Diversity and distribution of Archaea and bacteria in marine lakes, Palau

Archaea and bacteria affect the chemistry, biology, and ecology of ecosystems around the world. With anthropogenic activities altering terrestrial and aquatic systems (e.g. fertilizer runoff changing the chemistry of coastal marine waters), knowledge about the tolerances of microbes to changing environmental conditions is critical. While having been extensively studied in saline and marine systems (e.g. oxygen minimum zones, the Black Sea, and Mono Lake), microbes are not well understood in marine lakes, especially those located in Palau. The marine lakes of Palau are ideal for microbial ecology because these unique habitats act like oceanic mesocosms – making studies of microbes found in other saline systems (e.g. the ocean) much more feasible. Using Automated Ribosomal Intergenic Spacer Analysis (ARISA) and a next generation sequencing technique, 454 pyrosequencing, the richness, diversity, and composition of microbial communities in the marine lakes was analyzed. Lake bacterial groups showed a strongly supported dissimilarity (100% for ~11% similarity) between those from all but one low oxygen (<5 μM) depth and those from all but two higher oxygen (>10 μM) depths, and bacterial community similarities decreased with increasing depth (decreasing oxygen) in the meromictic lakes. While some bacterial groups were ubiquitous among the lakes, ones that participate in biogeochemical cycling of carbon, nitrogen, and sulfur were found in the low oxygen (<5 μM) waters of the meromictic lakes. This research helps show the significance of marine lakes to microbial ecology as well as to understanding other saline systems