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Harmless orange tide returns to harbor

Near Nichols Brothers Boat Builders in Holmes Harbor, an orange sheen can be seen on the water. The algae bloom is not known by the county to be dangerous to shellfish and those who eat them. - Jennifer Conway
Near Nichols Brothers Boat Builders in Holmes Harbor, an orange sheen can be seen on the water. The algae bloom is not known by the county to be dangerous to shellfish and those who eat them.
— image credit: Jennifer Conway

An annual orange algae bloom in Holmes Harbor caught the eye of many last weekend.

Kathleen Parvin, an environmental health specialist for the Island County Health Department, said the orange bloom is composed of the species dinoflagellate, a single-celled algae common in Holmes Harbor and Penn Cove. The reddish-orange water is a bloom of non-toxic algae variety noctiluca scintillans, also known as seasparkle. The Noctiluca glows phosphorescent on the water at night.

Parvin said it is likely some islanders might assume that the bloom is “red tide,” also known as paralytic shellfish poisoning (PSP). Noctiluca is not toxic, Parvin said, but noctiluca and the red blooms that carry PSP can occur at the same time. Parvin said shellfish harvesters should use caution when harvesting during an algae bloom.

The orange tide is prompted by warming weather and the salinity of the water. The algae — which can also bloom green or brown — is always present in the water, typically blooming twice a year.

“We usually see it in May and September,” Parvin said. “The spores are always there, when conditions are right it blooms.”

The bloom brought murky water and a distinctive fishy smell with it. The algae spores are gelatinous kernels which can accumulate up to 18 inches deep, making the water appear thick, like tomato soup.

Before harvesting shellfish, Parvin said, harvesters should check the Washington state Marine Toxin Hotline to determine whether shellfish are safe to eat. Parvin also noted water color is not an indicator of whether shellfish are safe to eat.

PSP can accumulate into unsafe levels in clams, mussels, oysters, geoduck and scallops, and can cause serious illness in those who eat them. A crab’s meat is considered edible during a PSP outbreak.

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