An IDEAL Center study in the Southern Ocean revealed how the proliferation of salps, poorly studied marine invertebrates, could reduce the abundance of a key link in the trophic webs of the white continent.

Salps are gelatinous organisms that can form large swarms.

A study led by Dr. Humberto González, director of the Research Center Dynamics of High Latitudes Marine Ecosystems (IDEAL) of the Universidad Austral de Chile, revealed how increasing temperatures in the Southern Ocean off Antarctica gave rise to a great proliferation of salps and diminishing numbers of krill, a key species in the ecosystems of the white continent.

Similar to jellyfish, salps are marine invertebrates that can form large groups known as “swarms”. Gelatinous, translucent, and made up of more than 95% water, salps can be found in all the world oceans. However, they are most heavily concentrated in the Southern Ocean. Krill, on the other hand, make up the principal food source for various Antarctic animals. Both salps and krill live in the water column, and they compete for food.

The study, which was conducted in Maxwell Bay and South Bay, began in 2017, after the second Antarctic expedition of the IDEAL Center. Exceptionally hot conditions were recorded during this cruise, with water temperatures that were 1 to 2 degrees higher than normal. The abundance of salps was also greater than in previous years.

Because of these higher temperatures in the Southern Hemisphere, salps are becoming more frequent in Antarctica, with the potential to generate competition with Antarctic krill for food.

“The summer of 2017 was very warm, and there was a massive growth of salps and, simultaneously, few krill. On the other hand, the summer of 2018, which was colder, had the opposite effect,” explains Dr. González.

What if there was no krill?

Environmental conditions do not favor large populations of krill every year. Low numbers of krill in summer are associated with reduced sea-ice formation during the previous winter.

Fewer krill could mean major problems for Antarctic food webs since this species is the main food source for predators such as penguins, whales, seals, seabirds, and fish.

“If this cycle of global warming continues, the most probable thing is that, slowly, salps will be favored to the detriment of the krill,” Dr. González asserts. He then concludes, “In this case, Antarctic food webs would be affected because krill is the key link in Antarctic marine systems.”