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Marine Ecology Progress Series

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MEPS 528:53-69 (2015)  -  DOI:

Local differences in phytoplankton-bacterioplankton coupling in the coastal upwelling off Galicia (NW Spain)

E. Teira1,*, V. Hernando-Morales1, A. Fernández1,4, S. Martínez-García1,5, X. A. Álvarez-Salgado2, A. Bode3, M. M. Varela3

1Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, 36200 Vigo, Spain
2CSIC, Instituto de Investigacións Mariñas, Eduardo Cabello 6, 36208 Vigo, Spain
3IEO, Instituto Español de Oceanografía, Centro Oceanográfico de A Coruña, Apdo. 130, 15080 A Coruña, Spain
4Present address: School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332, USA 5Present address: Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, 39182 Kalmar, Sweden
*Corresponding author:

ABSTRACT: We simultaneously studied microbial-mediated carbon fluxes at 2 contrasting sites within the coastal upwelling system off Galicia, near A Coruña and Vigo, Spain, over an annual cycle in order to compare the fraction of primary production released as dissolved organic carbon (DOC) and the degree of coupling between bacteria and phytoplankton. A significant fraction of primary production was released as DOC at both sites, averaging ~30%. DOC release accounted for, on average, 30% of the total bacterial carbon demand, which is indicative of a moderate trophic dependence of bacteria on phytoplankton in these coastal ecosystems. Nevertheless, differences in hydrographic conditions associated with stronger upwelling pulses off Vigo, and deeper upper mixed layers during the downwelling period off A Coruña, led to significant differences in phytoplankton dynamics and the subsequent direct coupling with heterotrophic bacteria. Strong direct coupling between phytoplankton extracellular release and bacterial production (BP) was found off Vigo, which could be related to the quality of the DOC produced by actively growing phytoplankton. By contrast, DOC release and BP rates were decoupled off A Coruña, likely due to unaccounted DOC associated with indirect trophic processes or to the low availability of freshly produced exudates associated with overflow or photoinhibition mechanisms.

KEY WORDS: Planktonic carbon dynamics · Coupling · Heterotrophic bacteria · Phytoplankton · Upwelling · DOC Production

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Cite this article as: Teira E, Hernando-Morales V, Fernández A, Martínez-García S, Álvarez-Salgado XA, Bode A, Varela MM (2015) Local differences in phytoplankton-bacterioplankton coupling in the coastal upwelling off Galicia (NW Spain). Mar Ecol Prog Ser 528:53-69.

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