For the most part, most research have focussed on the impact of oceanic temperature changes on adult animals, but few looked at the animals' early life stages. A study by researchers from the University of California, Santa Barbara gives a useful insight into this specific area. 

Focussing on the larvae of the Kellet's whelk, a common sea snail in Southern California, it showed that rising temperatures will adversely impact the larvae. 

“While young Kellet’s whelks are able to withstand a wider range of warmer temperatures than we expected, marine heatwaves remain a threat, especially as baseline temperatures rise,” said lead author Xochitl Clare, a doctoral candidate in the Hofmann Lab in the Department of Ecology, Evolution, and Marine Biology at the university.

Research Findings

She placed test-tubes of veligers (planktonic larvae) and hatchlings in a heat block for an hour. The heat block created a temperature gradient that ran from 15 degree Celsius on one end, to 37 degrees Celsius at the other end. This set-up allowed her to find out the temperature at which death and development abnormalities began to occur.

The results of the study showed that half of the subjects perished at roughly 34 degrees Celsius. Half of the hatchlings started experiencing abnormal development at 27.6 degree Celsius, while for veligers, it occurred at 24.9 degrees Celsius. 

Nonetheless, Clare remarked that focussing on only mortality levels misses the broader picture. “We have to consider it in an ecological context, which means looking at body function and behaviour.”

“While we may not experience a 33° Celsius ocean,” she said, “we may see conditions where the larvae are not able to swim, where they’re not able to feed.”

During a marine heatwave in the northeastern Pacific that ran from 2013 to 2016 (known as the Blob), water temperatures rose high enough to disrupt the development of the whelk larvae.

Currently, the whelk snail does not support a large fishery in California. Nonetheless, Clare felt that we could not consume the same foods repeatedly and that we had to diversify our diet in order to fish sustainably.

“As ocean warming continues to threaten our local seafood, it is critical that we understand which species will be resilient and remain ‘on the menu',” she added.

The findings of the study was published in the Journal of Shellfish Research journal.