Tiina Törmänen's Image

Tiina Törmänen (Finland) floats through sheets of cloud-like algae in search of fish.

Tiina was thrilled to meet a school of inquisitive European perch on her annual lake snorkel. During the previous three years she had only ever found dead fish. Submerged in the surreal scene, she framed the orange-finned fish flying through clouds of pink-tinged algae.

Although it created a beautiful scene, algal blooms like the one captured here can cause problems for underwater life. A common cause of algal blooms is pollution, most often from fertilisers present in agricultural run-off or sewage. This enriches the water with nutrients, causing the algae to flourish, use up the oxygen in the water, block out sunlight and sometimes produce harmful toxins.

Yet this lake is in the middle of the wilderness, with no conceivable source of pollution. Recently, the summers in Lappland have been unseasonably warm and the lake water has been unusually tepid, which suggests that global warming rather than pollution was behind this algal bloom.