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Puget Sound Harmful Algal Blooms Linked to Seasonal Patterns and Survival Probability

Published on: 04/23/2015
Primary Contact(s): quay.dortch@noaa.gov

In order to predict blooms and prevent undue economic loss of commercial shellfish in Puget Sound, NCCOS has sponsored research investigating the seasonal patterns and mechanisms of bloom formation of Alexandrium, a dinoflagellate that contaminates shellfish and causes paralytic shellfish poisoning (PSP) in humans. The study shows Alexandrium survives and spreads in Puget Sound in response to both favorable temperature and light conditions and a seasonal internal biological ‘clock,’ threatening public health and economic resilience.

Cysts of Alexandrium tamarense viewed under the microscope. (Credit D. Anderson, WHOI)

Cysts of Alexandrium tamarense viewed under the microscope. Credit: D. Anderson, Woods Hole Oceanographic Institution.

Past research indicates resting stages (cysts) of the harmful alga Alexandrium germinate in deep waters like the Gulf of Maine using 11–12 month internal (endogenous) clock mechanism. In shallow waters like Puget Sound, however, past research indicates that germination is triggered more by external (exogenous) environmental rhythms such as temperature and light and suggests that Alexandrium cysts in Puget Sound do not possess an endogenous biological clock.

The NCCOS sponsored study by the NOAA National Marine Fisheries Service and the University of Washington shows germination of Alexandrium cysts within Puget Sound depend more on environmental conditions but annual endogenous rhythms (‘secondary dormancy’) plays a role. The internal secondary dormancy clock prevents cysts from germinating when conditions are environmentally unfavorable for long term survival. For example, because of similar light and water conditions in spring and fall, cysts germinating in the fall would not survive the winter.

These findings suggest a need for a deeper and more precise experimental understanding of the conditions that lead to excystment to predict blooms and prevent undue economic loss of commercial shellfish in Puget Sound. The study is published in the scientific journal Harmful Algae.

Fore more information contact Quay.Dortch@noaa.gov.

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