Microorganisms play vital roles in the ecosystem processes that determine our quality of life. Despite their importance to human health and welfare, the microbial species and their activities in subsurface environments are largely unknown. This 2-year project will describe the microbial communities inhabiting newly discovered groundwater-supplied lake floor ecosystems (submerged sinkholes) in the Thunder Bay National Marine Sanctuary (NMS), Lake Huron. Due to the steep environmental gradients created by differences in water chemistry, sinkhole habitats are characterized by high microbial biomass and intense biological activity. These submerged sinkholes appear to be biogeochemical "hot spots" freshwater analogs to marine vent ecosystems that offer opportunities for discovering novel microorganisms and community processes. To better understand community function, the physical and chemical environments created by groundwater discharge into the lake floor will be characterized for three sinkhole communities located along a depth gradient; shallow (Misery Bay Sinkholes at <5 m), intermediate (Middle Island Sinkhole at 18 m) and deep (Isolated Sinkhole at 93 m). Microbial communities will be characterized using molecular techniques that target different markers. First, membrane lipid profiling will be combined with measurements of stable carbon isotope incorporation into individual fatty acids to provide an integrated view of community composition and activity. Second, genetic diversity profiles and DNA sequence data will provide a high-resolution view of community composition. Third, fluorescence microscopy and radioisotopic tracers will be used to directly assess microbial abundance and growth rates. Combined, these analyses will provide the first detailed picture of microbial life and processes in the submerged sinkhole ecosystems of the Laurentian Great Lakes.
This study initiates a new line of research linking land and water resources in the Great Lakes. It also describes novel organisms and unique habitats, recruits and trains underrepresented students, forges a strong collaboration between university researchers at two predominantly undergraduate institutions (Grand Valley StateUniversity and University of Wisconsin-Stout), integrates research and education into the curriculum at both institutions, trains K-12 educators in partnership with existing outreach programs, and builds data sharing infrastructure by linking a newly created Lake Huron sinkholes website to existing data networks at NOAA's Great Lakes Environmental Research Laboratory and NSF's North Temperate Lakes Microbial Observatory. Our findings will provide additional rationale for the continued protection of Thunder Bay National Marine Sanctuary, the only NMS located in a freshwater ecosystem. Ultimately, these studies will provide a better understanding of microbial life in the biosphere, a critical step in ensuring an economically and environmentally sustainable future.
