What Was Behind the Mysterious Whale Deaths on the Pacific Coast in 2015?

Since May, more than 30 whales have been found dead on the pacific coast without explanation.

11 fin whales, 14 humpbacks, one gray whale and four unidentified cetaceans were found dead in the western gulf of Alaska. Six more whales were found dead off the coast of British Columbia including four humpbacks, one sperm and one fin whale.

The unknown cause behind the deaths prompted the U.S. National Oceanic and Atmospheric Administration (NOAA) to declare it an “Unusual Mortality Event” last month. But after investigation, scientists think a widespread algae bloom located off the coast could be suspect in the deaths. NOAA spokesperson Julie Speegle told the Guardian:

“Our leading theory at this point is that the harmful algal bloom has contributed to the deaths. But we have no conclusive evidence. The bottom line is we don’t know what’s causing these deaths.”

Scientists have already been monitoring a large stretch of warm water that started out off the coast of Alaska two years ago and has grown to almost 500 miles across. “The Blob,” as it has been named, is several degrees warmer than the surrounding ocean and has caused a record algae bloom spanning the West Coast from Alaska to California.

Photo by NOAA

However, the fast rate of decomposition makes it nearly impossible to sample the dead whales, meaning there may never be a definitive conclusion. Scientists do know of one species of phytoplankton that produces a neurotoxin, which enters the food chain in smaller fish and birds, can cause disorientation and fatal seizures in severe cases.

Although the death count is almost three times the historic average annual mortality rate, whale populations are not overly affected. Marine mammal specialist with the Alaska Sea Grant marine advisory program and on-site coordinator of the UME investigation Bree Witteveen tells Yahoo Canada News:

“From a population perspective, the level of deaths that we’ve seen are not likely to have much of an impact. It’s more of a warning sign.”

Featured image by Sarah Nichols / CC BY-SA 2.0