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

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 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 equation

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

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 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 equation

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

International audienceThe 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 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 equation

Tendances environnementales et variabilité interannuelle du zooplancton en baie de Marseille (NO Méditerranée)

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High variability in temporal prey selectivity by Sardina pilchardus adults in the Bay of Marseille (North-Western Mediterranean Sea)

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Tendances environnementales et variabilité interannuelle du zooplancton en baie de Marseille (NO Méditerranée)

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Tendances environnementales et variabilité interannuelle du zooplancton en baie de Marseille (NO Méditerranée)

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Temporal variation in prey selection by adult European sardine (Sardina pilchardus) in the NW Mediterranean Sea

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An annotated checklist of Marine Phytoplankton taxa at the SOMLIT-Astan time series off Roscoff (Western English Channel, France): data collected from 2000 to 2010

International audienceA checklist of micro-phytoplankton. taxa based on net tow and Niskin bottle samples taken twice a month during the periods 2000-2003 and 2006-2010 at station SOMLIT-Astan (north of Roscoff, Western English Channel, France) is presented. SOMLIT-Astan is a coastal long-term monitoring station. It was established off Roscoff, where the water column seldom becomes stratified, and where continental influence is limited. Taxonomic identification was done based on light microscopy observations. The checklist includes 178 taxa (genus or species) among which 70 genera and 131 species of diatoms are recorded. Diatoms with benthic affinities make up 51% of the list of diatoms genera identified. Guinardia (especially G. delicatula) and Paralia sulcata appear as key taxa, becoming dominant in spring/summer and winter, respectively. Dinoflagellates are less diversified and never dominate. This work although not exhaustive, provides a reference list for micro-phytoplankton off Roscoff, and more generally for the permanently mixed waters of the Western English Channel, as well as information on the most common and/or abundant taxa in this habitat

Improving the management of Hyères saltmarshes (Provence, France) using an ecosystem-based approach

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