Aquatic Ecosystems and Fisheries: Current Research

Climate Impacts on Harmful Algal Blooms in the PNW


  • Nate Mantua UW Climate Impacts Group
  • Stephanie Moore NOAA Northwest Fisheries
  • Summary

    Paralytic shellfish toxins are produced by the harmful dinoflagellate species Alexandrium catenella and accumulate in filter feeding shellfish. Exceptionally toxic events have previously been attributed to large-scale patterns of climate variability, such as El Niño events.

    This objectives of this project are to:

    1. evaluate the role that climate and oceanographic variability plays in the frequency and distribution of Harmful Algae Blooms in Puget Sound;
    2. quantify the degree to which environmental monitoring and/or prediction can be used to skillfully predict the risks for HAB events to contaminate shellfish in Puget Sound; and
    3. quantify the temporal and spatial patterns of variability in Puget Sound oceanographic properties.

    The results of this research will provide quantitative assessments for the role that local to large scale climate variations play in the frequency and distribution of HAB events in Puget Sound. Our quantitative analysis found that a combination of high frequency “weather” conditions precede events of shellfish toxicity. Annual time periods when this combination of weather conditions occur are termed “Harmful Algal Bloom Windows Of Opportunity”, or HAB-WOOs. A sensitivity analysis of environmental precursors that comprise the HAB-WOO was conducted to contribute towards an assessment of the capacity for prediction of paralytic shellfish poisoning risk in Puget Sound. The development of risk assessment tools has potential decision-making applications for Washington’s Department of Health and the Puget Sound shellfish industry.

    A preliminary assessment of long-term trends in the width of the annual HAB-WOO from 1967 to 2007 discovered a substantial step increase in the late 1970s, coincident with the appearance of the toxins in Puget Sound and a shift in the Pacific Decadal Oscillation from cool to warm phase. Furthermore, the width of the annual HAB-WOO continued to increase, as did the frequency and geographic extent of toxic events in Puget Sound. Presently, funding is being requested from NSF to continue this research into the long-term trends of the annual HAB-WOO. The specific aims of this new proposal are to

    1. determine if the width of the annual HAB-WOO is related to natural climate variations (i.e., the Pacific Decadal Oscillation and El Niño Southern Oscillation) and/or anthropogenic climate change,
    2. identify which of the environmental precursors comprising the HAB-WOO are driving the observed long-term changes, and
    3. assess the potential impacts of anthropogenic climate change on the width of the annual HAB-WOO through until the late 21st century using regionally downscaled projections of climate change scenarios from the Intergovernmental Panel for Climate Change.

    Understanding these relationships and interactions is crucial for the development of effective management and mitigation of the impacts of toxic HABs on marine resources in a changing climate.


    NOAA Fisheries Northwest Fisheries Science Center’s West Coast Center for Oceans and Human Health

    Primary Funding

    NOAA Climate Dynamics/Experimental Prediction (CDEP) program

    Related Publications

    For more publications on CIG's research on climate and PNW aquatic ecosystems, please see CIG Publications.

    Moore, S.K., N.J. Mantua, J.P. Kellogg, and J.A. Newton. 2008. Local and large-scale climate forcing of Puget Sound oceanographic properties on seasonal to interdecadal timescales. Limnology and Oceanography 53(5): 1746-1758.

    Moore, S.K., N.J. Mantua, J.A. Newton, M. Kawase, M.J. Warner, and J.P. Kellogg. 2008. A descriptive analysis of temporal and spatial patterns of variability in Puget Sound oceanographic properties. Estuarine, Coastal and Shelf Science doi:10.1016/j.ecss.2008.09.016.

    Moore, S.K., N.J. Mantua, B.M. Hickey, and V.L. Trainer. 2008. Recent trends in paralytic shellfish toxins in Puget Sound, relationships to climate, and capacity for prediction of toxic events. Harmful Algae, doi:10.1016/j.hal.2008.10.003.

    Moore, S.K., V. L. Trainer, N. J. Mantua, M. S. Parker, E A Laws, L C Backer and L E Fleming. 2008. Impacts of climate variability and future climate change on harmful algal blooms and human health. Environmental Health, 7(Suppl 2): S4, doi:10.1186/1476-069x-7-S2-S4.