levels often results in polynya blooms. Biological production In general, polynyas tend to be more biologically productive as a result of containing more phytoplankton than the surrounding water. Therefore, due to the role of primary producers as the foundation of the marine food web, polynyas are a critical food source for a variety of organisms such as fish, birds, and marine mammals. Listed below are several examples of the importance of polynyas to polar communities. Increased seal mortality rates were observed during years when the Ross Sea Polynya did not open. In eastern Antarctica, 91% of Adélie penguin colonies are linked to a coastal polynya, where polynya size often correlates to colony size. The presence of polynyas in McMurdo Sound provides an ice-free area where penguins can feed, directly effecting the survival of the Cape Royds penguin colony. The downward transport of carbon (in the form of marine snow) from the surface to the seafloor associated with polynya blooms provides the nutrients necessary to sustain rich benthic communities. Human dependency Polynyas have also supported human populations throughout history. For example, the North Water Polynya, the largest and most biologically productive Arctic polynya, serves as a critical source of food in an otherwise barren region, enabling the existence of high-latitude human communities in the region for thousands of years. It may have served as a stepping stone for the original settlers of Greenland as they traversed through what is now northern Canada 4500 years ago. There are also indications that the North Water Polynya has aided Thule, Inuit, Norse, and western explorers throughout history. Today, the North Water Polynya enables the existence of Greenland's northernmost town, Qaanaaq. Arctic navigation When submarines of the U.S. Navy made expeditions to the North Pole in the 1950s and 1960s, there was significant concern about surfacing through the thick pack ice of the Arctic Ocean. In 1962, both the USS Skate and USS Seadragon surfaced within the same large polynya near the North Pole for the first polar rendezvous of the U.S. Atlantic Fleet and the U.S. Pacific Fleet. See also Lead (sea ice) North Water Polynya Weddell Polynya References External links Polynya north of Alaska at NASA Earth Observatory Bodies of water Glaciology Earth phenomena Arctic Ocean Polar regions of the Earth Geography terminology Geography of the Arctic Sea ice Geography of the Southern Ocean