Life in a Freshwater Sinkhole

A few miles from the Lake Huron shoreline is Middle Island, a small isle formerly used to house a U.S. Coast Guard station and lighthouse. A few yards from its northern beach is a sinkhole, a unique submerged geological formation where sulfur-rich groundwater pours steadily from a base of collapsed limestone. This ground water "fertilizes" resident freshwater bacterial communities that are so unique that scientists have been studying them continually for over 15 years. Seen here are two sampling instruments situated atop large purple bacterial mats.