The first of several dead fin whales, later named FW01, floats outside Marmot Bay on May 23. (MV Kennicott crew courtesy NOAA)

Alaskan researchers report that at least nine fin whales have been found dead in the water in recent weeks. It's rare for more than one such death to be discovered every year or so, they say, and they're exhaustively searching for a possible cause. It's possible that warming ocean temperatures could be partially to blame.

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Fin whales, the second-largest species of whale, are endangered. But their population is thought strong enough to handle the relatively small number of deaths reported. What's more troubling is that the cause remains unknown, meaning that more of the whales could be at risk of meeting the same fate.

The first dead whale was reported on May 23, with other boaters and pilots reporting additional finds over the next two weeks. Given the reports and photo evidence, researchers at the University of Alaska Fairbanks and the National Oceanic and Atmospheric Administration (NOAA) have put the death toll at nine, and say the carcasses were all spotted within a fairly small area.

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In examining one of the casualties -- a whale that washed up onto shore -- UAF marine mammal specialists found no sign of injuries. In fact, the whale had a healthy layer of blubber, indicating that it wasn't malnourished when it died.

“It was a really healthy animal; there weren’t any obvious signs of cause of death,” researcher Bree Witteveen told the Alaska News Dispatch.

Researchers are also investigating the death of some 25 walruses and an unusual number of seabirds within a few hundred miles of the fin whale carcasses. It's not clear if the unexpected deaths are related.

Hopefully no more whales will join this cluster, and in that case scientists may never be totally sure what happened. But for now, the prime suspect is an algae bloom.

Water surface temperatures are around 0.9 to 3.6 degrees above average, Alaska News Dispatch reports. When waters are warm, the wrong species of algae can thrive in oceans, leading to sudden "blooms" of toxic species that take over. Fin whales don't eat algae, but they do filter and eat tiny marine creatures like krill. That keeps the whales very close to the toxic algae on the food chain, leaving them susceptible to quick poisonings. It's unusual, however, that large die-offs haven't been observed in the whales' prey yet.

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Thousands of miles away, another group of endangered whales may also be suffering from poisoned algal bloom. Just weeks ago, Chilean researchers theorized that as many as 30 sei whales had been killed by food poisoning of this nature.

And days ago, NOAA representatives announced that the largest West Coast toxic algae bloom in over a decade was closing fisheries from California to Washington.

The Alaskan researchers will soon take to the skies to look for more carcasses -- or signs of a toxic algal bloom.

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