N-217. Photosynthetic Mats and Surface Sediments in Lake Huron Sinkholes Contain Cyanobacteria Related to Antarctic Clones and Sulfate Reducing Proteobacteria
Lake Huron sinkholes discharge anoxic groundwater with high sulfate concentration and high conductivity into the normally oxygen-rich lake ecosystem. To describe the composition of the microbial communities inhabiting a variety of sinkhole habitats, we obtained Automated Ribosomal Intergenic Spacer Analysis (ARISA) community profiles from samples collected at El Cajon (<1 m depth), Middle Island (22 m), and Isolated (92 m) sinkholes near Alpena, MI. We also obtained 16S rDNA+intergenic transcribed spacer (ITS) sequence data from the organic-rich sediment and overlying cyanobacterial mats surrounding the El Cajon and Middle Island Sinkholes. Multidimensional scaling analysis of ARISA profiles revealed differences between sampling sites and within sites since the overlying mat communities differed from underlying sediments. 16S rDNA+ITS clone libraries created from the overlying cyanobacterial mat (0-0.1cm) at Middle Island sinkhole and El Cajon sinkholes were dominated by sequences closely related to Microcoleus and Oscillitoria, but also contained proteobacterial sequences (β, γ, δ, ε subdivisions). I nterestingly, GenBank BLAST searches resulted in high similarities between our Oscillitoria sequences and sequences detected in a permanently ice-covered lake in Antarctica (Lake Fryxell). In addition to cyanobacterial sequences, Middle Island sediments (0-2 cm depth) included representatives of the Verrucomicrobiales, Flavobacterium, δ-Proteobacteria, and Actinobacteria lineages. Some of the δ-proteobacterial sequences were similar to known sulfate-reducing bacteria. These data support findings from lipid profiling studies in these habitats. We are currently linking the 16S rDNA+ITS sequence data to ARISA profiles from the habitat to more fully understand microbial community dynamics in Lake Huron sinkholes.