The results of a study published in Nature suggest that more attention should be paid to Arctic zooplankton. Sea ice retreat could reduce the productivity of these invertebrates that are at the base of the food chain.
A pair of feelers, a segmented body and jerky movements. Zooplankton in the Arctic Ocean could well be deprived of food during increasingly austere winters, with dramatic consequences for predators such as cod and seals, and for the lives of the Inuit.
These findings were published in the journal Nature on 28 August by a team of scientists from the Alfred Wegener Institute, the British Antarctic Survey and the Universities of Newfoundland, Plymouth and College of London
During autumn, winter and spring – seasons that have been very poorly documented in this region – the migration in the water column of copepods, krill and other small crustaceans that live in planktonic form should change rhythm in the future. They would obviously spend more time at greater depths.
The cause is daylight, which reaches deeper and deeper layers. These animals are highly sensitive to sunlight and can detect variations in light intensity as small as 0.00024 watts per m2, or 50,000 times less than the light recommended in a bathroom.
The sun is in no way responsible for this influx of light. The warming of the ocean and the atmosphere is thinning the ice pack and the snow cover; the ice disappears earlier in the spring, allowing light to penetrate more easily.
A second mechanism should be triggered. The early retreat of the pack ice and its late reconstitution will encourage phytoplankton blooms. The formation of these microalgae will slow down before the ice forms again, preventing them from reseeding the autumn ice.
“This, in combination with their delayed rise to the surface, could lead to more frequent food shortages for the zooplankton in winter”, says Hauke Flores, the study’s principal investigator. “If that comes to pass, it will have fatal consequences for the entire ecosystem, including seals, whales and polar bears”.
The authors stress the importance of conducting studies in the Arctic in winter “to be able to predict whether the Arctic Ocean will become a new oasis or a desert if the climate crisis is not controlled”.
The researchers worked on data taken by observation buoys deployed during the Polarstern‘s drift. This German oceanographic vessel was trapped in the ice and currents of the Arctic Ocean between 2020 and 2021.
Other research organisations could also look into the matter, given the scale of the current results. Information that is in line with the concerns of the Arctic Council, non-fishing agreements in international waters and treaties aimed at reducing greenhouse gas emissions.
Camille Lin, PolarJournal
Source Flores, H., Veyssière, G., Castellani, G., Wilkinson, J., Hoppmann, M., Karcher, M., Valcic, L., Cornils, A., Geoffroy, M., Nicolaus, M., Niehoff, B., Priou, P., Schmidt, K., Stroeve, J., 2023. Sea-ice decline could keep zooplankton deeper for longer. Nat. Clim. Chang. 1–9. https://doi.org/10.1038/s41558-023-01779-1
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