Business as usual for Antarctic krill even though ocean acidification is increasing


A new study of the Institute for Marine and Antarctic Studies (IMAS) has found that Antarctic krill is resistant to increased ocean acidification because it absorbs more CO2 from the atmosphere due to anthropogenic carbon emissions.

Krill is one of the most abundant organisms on Earth and an important part of the ocean ecosystem of the Southern Ocean.

While previous research showed several life stages of Antarctic crutches might be susceptible to ocean acidification, a study published in the journal Nature Communications Biology found that adult crill was largely unaffected by the estimated level of ocean acidification in the next 100-300 years.

The study's lead author, IMAS PhD student Jess Ericson, imagined, said that long-term laboratory research was the first of its kind.

"Our study found that adult krill can survive, grow and mature when exposed to one year to the level of ocean acidification this century can expect," Ericson said.

"We are raising adult krill in a laboratory tank for 46 weeks in seawater at various pH levels, including at present, levels predicted in 100-300 years, and to extreme levels.

"We measured a number of physiological and biochemical variables to investigate how future ocean acidification can affect survival, size, fat storage, reproduction, metabolism and extracellular fluid in krill.

"Our results show that their physiological processes are largely unaffected by the pH level they are expected to face in the next century.

"The adult krill we monitor is able to actively maintain the acid-base balance of their body fluids when the pH level of seawater decreases, thereby increasing their resistance to ocean acidification."

Ms Ericson said the findings were important because krill was the main link in the Antarctic food chain.

"Smoke acidity caused by anthropogenic carbon dioxide emissions is predicted to occur most rapidly in high latitudes, such as in the Southern Ocean.

"Krill is the main prey item for marine mammals and seabirds, and any decrease in its abundance due to ocean acidification can produce significant changes in the Southern Ocean and Antarctic ecosystem.

"Increasing ocean acidity is known to have a negative effect on various marine invertebrates, causing a decrease in mineralization or dissolution of calcium carbonate shells, decreased or delayed growth, increased delayed mortality and reproduction or abnormalities in offspring, including Antarctic krill embryo development.

"Our findings that adult Antarctic crilla appear to be resilient to such conditions, therefore, are interesting and significant results.

"However, the changing persistence of krill in the oceans will also depend on how they respond to ocean acidification in synergy with other stressors, such as warming the ocean and decreasing sea ice," Ericson said.

The study also included researchers from ACE CRC, CSIRO Oceans & Atmosphere, the Australian Antarctic Division, and Aker Biomarine in Norway.

Image credit: Wendy Pyper.

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