Picoplankton from shallow lakes with contrasting light penetration and development of submerged

LUZ ALLENDE; JULIETA SILVOSO; GONZALO PÉREZ; ANA TORREMORELL; IRINA IZAGUIRRE

Montreal, Quebec, Canadá

Congreso; 30th Congress of the International Association of Theoretical and Applied Limnology; 2007

Six shallow lakes from Salado River Basin (Buenos Aires) characterized by their different alternative steady state following the model proposed by Scheffer et al. (1998) (clear water and turbid water phases), were studied with a seasonal periodicity. In each of them, an analysis of the light quality was held and the picoplankton (picophytoplankton and heterotrophic bacteria) was studied. Picocyanobacteria were dominant over picoeukaryotic algae in all water bodies, and their densities ranged from 6.5 x 103 to 8.8 x 106 cells ml-1. Picoeukaryotic algae also strongly differed among lakes (0 to 9.8 x 104 cells ml-1). Turbid water bodies presented higher bacterioplankton densities (2.5 x 106 cells ml-1). The analyses of the proportion picophytoplankton/bacterioplankton revealed a clear dominance of picoplanktonic algae in clear water bodies but no clear trend was identified for turbid lakes. This is the first study of the picoplankton community of these shallow lakes, and gives a descriptive base for future analyses of structure and dynamics of the picoplancton and its relation with the alternative steady state. It is hypothesized that the state of the shallow lakes would affect picoplankton by means of differences in availability of nutrients, light conditions, and their interactions with phyto and zooplankton.