Warming seawater will push Antarctic krill farther south

Rising ocean temperatures will alter the distribution and life cycles of Antarctic krill in the coming decades, according to a new study led by the University of Tasmania.

Antarctic krill are ecologically and commercially important animals.  They are the main food source for hundreds of marine species, including whales, seals, ice fish, and penguins.

The researchers investigated how changing ocean temperatures will affect the habitat and preferred food of krill, which is phytoplankton.

The study showed that 85 percent of the Southern Ocean will be impacted, and krill will likely move farther south where conditions are more favorable. 

Study lead author Devi Veytia said the findings forecast a change in the seasonal distribution of krill habitat, particularly around fishing grounds near the Antarctic Peninsula.

“Understanding how krill will respond to climate change and the ecological impacts of those changes is important to both conservation efforts and the management of the fishery, the largest in the Southern Ocean,” said Veytia.

“Our study combined projections of sea surface temperatures and phytoplankton using climate change scenarios with an established krill growth model.”

“We found that over the coming decades krill habitat quality can be expected to improve in spring, particularly further south and on the continental shelf.”

“In summer, there was little net change, but good habitat redistributed, increasing at high and low latitudes and declining in mid-latitudes.”

Veytia said that the greatest decline in habitat quality and range will occur in the fall, mainly in sub-Antarctic regions. As a result, krill will shift south into higher latitudes.

“At the same time there will be a change in the time of year when krill habitat is optimal, improving in spring, but declining in important regions during summer and autumn.”

According to Veytia, the shift in seasonal habitat quality, especially around the Antarctic Peninsula, could disturb the synchronization between krill and the annual cycle of this important ecosystem.

“Synchronization usually allows krill to capitalize on seasonally available food sources, allowing growth, reproduction and storing of reserves to survive the winter,” said Veytia.

“A temporal shift in habitat quality could create a timing mismatch, potentially affecting krill reproduction and population dynamics.”

“The commercial fishery, which is currently centred on the Antarctic Peninsula and south Scotia Sea, could also be affected, leading to shifts in the distribution and timing of the fishing effort.”

“The geographical shift of krill habitat towards more southerly waters is also likely to have ecosystem impacts, particularly for land-based predators at sub-Antarctic islands that have limited capacity to follow their preferred food source.”

The study is published in the journal Nature Climate Change.

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By Chrissy Sexton, Earth.com Staff Writer