This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: New research shows that larval Antarctic krill could be carried far from their birthplace by drifting sea ice, linking distant ecosystems in ways conventional models may miss. Published in Global Change Biology Communications, the study models how ocean circulation, sea ice drift and vertical migration influence the overwinter transport of Antarctic krill in the southwest Atlantic sector of the Southern Ocean.
Lead author Aditya Sharma, a Ph.D. student with the Australian Antarctic Program Partnership at the University of Tasmania, said krill don't simply drift wherever ocean currents take them. "Krill spend time sheltering in sea ice and use the ice as an extra transport system that moves and connects populations more widely than ocean currents alone. Krill migrate vertically between ocean and ice habitats and swim horizontally while in the ocean.
Their vertical migration changes the pathways they follow, and spending more time associated with sea ice allows them to travel farther and reach more distant regions," he said. The primary driver of interannual krill abundance and population dynamics is krill recruitment, defined as the survival of krill to 1 year old. Krill larvae depend on sea-ice habitats for food and shelter to survive the winter and then recruit to the population the following spring.
"Understanding where krill go during winter could be just as important as understanding where they are found in summer. From year to year, the same starting population of krill can experience very different transport pathways, highlighting how variable the Southern Ocean can be," Sharma said. Using 32 years of high-resolution ocean current and sea ice simulations, the modeling shows that greater exposure to sea ice drift reduces krill retention near the Antarctic Peninsula while increasing northward transport toward the Scotia Sea and South Georgia.
With a particle-tracking scheme, virtual "krill" were "released" in the southwest Atlantic sector of the Southern Ocean and tracked from April to October, a key period for the survival of juvenile krill and interannual krill abundance more generally. "By including extreme cases where simulated krill spend all their time either in sea ice or in the open ocean, we could assess the maximum possible influence of behavior on transport pathways and distribution," Sharma said. The model indicates a strong tendency for krill to move eastward away from the Antarctic Peninsula, largely due to the prevailing Antarctic Circumpolar Current.
With ocean currents alone, 4% moved west and 17% moved east into the open ocean. But when particles spent all available time associated with sea ice, 21% moved west and 48% moved east away from the peninsula. Antarctic krill are integral to the marine ecosystem and food web and play an important role in nutrient cycling and carbon storage.
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