Oceanografia

In order to contribute to the baseline of knowledge that is being built of the Gerlache Strait and the adjacent areas, the echinoderms collected during the Scientific Expeditions from Colombia to Antarctica carried out between 2016 and 2019 as part of the project “Biodiversity and oceanographic conditions of the Gerlache Strait, Biogerlache-Antartica” are presented. Eleven stations between 54 and 523 m deep were sampled, using sediment dredgers that captured incidentally some individuals from the mega and macro-epifauna, which were separated, reviewed, and identified. Twentynine (29) individuals were obtained in five of the sampled stations, belonging to 13 morphotypes. Ophiuroidea was the richest class (five morphotypes), followed by Holothuroidea (four), Asteroidea (two), and Crinoidea (two). Morphological and distribution comments are presented, as well as general and detailed images of each morphotype. Among
the contributions to the inventory of echinoderms in the area, it is highlighted the sea cucumber genus Taeniogyrus Semper, 1867 that is registered for the first time for the Antarctic peninsula and the crinoid species Anthometrina adriani (Bell, 1908) that extends its geographical distribution, confined to the high-Antarctic shelf, up to the Gerlache Strait (64º39 ‘S).

The Brazilian continental margin (BCM) extends from the Tropical to the Subtropical Atlantic Ocean, with much of its seafloor within deep waters, supporting rich geomorphological features and under wide productivity gradients. Deep-sea biogeographic boundaries on the BCM have been limited to studies that used water mass and salinity properties of deep-water masses, partly as a result of historical under sampling and a lack of consolidation of available biological and ecological datasets. The aim of this study was to consolidate benthic assemblage datasets and test current oceanographic biogeographical deep-sea boundaries (200–5,000 m) using available faunal distributions. We retrieved over 4,000 benthic data records from open-access databases and used cluster analysis to examine assemblage distributions against the deep-sea biogeographical classification scheme from Watling et al. (2013). Starting from the assumption that vertical and horizontal distribution patterns can vary region...

Ecosystem functioning, i.e. the transfer of material through a system, supports the ecosystem services deep-sea sediments provide, including carbon sequestration, nutrient regeneration, and climate regulation. To date, seven studies globally have researched in situ how various benthic groups contribute to organic matter degradation in abyssal sediments through stable isotope tracer experiments, of which only one in the Atlantic (at the Porcupine Abyssal Plain or PAP). To expand the limited knowledge base on abyssal ecosystem functioning, we performed in situ stable isotope experiments in the Cabo Verde Abyssal Basin (CVAB, tropical NorthEast Atlantic). The Cabo Verde marine region is an oceanographically interesting region with complex currents, resulting in strong gradients of productivity and unique ecological characteristics. We conducted 2-day in situ incubations with organic substrate (lyophilised diatom culture) labelled with 13 C and 15 N stable isotopes through five benthic lander deployments to 4,200 m in an area presumed mesotrophic. We assessed sediment community oxygen consumption (SCOC), dissolved inorganic carbon (DI 13 C) production, nutrient fluxes, and label incorporation into bacteria, large Foraminifera (>300 μm), meiobenthos, and macrofauna. Results were specifically compared across the Atlantic basin to the eutrophic PAP for which all the same system components were reported (Witte et al. 2003). At CVAB, bacteria and meiobenthos dominated phytodetritus processing (91% and 8%, respectively), in contrast to PAP where macrofauna dominated (98%). Phytodetritus remineralisation was two to three times lower at CVAB compared to PAP, most likely due to the low abundance of fast responding macrofauna. However, overall phytodetritus processing efficiency at CVAB was four times greater compared to PAP. Our results support a mesotrophic regime at the CVAB lander site, and provide a unique first insight into ecosystem functioning of tropical (low-latitude) abyssal systems in the Atlantic Ocean. A better understanding of abyssal ecosystem functioning in various ocean regions, to which this study contributes, provides insight into main regulators of abyssal communities and thus may have implications for our understanding of abyssal systems under future climate scenarios.