A new study by the British Antarctic Survey, published Thursday in the journal Current Biology, shows how warming oceans may affect sea life. Researchers dropped heated panels to heat the sea floor off the Antarctic coast, tracking its effects on several marine species. To the scientist’s surprise, several species doubled their growth in response. However, evidence also showed that the species which benefit from the higher temperatures could crowd out more sensitive species.
The oceans around Antarctica, unlike the dry continent itself, support a wide variety of life, from single-celled algae and bottom-dwelling worms to predators such as fish, penguins, and whales.
Greenhouses gases such as carbon dioxide make their most dramatic impacts near the poles. Computer modeling has predicted warming in the Southern Ocean of 1.8 degrees Fahrenheit in 50 years, and 3.6 degrees in 100 years.
According to Gail V. Ashton, a marine ecologist with the Smithsonian Environmental Research Center in Tiburon, California, and a co-author of study, “We’re going to start to see changes there first.”
To anticipate those changes and their effects on marine life, researchers look at clues such as the current natural range of Antarctic species, to determine what temperatures they can tolerate. Some scientists have put species in laboratory tanks where the environment can be manipulated and the effects observed. These approaches, however, have their own drawbacks.
“Too much control may yield unnatural responses,” cautioned marine ecologist Rebecca L. Kordas, from Imperial College London. Kordas was not involved in the new study, but has, alongside other researchers, recently attempted experiments that involve heating the ocean itself. Typically, this has involved using heated panels to raise the temperature in coastal areas, and observing how this affects the growth of small animals on the ocean floor. The method has been employed near the coasts of British Columbia and Australia.
The new experiment uses the method in tougher conditions, in waters 45 feet deep in the Southern Ocean, off of the Antarctic peninsula.
The scientists had to connect cables from the shore to power the panels, which were at one point severed, most likely by a ship or iceberg, in 2014. The project was restarted afterwards, and lasted until March 2015.
Dr. Ashton herself says she did not expect to see much change in sea life. Some researchers thought animals in the warmer areas could grow as much as 10 percent faster. The scientists were surprised to find animals growing as much as 70 times faster – in that case, a species of worm on a panel heated by 1.8 degrees. Filter feeding animals called bryozoans grew twice as quickly. On the 3.6 degree heated panels, some animals grew even more, while others grew less.
Researchers are now interpreting the results. Dr. Ashton is investigating whether special growth genes could be switched on by higher temperatures. But ultimately, she admitted that for the time being, “We don’t really know” what causes the increased growth.