Proof that the small organisms survives under the Arctic sea ice during the winter

Important groups of calcifying zooplanktons (planktic foraminifera and shelled pteropods) were examined under the sea ice cover to see how they cope with changes of physical and chemical properties in the Arctic Ocean, such as ocean warming and changes in carbonate ocean chemistry during the polar night in December 2019. They are doing well!

Katarzyna Zamelczyk (UiT) is the lead author in this publication and can tell us more about the result of their last work.

Kasia presenting her poster at NL annual meeting 2021

Katarzyna Zamelczyk (to the right) is presenting her poster at the Nansen Legacy  annual meeting in October this year. Photo: Charlotte Stark, UiT

– Planktic foraminifera and shelled pteropods are important groups of zooplankton in all oceans.

These marine organisms use calcium carbonate minerals that are available in the ocean water to build their shells and are therefore important indicator of ocean acidification.

Changes in ocean carbonate chemistry and continued ocean acidification is causing many parts of the ocean to become undersaturated with these minerals, which affects the ability of these organisms to produce and maintain their shells, she informs.

Moreover, planktic foraminifera and shelled pteropods are important constituents of the food-web and contribute significantly to the vertical flux of calcium carbonate in polar pelagic ecosystems.

Studying these marine organisms can help to explore how aquaculture, wild fisheries, and food webs may change as ocean environment changes, says Zamelczyk.  

Zooplankton sample with the concentration of shelled pteropods in the middle of the petri dish.

Zooplankton sample with the concentration of shelled
pteropods in the middle of the petri dish. Photo: Katarzyna Zamelczyk 

: Under the microscope: Subpolar species Limacina retroversa collected in the Nansen Basin

Under the microscope: Subpolar species Limacina retroversa collected in the Nansen Basin (station P6 – see map further down). Photo: Katarzyna Zamelczyk 

How do organisms cope in a rapidly shifting environment?  

Recently published research from the Nansen Legacy project provided, for the first time, information on the under-ice planktic foraminifera and shelled pteropod abundance and diversity and vertical distribution in the Nansen Basin and the northern Barents Sea during the polar night in December 2019. The two groups of calcifies were examined in different environments to see how they cope with changes of physical and chemical properties in the Arctic Ocean under the sea ice cover.

– The abundances of shelled pteropods under the sea ice were similar to abundances found in the open ocean, says Zamelczyk. Moreover, the polar pteropod species Limacina helicina, that was represented mainly by the juveniles, were found in the surface water (0–50 m depth) showing a preference toward cold polar waters with temperatures under – 0.4C. This indicates that the organisms studied were coping well with the harsh conditions, she adds.

The abundance of planktic foraminifera was generally very low in the study area. Only a slightly higher occurrence was recorded in the proximity of the Polar Front.

Still not enough data

Abundances of living pteropods were, however, markedly lower than the abundances of empty shells of larval forms of pteropods. More research and data are needed to explain the dynamics of these planktic calcifiers during Arctic winter.

– Nevertheless, this study offers a unique contribution to our understanding of the inter-seasonal variability of planktic foraminifera and shelled pteropods abundance, distribution and population size structure in the Arctic Ocean, the researcher concludes.

Map from the Nansen Legacy cruise in 2019.