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Ocean Dispersal from Heavily Infested Bays: Drift Card Study Results

This study presents findings from a West Coast drift card study focusing on biological transport patterns. Results reveal return rates, recovery times, and seasonal dispersal patterns from three bays. Limitations, applications, and future research implications are discussed.

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Ocean Dispersal from Heavily Infested Bays: Drift Card Study Results

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  1. Inferences for Biological Transport:Results from a West Coast DriftCard Study Vanessa M. Howard & Mark Sytsma Portland State University Alternative Ballast Water Exchange Areas Workshop June 21, 2006 – Seattle, Washington

  2. Outline Background Methods Results Return rates & recovery time Recovery patterns - spatial & seasonal Summary

  3. Schwartzlose 1963 Background www.noaanews.noaa.gov 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 2002-04 Hawaii Drift Card Study)

  4. Photo courtesy of NRCS 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

  5. 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 2002-2004)

  6. Willapa Bay Humboldt Bay San Francisco Methods – Releases • Three release locations • September 2005 through August 2005 • 200 cards • Within two hours of high tide

  7. Results – return rates Willapa 41.8%

  8. Results – return rates Humboldt 26.2%

  9. Results – return rates San Francisco 43.8%

  10. Recovery time

  11. Results – bay vs. coast

  12. Results – near vs. long distance

  13. WB releases • Max North ~ 2,000 km (129 days) • Max South ~ 300 km (227 days)

  14. WB releasesSeasonal Patterns

  15. Willapa: Estimated velocitiesmean (range)

  16. HB releases • Max North ~ 2,800 km (214 days) • Max South ~ 530 km (45 days)

  17. HB releases Seasonal Patterns

  18. Humboldt: Estimated velocitiesmean (range)

  19. SF releases • Max North ~ 630 km (56 days) • Max South ~ 400 km (151 days)

  20. Known S. alterniflora x foliosa hybrid SF releases Seasonal Patterns

  21. San Francisco: Estimated velocitiesmean (range)

  22. 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

  23. 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

  24. Acknowledgements 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

  25. Questions ?

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