This static layering, called meromixis, has affected the lake's unique food chain. Annual mixing recycles decayed organic matter from the bottom of the lake to the top. This organic matter, along with sunlight, spurs the growth of algae, upon which brine shrimp and brine flies feed. These shrimp and flies, in turn, become food for breeding and migrating birds. But without annual mixing, fewer nutrients are recycled to the top of the lake and algae growth is depressed, says Robert Jellison, a scientist at the University of California's Sierra Nevada Aquatic Research Laboratory in Mammoth Lakes who specializes in plankton dynamics.
Fewer algae mean fewer shrimp and flies, which means less food for the birds.
Mono Lake's California gulls, the most raucous and perhaps most significant of the basin's birds, have suffered most dramatically. Since 1995, scientists have documented an alarming decline in their breeding. Gulls have annually produced an average of slightly more than one fledgling per nest since 1983, when monitoring began. But in 1998, the average dropped to between 0.1 and 0.46 chicks per nest. Last year it was even worse, says Joseph Jehl, a biologist at the Hubbs Sea World Research Institute of San Diego.