Exploration of a Submerged Sinkhole Ecosystem in Lake Huron |
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Authors: | Bopaiah A Biddanda Dwight F Coleman Thomas H Johengen Steven A Ruberg Guy A Meadows Hans W Van Sumeren Richard R Rediske Scott T Kendall |
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Institution: | (1) Annis Water Resources Institute and Lake Michigan Center, Grand Valley State University, 740 W Shoreline Drive, Muskegon, Michigan 49441, USA;(2) Institute for Exploration, 55 Coogan Blvd., Mystic, Connecticut 06355, USA;(3) Cooperative Institute for Limnology and Ecosystems Research, University of Michigan, 2205 Commonwealth Blvd., Ann Arbor, Michigan 48105, USA;(4) National Oceanic and Atmospheric Administration, Great Lakes Environmental Research Laboratory, 2205 Commonwealth Blvd., Ann Arbor, Michigan 48105, USA;(5) Department of Naval Architecture & Marine Engineering, University of Michigan, 1085 South University Ave, Ann Arbor, Michigan 48109, USA;(6) Graduate School of Oceanography, University of Rhode Island, South Ferry Road, Narragansett, Rhode Island 02882, USA |
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Abstract: | Dissolution of the Silurian-Devonian aquifer in the Lake Huron Basin has produced several karst formations in the bedrock
(sinkholes), through which groundwater emerges onto the lake floor. During September 2003, we explored a recently discovered
submerged sinkhole ecosystem (55 m × 40 m × ∼1 m) located at a depth of 93 m with a remotely operated vehicle (ROV) equipped
with a conductivity-temperature-depth (CTD) system, an acoustic navigational system, a video camera, and a water sampling
system. In addition to two morphotypes of benthic mats, a 1–2 m thick visibly cloudy near-bottom nepheloid-like layer (sinkhole
plume) with a strong hydrogen sulfide odor prevailed just above the seepage area of clear water. Relative to lake water, water
samples collected within the sinkhole plume were characterized by slightly higher (by 4°C) temperatures, very high levels
of chloride (up to 175 mg l−1) and conductivity (1,700 μS cm−1), as well as extremely high concentrations of sulfate (1,400 mg l−1), phosphorus (3 mg l−1) and particulate organic matter (400 mg C l−1). Compared to background lake water, sinkhole plume water was characterized by approximately twofold lower C:N ratios and
tenfold higher levels of dissolved organic carbon, bacterial biomass as well as heterotrophic bacterial production. Significant
uptake of 14C-bicarbonate in dark incubations provided preliminary evidence for occurrence of chemosynthesis, possibly mediated by specialized
Bacteria and Archea present in this submerged sinkhole ecosystem in the Laurentian Great Lakes. |
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Keywords: | Laurentian Great Lakes Basin submerged sinkholes remotely operated vehicle groundwater seep nutrients heterotrophic microbes chemosynthesis Lake Huron |
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