Carbon intake by zooplankton. Importance and role of zooplankton grazing in the Indian sector of the Southern Ocean

• Published in: Deep-sea research. Part 2. Topical studies in oceanography 2002, Vol.49 (16), p.3169-3187
• Main Authors: Mayzaud, P., Tirelli, V., Errhif, A., Labat, J.P., Razouls, S., Perissinotto, R.
• Format: Article
• Language: English
• Subjects: Algae; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Calanoides acutus; Calanus propinquus; Calanus simillimus; Clausocalanus laticeps; Copepoda; Ctenocalanus citer; Earth Sciences; Euphausia superba; Fundamental and applied biological sciences. Psychology; Marine; Metridia gerlachei; Oceanography; Oithona; Protozoa; Pteropoda; Rhincalanus gigas; Salpida; Sciences of the Universe; Sea water ecosystems; Synecology
• ISSN: 0967-0645; 1879-0100
• DOI: 10.1016/S0967-0645(02)00077-2

Ingestion by mesozooplankton and micronekton was monitored during two of the ANTARES cruises in the Indian sector of the Southern Ocean in spring and summer. The composition of the mesozooplankton populations varied in space and with season. Copepods always dominated in number and biomass, but salps and pteropods were present in the northern part of the transect in summer. Five species of large copepod ( Calanus simillimus, Calanoides acutus, Rhincalanus gigas, Calanus propinquus and Metridia gerlachei) dominated the biomass with a North–South gradient. Smaller species ( Oithona spp., Ctenocalanus citer, Clausocalanus laticeps) were also present. Biomass showed a definite trend with highest levels towards the polar front zone and permanent open-ocean area. Feeding activity was monitored either for the total population (summer) or specific individuals (spring). In summer, depending on the area considered, grazing rates by mesozooplankton appeared to have a significant impact on phytoplankton primary production. In the northern part of the transect (polar front zone or PFZ), salps and to a minor extent pteropods and copepods contributed mostly to the feeding pressure. Maximum intensity was observed in the Coastal Antarctic Zone (CCSZ) where Euphausia superba (adults and calyptopis larvae) could ingest more than 100% of the daily primary production. In spring, the impact of copepods dominated the zooplankton community. Small calanoids and young stages of large species of copepods rather than adult stages were the dominant contributors to grazing pressure. In summer, respiration rates of the dominant copepod species showed that energy expenditure exceeded by far chlorophyll ingestion. This is generally interpreted as the consequence of ingestion of alternate non-chlorophyll food source. The inverse correlation between the biomass of microzooplankton and the area of maximum difference between grazing and respiration confirmed that in summer the protozoans are strongly controlled by the copepod community. La consommation de carbone particulaire par le zooplancton et le micronecton a été étudié pendant deux des campagnes ANTARES dans le secteur sud-Indien de l’océan Antarctique au printemps et en été. La composition des communautés du mesozooplancton varie dans le temps et l’espace: les copépodes dominent généralement en nombre et biomasse mais les salpes et ptéropodes sont présents dans la partie Nord de la zone d’étude en été. Cinq espèces de grands copépodes c