Microbial colonies: hairy growths (top), purple mats, and fiber networks around a discharge hole (S. Nelson).
On this occasion much organic debris from the colonies was suspended in the strong current. The divers noticed many small fish apparently feeding on this material. Occasional dead fish seen on the bottom within the discharge layer suggests that they had accidentally suffocated in the oxygen-poor water. If such underwater springs are common, they may represent an important local source of productivity in the lake ecosystem.
Microbial Communities
Our partners in the Middle Island study are scientists at the Annis Water Resources Institute at Grand Valley State University. They had earlier investigated a deeper sinkhole in the same area, finding similar looking colonies of
AWRI scientist, Scott Kendall, demonstrates a water quality probe to Sea Cadets on board the Pride of Michigan.
microbes around an underwater spring there. Currently AWRI staff are investigating the identity of the organisms we collected at the Middle Island sinkhole. They suspect that these microbes include photosynthetic, chemosynthetic and heterotrophic bacteria similar to those found in some caves and around hydrothermal (hot water) vents in the deep sea.. One common feature of these microbial environments is the mineral-rich and poorly-oxygenated water. Scientists agree that such microbes are among the most primitive and adaptable organisms on earth. Further investigations of the Middle Island springs and their fascinating life forms are planned for 2006.
