Bacterioplankton biodiversity: Regional distribution pattern in shallow lakes from the Pampa plain (Argentina) characterized by contrasting alternative steady states

LLAMES, M.E.; DEL GIORGIO, P.; IZAGUIRRE, I.; FERRARO, M.; ZAGARESE, H.E.

Rostock

Simposio; 12th Symposium on Aquatic Microbial Ecology; 2011

Universität Rostock & IOW

The main objectives of the present work were to evaluate the influence of spatial and environmental factors in shaping bacterial community structure in a set of shallow lakes characterized by contrasting alternative states (sensu Scheffer et al.1993) and to assess the impact of different taxonomic resolution on the biogeographical pattern observed. Six temperate shallow lakes from the Pampa Plain (Argentina) were sampled every two months during a whole year. Within the framework of the Metacommunity concept we compared two molecular analyses with different genetic resolution: a 16S rDNA analysis (lower genetic resolution) was performed by means of DGGE profiles and an ITS analysis (higher genetic resolution) was conducted by means of ARISA profiles. The results revealed marked differences in the community structure among clear-vegetated, inorganic-turbid and phytoplankton-turbid shallow lakes. Moreover, the alternative equilibrium state that characterized the different shallow lakes played a major role in structuring the community while seasonality resulted of a lesser importance. Interestingly, the higher the genetic resolution of the analysis, the tighter the relationship found between community composition and alternative steady state. On the other hand, the spatial effects evidenced by means of DGGE reflected the non-random distribution of the systems and were lost when the analysis was performed at a higher genetic resolution level. Altogether, these results indicated that the Species Sorting perspective best explained the regional pattern observed.