Blog from the Zooplankton group

Strong winds from the north put the work on board on hold for a day. After two days close to the coast of Nordaustlandet we sought shelter in the northern pack ice to weather the storm. Considering the strong wind outside, Lance lays surprisingly calm in the ice, but working outside is not recommended. So there is some time to spend with punching data or fixing equipment. Being able to “fix things” is a crucial soft skill required for every polar researcher. The plankton group has been particularly busy with sewing things, as our nets often get holes (or have been left home and need a hand-made replacement).

The copepod Calanus finmarchicus: green algae can be observed in its guts.

The copepod Calanus finmarchicus: green algae can be observed in its guts. Photo: Anette Wold / Norwegian Polar Institute

Ice fishing.

Ice fishing. Photo: Malin Daase / Norwegian Polar Institute

Zooplankton catch of the day: a piece of modern art.

Zooplankton catch of the day: a piece of modern art. Photo: Malin Daase / Norwegian Polar Institute

Midnight in the ice - a perfect time to take Multinet samples.

Midnight in the ice – a perfect time to take Multinet samples. Photo: Malin Daase / Norwegian Polar Institute

Ingeborg makes a hand net for the divers to catch polar cod under the ice.

Ingeborg makes a hand net for the divers to catch polar cod under the ice. Photo: Malin Daase / Norwegian Polar Institute

The ice amphipod Gammarus wilkitzkii with young.

The ice amphipod Gammarus wilkitzkii with young. Photo: Jago Wallenschus

By Malin Daase, Jago Wallenschus and Ingeborg G. Hallanger

But now wind has calmed down and we are back in business: Nets are put in the water and hauled up, different sizes of zooplankton from different depths are taken. We sample very small organisms to rather big ones (about 5 cm, and that is HUGE for us), all the way from the bottom to close to the surface.  Anette, Malin and Jago, responsible for the zooplankton sampling have everything under control. Ingeborg is also getting in the action, but she is only interested in the levels of the contaminants in our tiny creatures.

Philipp and Mirko, our phytoplankton experts, told us that the spring bloom has started. Phytoplankton, sun nourishing algae living in the sea water and under the ice, is the number one food source for zooplankton. It is all about timing! The key species in our study area are herbivorous (plant/algae eating) copepods of the genus Calanus. They are around 1-10 mm long and spend their winter at greater depth where they hibernate. Large lipid storages sustain the copepods during winter, but in spring they need extra energy to fuel reproduction and the development of the new generation. So at this time of the year the Calanus species are ascending from their overwintering depths to feed on the algae bloom.

And the bloom is on!

Zillions of adult females with telltale green colored guts (see picture), indicate that the feast started. But not only Calanus is timing their life dependent on the algae bloom, in fact most animals are connected to it in one way or another. The samples the divers took under the ice focused on larger species. They caught a lot of amphipods, some up to 3 cm long. And a few of these amphipods had already hatched their young but not released them (see picture). The only chance of the young to survive is to time their hatching with the algae bloom.

As our sampling is done from the boat the zooplankton group is rather confined to Lance while our colleagues are freezing on the ice. Nevertheless we are eager to get our feet on the ice and often volunteer as polar bear guards. The main predator for most of our zooplankton is polar cod, and Ingeborg is interested in its contamination level. So we tried our luck in ice fishing which turned out to be a rather inefficient way to catch polar cod. However, it was a brilliant excuse to get on the ice without being polar bear guard.