Lake Mogilnoe

In the waters of the Barents Sea, near the Kola Peninsula, is the rocky Kildin Island. The main feature of the island is the extremely interesting and unique Lake Mogilnoe with an area of more than 9 hectares. Its depth is 17 m, its length is about 400 m, and its greatest width is 250 m.

The main feature of the island is the extremely interesting and unique lake Mogilnoe with an area of more than 9 hectares

Lake Mogilnoe is interesting because the water in it consists of five layers - "floors", on each of which live its inherent fish, animals and plants.

The waters of the lower "floor" of lake Mogilnoye are saturated with hydrogen sulphide. Here live only bacteria that can exist without oxygen. On the second "floor", water has red color, because of the large number of red bacteria. These bacteria are a living "checkpoint" that absorbs hydrogen sulphide rising from the bottom. Thanks to bacteria, the upper layers of the lake become livable. The third "floor" is filled with clear salt water. The animal and plant world here is typically marine: cod, sea bass, and so on. From relatives who live in the Barents Sea, they are much smaller in size. Scientists call these sea fish "captives" of lake Mogilnogo. The fourth "floor" contains a layer of less salty water. Here, along with freshwater fish, live some marine organisms (jellyfish, crayfish). The upper "floor" of Mogilnoye consists of a six-meter layer of fresh water - the realm of freshwater fish and organisms.

It is established that the lake Mogilnoye is part of the sea that once covered the whole island with its waters. When the sea receded, in this place first formed a small sea bay. Over time, the bay turned into lake Mogilnoye, separated from the sea by a pebble of pebbles and sand.

How did the sea and freshwater fish appear in the lake? During tide sea water seeps through the isthmus to the lake Mogilnoye exactly in the place where there is a layer of salt water, and at low tide, when the level becomes higher than sea level, the salt water returns to the sea. This is why the water on the third floor is continuously updated. This makes it possible for marine organisms to exist here. For a long time, marine fish and other organisms that have remained since the time when lake Mogilnoe was a bay have adapted to the environment and decreased in size.

But why is the water in the lake placed in layers and does not mix? All because salt water is heavier than fresh water. In addition, the first enters the lake Mogilnoye from below, and the second one, with rain and thawed snow, flows into the lake from above.

In North America, there are lakes like Mogilnoy. For example, at Cape Barrow, in Alaska, there is an unusual lake Nuwuk. But unlike Mogilnoye, it is smaller and has only two "floors": the upper one - freshwater and the lower one - salty. Just like Lake Mogilnoe, each "floor" of this lake has its plant and animal kingdom. Scientists believe that Lake Nuvuk, like Mogilnoye, was formed from a bay cut off from the sea.

The largest of the known "multi-storey" lakes is in Canada. Lake Powell Lake has a length of 50 km and at a depth of 300 m the upper layer of fresh water reaches a depth of 100 m.