and the Remotely Operated Vehicle (ROV) SQUID (MARUM, Bremen, Germany). To investigate potential food sources of the benthic megafauna, three types of Particulate Organic Matter (POM) were collected: Suspended Particulate Organic Matter (SPOM) was collected with a McLane phytoplankton pump; settling SPOM was collected with a sediment trap (SPOM trap) and sediment samples were collected with a box corer and a grab sampler. Analyses of benthic megafauna were performed using a Elementar IsoPrime 100 isotope ratio–mass spectrometry (IR–MS) (IsoPrime Ltd.) coupled to a CNS elemental analyzer (Elementar Vario Pyro Cube EA CNS; Elementar Analysensysteme GmbH), while POM samples were analyzed by a Delta V Advantage IR–MS coupled online to an elemental analyzer (Flash 2000 EA-IRMS) by a ConFlo IV (Thermo Fisher Scientific Inc.). Vienna Pee Dee belemnite (V.P.D.B.) for carbon, and atmospheric N2 (Air) for nitrogen, were used as reference materials, and stable isotope values are reported in respect to that.