FWF project P 14238 - Summary for public relations work
This project studied the Distribution, diversity, and population dynamics of
autotrophic picoplankton in the lakes of the ‘Salzkammergut’ area (Austria). The
autotrophic picoplankton (APP) in freshwater lakes is primarily composed of minute
(<0.002 mm), freely floating single celled cyanobacteria. These cells reach numbers
up to one billion per litre, are, like plants, photosynthetically active and thus
contribute substantially to the primary production of algae in pristine and moderately
polluted lakes. It is impossible to identify species and strains of the picocyanobacteria
with conventional microscopic techniques, and the biological diversity of the APP is
therefore largely unknown. We used novel, advanced optical and molecular
techniques to characterize the genetic and ecological diversity of picocyanobacteria in
deep, subalpine lakes. We isolated, cultured and sequenced parts of the genome of
more than 20 picocyanobacterial strains from Mondsee and other Salzkammergut
lakes. Our analyses revealed that picocyanobacteria are a highly diverse and dynamic
assemblage. The isolates were grouped into six to seven clusters, depending on their
genetic affinity. Some of the new strains and clusters were found in the
Salzkammergut lakes only, others were hitherto known from very different
environments such as shallow Japanese lakes. More research is needed to answer the
question if all picocyanobacteria are globally distributed or if some strains have
restricted biogeographies. We found obvious differences in growth and grazing rates
among genetically closely related strains of our new isolates, i.e. there was no close
match between the genetic identity and ecophysiological performance of the isolates.
Overall, the results of this study demonstrate that the biodiversity of aquatic
microorganisms is considerably higher than previously recognized. This finding
should be considered in an improved future monitoring of freshwater quality.
Original publications directly orginating from the project:
Crosbie, N.D., Teubner, K. & Weisse, T. (2003). Flow-cytometric mapping provides
novel insights into the seasonal and vertical distribution of freshwater
autotrophic picoplankton. Aquat. Microb. Ecol 33.: 53-66.
Crosbie, N.D., Pöckl, M. & Weisse, T. (2003). Dispersal and phylogenetic diversity
of non-marine picocyanobacteria, inferred from 16S rRNA gene and cpcBAintergenic spacer sequence analyses. Appl. Environ. Microbiol. 69: 5716-5721.
Crosbie, N.D., Pöckl, M. & Weisse, T. (2003). Rapid establishment of clonal isolates
of freshwater autotrophic picoplankton by single-cell and single-colony sorting.
J. Microbiol. Meth. 55: 361-370.