Exploration of Submerged Sinkholes in Thunder Bay National Marine Sanctuary, Lake Huron

Bopi Biddanda, Ph. D.
Research Scientist, Annis Water Resources Institute, Grand Valley State University

Karst sinkholes discharging groundwater onto the Lake Huron floor through Paleozoic bedrock have created unique habitats characterized by steep environmental gradients and conspicuous benthic mats. We have recently identified three sinkhole communities along a depth gradient in Thunder Bay National Marine Sanctuary. Due to prevailing low dissolved oxygen and high dissolved sulfate conditions in the ground water emerging at these sites, the sinkhole ecosystems are microorganism-dominated and feature high microbial biomass and activity - biogeochemical "Hot Spots" where nutrients recycle rapidly. We view these submerged sinkholes as freshwater analogs to marine vent ecosystems, and think they offer similar opportunities for discovering novel organisms and community processes. However, little is known regarding the inhabitants and their activities in freshwater sinkhole ecosystems. Our work seeks to provide the first glimpse into the varied and prolific life inside Lake Huron?Äôs submerged sinkholes.

This 2-year collaborative project is a Grand Valley State University (GVSU; Bopi Biddanda) and University of Wisconsin-Stout (UWS; Stephen Nold)-led, National Science Foundation (NSF)-funded, National Oceanic and Atmospheric Administration (NOAA's Great Lakes Environmental Research Laboratory-GLERL and Thunder Bay National Marine Sanctuary-TBNMS; Steve Ruberg, Russ Green, Wayne Lusardi, Jeff Gray, Tane Casserley, Joe Hoyt) and Noble Odyssey Foundation (NOF; Luke Clyburn, Elliott Smith)-supported study (2006-2008). The project goals are to (1) Describe the abundance, diversity and activities of the microbial community in the submerged sinkhole ecosystems located along the depth gradient, (2) Determine how the changing environmental gradients in submerged sinkhole ecosystems impact microbial composition and processes, and (3) Share the resulting knowledge with students, teachers, scientists and the public.

NOAA's TBNMS is providing the project with dive, ROV (remotely operated vehicle) and ship support, NOAA's GLERL scientists are helping with mapping the hydrography and NOF staff are assisting with develping bathymetric maps of the sinkhole sites. Microbial communities are currently being characterized by UWS scientists using molecular techniques that target different molecules specific to their ecological function and taxonomic classification. Additionally, microscopy and isotopic tracers are being used by GVSU scientists directly assess microbial abundance and growth rates. Additionally, student-led projects are examining the link between microbial production at sinkholes and the food web of surrounding Lake Huron. We are using these tools and approaches to test the hypothesis that photosynthesis-dominated communities in shallow sunlit sinkholes give way to chemosynthesis-dominated sinkhole communities in deep aphotic water. These analyses will provide a working picture of microbial life in sinkhole ecosystems of the Laurentian Great Lakes. A better appreciation of the diversity of life and life processes prevailing at the sinkholes should help us preserve and protect these unique ecosystems.


 

¬Ý¬Ý¬Ý¬Ý¬Ý¬Ý¬Ý¬Ý¬Ý¬Ý¬ÝAerial View of Coastal Sinkhole
Submerged Sinkholes:¬Ý What?Äôs Inside?

Dr. Bopaiah A. Biddanda, Grand Valley State University, 740 West Shoreline Dr., Muskegon, MI 49441; Tel: 616 331 3978 (Office) Email: biddandb@gvsu.edu
Website: http://www.gvsu.edu/wri