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Aquatic Microbial Ecology

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AME 63:123-131 (2011)  -  DOI:

Group-specific effects on coastal bacterioplankton of polyunsaturated aldehydes produced by diatoms

Cecilia Balestra1, Laura Alonso-Sáez2,3, Josep M. Gasol2, Raffaella Casotti1,*

1Stazione Zoologica A. Dohrn, Villa Comunale, 80121 Naples, Italy
2Institut de Ciències del Mar, CSIC, Passeig Maritim de la Barceloneta 37–49, 08003 Barcelona, Catalonia, Spain
3Present address: Centro Oceanográfico de Xixón, Instituto Español de Oceanografía, Camín del L'Arbeyal s/n, 33212 Xixón, Spain
*Corresponding author. Email:

ABSTRACT: Polyunsaturated aldehydes (PUAs), produced as secondary metabolites by diatoms, have been shown to induce toxic effects on a variety of organisms, including copepods and phyto- and bacterioplankton. However, the nature of and the players in this interaction remain poorly understood. We tested the effect of 3 PUAs commonly produced by marine diatoms—2E,4E/Z-heptadienal (HEPTA), 2E,4E/Z-octadienal (OCTA), 2E,4E/Z-decadienal (DECA) and a mix of HEPTA and OCTA (MIX)—on a natural bacterial community from a coastal area of the NW Mediterranean Sea (Blanes Bay, Spain). Little effect on total or relative cell abundance or bulk bacterial production was observed after 6 or 24 h exposure to 7.5 nM of the 3 different PUAs for the different bacterial phylogenetic groups (Gammaproteobacteria, Bacteroidetes, Rhodobacteraceae and SAR11), assessed by catalysed reporter deposition (CARD)-fluorescence in situ hybridisation (FISH). Metabolic activity, i.e. single-cell activity as determined by microautoradiography combined with CARD-FISH (MAR-CARD-FISH), was least affected by the addition of single PUAs in Gammaproteobacteria, markedly in Bacteroidetes and most markedly in Rhodobacteraceae, leading to a decrease in Rhodobacteraceae abundance by 21% (by 38% of the active cells assessed by leucine uptake) compared to the control. Bacteroidetes, although markedly affected in single-cell activity, were the most abundant group (54% of total cell counts). The addition of a mixture of OCTA and HEPTA produced a more pronounced decrease in the metabolic activity of all groups than the incubation with the single PUAs, suggesting a synergistic effect. Our results demonstrate that PUAs have a differential effect on the single-cell activity of distinct bacterial groups in natural communities. PUAs may therefore play an important role in shaping bacterial community composition by conferring a competitive advantage to PUA-resistant groups, allowing them to preferentially use the organic matter released by diatoms.

KEY WORDS: PUAs · Bacterial composition · Metabolism · MAR-CARD-FISH · Diatoms

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Cite this article as: Balestra C, Alonso-Sáez L, Gasol JM, Casotti R (2011) Group-specific effects on coastal bacterioplankton of polyunsaturated aldehydes produced by diatoms. Aquat Microb Ecol 63:123-131.

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