This summer and fall several dead whales were spotted in the Western Gulf of Alaska, with the majority clustered around Kodiak Island. The number of deaths now stands at 43 whales, including fin whales, humpbacks, and, at least, one gray whale. So far, none of the whale carcasses that could be accessed have been in good enough shape to provide a clue to the cause of the deaths, but the National Oceanic and Atmospheric Administration (NOAA) is so concerned that they have classified the deaths an “unusual mortality event” (UME). A UME is defined as a significant die-off of a marine mammal population, and such an event demands an immediate response and triggers a focused, expert investigation into the cause.
At nearly the same time dead whales were being discovered in Alaska, whales were also dying off the coast of southern Chile. In November, biologists in Chile announced that in June, 337 sei whales were found beached in a region of southern Patagonia in Chile. This is one of the largest whale strandings ever recorded. While these whales were found beached, researchers think they died at sea and washed up on the beach.
What caused the deaths of the whales in Alaska and Chile, and did they all die from the same cause? Sadly, we may never know the answers to these questions, but biologists in both Alaska and Chile suspect a harmful algae bloom may be the culprit. Most of the dead whales are baleen whales that feed low on the food chain, making them highly susceptible to a toxic algae bloom. What makes this scenario even more believable is that abnormally warm water conditions in the Pacific Ocean this summer led to a massive toxic algae bloom of the single-celled algae Pseudo-nitzschia.
Pseudo-nitzschia produces domoic acid, a powerful neurotoxin. Under normal circumstances, a domoic acid concentration of 1,000 nanograms per liter is considered high, but in mid-May, concentrations 10 to 30 times this level were found in the North Pacific. Domoic acid accumulates in zooplankton, shellfish and fish, and when mammals and birds eat these organisms, the accumulated acid overstimulates the predator’s nervous system, causing the animal to become disoriented and lethargic. Ingestion of high concentrations of domoic acid can lead to seizures and death.
In addition to Pseudo-nitzschia, the warm-ocean-water conditions in the Pacific also may have resulted in blooms of other toxic algae, but if toxic algae are the culprit, why aren’t other mammals or birds dying as a result? These are questions researchers are scrambling to answer, and recently they have been rechecking photos to see if there is any evidence that the whales may have starved to death. Warmer ocean conditions may also have led to a reduction in the prey of these huge whales that must eat nearly continuously all summer to build a large enough blubber layer to last them through the winter.
There is no time frame for when a UME must end, and biologists plan to keep researching the whale deaths for a while longer, but they admit the cause may never be known. One dead whale washed up a few miles from where we live, but we saw many other whales this summer that seemed to be feeding and acting normally, and I hope the whale deaths were an anomaly that won’t continue next spring and summer.
Next week I’ll go into more detail about toxic algae blooms. For those of you who have read my novel, Murder Over Kodiak, you may remember that Jane Marcus was studying paralytic shellfish poisoning, a condition caused by a poisonous algae bloom, and since toxic algae have been in the news this year, I think it will be an interesting topic to tackle.
I am FINALLY ready to send my first Mystery Newsletter to those who have signed up for my list. I plan to mail it on January 6th, so if you haven’t signed up for my list yet, do so soon on my home page. My first newsletter will chronicle the events of the McCarthy massacre of 1983. Thanks, and be sure to leave a comment to let me know what you think of my post!