Figure 2: (Top image) From inside the Alcove, the nearly pure groundwater that fuels purple cyanobacterial mats spills over the wall into the Arena (photo by Russ Green, Thunder Bay National Marine Sanctuary). (Bottom) With a 9-meter (25.5 foot) long Boston Whaler for scale, the Middle Island Sinkhole is open to Lake Huron, creating a gradient of biological activity (aerial photo by Scott Kendall and Bopi Biddanda, Grand Valley State University).
Related Links
Thunder Bay Sinkholes 2008: Mission Plan
