Diversity Of Zoosporic True Fungi And Heterotrophic Straminipiles In Las Canas Stream (Buenos Aires, Argentina): Assemblages Colonizing Baits

Zoosporic true fungi and heterotrophic straminipiles are phylogenetically unrelated groups of microorganisms playing similar ecological roles in food webs in fresh water ecosystems. As saprotrophs they are important decomposers of organic matter of animal and vegetal origin. However, there is still little research on most aspects of the ecology of these microorganisms. In this study the species composition of zoosporic true fungi (Blastocladiomycota and Chytridiomycota) and heterotrophic straminipiles ( Hyphochytriomycota and Peronosporomycota), and their frequency, abundance and diversity on different types of baits were analyzed. Samples for characterizing the species composition were collected over a four-year period and for characterizing the structure of the assemblages at four dates during a one-year period. The relationship between some biological and environmental parameters were analysed. We expected that fluctuations in environmental factors during the year might lead to changes in the species composition and structure of the assemblages. Sixty-eight taxa were recovered with the baiting technique during the four-year period. The species composition was dependent primarily on the type of bait used. The structure of the assemblages also appeared to be more influenced by the type of baits available for colonization than by other environmental parameters. Even though the abundance of the taxa was associated with pH, nitrite, sulfate, soluble reactive phosphorous and dissolved oxygen concentrations. We did not find any differences in their richness, frequency, abundance and diversity during the year as expected.