Seminar Abstract

Stephanie Moore and Nate Mantua

Thursday, April 19, 2007

Climate impacts on Puget Sound oceanography and harmful algal blooms

Stephanie K. Moore(1), Nathan J. Mantua(2), Vera L. Trainer(3), and Barbara M. Hickey(1)

Climate impacts on Puget Sound oceanographic properties are investigated on seasonal to interannual timescales using continuous profile data from the Washington State Department of Ecology's Marine Waters Monitoring Program from 1993 to 2002. Principle component analysis identified indices representing 42, 58 and 56% of the total variability at depth-station combinations for temperature, salinity and density, respectively, and 22% for water column stratification. Long term records of sea surface temperature and salinity from a single location (Race Rocks) extend the time series of the leading principal components to 1950 and allow an examination of climate impacts on decadal timescales. In general, regional climate forcings strongly influence oceanographic properties with significant relationships between air and water temperature, and between streamflow, salinity and density. Large scale patterns of climate variability, such as El Niño/Southern Oscillation and Pacific Decadal Oscillation, also significantly influence oceanographic properties but relationships are less pronounced and exist only during winter and fall. Patterns of ocean-climate variability are compared with indices describing paralytic shellfish toxin (PST) concentrations in shellfish determined by the Washington Department of Health Marine Biotoxin Program. PSTs are produced by the harmful dinoflagellate species Alexandrium catenella and can be used as a proxy for blooms. Exceptionally toxic events are preceded by low streamflow, weak winds and small tidal variability. This combination of environmental conditions typically occurs in early fall following seasonal warming of surface layer temperatures. On decadal timescales, toxicity covaries with warm phases of the Pacific Decadal Oscillation and the window of optimal growth conditions for A. catenella as determined by sea surface temperatures warmer than 13°C. This study demonstrates the linkages between climate, oceanography and the frequency, duration and magnitude of harmful algal blooms. Results will be used to develop PST risk forecasts and to evaluate the potential influence of global warming on the occurrence of future toxic events in Puget Sound.

(1) School of Oceanography, University of Washington, Box 355351, Seattle WA 98195-5351 , United States. E-mail:
(2) Climate Impacts Group and School of Aquatic and Fishery Sciences, University of Washington, Box 354235, Seattle WA 98195-4235, United States.
(3) NOAA Fisheries Marine Biotoxins Program, Northwest Fisheries Science Center, 2725 Montlake Blvd. E., Seattle WA 98112-2013, United States.

Speaker bio:

Dr. Stephanie Moore is a research associate with the University of Washington's School of Oceanography and Climate Impacts Group. Currently she is investigating the role of climate variability on harmful algal blooms in Puget Sound. Broader research interests include temporal and spatial variability and physical-biological interactions of plankton, and nutrient enrichment and limitation in coastal systems. Stephanie obtained her PhD from the University of New South Wales, Australia, where she researched tracers and indicators of anthropogenic nutrient enrichment in subtropical east Australian estuaries. She has worked with local government in Australia to develop and prepare the Estuarine Management Plan for Wallis Lake, the largest commercial oyster producing area and largest area of seagrass habitat on the New South Wales coast.

Dr. Nate Mantua is Associate Director for the Center for Science in the Earth System, a Principal of the Climate Impacts Group, Assistant Professor at the UW Department of Atmospheric Sciences, and Research Associate Professor at the UW School of Aquatic and Fishery Sciences.