Trophic ecology of Angolan cold-water coral reefs (SE Atlantic) based on stable isotope analyses

Abstract

Cold-water coral (CWC) reefs of the Angolan margin (SE Atlantic) are dominated by Desmophyllum pertusum and support a diverse community of associated fauna, despite hypoxic conditions. In this study, we use carbon and nitrogen stable isotope analyses (δ13C and δ15N) to decipher the trophic network of this relatively unknown CWC province. Although fresh phytodetritus is available to the reef, δ15N signatures indicate that CWCs (12.90 ± 1.00 ‰) sit two trophic levels above Suspended Particulate Organic Matter (SPOM) (4.23 ± 1.64 ‰) suggesting that CWCs are highly reliant on an intermediate food source, which may be zooplankton. Echinoderms and the polychaete Eunice norvegica occupy the same trophic guild, with high δ13C signatures (-14.00 ± 1.08 ‰) pointing to a predatory feeding behavior on CWCs and sponges, although detrital feeding on 13C enriched particles might also be important for this group. Sponges presented the highest δ15N values (20.20 ± 1.87 ‰), which could be due to the role of the sponge holobiont and bacterial food in driving intense nitrogen cycling processes in sponges’ tissue, helping to cope with the hypoxic conditions of the reef. Our study provides first insights to understand trophic interactions of CWC reefs under low-oxygen conditions.

Ensemble modelling to predict the distribution of vulnerable marine ecosystems indicator taxa on data‐limited seamounts of Cabo Verde (NW Africa)

“…Nonetheless, model predictions showed that all seamounts present suitable areas where VMEs are likely to occur, supporting the expected ecological relevance of the seamounts in the region. Indeed, available image data showed pristine and diverse CWC gardens on Cadamosto Seamount (Orejas et al., 2022; Vinha et al., 2022) and exceptional sponge and crinoid fields and scleractinian coral reefs on Nola Seamount (Hansteen et al., 2014). In addition, three of the seamounts considered in our study – Boavista, Cabo Verde and Nola – are currently included in designated ecologically and biologically significant areas (EBSAs) (UNEP/CBD/COP/DEC/XII/22, 2014), where significant fishing activity occurs (Martins et al., 2022; Roast et al., 2023).…”

“…One decade later, in 2021, the multidisciplinary research expedition iMirabilis2 (Orejas et al., 2022), part of the Horizon 2020 project iAtlantic, on board the R/V Sarmiento de Gamboa (UTM‐CSIC), was the first expedition dedicated to exploring the deep‐sea benthic communities of SW Cabo Verde. The recorded video transects, conducted using an ROV, revealed pristine CWC communities at Cadamosto Seamount (SW of Brava Island), including over 60 CWC morphospecies (Vinha et al., 2022).…”