Arctic Food Web
The Arctic is cold. In winter, there is little or no sun. In summer, no darkness. At sea, there is a burst of plankton growth in spring that sustains all living things for much of the rest of the year. For at least 800,000 years, there has been at least some sea ice in the Arctic Ocean throughout the year. Not surprisingly, Arctic animals have adapted in many ways to cope with these conditions.
Today, however, those conditions are changing rapidly. Importantly, none of the climate models that incorporate sea ice had projected such a rapid decline, suggesting that Arctic sea ice is more susceptible to climate change than was previously known. Indigenous hunters report an array of changes to the environment, its animals and the ability of hunters to provide food for their families.
The rapid loss of sea ice leaves even less time for adaptation by fish, wildlife, and humans to the new conditions they will soon experience. The Arctic ecosystem is restructuring into a new, unknown Arctic system.
In 2011, scientists working the Chukchi Sea were surprised to discover massive phytoplankton blooms beneath pack ice, far from the ice edge. The thinning ice and increasing extent of melt ponds on top of the ice is allowing more sunlight to reach the water below, fueling the larger blooms. Primary productivity in such areas may be considerably higher than previously thought.
Changes in the Arctic food web are already apparent. The distribution of species is changing along with the structure of food webs. Changes in ocean circulation appear responsible for the first exchanges of zooplankton between the North Pacific and North Atlantic regions in perhaps 800,000 years.
Changes in distributions allow the transmission of diseases from subarctic animals to Arctic ones and vice versa, posing an additional threat to species already stressed by habitat loss and other impacts. Where these changes lead is not yet clear, but are likely to have far-reaching impacts on Arctic marine ecosystems.
Arctic Food Web
These animals use blubber to stay warm and to store energy. They have evolved in response to an environment with sea ice. With less and less sea ice, today’s Arctic marine mammals will likely suffer while subarctic species move northwards. Industrial development can cause marine mammals to shift their migratory patterns. Environmental contaminants may pose a health risk for some animals.
Many species of seabirds are found in the Arctic, as well as diving ducks such as eiders. They migrate northwards in spring, seeking nesting habitat and the rich feeding that comes with the spring bloom of plankton. Some seabird colonies number in the millions. Birds get entangled in fishing nets, and contaminants can weaken eggs and reduce reproductive success.
The Arctic or polar cod is a key species in Arctic food webs. This abundant fish is the main connection between plankton and larger animals. Other fishes are also found in the Arctic, including turbot, different types of cod, various whitefishes and Arctic char. In the Bering Sea, salmon and pollock are the basis for large commercial fisheries. Salmon also sustain traditional communities in the region.
Arctic oceanic food web dependence on Arctic cod (Boreogadus saida)
Arctic animals are abundant in some locations, but such aggregations can be vulnerable to disturbance or disaster. Bowhead whales migrate in open leads in the spring sea ice. Seabirds feed in large groups and breed in huge colonies. Many fishes school or concentrate to spawn. All could suffer greatly from oil spills, overfishing, entanglements in fishing nets or other accidents or mismanagement.
Increased industrial access to the Arctic brings new threats to the area, at a time when climate change is already altering ecosystems in ways we are only beginning to understand, much less predict. Bowhead whales change course when they hear the sound of offshore drilling. It is not clear what the bowhead would do if they had to navigate a series of oil wells or how Iñupiat whalers would be able to reach whales that swam far from shore.
Seabirds require suitable cliffs and other habitat for nesting that are also close enough to food sources to feed vast numbers of birds. If the feeding grounds move or are disturbed, the birds will be forced to nest in less desirable areas or travel further and further to find food. Either course would likely result in lower productivity and eventual declines in numbers.
The first admonition for medical doctors is “Do no harm.” The same principle can also be applied to environmental impacts and management. Arctic marine ecosystems are changing rapidly in ways we do not yet understand. It is thus impossible to predict the consequences of our actions. Sustaining Arctic marine ecosystems requires caution and prudence.
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