Harmful Algal Blooms

An aerial photo of the ocean shows patches of yellowish-green colored algae on the surface of the water.
Photo: NOAA

Harmful algal blooms (HABs) are blooms of marine algae that produce toxins that can harm people, fish, shellfish, marine mammals, and birds. HABs of greatest importance in the Pacific Northwest stem primarily from two sources: neurotoxins produced by dinoflagellates in the genus Alexandrium, which cause paralytic shellfish poisoning (PSP), and domoic acid, a neurotoxin produced by diatoms in the genus Pseudo-nitzschia. HABs have been identified as a concern for the Olympic Coast since the early 2000s, prompting significant investments by NOAA, the state of Washington, Coastal Treaty Tribes, and the development of partnerships like the Olympic Region Harmful Algal Bloom (ORHAB) program. Climate change is expected to increase the frequency of HABs due to the prevalence of warmer sea surface temperatures, which may intensify negative impacts to coastal communities through repeated and lengthy closure of fishery resources critical to commercial, recreational, and subsistence harvests.