BASTIDAS NAVARRO marcela Alejandra
Precipitation patterns, dissolved organic matter and changes in the plankton assemblage in Lake Escondido (Patagonia, Argentina)
BASTIDAS NAVARRO, M.; MODENUTTI, B.
Año: 2012 vol. 691 p. 189 - 202
Global warming affects the hydrological cycle by increasing the frequency and intensity of extreme rainfall events and dry spells. These events affect the dissolved organic matter (DOM) input into lakes. In the current study, we investigated if changes in precipitation over a three-year period correspond to changes in DOM that in turn affect light attenuation and plankton community composition. We carried out field studies in a shallow, oligotrophic Andean lake, analyzing coloured DOM and plankton community composition. During the study period, we observed that variations in the precipitation regime correlated with DOM parameters (water colour and molecular weight), and this, in turn, affected the plankton composition. We observed differences in the Bacteria:Archaea ratio suggesting that Archaea were favoured under high DOM molecular weight, water colour, and TDP. Chlorophyll a concentrations of both phytoplanktonic fractions (< and > 2 µm) were also related to water colour and TDP. We observed in the small fraction (< 2 µm) an increase in phycocyanin-rich cells during periods of low transparency. Larger phytoplanktonic cells (> 2 µm) presented two biomass peaks corresponding to increases of the cyanophyte Chroococcus planctonicus and of the haptophyte Chrysochromulina parva. As precipitation decreased, the lake became more transparent, favouring C. planctonicum and mixotrophic oligotrich ciliates with endosymbiotic Chlorella. In the context of global climate change, our results highlight the impact of changes in precipitation patterns and, consequently, in DOM quality on the plankton community of shallow oligotrophic lakes.