Patterns and Variability of Water Properties in 2003 in the ECOHAB PNW Region

Barbara M. Hickey¹, William Cochlan², Vera L. Trainer³, Nancy Kachel¹, Susan Geier¹, Amy MacFadyen¹ and Nicolaus Adams³

1 School of Oceanography, University of Washington, Box 355351, Seattle, WA 98195, USA
EMAIL: bhickey@u.washington.edu
2 Romberg Tiburon Center for Environmental Science, San Francisco State University, Tiburon, CA 94920, USA
3 Northwest Fisheries Science Center, Marine Biotoxin Program, Seattle, WA 98112, USA

Time series of domoic acid in razor clams on Washington beaches are consistent with intermittent toxic events that primarily follow storms and onshore transport over the shelf. A new program, ECOHAB Pacific Northwest (PNW), has begun to address the origin of these events by studying the physiology, toxicology, ecology and oceanography of toxic Pseudo-nitzschia species off the Pacific coast of Washington (WA) and British Columbia. Over the course of five years we expect to determine the physical/biological/chemical factors that appear to make the Juan de Fuca eddy region more viable for growth and sustenance of toxic Pseudo-nitzschia than the nearshore WA upwelling zone; to determine the combination of environmental factors that regulate the production, accumulation, and/or release of domoic acid (DA) from Pseudo-nitzschia cells in the field; and to determine possible transport pathways between DA initiation sites and shellfish beds on the nearby coast. June and September cruises took place in 2003. On each cruise, the strategy was to interperse large scale surveys of water properties, including nutrients, fluorescence, species and particulate domoic acid, with laboratory studies following water masses from the eddy and also from the coastal upwelling region.
During the June cruise, the Juan de Fuca eddy was persistent throughout the cruise, although its location changed with time. The robust nature of the eddy and of the coastal front was confirmed with surface drifters, whose tracks were very similar to those released much later in the upwelling season and in different years. The transport pathway from the eddy region to the inner shelf and to the shelf from Washington and even to California was confirmed by surface drifters deployed in June in the eddy and even in the strait—those drifters escaped the eddy and traveled south southeast at speeds of 15-20 miles per day. However, during a downwelling event drifters in the water at that time moved onshore toward the WA coast, with one drifter moving to within 7 miles of the beach. It then traveled north about 20 miles before turning south again after upwelling resumed. Surface fluorescence and satellite imagery during upwelling showed two regions of high values—one southeast of Barkley Sound, the other, adjacent to the Washington coast in the upwelling zone. A region of lower fluorescence emanated from the strait appearing to “wrap around” higher chlorophyll water. Macro nutrients were as high at the mouth of the strait as in the upwelling region near the WA coast. These and other property patterns from both cruises will be discussed in terms of the physical forcing. Seasonal changes in water property structure as deduced from moored sensors in the eddy, in the strait and off the WA coast will also be discussed.