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Poster De Conférence Année : 2022

Comparative zooplankton structure and functioning in epipelagic layers of different Mediterranean regions during the Hippocampe cruise

Résumé

The structure and functioning roles of the zooplankton community were estimated at ten stations along a North-South transect from French coast (Toulon, Marseille) to the Tunisian cost (Gulf of Gabes) during the Hippocampe cruise carried out between April and May 2019. This sampling were therefore realized in different ecoregions. The zooplankton data were collected with three different types of net tows at each station: a double vertical net tows from 200 m deep (or bottom) to surface (60 and 200 µm mesh sizes), an horizontal net tows in surface with Manta net, and an horizontal net tows at the DCM with Hydrobios closing nets (both nets were of 60 µm mesh size). The samples were splitted in two sub-samples: one for dry-weight and the other one for image treatment. For this latter treatment, the sub-samples were fractionated into groups of fractions: one treated by FlowCAM for fractions < 500 µm and another treated with ZOOSCAN for fractions > 500 µm to obtain a complete size structure of the zooplankton community from 60 µm to few mm. The imagery treatment allowed to differentiate in each sample different components; microphytoplankton, detritical material (marine snow, aggregates,…), and several taxonomic groups of metazooplankton: nauplii, copepods, chaetognaths, appendicularians, other gelatinous – salps, jellyfish, siphonophores-, other crustaceans, and other zooplankton in order to estimate their contribution in the observed size spectrum. One of our main objectives was to compare the zooplankton taxonomy and size spectrum between the different water layers (surface and DCM) and the entire water column across regions. We also analyzed the relationships between the biological and the environmental variables, particularly the Chla profile and the content of detritus. The comparison of the taxonomic compositions highlighted some particularities of the DCM and the surface layers with the whole water column. The DCM was characterized by high dominance of nauplii but lower dominance of adults and copepodites of copepods, and nearly absence of appendicularians, whereas the neustonic layer (surface) presented lower nauplii concentrations and higher appendicularians and other zooplanktonic organims. The contributions of the different zooplanktonic groups to the whole zooplankton biomass for each layer were as well estimated. The relative proportions of zooplankton and detritus within the weighted biomass was as well estimated for each layer. In general, the highest concentrations of detritus were observed at the DCM and most often exceeded the zooplanktonic biomass. The contribution of the different taxonomic group to the biomass was estimated using allometric relationships. Finally, to estimate the functioning role of the zooplankton community during the spring bloom in the different ecoregions, grazing, respiration and excretion rates were derived using established allometric equations
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hal-04276420 , version 1 (09-11-2023)

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  • HAL Id : hal-04276420 , version 1

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Pamela Fierro-González, Marc Pagano, Loic Guilloux, Makhlouf Nouha, François Carlotti. Comparative zooplankton structure and functioning in epipelagic layers of different Mediterranean regions during the Hippocampe cruise. SIBECOL-AIL Meeting 2ndMeeting of the Iberian Ecological Society (SIBECOL) XXI conference of the Iberian Association of Limnology (AIL) 21stNational Congress of the Portuguese Ecological Society (SPECO), Jul 2022, Aveiro, Portugal. ⟨hal-04276420⟩
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