The bottom layer of the lake, the monimolimnion, is poor in oxygen and therefore lacks life, the central layer, or chemocline, has some occasional visitors, such as bacteria and small water insects, but is not very lively as well. Only the top layer, or mixolimnion, is rich in life, though bigger life forms permanently living in the lake, such as fish, are rare. The only vertebrates that are common in the lake are small reptiles and amphibians, as well as occasionally visiting birds and mammals.