Algal bloom not harmful, tapering off, say experts

A huge algal bloom present in the Pacific Ocean from Monterey Bay, Calif., to Alaska has been seen in Kachemak Bay, but so far has not been in large enough concentrations to cause problems here. Known sometimes as a red tide, the bloom of a plant, or phyto, plankton called pseudo-nitzschia closed razor clamming and shellfish harvesting in areas off the Oregon and Washington coast. Of concern is a chemical given off by the plankton, domoic acid.

In Kachemak Bay, no domoic acid has been seen in shellfish samples, and pseudo-nitzschia plankton counts have dropped from a high of 2.5 million cells per liter in late May to 96,000 cells per liter.

“From most recent samples, it looks like the algal bloom has begun to taper off a bit. To date we have no indication it’s toxic,” said Jessica Ryan-Shepherd, acting director for the Kachemak Bay Research Reserve.

Observations taken in Kachemak Bay since late May by scientists with the Kachemak Bay Research Reserve, or KBRR, and the National Oceanic and Atmospheric Administration Kasitsna Bay Laboratory show higher-than-normal concentrations of pseudo-nitzschia in China Poot Bay, the Homer Harbor, Tutka Bay, Peterson Bay, Jakolof Bay and Sadie Cove. The blooms put scientists on alert, said Kris Holderied, director of the Kasitsna Bay Lab.

“It means keep an eye on it. You know it’s out there,” she said.

Domoic acid measurements done by the NOAA Charleston, S.C., lab show counts of 235 nanograms per liter, way below the 30,000 ng/l counts seen in Monterey Bay, Calif.

Tests done on blue mussels in Jakolof Bay, Sadie Cove and China Poot Bay show negative for domoic acid. That’s significant.

“They sample the phytoplankton for you,” Holderied said of the mussels. “They’ve done it over time.”

Through cooperation with private scientific test manufacturers and NOAA, cheap, rapid-response kits that test for harmful chemicals like domoic acid have been developed. Kachemak Bay oyster farmers have been using the test kits in cooperation with NOAA and KBRR.

KBRR has been doing weekly plankton tows, where samples are taken by dragging small nets. In a report by Syverine Abrahamson of KBRR, she wrote that plankton samples have been quite thick and also contain a mix of copepods, another phytoplankton called rhizosolenia and jelly fish. Copepods are food for fish like salmon. NOAA biologist Dominic Hondolero has been counting cells sampled.

Another NOAA biologist, Amy Holman, is currently out on the NOAA ship Fairweather on a trip to Dutch Harbor. As part of her trip, she has been doing plankton tows to assess the northern spread of the algal bloom. 

“Think of it as a kind of detection network. Do any of these bad actors start creeping up and do we have a bloom?” Holderied said.

Warm ocean temperatures have an effect on algal blooms and might be contributing to the latest harmful algal bloom. “The blob,” a huge patch of warm water in the Pacific Ocean from California to Alaska, may be causing the latest blooms. Scientists also have seen sea lion pups and murres that appear emaciated and starved.

Kachemak Bay is the only Alaska coastal area being monitored for harmful algal blooms, so it’s unknown where else in Alaska blooms might occur.

“Kachemak Bay, we do more,” Holderied said. “We just do stuff that’s not done elsewhere.”

Testing will be done throughout the summer, with reports issued every two weeks. 

Michael Armstrong can be reached at michael.armstrong@homernews.com.

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