Bottom depth carving the pelagic spatial organisation in large marine ecosystem: The case of North West Africa
Year: 2024
Type: article
Abstract: This study aimed to examine the spatial organization of pelagic communities within the water column along a horizontal gradient extending from the coast to the offshore area, categorized into three zones: inshore, offshore, and transition. A total of 29,000 nautical miles of acoustic transects collected during 14 annual standardized surveys were analyzed using two complementary acoustic methods: (i) extraction of sound scattering layers (SSL) and (ii) echointegration (EI) across the entire water column, both horizontally and vertically averaged. The results revealed significant differences between the three bathymetric areas based on SSL and EI descriptors, with nektonic communities in the transition area exhibiting intermediate characteristics between those in the inshore and offshore areas. The relative abundance of nektonic communities decreased from shallow coastal areas to deep offshore areas. The inshore area is different from transition and offshore area, which is confirmed by diel vertical migration (DVM) analyse through vertical profiles. All areas exhibited classic DVM type I; however, offshore and transition areas also presented unexpected DVMs of type II, i.e., organisms descend deeper during the night, displaying distinct vertical profiles compared to the inshore area. This suggests that the functional and specific composition of pelagic nektonic communities differed between inshore and offshore areas, indicating that organisms adjust their responses to their environment. Over two decades, the three bathymetric areas showed a significant increase in pelagic relative biomass and variation in SSL spatial structure. Nevertheless, nektonic communities reacted differently to interannual changes depending on the bathymetric areas, such as the minimal depth of the shallowest SSL. Fluctuations in SSL descriptors were highlighted over the study period, which may be related to multi-decadal oscillations in the Atlantic Ocean.
Source: Continental Shelf Research
Institutions: Biologie des Organismes et Écosystèmes Aquatiques, Muséum national d'Histoire naturelle, Institut Universitaire Européen de la Mer, Laboratoire des Sciences de l'Environnement Marin, Institut de Recherche pour le Développement, Institut Mauritanien de Recherches Océanographiques et des Pêches, Institut National de Recherche Halieutique, PatriNat
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Life below water
Open Access status: hybrid
Estimated APC paid: $3,350
Funders: Foundation for Appalachian Ohio, Institut de Recherche pour le Développement, Havforskningsinstituttet, European Commission, Bundesministerium für Bildung und Forschung, Muséum National d'Histoire Naturelle, Région Bretagne, Horizon 2020 Framework Programme, Horizon 2020, H2020 Science with and for Society, FP7 Environment
Awards: G3196650022, Tropical and South Atlantic climate-based marine ecosystem predictions for sustainable management, G434337789, G4418844173, Verbundprojekt: Der Ökosystemansatz im Fischerei- und Umweltmanagement der Meeresgebiete Westafrikas (AWA), Teilprojekt: TPG4 - Variabilität und Produktivität ästuariner Fischgemeinschaften am Beispiel der Art Bonga Shad und des Ichthyoplanktons, sowie Unterstützung beim Aufbau von Ausbildungsstrukturen, Enhancing prediction of tropical Atlantic climate and its impacts, G6347254535, G6507300482, Next Generation Earth Modelling Systems, Verbundprojekt: Der Ökosystemansatz im Fischerei- und Umweltmanagement der Meeresgebiete Westafrikas (AWA), Teilprojekt: TPG1 - GEOMAR - Beobachtung und Modellierung der Ozeanphysik und Biogeochemie für einen Ökosystemansatz im Management der Fischerei und der Meeresumwelt
OpenAlex ID: W4404770980