Sea ice around Antarctica has decreased significantly in the past few decades. In 2022 we reached the lowest level of sea ice in over 40 years, at almost 30% less than the average level over the past 10 years.[1] Not only does the melting sea ice contribute to the global rising of sea levels, but research has shown that vital Antarctic ecosystems are also being affected by decreasing sea ice and ice-shelf retreat.
Antarctic krill are small, shrimp-like creatures, which form the basis of the Antarctic food web and are a major food source for fish, squid, penguins, seals, whales and various seabirds. Virtually all of the larger Antarctic animals, as well the environments at the lowest level of the sea, are either directly or indirectly dependent on krill.
Krill themselves feed on small plants, including phytoplankton and algae that grows under the sea ice. They use the sea ice to protect themselves and feed from the various microorganisms inside it. Just like trees on land, phytoplankton take in carbon dioxide and photosynthesise to create the food that they need to survive. In doing this, the carbon is stored in plant cells, which in turn are eaten by the krill as they feed upon the phytoplankton. This carbon is then released in a faecal string, which sinks quickly to the bottom of the ocean. This cycle highlights the critical importance of krill in removing carbon from the atmosphere – in fact, it’s estimated that Antarctic krill remove around 39 million tons of carbon from the surface ocean annually. Therefore, krill are not only essential in providing food and maintaining the Antarctic ecosystems, but they are also vital for removing carbon and slowing down the effects of global warming.
Sadly, Antarctic krill populations are plummeting due to climate change, and as the base of the Antarctic food webs, their decline is having a domino effect on the other marine life in Antarctica. In areas where the sea ice disappears, krill populations will decrease further, creating a food shortage, and wildlife will be forced to shift closer to shore in order to access their food. At the same time, earlier spring snowmelts along the peninsula will flood the nests of newly-hatched Adélie penguins, meaning that they will be more vulnerable than other species who nest later, such as the Gentoos and Chinstraps. As the ocean temperatures continue to rise and the sea ice continues to melt, krill populations may be further threatened by other filter feeders such as salps, which also eat phytoplankton and thrive in warmer water temperatures.
While climate change is significantly impacting the Antarctic ecosystems, human activity is having a direct influence as well. Up to 300 000 tons of krill is caught annually and used for human consumption (‘Omega 3’ oil supplements), fish feed, and sport fishing bait[2] There are current concerns that we soon may over-fish krill due to the growing demands of aquaculture.
We need to act proactively and reactively by implementing the Sustainable Development Goals 12 (responsible consumption and production), 13 (climate action) and 14 (life below water) and addressing the issues of climate change and human impact – particularly in Antarctica, where it has the potential to affect fragile but incredibly vital ecosystems. We are continuing to learn how the distant, seemingly uninfluential land of Antarctica and its ecosystems are increasingly important to us and our survival and need our protection.
[1] The Guardian, 2022: https://www.theguardian.com/world/2022/feb/23/antarctic-sea-ice-falls-to-lowest-level-since-measurements-began-in-1979; . Research Organization of Information and Systems, 2022: https://scitechdaily.com/30-less-than-average-antarctic-sea-ice-levels-lowest-ever-recorded/
[2] Daily Mail, 2016: https://www.dailymail.co.uk/news/article-3552089/The-huge-drop-numbers-krill-having-massive-impact-life-penguins.html; “What Is Krill?”, 2019: https://www.thoughtco.com/krill-facts-4153991
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