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Marine Ecology Progress Series

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MEPS 489:75-85 (2013)  -  DOI:

Carbon fluxes through estuarine bacteria reflect coupling with phytoplankton

Xosé Anxelu G. Morán1,*, Hugh W. Ducklow2,3, Matthew Erickson

1Instituto Español de Oceanografía, Centro Oceanográfico de Xixón, Camín de L’Arbeyal, s/n 33212 Xixón, Asturies, Spain
2The Ecosystems Center, 7 MBL Street, Woods Hole, Massachusetts 02543-1015, USA
3Present address: Lamont Doherty Earth Observatory, Palisades, New York 10964, USA

ABSTRACT: Microbial plankton carbon fluxes were comprehensively assessed at 4 contrasting sites in Waquoit Bay estuary (Massachusetts, USA) in 2008, focussing on the role of phytoplankton as dissolved organic matter suppliers for heterotrophic bacterioplankton. Strong seasonal patterns in environmental and microbial variables were observed, with concurrent summer maxima and minima in December for bacterial biomass (17.7-164.7 µg C l-1) and production (4.8-121.5 µg C l-1 d-1). Phytoplankton biomass (0.7-32.6 µg chlorophyll l-1) and primary production (PP, 164-3570 µg C l-1 d-1) varied similarly to bacterial variables, with dissolved PP (DPP), i.e. released extracellularly, ranging from 3 to 36% of the total PP. The flux of DPP represented between 0.4 and 20% of bulk dissolved organic carbon (DOC, 92-346 µmol C l-1) daily turnover. In addition to temperature, moderate bottom-up control of bacterial assemblages was suggested by biomass-production regressions. Bacteria apparently depended more on phytoplankton-derived DOC than on its total concentration. The difference became larger when the total flux of carbon or bacterial carbon demand (BCD, 19-468 µg C l-1 d-1) was considered, with DPP explaining 53% of its variance compared with 37% from bulk DOC. On average, DPP could meet 50% of BCD, indicating a larger than expected trophic dependence of bacteria on phytoplankton in the whole estuarine ecosystem.

KEY WORDS: Bacteria · Phytoplankton · Carbon fluxes · Trophic coupling · Estuaries

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Cite this article as: Morán XAG, Ducklow HW, Erickson M (2013) Carbon fluxes through estuarine bacteria reflect coupling with phytoplankton. Mar Ecol Prog Ser 489:75-85.

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