Contribution of heterotrophic plankton to nitrogen regeneration in the upwelling ecosystem of A Coruña (NW Spain)

• Published in: Journal of plankton research 2004, Vol.26 (1), p.11-28
• Main Authors: BODE, A, BARQUERO, S, GONZALEZ, N, ALVAREZ-OSSORIO, M. T, VARELA, M
• Format: Article
• Language: English
• Subjects: Algae; Ammonium; Ammonium compounds; Animal and plant ecology; Animal, plant and microbial ecology; Bacteria; Biological and medical sciences; Biomass; Chlorophyll; Chlorophylls; Ciliates; Ciliophora; Coastal upwelling; Excretion; Flagellates; Food webs; Fundamental and applied biological sciences. Psychology; Grazing; Heterotrophic organisms; Heterotrophs; Labelling; Marine; Nitrogen isotopes; Nutrients; Ocean circulation; Organic matter; Phytoplankton; Plankton; Primary production; Regeneration; Sea water ecosystems; Synecology; Uptake; Upwelling; Urea; Water column; Zooplankton
• ISSN: 0142-7873; 1464-3774; 1464-3774
• DOI: 10.1093/plankt/fbh003

The contribution of heterotrophic plankton to nitrogen (N) regeneration in the water column, and its significance for the requirements of phytoplankton, were studied at the seasonal scale in the coastal upwelling ecosystem of A Coruna (Galicia, NW Spain). During 1995-1997, monthly measurements were taken of hydrographic conditions, dissolved nutrients, and abundance and biomass of microplanktonic heterotrophs (bacteria, flagellates and ciliates), phytoplankton and mesozooplankton (>200 [mu]m). Additionally, series of experiments were conducted to quantify N fluxes, including primary production (14C method), phytoplankton uptake of nitrate, ammonium and urea (15N-labelling techniques), microheterotrophic regeneration of ammonium, mesozooplankton grazing (chlorophyll gut-content method) and excretion of ammonium by mesozooplankton. Two N budgets were built for the average situations of high (>100 mg C m-2 h-1) and low (