Marine heatwaves could wipe out all common starfish by 2100

Ocean warming simulations show that future marine heatwaves that last more than 13 days will kill every common starfish in the world.

By the end of the century, increasingly hot and prolonged marine heatwaves could kill all common starfish. The extinction of this key ocean predator could lead to cascading ecological consequences, including an oversupply of their main prey, the mussel.

Fabian Wolff of the GEOMAR Helmholtz Ocean Research Center in Kiel in Germany and colleagues tested how these orange Atlantic starfish or “starfish” (Asterias Rubens) will occur during sea heats—short periods when the ocean becomes unusually warm, usually due to pockets of hot air overhead.

Using 10 large tub-sized seawater tanks, the team subjected 60 starfish to five temperature scenarios: current average temperatures in the starfish’s range, hypothetical conditions without marine heatwaves, and temperatures expected in marine heatwaves by the end of the century. under three warming scenarios. The coldest conditions included the absence of heatwaves as a baseline – a stable temperature of 18.4 °C (65 °F), while the hottest peaks were 26.4 °C (79 °F), the temperature, according to researchers, is possible, given the scenario of the most extreme warming. .

They maintained a stable heat wave for 13 days, a predicted duration of a severe sea heat by 2100, followed by several days of cold, low oxygen water that simulated the rise of deeper waters that often follows coastal heatwaves. During the two-month study, the researchers fed starfish blue mussels and measured their size and weight regularly. They also recorded the time it took for each starfish to straighten up after being turned on its back, which is critical for nutrition.

In the strongest warming scenario, 100 percent of the starfish died before the end of the 13-day heat wave. In all three future warming scenarios, starfish ate less mussels, although the animals in the absence of extreme heat and in the current conditions maintained a healthy appetite and weight. The starfish in the two warmest scenarios took the longest to recover after being capsized. “The longer the heat wave lasted, the stronger the effect became,” says Wolf.

The starfish used in the study were collected off the coast of Germany, so it’s possible that some of the species from warmer parts of the Atlantic may have higher heat tolerance, says Lloyd Peck of the British Antarctic Survey, who was not involved. at work.

Surprisingly, starfish that survived the heat waves in each scenario were more likely to survive the subsequent cold water shock, simulating upwelling that can stress animals by depleting their oxygen. “We thought that there would be an accumulation of stress, but in fact it was the other way around,” Wolf says.

He doesn’t yet know the mechanism behind this ability, but he suspects that animals that survive at elevated temperatures have higher expression of so-called heat shock proteins, which help protect existing proteins from stress-induced damage.