AME 74:235-249 (2015)  -  DOI: https://doi.org/10.3354/ame01738

Effect of sunlight on prokaryotic organic carbon uptake and dynamics of pigments relevant to photoheterotrophy in the Adriatic Sea

Mauro Celussi1,*, Alessandra A. Gallina1,2,6, Josephine Ras3,4, Michele Giani5,7, Paola Del Negro

1OGS (Istituto Nazionale di Oceanografia e Geofisica Sperimentale), Sezione Oceanografia, v. A. Piccard 54, 34151 Trieste, Italy
2Dipartimento di Scienze della Vita, Università di Trieste, v. Valerio 28/A, 34127 Trieste, Italy
3Centre national de la Recherche Scientifique, UMR 7093, Laboratoire d’Océanographie de Villefranche, BP 28, 06234 Villefranche sur mer, France
4Université Pierre et Marie Curie, Université Paris 06, UMR 7093, Laboratoire d’Océanographie de Villefranche, BP 28, 06234 Villefranche sur mer, France
5Istituto Superiore per la Ricerca e la Protezione Ambientale, Località Brondolo, 30015 Chioggia (VE), Italy
6Present address: Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
7Present address: OGS (Istituto Nazionale di Oceanografia e Geofisica Sperimentale), Sezione Oceanografia, v. A. Piccard 54, 34151 Trieste, Italy
*Corresponding author:

ABSTRACT: Marine photoheterotrophic microorganisms are capable of using light to meet their energy requirements and organic compounds as both carbon and energy sources. We still have little knowledge of the extent to which stimulation of these microorganisms by light could affect the estimates of organic carbon uptake. We evaluated the light and dark prokaryotic organic carbon uptake (3H-leucine) rates in a grid of stations covering the whole Adriatic Sea during winter and late summer. Light-exposed (photosynthetically active radiation and ultraviolet radiation [UVR]) surface samples were either unaffected, photostimulated or photoinhibited without any clear geographical or seasonal pattern. Light-enhanced leucine uptake occurred only in 23% of assays, suggesting that photoheterotrophy is not a major metabolic strategy and/or it is often counterbalanced by negative effects caused by UVR. Concentrations of bacteriochlorophyll a, zeaxanthin and divinyl chlorophyll a were measured in order to relate 3H-leucine uptake to the distribution of aerobic anoxygenic phototrophs (AAPs), total Cyanobacteria and Prochlorococcus populations, respectively, together with direct estimates of total prokaryotes and Synechococcus abundance. No relationship between light-enhanced leucine uptake and presence of picocyanobacteria or AAPs was evident. Divinyl chlorophyll a concentration was below the limit of detection in February, whereas in late summer the highest values were found around 50 m depth in the central and southern basins. In contrast, bacteriochlorophyll a concentration was correlated to total prokaryote abundance and dissolved organic carbon. Since locally leucine uptake in the light was markedly different from dark controls, in situ light incubations should be more appropriate than dark incubations when carbon budget calculations are intended.


KEY WORDS: Prokaryotic production · Bacteriochlorophyll a · Divinyl chlorophyll a · Zeaxanthin · Light


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Cite this article as: Celussi M, Gallina AA, Ras J, Giani M, Del Negro P (2015) Effect of sunlight on prokaryotic organic carbon uptake and dynamics of pigments relevant to photoheterotrophy in the Adriatic Sea. Aquat Microb Ecol 74:235-249. https://doi.org/10.3354/ame01738

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