Does chemistry help Antarctic benthic fauna against invaders? | Polarjournal
Bottom-dwelling organisms such as starfish and anemones cannot swim away from predators. They make do with chemical defenses designed to deter enemies. But studies on whether this also works in Antarctic waters do not exist in great numbers. Image: Conxita Avila, University of Barcelona

The seafloor around Antarctica is not empty and barren. Numerous different animal groups have adapted to the cold, darkness and pressure there, enjoying the remoteness and isolation caused by the Antarctic convergence and the great depth of the Southern Ocean. But this curtain is slowly punctured due to climate change, and Antarctic benthi animals are left with only chemical defenses against new possible invaders. A study investigated the question of whether this is enough.

If small amphipods were to migrate toward Antarctica from temperate waters north of the Antarctic convergence line, most Antarctic animals living on the seafloor could rely on their chemical defenses. The situation is different when larger crab species, such as hermit crabs or even king crabs, spread towards Antarctica. The substances hardly help against these and would therefore not provide any protection against predation. This is the result of a study by Professor Conxita Avila of the University of Barcelona and a team of Spanish scientists, which was published in August in the journal Marine Drugs .

The seafloor around Antarctica is covered with many different species, especially along the Antarctic Peninsula, where rocks and stones were transported into the sea with the glaciers. These form the basis for many sessile species. These have been successfully defending themselves against predators such as fish or crabs for millions of years. Image: Screenshot Youtube video Ocean X

For their study, which is a baseline study and the first of its kind, according to the team, they spiked the diets of hermit crabs and amphipods native to temperate regions with chemicals known from a total of 29 different Antarctic species from seven different animal phyla. These include sponges, worms, echinoderms, and tunicates that are part of the Antarctic benthic fauna. This showed that amphipods mostly rejected the treated food, while hermit crabs were not deterred. Only the chemical mace of a species of sponge and a species of tunicate showed significant deterrent responses in the potential predators.

Thanks to ever new technical developments in the field of underwater vehicles and cameras, ever new areas of the Antarctic depths can be explored. In the process, researchers discover the richness of the region. But this is threatened by warming and the immigration of new species that are better adapted to these new conditions. Video: Youtube Ocean X

The authors emphasize that the predators used as test objects are not themselves on their way to Antarctica, as they originate from the Mediterranean or temperate marine areas in the north. But related species have similar food preferences and also similar ways of tracking down food. And such species are already knocking on the door, with some studies already discovering newly invading species such as crabs and mussels near Antarctica. “The Antarctic seafloor ecosystem is in danger for many reasons, and this is just one more,” says Conxita Avila. “When animals like king crabs come up, they will decimate populations of Antarctic animals and completely change those communities.”

A study from two years ago showed that mussels already live in Antarctic waters, likely introduced by ships. Various programs and projects have been initiated to make such invasions more difficult. Images: Cardenas et al (2020)

In order to at least make it more difficult for potentially dangerous species to get there, various initiatives and programs are active in Antarctica. These include, for example, the “Don’t pack a pest” initiative of the International Association of Antarctic Tour Operators IAATO or the “Safeguarding South Georgia’s Blue Belt” project of the South Georgia and South Sandwich Islands GSGSSI administration. But these target only the transportation pathway. According to Professor Avila and many experts, however, the warming, which is becoming increasingly severe, especially along the Antarctic Peninsula, must be brought under control. Only in this way will Antarctic benthic fauna have a chance to survive and humans have the opportunity to learn more about this unique and fascinating world before it disappears into the stomachs of invasive species.

Dr Michael Wenger, PolarJournal

Link to the study: Avila C et al (2022) Mar Drugs 20 (543) Would Antarctic Marine Benthos Survive Alien Species Invasions? What Chemical Ecology May Tell Us;

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