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Aquatic Microbial Ecology

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AME 72:155-173 (2014)  -  DOI:

Effects of enhanced temperature and ultraviolet B radiation on a natural plankton community of the Beagle Channel (southern Argentina): a mesocosm study

S. Moreau1,2,*, B. Mostajir3,4, G. O. Almandoz5,6, S. Demers2, M. Hernando7, K. Lemarchand2,  M. Lionard2,8, B. Mercier2, S. Roy2, I. R. Schloss2,5,9, M. Thyssen2,10, G. A. Ferreyra

1Université catholique de Louvain (UCL), Louvain-la-Neuve 1348, Belgium
2Institut des Sciences de la Mer (ISMER), Université du Québec à Rimouski (UQAR), Rimouski, Québec G5L 3A1, Canada
3Laboratoire d’Ecologie des systèmes marins côtiers (ECOSYM), Université Montpellier 2-CNRS-IFREMER-IRD-Université Montpellier 1 (UMR 5119), 34095 Montpellier, France
4Centre d’écologie marine expérimentale MEDIMEER, Université Montpellier 2-CNRS (UMS 3301), 34200 Sète, France
5CONICET, C1033 AAV, Buenos Aires, Argentina
6División de Ficología, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, B1900 FWA, La Plata, Argentina
7Comisión Nacional de Energía Atómica, Dpto. Radiobiología, B1650 KNA, San Martín, Argentina
8MERINOV, Centre d’Innovation de l’Aquaculture et des Pêches du Québec, Centre de la Côte-Nord, Direction de la production de la biomasse, Sept-Îles, Québec G4R 5B7, Canada
9Instituto Antártico Argentino, C1010 AAZ, Buenos Aires, Argentina
10Laboratoire d’Océanologie et de Géosciences UMR 8187, Maison de la Recherche en Environnements Naturels, 62930 Wimereux, France
*Corresponding author:

ABSTRACT: Marine planktonic communities can be affected by increased temperatures associated with global climate change, as well as by increased ultraviolet B radiation (UVBR, 280-320 nm) through stratospheric ozone layer thinning. We studied individual and combined effects of increased temperature and UVBR on the plankton community of the Beagle Channel, southern Patagonia, Argentina. Eight 2 m3 mesocosms were exposed to 4 treatments (with 2 replicates) during 10 d: (1) control (natural temperature and UVBR), (2) increased UVBR (simulating a 60% decrease in stratospheric ozone layer thickness), (3) increased temperature (+ 3°C), and (4) simultaneous increased temperature and UVBR (60% decrease in stratospheric ozone; + 3°C). Two distinct situations were observed with regard to phytoplankton biomass: bloom (Days 1-4) and post-bloom (Days 5-9). Significant decreases in micro-sized diatoms (>20 µm), bacteria, chlorophyll a, and particulate organic carbon concentrations were observed during the post-bloom in the enhanced temperature treatments relative to natural temperature, accompanied by significant increases in nanophytoplankton (10-20 µm, mainly prymnesiophytes). The decrease in micro-sized diatoms in the high temperature treatment may have been caused by a physiological effect of warming, although we do not have activity measurements to support this hypothesis. Prymnesiophytes benefited from micro-sized diatom reduction in their competition for resources. The bacterial decrease under warming may have been due to a change in the dissolved organic matter release caused by the observed change in phytoplankton composition. Overall, the rise in temperature affected the structure and total biomass of the communities, while no major effect of UVBR was observed on the plankton community.

KEY WORDS: Plankton · UVBR · Ozone hole · Increased temperature · Patagonia

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Cite this article as: Moreau S, Mostajir B, Almandoz GO, Demers S and others (2014) Effects of enhanced temperature and ultraviolet B radiation on a natural plankton community of the Beagle Channel (southern Argentina): a mesocosm study. Aquat Microb Ecol 72:155-173.

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