Toxins produced by harmful algal blooms are showing up in Alaska marine mammals as far north as the Arctic Ocean -- much farther north than ever reported previously, new study published Thursday finds.

The study, by scientists at the National Oceanic and Atmospheric Administration, the Alaska Department of Fish and Game and other organizations, details findings from a decade's worth of sampling of 13 marine mammal species in Alaska.

The study was published online in the journal Harmful Algae, and is the first-ever documentation of algae-related toxins in marine mammals north of the Arctic Circle, said co-author Frances Gulland of the Marine Mammal Center in California.

"This is really the first time that the levels are appearing in Arctic animals," said Gulland, who was in Anchorage Thursday for a meeting of the U.S. Marine Mammal Commission, on which she serves.

The animals tested included whales, walruses, seals, sea lions, porpoises and sea otters, most of which were tested after they were harvested by hunters or turned up stranded on a beach.

In all, 905 marine mammals collected between 2004 and 2013 were tested for two types of toxins produced by algae -- domoic acid and saxitoxin. Domoic acid has been tied to past die-offs of marine animals, such as sea lions and whales, at latitudes farther south. It was found among all 13 species tested, with the greatest prevalence among bowhead whales and harbor seals. Saxitoxin, a compound associated with paralytic shellfish poisoning, was found in 10 of the species.

Concentrations of the toxins that were discovered in the animals were well below limits set in seafood-safety regulations, NOAA Fisheries said in a statement.

Harmful algal blooms are commonly associated with warm waters. While the study did not specifically pin the blame for their presence on the heated-up waters around Alaska, it warned that more harmful algal blooms -- and more toxins -- can be expected given "the current trend of decreasing sea ice and warming ocean waters."

Alaska ocean waters have warmed considerably in recent years, and temperatures in the eastern Bering Sea shelf rose by 3 degrees Celsius over the past decade, the study notes.

The findings showed just the first signs of ingestion of algal toxins. The toxins were found in the things the mammals ate and, in some cases, excreted -- in contents of intestinal systems, in feces, urine, serum, milk or amniotic fluid.

The discoveries show the need for more work, Gulland said.

"It's kind of the trigger that we really need to step up the surveillance and monitoring," she said.

Researchers still don't know whether the toxins had collected in the animals' muscle tissue or if the toxins had any ill effects on the animals.

Domoic acid in particular is a leading suspect in last summer's deaths of about 30 large whales in the Gulf of Alaska, which grew significantly warmer in recent years thanks to a mass of stationary water nicknamed "the Blob."

But domoic acid is water-soluble, so it doesn't last long in body tissue, making it difficult to find in the muscle of marine animals, Gulland said. And many of the whales that died last summer in the Gulf of Alaska weren't tested because most were floating in remote locations.

Among the 905 animals evaluated in the study, 46 were found to have both types of toxins in their systems. Domoic acid was also was found in fetuses of three animals: a beluga whale, a harbor porpoise and a Steller sea lion.

Pacific walrus showed the highest concentrations of both toxins, with levels of domoic acid similar to those found in California sea lions afflicted by toxin-related seizures, the study found.