PROJECT SUMMARY

Intellectual Merit. We recently discovered karst sinkholes on the floor of Lake Huron. Aquifers are discharging groundwater onto the lake floor through these submerged sinkholes, creating highly unique habitats characterized by steep environmental gradients. Preliminary studies suggest that submerged sinkholes are sites of high microbial biomass and intense activity (Biddanda et al. In press, Ecosystems) - biogeochemical Hot Spots where nutrient cycling is rapid compared to the surrounding landscape. We view these submerged sinkholes as freshwater analogs to marine vent ecosystems, and think they offer similar opportunities for discovering novel microorganisms and community processes. However, little is known regarding the microbial inhabitants and their activities in freshwater sinkhole ecosystems.

We seek to better understand the microbes living in these habitats. We want to explain the patterns of microbial diversity, abundance, and activity by understanding the physical and chemical environments created by groundwater discharge onto the lake floor. We have identified three sinkhole communities 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), each possessing distinct life inventories including benthic microbial mats. We have developed a discreet set of hypotheses concerning how physico-chemical changes impact the microorganisms along this gradient. The principle goals of this 2-year (5/06-4/08) study are to: (1) Describe the abundance, diversity and activities of the microbial community in the submerged sinkhole ecosystems located along the depth gradient, and (2) Determine how the changing environmental gradients in submerged sinkhole ecosystems impact microbial composition and processes.

Working in concert with another project that focuses on hydrologic monitoring (pending NOAA funding will provide ship time and logistical support), we will describe the microbial biomass, diversity, and activities in submerged sinkholes in the Thunder Bay National Marine Sanctuary, Lake Huron. We will use a combination of limnological, microbiological, and molecular biological techniques to achieve our goals. This project will provide the first detailed picture of microbial life and processes in sinkhole ecosystems in the Laurentian Great Lakes.

The interdisciplinary team brings together researchers from two predominately undergraduate institutions GVSU and UW-Stout. Biddanda is an aquatic ecologist with expertise in microbial process measurements and physico-chemical characterizations. Nold is a molecular microbial ecologist with expertise in community diversity measurements using techniques that relate microbial diversity to activity in nature. Both are dedicated to providing outstanding research and educational opportunities for their students.

Broader Impacts. This proposed study initiates a new line of research linking atmospheric, land, and water resources, describes novel organisms and unique habitats, recruits and trains underrepresented graduate and undergraduate students, forges a strong collaboration between two university researchers with complimentary interests, integrates research and educational efforts in the curriculum at both institutions, trains K-12 educators in a partnership with existing outreach programs at GVSU, and builds data sharing infrastructure by linking a newly created Sinkholes MIP website (housed at UW-Stout) to existing dissemination networks at NOAA and the North Temperate Lakes LTER Microbial Observatory. Our findings will provide additional rationale for the continued protection and conservation of the Thunder Bay National Marine Sanctuary and Underwater Preserve, the only NMS located in a freshwater body. Opportunities offered by this study will also improve research and educational infrastructure at the participating institutions.