Metabolic state along a summer north-south transect near the Antarctic Peninsula: a size spectra approach

• Published in: Journal of Plankton Research
• Main Authors: García-Muñoz, Cristina, García, Carlos M., Lubián, Luis M., López-Urrutia, Ángel, Hernández-León, Santiago, Ameneiro, Julia
• Format: Text
• Language: English
• Published: Oxford University Press 2014
• Subjects: Article; Antarctic; Antarctic Peninsula; The Antarctic; Antarc*; Copepods
• Online Access: http://plankt.oxfordjournals.org/cgi/content/short/fbu042v1; https://doi.org/10.1093/plankt/fbu042

To establish a metabolic state along a north–south transect in Antarctic waters, we approached community respiration (CR) from a combined perspective based on the metabolic theory of ecology (MTE) and the size-scaling of the whole planktonic community. A detailed analysis of a summer integrated multi-trophic normalized biomass size spectra (NBSS), from heterotrophic bacteria to zooplankton, was carried out. To acquire individual size data, different techniques were combined: flow cytometry for smaller fractions (<20 µm of equivalent spherical diameter), FlowCAM for larger nano- and microplankton and scanning and image analysis for the zooplankton fractions. The distribution of the NBSS was linear at all stations ( R 2 values: 0.87–0.93) but dome-shape features appeared related to phytoplankton cell distribution which are responsible for a large fraction of microbial respiration. Generally, the region showed an autotrophic budget south of the archipelago due to gross primary production (GPP) values up to 2804 mg C m−2 day−1, where salps could significantly contribute to the carbon export flux. Contrastingly, higher CR rates (>1000 mg C m−2 day−1) were found at the northern stations due to a higher phytoplankton respiration activity associated with increasing sea water temperatures and a higher presence of heterotrophic organisms (microheterotrophs, chaetognaths and copepods) resulting in a net heterotrophic metabolic state (GPP/CR < 1).