Fish that live on or near the seafloor -known as demersal or groundfish- barely feel the impact of marine heatwaves, according to new research that highlights the need to keep seas from warming further.

In a new paper published in Nature, an international team of researchers assessed the impacts, on groundfish, of 248 sea-bottom marine heatwaves, defined as periods of at least five days with sea-bottom temperature anomalies that are well above the level expected for the season. They found that although declines in biomass did occur in some instances after short-term heat events, these were the exception and not the rule — which raises questions about the causes of this variability and demonstrates that oceans have some resilience left if we can keep to 2019 temperatures.

“There is an emerging sense that the oceans do have some resilience, and while they are changing in response to global warming, we don’t see evidence that marine heatwaves are wiping out fisheries. However, climate change-driven marine heatwaves have been previously associated with coral bleaching, species displacement and/or population changes in the affected habitat,” said Alexa Fredston, a researcher at the University of California, Santa Cruz and lead author of the study. “The extent to which marine heatwaves in general have negative ecological impacts, or whether they can be distinguished from natural and sampling variability in marine systems, remains unclear.”

Fredston and her colleagues focused on heatwaves registered between 1993 and 2019 in Northern Hemisphere shelf ecosystems in climates that range from the sub-tropics to the Arctic. Over 22 million observations were made during the study period from more than 82,000 separate hauls that comprised 1,769 demersal fish species.

These were collected from 18 long-term scientific trawl surveys covering 45 degrees of latitude in the northwest and northeast Atlantic Ocean, and the northeast Pacific Ocean.

Further information can be read here and the full paper in Nature can be found here.