Short-term responses of unicellular planktonic eukaryotes to increases in temperature and UVB radiation
1 INRA, UMR 42 CARRTEL, 75 avenue de Corzent, BP511, Thonon-les-bains, F-74200, France
2 Clermont Université, Université Blaise Pascal, CNRS, UMR 6023, LMGE, BP 10448, Avenue des Landais, Clermont Ferrand, F-63000, France
3 Université Montpellier 2, UMR 5119 ECOSYM, CNRS, IRD, Ifremer, Université Montpellier 1, Place E Bataillon, cc 093, Montpellier cedex 5, 34095, France
4 CNRS, UMR 7621, LOMIC, Observatoire Océanologique, Avenue de Fontaulé, Banyuls/mer, F-66651, France
5 LIttoral ENvironnement et Sociétés (LIENSs) - UMR 6250, Université de La Rochelle, Institut du Littoral et de l’Environnement (ILE), 2 rue Olympe de Gouges, La Rochelle, 17 000, France
BMC Microbiology 2012, 12:202 doi:10.1186/1471-2180-12-202Published: 11 September 2012
Small size eukaryotes play a fundamental role in the functioning of coastal ecosystems, however, the way in which these micro-organisms respond to combined effects of water temperature, UVB radiations (UVBR) and nutrient availability is still poorly investigated.
We coupled molecular tools (18S rRNA gene sequencing and fingerprinting) with microscope-based identification and counting to experimentally investigate the short-term responses of small eukaryotes (<6 μm; from a coastal Mediterranean lagoon) to a warming treatment (+3°C) and UVB radiation increases (+20%) at two different nutrient levels. Interestingly, the increase in temperature resulted in higher pigmented eukaryotes abundances and in community structure changes clearly illustrated by molecular analyses. For most of the phylogenetic groups, some rearrangements occurred at the OTUs level even when their relative proportion (microscope counting) did not change significantly. Temperature explained almost 20% of the total variance of the small eukaryote community structure (while UVB explained only 8.4%). However, complex cumulative effects were detected. Some antagonistic or non additive effects were detected between temperature and nutrients, especially for Dinophyceae and Cryptophyceae.
This multifactorial experiment highlights the potential impacts, over short time scales, of changing environmental factors on the structure of various functional groups like small primary producers, parasites and saprotrophs which, in response, can modify energy flow in the planktonic food webs.