Lake

The lake biome, known to ecologists as a lentic freshwater system, covers standing bodies of fresh water from small ponds to vast lakes such as the African Great Lakes or Lake Baikal, distinguished from the river biome by its still or very slowly circulating water rather than a continuous downstream current. Larger lakes typically stratify into distinct zones, a sunlit, plant-rich shallow margin near shore, an open-water zone where light still supports plankton, and a deep, dark zone below where light cannot reach, and many temperate lakes also stratify by temperature and mix seasonally as surface water warms and cools with the year. Lakes can persist for a human lifetime or, in the case of the oldest ancient lakes, for millions of years, giving some the time to develop remarkable levels of endemic species found nowhere else.