Polar News

Antarctic Krill Show Resilience Under Future Climate Conditions

Scientists have discovered that Antarctic krill may have developed a resilience to ocean acidification

The marine life inhabiting the freezing waters surrounding Antarctica are specialists in their environment, having been subjected to low and relatively stable temperatures for the past ten million years. But Antarctica is also one of the fastest changing environments on Earth, with areas such as the western Antarctic Peninsula experiencing an increase in atmospheric temperature of 3℃ since 1951. This rapid increase in carbon dioxide levels has the potential to make the Southern Ocean more acidic, raising questions as to how marine animals will survive there in the future.

One such species, the Antarctic krill (Euphausia superba), was once thought to be particularly vulnerable to ocean acidification. Krill are a major prey item for marine mammals and seabirds, and any decrease in their abundance as a result of ocean acidification could result in significant changes in the Southern Ocean and Antarctic ecosystem. However, new research carried out by scientists at the University of Tasmania has suggested that the future may not be so bleak for the crustacean. The study, published in the journal Communications Biology, has discovered that Antarctic krill may have developed a resilience to ocean acidification with their physiological processes being largely unaffected under future acidic conditions.

Jess Ericson, the lead author on the paper, said that this was the first long-term study of its kind. “Understanding how organisms will respond to high CO2 requires laboratory experiments that measure a wide range of physiological performance indicators over periods of months or years.”

“We measured a suite of physiological and biochemical variables to investigate how future ocean acidification may affect the survival, size, lipid stores, reproduction, metabolism and extracellular fluid of krill.” Said Ericson.

Adult krill were reared in seawater tanks for 46-weeks with a range of pH levels, including those in the present day, levels predicted within 100-300 years, and up to an extreme level. Their results showed that their physiological processes were largely unaffected by pH levels that they are expected to counter over the coming century. "The adult krill we monitored were able to actively maintain the acid-base balance of their body fluids as seawater pH levels decreased, thereby enhancing their resilience to ocean acidification."

This finding is an important step in understanding what the future holds for Antarctic krill and therefore most of the Antarctic food web that depends on them as a food source. However, Ericson noted that the persistence of krill in a changing ocean will also depend on how they respond to ocean acidification in synergy with other stressors, such as ocean warming and decreases in sea ice extent.

By Ellis Moloney

Ericson, J., Hellessey, N., Kawaguchi, S., Nicol, S., Nichols, P., Hoem, N., & Virtue, P. (2018). Adult Antarctic krill proves resilient in a simulated high CO2 ocean. Communications Biology, 1(1). doi: 10.1038/s42003-018-0195-3

This research was funded by an Australian Research Council Linkage Grant LP140100412 between the Australian Antarctic Division, Commonwealth Scientific and Industrial Research Organisation, Institute for Marine and Antarctic Studies (University of Tasmania), Aker Biomarine and Griffith University.

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