The Bering Sea, a northern extension of the North Pacific Ocean, is the world's third largest semi-enclosed sea. The Bering Sea ecosystem is home to a rich variety of biological resources, including the world's most extensive eelgrass beds; at least four hundred and fifty species of fish, crustaceans and mollusks; fifty species of seabirds; and twenty five species of marine mammals. Furthermore, many unique and endemic species, such as red-legged kittiwakes and whiskered auklets, inhabit the Bering Sea. The abundant fish and wildlife of this area were the source of provisions for Asians and North Americans since the prehistoric times.
Marine mammals, birds and fish are now subject to the range of international agreements, aimed to protect the Bering Sea ecosystem. Everything possible has been made to prevent the intervention to its wild life. Some species of the Bering Sea and neighboring regions have recently experienced large and sometimes sudden population fluctuations. While the supreme cause of this instability is still unknown, it could be a reflection of either natural, climate related changes or a human-induced change.
The variations in the atmosphere, ocean and populations of marine species are occurring in the Bering Sea ecosystem on annual, decadal and longer time scales. Such transformations extend from a reduction in marine mammals to a stratospheric cooling and a sea ice melting. Alaskan natives, settling down on the coast of the Bering Sea, confirm that the spring has become warmer lately. The snow has begun to melt earlier then in the past, and the ice has become notably thinner. At the same time, the ice cover of the Bering Sea has a profound influence on the physical and biological ocean environment. Thinner ice allows the ocean to absorb more solar energy, resulting in a slower ice formation in the following winter.
One more striking change in the Bering Sea environment is a considerable decrease of the king crab population, while the population of Pollock enlarged by four hundred percent. Some scientists explain this fact due to the over-fishing in part, the others say that the reason for this is a climatic and environmental change. The decrease of some species of mammals, such as fur seals, Steller sea lions and recently sea otters, take place in the Bering Sea ecosystem as well. Remarkable transformations in physical conditions of this area, driven by atmospheric processes lead to key biological changes.
First of all, it is seen from the shift in a biological regime of the Bering Sea ecosystem. There considered to be two shifts in climate, which had the consequences of warmer temperatures: the first in the late 1970s and again around 2000. The first shift has led to thinner sea ice, significant warming of the ocean and unstable weather conditions in spring. In the late 1990s, higher temperatures became even more evident, resulting in a massive die-off of seabirds and the appearance of the exotic phytoplankton species, rarely found in the Bering Sea.
This Bering Sea impact represents a transition from primarily cold Arctic ecosystems of the 20th century to sub-Arctic conditions. To save the Bering Sea ecosystem, it is vital to understand the specific reasons for population fluctuations as well as the relationship among species and environment they inhabit.