| Summary: | Aquatic Sciences Meeting, Aquatic Sciences: Global And Regional Perspectives - North Meets South, 22-27 February 2015, Granada, Spain Small eukaryotes of pico and nanoplanktonic size (0.2-5 µm, hereafter named picoeukaryotes, Peuk) are responsible for numerous ecosystem functions and processes in most aquatic ecosystems. However, despite their recognized importance, the factors governing their community structure and biogeographical patterns are still poorly understood. We studied the latitudinal variation of Peuk in 40 freshwater bodies from Argentinean Patagonia (45°S) to Maritime Antarctica (63°S), to find out factors that influence Peuk community composition (PeukCC). PeukCC was assessed by a 18S rRNA gene fingerprinting approach (denaturing gradient gel electrophoresis, DGGE). Diversity was also assessed for some of the water bodies with next-generation sequencing (HiSeq Illumina). The abundance of Peuk (both autotrophic and heterotrophic) decreased significantly towards higher latitudes and increased significantly with nutrient content. The number of dominant operational taxonomic units (OTUs) increased significantly with increasing trophic gradient. The regional dominant OTU number decreased faster than the local one toward higher latitudes. The partial canonical ordination analysis showed that not only local environmental factors, but also geographic distance exerted influence on PeukCC. Significant differences were found in PeukCC between Antarctic and Patagonian water bodies Peer Reviewed
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