Latitudinal assemblages and vertical distribution of micronektonic crustaceans in the North Atlantic Ocean

Abstract

The study of micronektonic organisms in the mesopelagic zone has increased in recent years because of their role in the biological carbon pump. However, most previous studies were focused on fishes, while other significant groups remained unaddressed. Here we analysed the community of micronektonic crustaceans in the North Atlantic Ocean from 20 to 55 degrees N, at different depth layers from the surface to 2000 m depth, and during the day- and nighttime. We identified a total of 111 species belonging to 10 different families of the orders Decapoda, Euphausiacea, and Lophogastrida. Euphausiids were the most abundant organisms (18.3 and 77.0 ind. 1000 m-3 during the day and night, respectively), while the Acanthephyridae family (Decapoda) contributed the most to the total biomass (31.9 and 59 g C 1000 m-3 during the day and night, respectively). Statistical differences in weighted mean depth showed diel vertical migrants (families Oplophoridae, Pandalidae, Penaeidae, Sergestidae, and Euphausiidae) and families with only some species migrating (Acanthephyridae, Benthesicymidae, Pasiphaeidae, Eucopiidae, and Gnathophausiidae). Based on species composition and abundance, the analyses highlighted 6 different assemblages consistent with existing ecoregions, where temperature and salinity emerged as the primary drivers. Our analysis also revealed connections between the epi- and bathypelagic zones driven by diel vertical migrations. The present study highlights the importance of micronektonic crustaceans in the meso- and bathypelagic zones and calls for more comprehensive research to elucidate their role in the biological carbon pump.