SALT LAKE CITY — The ecosystem of the Great Salt Lake — from brine shrimp and brine flies to the millions of migratory birds that live along the shore — depends on structures called microbialites. They’re rocks coated with salt-tolerant bacteria that live in shallow water and convert sunlight into food by photosynthesis. But they’re threatened by declining water levels in the lake, which are approaching record lows.

“The brine flies and brine fly larvae crawl on them and eat them, and also brine shrimp will graze on them,” said Professor Bonnie Baxter, head of the Great Salt Lake Institute at Westminster College.

If the the microbialites are exposed, the bacterial mats can die off very quickly. And they don’t come back right away when water levels go up.

“If lake levels come back up and these things are re-submerged, it takes several seasons or several years for the microbes to even think about recolonizing and reforming on these structures,” said Michael Vanden Berg, Energy and Minerals program manager with the Utah Geological Survey.

Vanden Berg said some areas of microbialites have already been exposed as the lake level has dropped. And more could be as before it reaches its seasonal low in October or November.

Baxter said the ecosystem of the lake is just one of the reasons Utahns should be concerned about how the lake level is managed. Blowing dust from areas left dry is another.

“It’s critical for our air quality. It’s critical for our snow. Otherwise dust lands on the snow and melts it more quickly. So it’s critical for our water supply,” she told KSL Newsradio.

Vanden Berg says it’s hard to predict what the ultimate impact of losing more microbialites will be. “We’re basically in new territory,” he said.