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 lS cm

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A numerical circulation and transport model is used to simulate currents and trajectories in Lake St. Clair. Results from the model are compared to three different types of measurements, namely, (1) mean currents from an array of fixed current meters, (2) currents measured from a ship during seven synoptic surveys of the lake, and (3) trajectories of satellite‐tracked drifting buoys during four different experiments. The model is then used to predict the effects of storms on the residence time of water entering the lake from eight tributaries and the probable horizontal distribution in the lake of water from a particular tributary. Results show that although the average residence time of the lake is about 9 days, actual residence times range from less than 2 days to over 30 days depending on wind conditions. The calculated distribution patterns of water from various tributaries coincide closely with observed distributions of some water quality parameters and biota.