A boat is frozen into the ice covering the western shore of Lake Baikal near Bolshiye Koty, a rural location in Irkutsk Oblast, Russia.
In Burntside Lake, Minnesota, Kirill Shchapov, a doctoral candidate in biology at the University of Minnesota in Duluth, conducts a zooplankton tow, collecting the microscopic creatures by dragging a fine mesh net through the water.
In northern Lake Michigan in January 2013, the Coast Guard icebreaker U.S.C.G.S Mackinaw is "hove-to" — in a stationary position facing the wind — during "ice liberty," a period when the crew is permitted to disembark and climb the ice.
Lake Erie in February 2011.
Ice on Lake Baikal, Russia. The lake's water is so clear that it appears blue when it freezes.
This image of frozen Lake Winnipeg in Manitoba, Canada was taken during a February 2014 snowmobile survey. The ice ridges contain particulate matter, much of which were colonies of diatoms, a type of algae.
Field work on Minnesota's La Salle Lake. At 213 feet (65 meters) in depth it is the second-deepest lake in the state.
In March 2015, researchers gathered samples from Lake Lämmijärv, part of Lake Peipus on the boundary between Estonia and Russia.
Ice melt at Lake Mälaren, Sweden. Mälaren is the third largest lake in Sweden, with a surface area of approximately 440 square miles (1,140 square kilometers).
Tech and samples
At West Long Lake, Nebraska in the Valentine National Wildlife Refuge, in January 2008, a researcher uses an integrated water column sampler to collect samples for processing.