By Jaime González
Experts warn that it is still too early to draw conclusions about what could have caused the death of these apparently healthy cetaceans, although there is a suspect. It is a huge bloom of algae from the Pseudo-nitzschia family, which for a few months has been affecting the waters of the west coast of North America, from southern California to Alaska.
This seaweed tide, the largest of its kind ever recorded, is accompanied by a high concentration of domoic acid, a neurotoxin that is wreaking havoc on the region's fauna. Domoic acid accumulates in sardines, anchovies, and other small fish that feed on algae, as well as in mollusks.
This makes the mammals and birds that eat these fish sick due to the toxin, which can also affect humans who eat contaminated mollusks, producing "amnesic shellfish poisoning", which in the most severe cases can lead to cause permanent brain damage and even death.
In recent months there has been a high mortality of sea lions and certain species of birds, so it is not ruled out that domoic acid may have had something to do with the death of the whales found in Alaska.
The high concentration of this toxin in waters of the states of Washington and Oregon caused the authorities to order the paralysis of the activities of the seafood industry, causing millions in losses.
A mystery As in other regions of the planet, the blooms of unicellular algae such as Pseudo-nitzschia are not unusual on the west coast of North America, although the one registered since last May has surprised scientists by its magnitude and duration in the weather.
"It is the largest algae tide that we have seen since we began to take samples in the ocean in 1991. It has never been as large or toxic as this one," explains Vera Trainer, an expert from the National Oceanic Administration and Atmospheric United States (NOAA).
"It is made up of microscopic organisms that can form large chains of 20 and 30 cells. When there are more than a million cells per liter is when the water changes color," says Trainer. According to the NOAA expert, "this is a natural phenomenon that is usually beneficial, since algae produce 50% of our planet's oxygen."
"The problem with Pseudo-nitzschia is that it can produce domoic acid, which is not only harmful to animals but also to humans." According to Trainer, the current bloom may be related "to the unusually high temperatures that have been recorded on the Pacific coast of North America in recent months." It is what scientists have dubbed "the blob" (The Blob, in English).
NOAA experts have been sampling the ocean for months to follow the evolution of algae. It is a huge mass of hot water about 1,600 kilometers long and about 90 meters deep that extends along the coast, from Alaska to Mexico and whose temperature in some places is about 2.7 ºC higher than the average. Scientists believe that the hot water spot could be the result of an unusual high-pressure system that was installed in late 2013 in the northeast Pacific, calming ocean waters and causing them not to cool in winter as usual.
This system would also be the cause of the lack of rainfall that has been registered in the last two years in the southwestern United States and of the harsh winters that have been experienced in the northeast of the country.
As Nicholas Bond, a researcher at the Joint Institute for the Study of the Atmosphere and Ocean at the University of Washington (JISAO, for its acronym in English) explained to BBC Mundo, "this hot water has had a great impact on marine ecosystems. from the ocean. "
"It is a major problem for the food chain on which many animals depend," said the expert. NOAA's Vera Trainer believes that the hot water spot along with the presence of "some types of nutrients" could be behind the algae surge that affects the Pacific coast of North America.
They are like the plants of a garden, that when the good weather arrives and the heat they grow faster, it aims. Some scientists believe that increased fertilizer use in near-shore agricultural areas could be playing an important role in the current bloom, although Trainer rules this out in the case, for example, of Washington state, where algae have appeared "in pristine waters."
The NOAA expert thinks the toxic algae tide is likely to continue to affect the region until the start of winter storms starting in October, which could help dissipate. In any case, the experts point out that given the increase in the temperature of the ocean waters that is being registered at a global level, episodes such as that of the North American Pacific coast can become commonplace, with dire consequences for marine fauna and flora .