| Ultraviolet radiation (UVR) and temperature effects on bacterioplankton community structure were analyzed after a ten-day microcosm study following spring ice melt-out in Lake Giles, PA. Bacterial community DNA patterns and subsequent phylogenetic assignments were produced using terminal restriction length polymorphisms (T-RFLP) and matched to ribosomal database project (RDP-II) gene sequence entries. The primary environmental stressor shifting community composition was UVR, while warm or cold water incubations, at 5-degree increments, either increased or decreased the shift. All UVR exposed samples had decreased diversity and richness compared to UVR blocked samples. Warm water incubations under UVR stress maintained more diversity than cold-water incubations. Species dominance patterns were altered between phyla and within classes of bacteria in each sample. Specifically, Alphaproteobacteria, a dominant bacterial class with diverse members, had different species composition in UVR exposed and blocked samples. Possible UVR tolerance was assigned to different phyla or classes of bacteria. Alpha- and Betaproteobacteria, Firmicutes and Chlorobi were assigned as UVR resistant. With less certainty Gammaproteobacteria and Cyanobacteria were also assigned UVR resistant. Phylum Tenericutes was assigned as UVR sensitive. The results present a first approximation of UVR resistance and sensitivity to bacterioplankton from Lake Giles using TRFLP and predicted gene sequences. |
