Scientists tasked with figuring out what killed dozens of whales found dead along the Pacific Coast are looking closely at whether there may be a link to a massive algae bloom off the coast.
Thirty whales have been found dead in the western Gulf of Alaska since the spring, prompting the U.S. National Oceanic and Atmospheric Administration (NOAA) to declare an “Unusual Mortality Event” last month.
Six more whales have been found dead off the coast of British Columbia.
The team of American scientists investigating the deaths held a teleconference this week.
“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,” Bree Witteveen, a marine mammal specialist with the Alaska Sea Grant marine advisory program and on-site co-ordinator of the UME investigation, tells Yahoo Canada News.
“Having this big, charismatic animal die in such large numbers is something we need to take seriously because it’s, in my mind, signifying something else is happening.”
Since May, 14 fin whales, 11 humpback whales, one gray whale and four unidentified whales have been found in the western Gulf of Alaska. The average annual mortality rate is eight.
In B.C., four humpbacks, one sperm and one fin whale were found dead in August, Paul Cottrell, Pacific Marine Mammal co-ordinator for the federal Department of Fisheries and Oceans, told reporters when NOAA declared the event a couple of weeks ago. All were found along the north and central coast.
Two of the humpbacks were fairly recently dead and researchers were able to perform necropsies.
Andrew Trites, director of the marine mammal research unit at the University of British Columbia, says those humpback deaths remained unexplained.
“There was no obvious sign of death for what appeared to be two healthy whales,” Trites tells Yahoo Canada News. And “it does coincide with the time of the unexplained deaths in Alaska” suggesting there may be a link.
Scientists were already monitoring a large expanse of warm water that began as a patch of water off the coast of Alaska two years ago. It has now grown to a circular patch about 800 kilometres across.
“The Blob,” as its been dubbed, is several degrees warmer than the surrounding ocean and has been blamed for a record algae bloom stretching down the West Coast from Alaska to California.
“The most likely explanation would be food poisoning and it would be related to this blob of warm water and the large algae bloom,” Trites says.
The state of decomposition poses a challenge for the scientists on both sides of the border, making it impossible to obtain some samples.
That means scientists may not be able to make a definitive link, Trites says.
But one species of phytoplankton can produce a neurotoxin that enters the food chain in smaller fish and bird species, he says.
“It causes animals to become disoriented and in the most severe cases, it can cause seizures that kill the animal,” he says.
Overall, whale populations off the B.C. coast are recovering, Trites says, but the algae bloom and the whale deaths are worrying signs of a changing ocean.
“There is a good chance that the event that happened this summer is something that’s going to happen again and more frequently,” he says. “Climate change is happening.”
No more whale carcasses have been found since the UME was declared, Witteveen says, but she admits there could be more that have not been found.
“I’m pretty sure that we would miss some. As I’m sure you can imagine, the coastline of Alaska is very large and very complex. There’s a lot of this area that’s just inhabited and no one ever lays their eyes on it so it’s quite possible that we’ve missed carcasses.”
“I’m sure there are at least a few more out there.”
A biotoxin remains the leading hypothesis but there has been no determination.
“Because that bloom is off the West Coast and has been pretty prominent for the whole summer, it’s definitely something we’re looking at pretty strongly.”