Microzooplankton feeding impact in a coastal upwelling system on the NW Iberian margin: The Ría de Vigo

• Published in: Estuarine, coastal and shelf science Vol. 91; no. 1; pp. 110 - 120
• Main Authors: Teixeira, Isabel G., Figueiras, Francisco G., Crespo, Bibiana G., Piedracoba, Sílvia
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 2011; Elsevier
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Bacillariophyceae; Bacteria; Biological and medical sciences; Brackish water ecosystems; Carbon; Coastal; coastal upwelling systems; Consumption; dilution technique; Foods; Fundamental and applied biological sciences. Psychology; microbial food web; Microorganisms; microscopic enumeration; microzooplankton; Nanostructure; Ría de Vigo; Synecology; Upwelling; ANE, Spain, Galicia; ANE, Spain, Galicia, Pontevedra, Ria de Vigo; coastal upwelling systems; microbial food web; dilution technique; microzooplankton; microscopic enumeration; Ría de Vigo; Brackish water environment; Enumeration; Ria de Vigo; Feeding; Iberian Peninsula; Dilution; Food web; Upwelling; Microorganism; Zooplankton
• ISSN: 0272-7714; 1096-0015
• DOI: 10.1016/j.ecss.2010.10.012

The dilution technique, combined with identification and enumeration of pico-, nano- and micro-plankton by microscopy, was used to estimate microzooplankton impact on the microbial community in surface waters of a coastal embayment on the NW Iberian upwelling system. Microzooplankton were important consumers of autotrophic and heterotrophic plankton in this system, feeding up to 93% of standing stock and more than 100% of production of several groups. Heterotrophic bacteria and heterotrophic picoflagellates experienced the highest and constant impact, with 75–84% of their standing stocks and 85–102% of their production being channelled through the microbial food web. Pico- and nano-phytoplankton were also consumed, although maximum grazing occurred on diatoms during upwelling events, coinciding with highest primary production. Predation on pico-nano-heterotrophs was especially relevant under downwelling conditions, when consumption of total carbon and particularly autotrophic carbon was considerably lower than during upwelling. The results suggest that the existence of a multivorous food web, extending from the microbial loop to the herbivorous food web, could be a major feature in this coastal upwelling system. The microbial loop, which occurs as a permanent background in the system, would contribute to sustain the microbial food web during downwelling, whereas the herbivorous food web could coexist with a microbial food web based on large diatoms during upwelling. The multivorous food web would partially divert diatoms from sinking and hence favour the retention of organic matter in the water column. This could enhance the energy transfer to higher pelagic trophic levels in coastal upwelling systems. ► Microzooplankton consumes a significant fraction of plankton in the Ría de Vigo. ► Consumption of small heterotrophs relatively constant through the year. ► Consumption of diatoms very important during upwelling conditions. ► During non-upwelling, the microbial food web basicaly sustained by the microbial loop. ► In upwelling, the classical must coexist with the microbial food web based on diatoms.