What changes when you warm the Antarctic Ocean just 1 degree? Lots

After warming a natural seabed in the Antarctic Ocean by just 1° or 2° Celsius, researchers observed massive impacts as growth rates nearly doubled.

The findings of what the researchers call the ‘most realistic ocean warming experiment to date’, and reported in Current Biology, show that the effects of future warming may far exceed expectations.

Warming up the sea

Predicting the response to climate change in the future remains a major challenge, so Ashton and her colleagues decided to actually warm an area of seabed around the Rothera Research Station and watch what happened.

They deployed heated settlement panels to warm a thin layer of water by 1°C or 2°C above the ambient temperature. Those increases in global temperature are expected within the next 50 and 100 years, respectively.

A 1°C rise

The experiment showed that with a 1°C increase in temperature, a single pioneer species of bryozoan (Fenestrulina rugula) took off. That one species ultimately dominated the community, driving a reduction in overall species diversity and evenness within two months.

Individuals of a marine worm, Romanchella perrieri, also grew to an average size 70% larger than those under ambient conditions, the researchers report.

‘I was quite surprised. I wasn’t expecting a significant observable difference in communities warmed by just 1°C in the Antarctic. I have spent most of my career working in temperate climates where communities experience much greater temperature fluctuations and wasn’t expecting such a response to just 1°C of change.’

British Antarctic Survey and Smithsonian Environmental Research Center

A 2°C rise

The responses of organisms to a 2°C rise in temperature were much more variable, with growth-rate responses differing among species, ages and seasons.

Species generally grew faster with warming through the Antarctic summer, though different responses among species were observed in March, when both food availability for suspension feeders and ambient temperature declined, the researchers report.

Winners and losers of warming

The researchers say the findings suggest that climate change could have even greater effects on polar marine ecosystems than had been anticipated. As the planet warms, there will be winners (like the bryozoan Fenestrulina rugula) and losers.

The researchers say they now plan to expand the use of this technology to investigate the response to warming in other locations and communities, including the Arctic.