Faces of Climate Change: Life on the Ice

0
44

The ocean sustains us in every way. It's the basis of our language. It's the basis of our rhythm in life. Everything that we are is defined by the sea. For part of the year the sea is covered with ice. The ice, the shallow sea below and the sky above is full of life. From dense clam beds on the seafloor to open leads, where bowhead whales swim and spectacled eiders gather by the hundreds of thousands to frozen haul-outs that provide pupping and feeding platforms for ringed seals and walruses. These habitats and animal communities form a special place at the top of the world. A place that is changing. This world will be a lot less rich a place if if we don't have these organisms that evolved over all these millions of years to operate and live in a in an ice-edge environment.

There's a whole suite of top predators that have evolved to eat those animals on the bottom. So they are things like diving ducks or spectacled eiders or king eider. There's bearded seals, there's gray whales that migrate all the way up here from Baja California that specialize in diving to the bottom eating amphipods on the bottom. And walruses are another famous part of the fauna up here that really depend upon having sea ice, shallow water column, and lots of animals on the bottom to feed on. The amazing thing with the spectacled eiders for instance that they all come to the same place in the Bering Sea and people didn't know why they came there. In fact it's only been about a dozen years that people knew where they spent the winter. If you have an old bird book and you look at it, it says something to the effect of "winter range poorly known somewhere in Bering Sea". Spectacled eiders nest in Russia, and on coastal tundra in Western Alaska. Since the 1970's their populations have decreased by 97%.

They winter off Saint Lawrence Island in leads in the pack ice where they dive from 40 to 70 meters for food in water that is -1.8 degrees centigrade. 270,000 birds winter here, only here, and that makes them vulnerable to ocean changes. Living on ice far from being a chilling challenge for the eiders actually helps them survive by saving them energy. Being out on the ice costs them about 50% less than being in the water. Water has a very high specific heat, and has a very high conductivity. If you were to stay in water at even 50°C you become very very cold. It's not really that cold, but the water just sucks that heat out of you. The same is true of these birds, and so being able to get out on the ice during long periods of time that we think they're not feeding is very important to them. Ice is also important for the eiders' food supply during the annual spring bloom. Nutrients from the ice combine with energy from the sun to create an explosion a oceanic phytoplankton: the base of the marine food web. But early spring blooms means that uneaten plankton falls to the shallow ocean floor before the season's growing population of zooplankton has a chance to eat its microscopic prey.

And the idea is that if you didn't have that ice that the spring, bloom would occur much later. It would be more protracted, and the zooplankton would of have had enough time to build up their numbers to where they could graze a lot of that material before it gets to the bottom. And you would switch from a kind of bottom dominated ecosystem to one that was more occurring in the water column, where much more of that energy was burned up in the water column and didn't get to the bottom to the animals that eiders like to eat. Ringed seals are one of the most ice-loving of all arctic animals. They can be found wherever there is sea ice. Ringed seals feed along the frozen coast and give birth to pups in hidden snowy lairs where they have greater protection from the cold as well as from predators like polar bears.

They're one of the smallest seals. So you have the seals breeding at the highest latitude with the smallest pups The pups maybe weigh 5 to 10 pounds when they're born. They're quite tiny and they don't have a blubber layer yet that the adults have. At the time of year they're born starting late March through April it's still quite cold in the high Arctic and they would perish very quickly from hypothermia were it not for being under this insulating snow cover. But like Arctic ice cover, snow cover is also decreasing and snow melts are coming earlier, making it even more essential to understand the seals life histories. Borrowing a trick from the Canadian Inuit, researchers use dogs to sniff out lairs and observed seals, collecting data on their condition and survival rates. Underwater researchers use hydrophones to track the adult seals foraging movements. These and other studies seek to understand how will seals cope as the climate continues to change.

Walruses use sea ice quite a bit and you know they're expected to be impacted by that. We would like to know how and in which ways. They seem to be designed pretty well to feed on clams. They root around in the bottom sediments and soft sediments and they use their whiskers to filter through the sediments and take just their prey that way. When they come upon a clam they purse the clam in their lips and suck the meat out of the shell and just drop the shell and move on. But they're very efficient feeders. They're pretty good at it. They need the sea ice to be able to haul out and rest. If they're in an area that's rich in food, if there isn't ice there for them use after they forage for a day or up to a few days at a time, they can't persist in those areas. The two things kind of go hand in hand. Obviously walruses use sea ice quite a bit and you know they're expected to be impacted by that. We'd like now how and which ways..

NO COMMENTS