Published on: 21.6.2021

Changing climate shapes aquatic life

As the climate warms up, so do lakes, rivers and the sea. The summer season is becoming longer, while the period of ice cover grows shorter. How is this change affecting aquatic species and the entire ecosystem?

Aquatic flora and fauna have adjusted to our current climate, in which ice cover is part of the yearly cycle, both in lakes and along the coast. Even offshore areas in the Gulf of Bothnia and Gulf of Finland used to freeze over, at least for part of the winter.

Climate change has already shortened the period of ice cover, which may mean a huge change for some species. It has negative effects on the breeding of the ringed seal both in Lake Saimaa and the Baltic Sea, and the reproduction of whitefish may also be hampered as the ice no longer protects hatchlings from the waves.

The warming of the waters also disrupts natural cycles in other ways. The warmth may trigger reproduction, causing a new generation to be born before enough food is available. Some species benefit from the warming, while those that thrive in cold waters decline or may even be lost.

A sufficient amount of oxygen is even more important for aquatic organisms than the right temperature. These two issues go hand in hand, however, as oxygen is depleted more quickly in warm water.

Eutrophication in waters is speeded up by warmth and exacerbated by increasing nutrient pollution caused by winter rains, as more nutrients are leached into waters when the rain falls on bare ground.

Image: © Harri Sandborg, Vastavalo