Inferences for Biological Transport: Results from a West Coast Drift Card Study Alternative Ballast Water Exchange Areas Workshop June 21, 2006 – Seattle, Washington Vanessa M. Howard & Mark Sytsma Portland State University
Outline Background Methods Results – Return rates & recovery time – Recovery patterns - spatial & seasonal Summary
Background Circulation patterns/currents (Schwartzlose 1963, Heath 1969, Dewees & Strange 1984) Situation of marine protected areas (Klinger & Ebbesmeyer 2001) Sewage outfall (Crone et al 1998, Sauers et al 2001) Floating materials – hypothetical oil spill (NOAA’s 2005 Safe Sancuary Drill in FL Keys NMS) – floating pollutants (NOAA’s Hawaii Drift Card Study) Schwartzlose
Objectives Understand potential seasonal &/or spatial patterns of ocean dispersal from three heavily infested bays Understand relative risk posed by various Spartina species Identify common debris collection zones Education & outreach Photo courtesy of NRCS
Methods – Card Design Buoyant plywood cards (10 cm x 15 cm) Biodegradable - designed to persist 3-6 months Coded for release date and location NOAA specifications (Oahu, Hawaii Drift Card Study )
Methods – Releases Three release locations September 2005 through August cards Within two hours of high tide Willapa Bay Humboldt Bay San Francisco
Results – return rates Willapa 41.8%
Results – return rates Humboldt 26.2%
Results – return rates San Francisco 43.8%
Recovery time
Results – bay vs. coast
Results – near vs. long distance
Max North ~ 2,000 km (129 days) Max South ~ 300 km (227 days) WB releases
WB releases Seasonal Patterns
Willapa: E stimated velocities mean (range) SOUTH (km/d)NORTH (km/d) Fall4.13 ( ) 2.75 ( ) Winter ( ) Spring2.58 ( ) 2.11 ( ) Summer2.88 ( ) 2.84 ( )
Max North ~ 2,800 km (214 days) Max South ~ 530 km (45 days) HB releases
HB releases Seasonal Patterns
Humboldt: E stimated velocities mean (range) SOUTH (km/d)NORTH (km/d) Fall0.48 ( ) 1.59 ( ) Winter3.41 ( ) 9.01 ( ) Spring1.29 ( ) 3.54 ( ) Summer0.80 ( ) 2.44 ( )
Max North ~ 630 km (56 days) Max South ~ 400 km (151 days) SF releases
SF releases Seasonal Patterns Known S. alterniflora x foliosa hybrid
San Francisco: E stimated velocities mean (range) SOUTHNORTH Fall1.41 ( ) 2.02 ( ) Winter1.19 ( ) 2.95 ( ) Spring1.45 ( ) 2.61 ( ) Summer1.51 ( ) 1.95 ( )
Discussion Limitations: Simulates surface transport only Does not account for life history or behavior May underestimate velocities Does not account for inter-annual variation Applications: Knowledge of near-shore, coast-wise transport Emphasizes seasonal nature of dispersal Identifies likely collection zones Inexpensive - allowing greater numbers of replicates
Summary Drift from these three locations has a large seasonal component, generally following known patterns of ocean currents Highest northward velocities & transport seen in WB & HB winter releases Lower velocities & transport from SF Local deposition more likely than distant, although rapid long-distance transport seen in certain instances Question of transport into estuaries? Additional releases of drift cards may help identify collection zones
Funding San Francisco Estuary Institute Oregon Department of Agriculture Washington Department of Fish & Wildlife Collaborators Kristen Ward, Golden Gate National Recreation Area (NPS) Travis Haring, Russell Nunez, Les Holcomb and David Heimer, WDFW Bill Pinnix, USDFW - Arcata office Volunteers Beachwatch (CA) COOAST (WA & OR) SOLV (OR) Beachcombers, tourists, children & many others Acknowledgements
Questions ?