We think we know what’s killing these baby Southern Right Whales, now

It’s CSI: Marine Mammal Edition, as an unprecedented series of deaths involving primarily young whale calves between 2005 and 2014 required scientists from the US National Oceanic and Atmospheric Association (NOAA) to get their sleuth on and investigate.

The deaths took place near Peninsula Valdes, a key calving ground for southern right whales on the coast of Argentina. During the nearly decade-long span the number of deaths spiked tenfold, from less than six per year prior to 2005 to 65 per year by 2014, the NOAA said.

Furthermore, the overwhelming majority of those deaths (90 percent) occurred in young whales less than three months old, suggesting that these relative newborns were being targeted. In some cases, more than 100 young southern right whales were lost in a single year.

Experts from NOAA Fisheries, NOAA Ocean Service, and colleagues from the US and Argentina investigated the deaths, and as they reported in a recent edition of Marine Mammal Science, they have at long last been able to pinpoint a possible culprit: toxic algae blooms similar to those that occasionally force clamming and selfish harvesting to be temporarily suspended.

Warming temperatures could ultimately make things worse

Specifically, they discovered that the frequency of the whale deaths correlated with the levels of a toxic algae known as Pseudo-nitzschia. The higher the density of Pseudo-nitzschia—some types of which can produce a powerful toxin known as domoic acid—the more young whale deaths had been reported. When the algae density decreased, so did the number of fatalities.

While this link does not definitively prove that the algae was responsible for the whale deaths, the statistics “hinge at the same point and have the same pattern.” This suggests that it likely played a role, NOAA oceanographer Cara Wilson, lead author of the new study, said in a statement. She added that it was unusual to see these events reoccur over such an extended period of time.

This discovery that this endangered whale species are vulnerable to these algal blooms could be bad news for marine mammal populations all over the world, as the researchers noted that these blooms are expected to become increasingly prevalent because of climate change. In fact, earlier this year the western US experienced large blooms due to unusually warm ocean temperatures.

“Given the lack of solid evidence,” the NOAA said, “the new study does not definitively prove that the toxic algae caused the spike in deaths of whale calves. But it does offer strong circumstantial evidence, and that puts researchers in a better position to understand the possible impacts of future algal blooms.”


Feature Image: Andrea Chirife, Southern Right Whale Health Monitoring Program