Submitted by Anonymous on Fri, 03/21/2008 - 08:23
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Bering Ecosystem Change

How has Global Warming effected the bearded seals? I read that they like to camp out on the sea ice away from land, and in a class I am taking called climate change, we have learned that walruses have been effected because the sea ice is retreating and now they have nowhere to rest while hunting. Has the receding ice effected the bearded seal too, or have they just adapted? If so, how has the climate change effected the bearded seals?

Fri, 03/21/2008 - 14:03

Craig Kasemodel

Hi,I asked Sue Moore of the National Marine Mammal Laboratory shipboard marine mammal observation program about bearded seals. Both walruses and bearded seals will be affected by climate change by the same mechanisms. The are two main effects in a warming climate, the benthos and sea ice habitat. The benthos effect will affect the bearded seals, as they are bottom feeders eating a wide variety of invertebrates, clams, snails, crabs and shrimp, and some fishes found on and in the bottom of the Bering and Chukchi Seas. The benthic environment is dependent of the spring algae bloom for the infusion of nutrients that fall to the bottom when the algae and the zooplankton (that feeds on the zooplankton) die. With the receding sea ice, less area will be infused with nutrients. Also, the first year ice is thinner leading to a reduction in the algae. This will lead to a reduction in the productivity of the bearded seal wintering areas which could reduce their survival and population if other habitats prove unsuitable. Another component is interspecfic competition, competition with other species for available prey. As the water column warms, even very slightly, other pelagic species (open water) could move in and prey on the zooplankton or the benthic environment. The researchers are seeing some shifts in the species composition of the North Pacific and the Bering Sea. Pollock are shifting their distributions northward.
The second effect on bearded seals from climate change is the reduction of sea ice as habitat. Bearded seals are generally solitary animals and adults are associated with the sea ice. They make seasonal migrations as they follow the movement of sea ice in the Bering and Chukchi Seas. In the winter time, the density of animals is quite low, as the ice typically, historically, covers a large area. During the spring, the seals will migrate northward through the Bering Strait from the Bering Sea. They reach the Chukchi Sea and Arctic Ocean in late summer. If the sea ice is beyond the sea floor shelf, the seals will be unable to reach the benthos to feed. During the autumn freeze-up, the animals will once again migrate southward and become widely dispersed throughout the northern Bering Sea. Like walruses, bearded seals will concentrate on land haulouts if necessary, however, the concern is that the available habitat will not support the populations at their historic averages.