In the peak of the Antarctic summer, the icy ocean sometimes takes on pinkish-red hue. This unusual coloration is actually a layer of krill (Euphausia sp.), a tiny shrimp-like crustacean the size of your pinky. They gather in large numbers to feed on the phytoplankton blooms, which only occur during the Antarctic summer. At this time, enough light reaches the South pole to allow the microscopic algae to reproduce quickly enough to form a large colony on the surface of the water. The krill are the stars of the Antarctic food web, passing on the energy from the phytoplankton to larger animals. Many of the species in the Southern Ocean, including fish, whales, seals and penguins depend heavily on krill.
In order to help the krill and the rest of the inhabitants of the Southern Ocean cope with climate change, the European Union has proposed a 1.8 million square kilometre nature reserve. This huge sanctuary, proposed in October of 2017, would be the world’s largest nature reserve. It would aim to protect much of the Weddell Sea and the Antarctic Peninsula, as well as the species that live there. The campaign has already international support and will be presented to a conference of Antarctic nations in October 2018, including France, the United Kingdom, Australia and Norway.
The original idea for the sanctuary came from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research in Germany. Julian Gutt, a researcher at the institute, says that the project could also have wider implications for ocean conservation: “This will bring huge benefits in protecting this amazing ecosystem, in preserving the biodiversity and ecosystem functions of the ocean and in the wider fight against climate change.”
If the proposal is accepted, it would prevent any industrial krill fishing within the reserve. Krill are harvested for fish bait, food for aquaculture as well as for their oils, which are used in omega-3 supplements. Antarctic krill fishing is currently regulated by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), and is promoted as a highly sustainable industry. However, proponents of the proposal argue that in light of climate change, krill fishing is an unnecessary extra pressure on a delicate ecosystem.
Climate change is likely the largest driver of the decline of Antarctic krill populations. Warming temperatures are beginning to melt sea ice, where the krill congregate to graze on ice algae. As the ice shelves shrink, the krill have fewer places to feed. Warmer temperatures also allow competitors to move in. As the krill populations have declined, there has been an increase in salps – a barrel-shaped, gelatinous tunicate that feeds on the same phytoplankton that krill do. Finally, the accumulation of carbon dioxide in the ocean is making the waters more acidic. Krill embryos are sensitive to these changes, and may not hatch properly in acidic waters.
The challenges facing krill have implications for the whole food web. The ability of krill to cope with climate change will determine the future of the entire ecosystem, including whale, penguin, and seal populations. Fortunately, the creation of nature reserves can help conserve vulnerable populations and protect them from additional threats. Intact communities are generally much more capable of coping with environmental variation and may be less impacted by climate change. If successful, this campaign could also create momentum for a network of marine protected areas to better preserve ocean ecosystems.
Megan Bull is studying environmental science at the University of British Columbia, while writing for the Ocean Wise’s multi-media site Ocean.org and the Aquablog.