Metabolism and biomass vertical distribution of zooplankton in the Bransfield Strait during the austral summer of 2000

[EN] The vertical distribution (0?550 m) of zooplankton biomass, and indices of respiration (electron transfer system [ETS]) and structural growth (aminoacyltRNA synthetases activity [AARS]), were studied in waters off the Antarctic Peninsula during the austral summer of 2000. The dominant species were the copepod Metridia gerlachei and the euphausiid Euphausia superba. We observed a vertical krill/copepod substitution in the water column. The zooplankton biomass in the layer at a depth of 200?500 m was of the same magnitude as the biomass in the layer at a depth of 0?200 m, indicating that biomass in the mesopelagic zone is an important fraction of the total zooplankton in Antarctic waters. The metabolic rates of the zooplankton community were sustained by less than 0.5% of the primary production in the area, suggesting that microplankton or small copepods are the main food source. Neither food availability nor predation seemed to control mesozooplankton biomass. The wide time lag between the abundance peak of the dominant copepod (M. gerlachei) and the phytoplankton bloom is suggested to be the main explanation for the low summer zooplankton biomass observed in these waters.

Migración y ecología trófica de peces migradores verticales dominantes del Atlántico nordeste subtropical: implicaciones en el flujo activo de carbono

[EN]Diel vertical migrants (DVMs) are mainly zooplankton and micronekton that migrate upward from 400-700 m depth every night to feed in the productive epipelagic zone and come back at dawn to the mesopelagic zone, where they release the ingested carbon. DVMs should contribute to the biological pump in the ocean and, accordingly, to thevglobal CO2 balance. A large portion of the DVMs biomass are the lanternfishes (myctophidae), which might represent a pathway accounting for a substantial export of organic carbon to the deep ocean. Nevertheless, the magnitude of this transport is still poorly known. The combined study of migration and feeding ecology is a good approach to improve our knowledge of the DVMs role in this active carbon flux. Two dominant myctophids in the Subtropical Eastern North Atlantic Ocean (Hygophum hygomii (Lütken, 1892) and (Lobianchia dofleini (Zugmayer, 1911)) were studied from several surveys carried out around the Canary Islands during the last decade. Our results showed a marked diel vertical migration and a prevailing nocturnal feeding with predation mainly on copepods and euphausiids. The digestion state of prey suggested a slow stomach evacuation rate and that most of the ingested carbon in the epipelagic is efficiently transported to the mesopelagic zone.

Astaxanthin determination in marine biological samples : an overview

Máster en Oceanografía