Scientists warn that marine heat waves are becoming more frequent and intense, those that occur when the temperature of the surface water is above the usual average for five consecutive days. And these heat waves are dangerous to the life of the beings that inhabit the oceans , including dolphins.
One of them, which took place in early 2011 and caused the water temperature to remain more than four degrees above the annual average, has had very negative impacts on the population of dolphins in Shark Bay, in Australia, an area It covers an area of 10,000 square kilometers and was declared a World Heritage Site by UNESCO in 1991.
Researchers from the University of Zurich have detected that this Australian heat wave caused a massive loss of seagrass , essential for the ecosystem in this coastal area. They have studied how the environment and the reproduction of dolphins have been affected.
To do this, they collected data from hundreds of these animals over a period of ten years, from 2007 to 2017, and their analyzes led them to detect that the survival rate of the dolphins had been reduced by 12% after the heat wave. 2011. Likewise, female dolphins gave birth to fewer pups, a circumstance that lasted until at least 2017.
An unprecedented negative influence
According to one of the authors of the study, Sonja Wild, from the University of Leeds, “the extent of the negative influence of the heat wave” has surprised them. “It is especially unusual that the reproductive success of females has not returned to normal levels even after six years, ” he stresses.
Although there are various explanations for this phenomenon, such as the abandonment of offspring, increased mortality of newborns, delayed sexual maturity or a combination of all , researchers have not yet been able to study them in detail.
Of course, the heat wave that these Australian waters suffered did not have the same effect on all groups of dolphins . Shark Bay bottlenose dolphins that use sponges plucked from the ocean floor to protect their snouts as they stir sand from deep waters to search for food – like a fisherman wears gloves – have not been as affected as those who do not wear gloves. technique.
“However, our work raises concerns that such sudden events (such as marine heat waves) may have quite negative long-term effects even on groups of marine mammals that tend to adapt well to new environmental conditions,” says Sonja Wild. .
With this study, researchers at the University of Zurich have shown for the first time that marine heat waves not only affect the most elemental organisms in the food chain , but also have a negative and long-term impact on the life of higher animals such as the Dolphins. “These heat waves are likely to occur more frequently in the future due to climate change,” says another of the study’s authors, Michael Krützen. “This is worrying not only for the long-term prospects for marine mammal populations, but also for all ocean ecosystems,” he concludes.
