Effects of solar ultraviolet radiation (UVR) on molecular diversity of plankton from the Chubut River estuary.

MANRIQUE, J.M.; HALAC, S.R.; CALVO,A. Y.; VILLAFAÑE, V. E.; JONES, L. R.; HELBLING, E. W.

Puerto Madryn

Congreso; XLVI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2010

Within the framework of a project designed to evaluate the impact of UVR upon estuarine plankton, we present here a molecular analysis of plankton diversity. Water samples were exposed to three radiation treatments (PAR, PAR + UV‐A and PAR + UV‐A + UV‐B) in microcosms for ca 10 days during the Austral summer. At the beginning (t0) and at the end of the experiment samples were filtered through 20, 10, 5 and 0.22 μm pore sizes. The DNA amount retained in each filter indicated that most of the plankton biomass was in the 0.22‐5 μm fraction at t0. In contrast, at the end of the experiment this proportion changed according to the radiation treatment and big cells (> 20 μm) dominated. An rDNA library was obtained from the DNA corresponding to the 0.22‐5 μm fraction. There was no relationship between treatments and the number and frequency of restriction genotypes. Analyses of 27 clones fraction from t0 indicated the presence of 3 genera of Rhodobacteraceae, one genus of Rhodospirillaceae, one SAR11 genus, one genus of Bacillaceae, an unclassified sequences of Alphaproteobacteria, Actinobacteria and Rhodospirillaceae. Also, there were 6 sequences similar to Ostreococcus tauri (Mamiellales). Even though the sequence analyses are still ongoing, our initial data suggest a big impact of UV‐B radiation in the amount and composition of the plankton community towards big cells.