The polar sea ice has its widest distribution during the late winter. The return of the sunlight in spring brings the algal bloom under the ice floes. As a result, zooplankton comes from deeper water layers to the ice to feed on the algae. These small animals are again prey for larger organisms such as fish and seals and thus, directly or indirectly, for the whole rest of the food chain up to polar bears. The basics of this system are common knowledge, but scientists are still working on many important details.
Marine biologists from the university in Longyearbyen (UNIS) have found out that the little crustaceae (in this case Calanus glacialis) are perfectly adapted to the seasonal development of sea ice in spring. The adult females eat as much as they can in the twilight under the closed sea ice cover, until they are able to reproduce. Two months later, their offspring is large enough to profit from a second algal bloom when the sea ice breaks up. These young, fat crustaceae are ideal food for polar cod, seals, seabirds such as guillemots and whales.
In case the sea ice is getting thinner and thinner due to climate change, the breakup will be earlier and the second algal bloom accordingly earlier. As a result, the young phytoplankton might not yet be old enough to feed sufficiently, which might lead to significant weakening of this important link in the arctic food chain, possibly leading to major disturbances of the arctic ecosystem as we know it.
The colouration of the ice is due to algae. In the middle a beached representative of the arctic marine fauna that depends on the algal bloom for food.
Source: Svalbard Science Forum