Crystals to ice
Scientists have discovered that frozen, wintry lakes can fuel the growth of certain types of algae and zooplankton that thrive during the cold season, blooming under the lake's icy cover.
Here, ice forms on the surface of Lake Pääjärvi, a lake in southern Finland.
Read the full story about how researchers are investigating life under the ice in frozen lakes.
Hidden life
Lake Erie, the fourth largest of North America's five Great Lakes, hides concentrated communities of algae under a layer of lake ice, mostly the filamentous diatom Aulacoseira islandica.
Frozen falls
Frozen waterfall on the River Jägala in Estonia, in March 2011.
More frozen falls
Another view of the frozen waterfall on the River Jägala in Estonia, in March 2011.
Shoreline ice
Breaking ice on Estonia's Lake Võrtsjärv, a shallow lake in southern Estonia, in April 2011.
Piles and piles
Along the shore of Estonia's shallow Lake Võrtsjärv in southern Estonia, ice breaks in April 2011.
Cracks and fractures
Another pile of breaking ice on the shores of Estonia's Lake Võrtsjärv, a shallow lake in southern Estonia, in April 2011.
A lake?
Frozen Lake Võrtsjärv in Estonia, in January 2014.
Frozen beauty
Võrtsjärv is large but shallow — though it measures 104 square miles (270 square kilometers) the lake is only 20 feet (6 meters) deep.
Icy tundra
In January 2014, the large but shallow Lake Võrtsjärv in Estonia is frozen.
Glowing ice
Ice on Russia's Lake Baikal, an ancient and enormous lake in Siberia. It measures approximately 400 miles (644 kilometers) in length and over 5,000 feet (1,637 meters) in depth, and is the oldest and deepest lake on Earth.
