Sea heat waves 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.

Increasingly hotter and longer marine heatwaves could kill all common starfish by the end of the century. 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 Helmholtz Center for Ocean Research GEOMAR in Germany and colleagues tested how these orange Atlantic starfish or “starfish” (Asterias Rubens (ur. will be true during marine heatwaves – short periods when the ocean becomes unusually warm, usually due to pockets of hot air overhead.

Using ten tanks of sea water the size of a large bathtub, the team subjected 60 starfish to five temperature scenarios: current average temperatures in the starfish habitat, 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 heat waves as a baseline and a stable temperature of 18.4 °C (65 °F), while the hottest peaks were 26.4 °C (79 °F), which, according to temperature researchers, perhaps given the most extreme warming scenario.

They maintained a stable heat for 13 days, the predicted duration of strong offshore heatwaves by 2100, followed by several days of low-oxygen cold water that simulated the rise of deeper waters that often follows coastal heatwaves. Over the course of a two-month study, the researchers fed starfish blue mussels and regularly measured their size and weight. They also recorded the time it took for each starfish to straighten up after being flipped 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 heatwave. In three future warming scenarios, starfish ate fewer mussels, although the animals in the absence of abnormal 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 damage to the cell.