Bacterial community structure in a latitudinal gradient of lakes: the roles of spatial versus environmental factors

SCHIAFFINO, M. R.; UNREIN, F.; GASOL, J. M.; MASSANA, R.; BALAGUÉ, V.; IZAGUIRRE, I.

FRESHWATER BIOLOGY (PRINT)

WILEY-BLACKWELL PUBLISHING, INC

Año: 2011 vol. 56 p. 1973 - 1991

0046-5070

To discriminate which are the factors that mainly determine bacterioplankton community structure, we analyzed the latitudinal variation of bacterioplankton in 45 freshwater environments (lakes, shallow lakes and ponds) across a >2,100 km transect, from Argentinean Patagonia (45º S) to Maritime Antarctica (63º S) in a gradient of increased climate severity. Bacterioplankton community composition was assessed by a fingerprinting method (denaturing gradient gel electrophoresis, DGGE) followed by band sequencing, whereas the abundance of total bacteria and picocyanobacteria was estimated by epifluorescence microscopy. Operational taxonomic units (OTUs) richness (number of DGGE bands) and total bacterioplankton abundance were observed to decline with increased latitude. On the other hand, we found a positive relationship between OTU richness and lake area. In a multiple regression analysis of OTU richness only latitude and lake area had a significant effect on the dependent variable and were selected by the model, while the same statistical analysis for total bacterioplankton abundances showed that phosphate, light diffuse attenuation coefficient (Kd) and latitude were significant and selected for the model. Of 76 different OTUs identified in the studied lakes, 45 were shared between Patagonian and Antarctic water bodies, 28 were present only in Patagonian lakes and 3 were exclusive of the Antarctic lakes. Among the sequences, 54% were similar to others reported from similar cold habitats elsewhere on the planet (glaciers, high mountain lakes, Arctic snow and water). Our results provide new evidences and support the hypotheses of biogeographic patterns of bacterial assemblages and that there are both spatial and environmental factors controlling bacterioplankton community structure.