Possible algae bloom turns seawater red off Juneau

In this Tuesday, July 31, 2018 photo, are reddish-brown patches in the water of Gastineau Channel as seen from the Douglas Bridge in Juneau. Department of Fish and Game habitat biologist Kate Kanouse says the red mass has not been identified but it could be an algae bloom brought on by rising water temperatures. Kanouse says Juneau’s warm summer may be a factor and she doesn’t expect the red mass to be dangerous. (Michael Penn/The Juneau Empire via AP, File)

JUNEAU – Residents are seeing red in the waters of Gastineau Channel.

A biological mass that may be an algal bloom in the seawater off Alaska's capital city is raising concern, the Juneau Empire reported.

Eric Prestegard, executive director of Douglas Island Pink and Chum Inc., saw the red water Sunday. He said he worried because the hatchery is midway through its egg-taking process.

Dave Pikul, an environmental program specialist at the Department of Environmental Conservation, reviewed the red water last week and concluded it was not a petroleum spill.

"It was pretty widespread," Pikul said. "Our observations down at the shoreline identified it was not oil, but it was some kind of biological mass."

The overriding theory is that it's a bloom of algae brought on by rising water temperatures, said Kate Kanouse, a habitat biologist for the Department of Fish & Game.

"We've had a nice warm summer, and it fits the criteria of what we would see of an algal bloom," Kanouse said. "I wouldn't expect it to be anything else, and I don't expect it to be dangerous."

Algae blooms can be harmful, but some are not. Vera Trainer, a research oceanographer with Northwest Fisheries Science Center, said blooms can deplete oxygen in the water and kill small fish. Harmful effects on shellfish are more common, she said.

"The most common in Alaska that are known of right now are the paralytic shellfish poisoning events that are resulting in accumulation of toxins in shellfish that can then be dangerous to humans," Trainer said.

Algae blooms in Alaska are old news, Trainer said. Aleuts have known about toxic shellfish for generations. People should pay attention to health authority websites and announcements about shellfish, she said.

Prestegard said he could not remember when algae or phytoplankton were this widespread, even in the hot summer of 2004. He has not detected effects at the hatchery but is concerned about the facility's aquariums.

Blooms likely will become more and more common in Alaska as ocean temperatures continue to rise, Trainer said. As ice melts, she said, sunlight will penetrate the water more easily and promote more growth among plant life such as algae.