Research by an Australian team has shown that krill, a tiny prawn-like creature, are more vulnerable to climate change than previously thought.

Ocean acidification is caused by man-made carbon dioxide from the atmosphere being absorbed by the ocean.

The work, published yesterday (October 13) found increased levels of carbon dioxide can kill the embryos of Krill.

The Australian Antarctic Division discovered that exposing krill embryos to higher levels of carbon dioxide stopped their development and none of them hatched successfully.

Krill feed off plankton and, as they exist near the bottom of the food chain, become food for whales, seals, penguins, squid and fish.

So, if the population of krill was hit by climate change it would have a devastating knock-on for species further up the food chain including humans.

Lead researcher and biologist, Dr So Kawaguchi, said: “We used the Antarctic Division’s krill aquarium to set up three sea water tanks bubbled with the current (380 parts per million (ppm)), medium (1000ppm) and high (2000ppm) levels of carbon dioxide.

“There was no change detected in the development of the krill embryos in the tanks with the current and medium levels, but in the tank with higher levels, none of the embryos survived to hatch.”

Dr Kawaguchi also pointed out the acidity of the ocean is not uniform throughout the water column, with higher levels of carbon dioxide found at greater depths.

He said: “Southern ocean carbon dioxide levels at depths could rise to 1400 ppm by the year 2100, when atmospheric carbon dioxide is expected to more than double to 788 ppm.

“If carbon dioxide increases to these levels and the ocean becomes more acidified, it could have a huge impact on krill populations and therefore the entire southern ocean ecosystem.

“Krill spawn eggs at the surface which then sink to between 700 and 1000 metres before the larvae hatch and swim back to the surface,”

“Hence vertically migrating animals like krill will experience one of the most drastic changes in the ocean and potentially face greater mortality.”

Further studies will be undertaken to identify the exact carbon dioxide concentration ‘tipping point’ and the potential impact of ocean acidification on the later stages of the life cycle of krill.

Luke Walsh

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