Warmer ocean waters can hurt dolphin populations, lowering reproduction and survival rates, a new study published in the journal Current Biology found.
Researchers studied dolphin populations in Western Australia’s Shark Bay during and after a 2011 heat wave, according to the study abstract, and found the spike in water temperatures had effects on Indo-Pacific bottlenose dolphins for years.
“One of many challenges in the conservation of biodiversity is the recent trend in the frequency and intensity of extreme climatic events,” the study’s authors wrote.
“The Shark Bay World Heritage Area, Western Australia, endured an unprecedented marine heatwave in 2011,” the study’s authors wrote. The heatwave led to “catastrophic losses of habitat-forming seagrass meadows” that, in turn, led to mass fish kills. For dolphins, reproduction rates dropped along with survival rates, according to the study.
“The extent of the negative influence of the heatwave surprised us,” study author Sonja Wild said, according to Science Daily. “It is particularly unusual that the reproductive success of females appears to have not returned to normal levels, even after six years.”
“Dolphins may be in serious trouble as temperatures rise with global warming,” CNN reported.
“Survival and reproduction are important parameters that inform us about the health of a population,” study author Michael Krützen, from the University of Zurich, told CNN. “It seems that extreme weather events appear to threaten marine mammal populations in their existence. If we want to conserve these populations, we have to think how the frequency of such events can be kept at a minimum.”
The rising water temperatures in the bay did not hurt all dolphin species, the study found.
“Dolphins that use sponges as tools – a socially learned foraging technique that helps dolphins to locate food in deep water – were not as badly affected as those that do not use this technique,” according to Science Daily.
“Nevertheless, our work raises concerns that such sudden events might have quite negative long-term effects even in groups of marine mammals that are known to adapt usually well to novel environmental conditions,” Wild said, Science Daily reports.