Polar marine species are experiencing, or are anticipated to experience, a large number of negative effects as the result of climate change. Habitats and forage bases are disappearing, risk of disease is increasing, human traffic related impacts are on the rise as sea ways open up, and in the Arctic species are facing increased pollution and greater competition as temperate species expand their ranges northward (2).  Organisms from algae and krill to sea birds to polar bears are already feeling pressure from climate induced changes, and projected impacts are expected to be more severe.

Algae and krill, at the base of the food chain, are already experiencing drastic reduction in population. Marine algae, which lives under the Arctic sea ice, is losing permanent habitat at an alarming rate. In the Beaufort Sea, most of the larger marine algae that has traditionally been present died out between the 1970s and 1990s and has been replaced by a less productive species more commonly found in freshwater. This replacement was made possible by the melting of sea ice, which has resulted in a 30 m thick layer of relatively fresh water forming at the surface of the sea (2). In the Antarctic, the reduction in the extent of pack ice has created problems for the krill population. Without the ice, the winter development of juvenile krill is no longer ensured, and successful breeding years have decreased in number recently because of this. Krill are part of the diet of a large number of Antarctic predators, so the far reaching implications of such a drop in population are rather significant (10).

Migratory birds and penguins are also struggling with the changing climate.  Sea birds in the North Sea, such as guillemots, puffins, razorbills and fulmars are facing significant population declines. In 2004, a study of six seabird species nesting on the Shetland and Orkney colonies in the North Sea showed that tens of thousands of breeding pairs failed to raise any chicks (14). Similar studies also done in the Shetlands yielded nearly the same results and one even uncovered evidence of starving adult Arctic skuas eating the chicks that did hatch (14).  This sort of critical breeding failure and falling population numbers are present throughout the Arctic sea bird species. Much of it is attributable to loss of habitat and similar decreases in prey populations. In the Antarctic, birds are not faring much better. Penguin populations are showing dramatic decreases. The Adelie penguin population has declined by 33%, the Emperor Penguin has decreased by 50% in some areas, and at Campbell Island, the Rockhopper penguin has experienced a 94% decline in population. Warmer temperatures and their impacts on the population of krill , which makes up a significant portion of the penguin diet, are to blame for many of these declines, though the inability of some penguin species to adapt quickly to change also contribute (14).

Large marine mammals are stressed just as severely. Polar bears in the Arctic are the most visible example of this. These bears are dependent on sea ice as places for pregnant females to build dens, as hunting grounds for ice dwelling seals, and as ice corridors that allow them to move from place to place. The continued loss of sea ice has resulted in poorer hunting, bears drowning after becoming exhausted from swimming long distances, and less hearty females, especially, who fast for up to 7 months after having their cubs in the winter. Polar bears in the southernmost reaches of the Arctic started exhibiting climate related stress in the latter part of the 20th century. Between 1981 and 1998 the number of cubs born and the weight of the average adult bear fell 15%. Unless polar bears are able to adapt to a more terrestrial way of life, odds are they will not survive as a species for too much longer (2). Walruses and seals are also suffering from the steady loss of sea ice. The ice dependent ringed seal, ribbon seal, and bearded seal all build their lairs, birth their pups, and forage around and under the ice. The earlier break up of winter sea ice poses particular problems for them as it separates mothers and pups before the pups are ready, which is leading to a higher mortality rate among the young. Walruses also rest and forage along the ice edge along the continental shelf where they have easy access to clams and other shellfish. As the sea ice retreats, access to this source of food is becoming more restricted, reducing their intake and forcing them to expend more energy to get to it (2).