Ballast water as a vector for marine invasive species: exploring the risk to coastal Alaska

Transcription

1 Ballast water as a vector for marine invasive species: exploring the risk to coastal Alaska Verna, Danielle 1, Harris, Bradley 2 1 Alaska Pacific University, 4101 University Drive, Anchorage, AK 99508, dverna@alaskapacific.edu 2 Alaska Pacific University, 4101 University Drive, Anchorage, AK 99508, bharris@alaskapacific.edu Marine invasive species have the potential to cause significant harm in Alaska s coastal waters by impacting species diversity, commercial fisheries, and even humans. Ballast water from ships is a primary vector for the transport of marine invasive species. Currently, ballast water exchange 200 nautical miles from shore is the primary method of controlling introductions via ballast water. However, reactionary policy implementation and exemptions from management requirements have left substantial room for invasion risk. Ballast water management (BWM) policy was initiated in the United States over twenty years ago, but not until 2004 did management, recordkeeping, and reporting become mandatory for areas other than the Great Lakes. We review vessel arrival and ballast water discharge patterns for coastal Alaska during the period The vast majority (76%) of vessel arrivals to Alaska were domestic traffic, often from other Alaskan ports or from highly-invaded west coast ports in California, Oregon and Washington. Vessels reported discharging over 78 million metric tons of ballast water during the nine year period, most commonly in places such as Valdez, Seward, Dutch Harbor, and Red Dog. We use this historical data to analyze the response of vessel behavior to changing regulations and make suggestions for improving BWM strategy in Alaska. Current and future increases in vessel traffic throughout Alaska could pose further risk of ballast-borne invasive species. We also assess the risk of invasion in bioregions and ports of Alaska as an initial step toward prevention.

2 Danielle Verna and Brad Harris, Ph.D. Fisheries, Aquatic Science & Technology (FAST) Lab Alaska Pacific University

3 Any substance that is used to increase vessel draft and stability, usually seawater The international shipping industry transports ~3-5 billion MT of ballast annually Responsible vector for marine invasions around the globe Changing environmental conditions have already resulted in vessel traffic in the Arctic & Bering Strait

4 Policy Review Objectives: Document changes in policy and identify drivers Assess implications for BWM Risk Assessment for Coastal Alaska Objectives: Assess ballast water discharge in Alaska, Develop risk assessment framework Model risk for coastal Alaska

5

6 Major Policy Shifts in BWM

7 Major Policy Shifts in BWM

8 ~72% of ballast discharge was sourced on the US west coast or BC 3,773 vessels Tankers discharge ~88% of all ballast 27,303 ballast tanks 7.5 x10 7 MT of ballast 67 named locations 910 geographic coordinates Only 33% of reported ballast is managed (BWE)

9

10 1.4E+07 Ballast Water Volume (MT) 1.2E E E E E E+06 Overseas Coastwise 0.0E Year Coastwise: ballast water does not transit beyond combined US & Canadian EEZs Overseas: ballast water does transit beyond combined US & Canadian EEZs

11 1.4E+07 Risk Assessment Ballast Water Volume (MT) 1.2E E E E E E E+00 Incomplete Overseas Coastwise Mandatory reporting EPA VGP? Declining Reporting? Year

12 1. Model risk as a function of environmental similarity, ballast water age and volume Between source and discharge regions Between source region and ports >50,000 MT Following other high-latitude risk assessments: Leppäkoski & Gollasch 2006 Chan et al Ware et al. 2013

13 Environmental Similarity (positively correlated with risk) 1) Low risk non-adjacent ecoregion 2) Medium risk adjacent ecoregion 3) High risk same ecoregion Spalding et al A weighted average was applied to the proximity ranking based on the volume per source ecoregion

14 Ballast water age (negatively correlated with risk) Number of days between source and discharge date

15 Ballast water volume (positively correlated with risk) Serves as a proxy for propagule pressure 0.1 correction factor applied to managed ballast to represent 90% efficacy rate of BWE (Ruiz & Reid 2007)

16 Environmental Similarity Age (days) Corrected mean volume of BW discharge: ecoregions & ports (log 10 MT) (1) Low < 1 > 10 < 2.6 (2) Medium (3) High > 2 < 6 > 5.1 Total Risk 9 Extremely High 7 8 High 5 6 Medium 3 4 Low

17 Marine Ecoregions of the World Spalding et al. 2007

18 Ports that received > 50,000 MT of ballast

19 Southcentral AK receives the greatest volume of ballast discharge Tankers pose the greatest risk due to ballast volume Policy exemptions elevate risk and hinder monitoring Alternative risk scales to better reflect Valdez as an outlier Finer-scale environmental similarity for ports Predictive modeling using trends and environmental projections

20 Acknowledgements

21 Risk Risk Kodiak Whittier Anchorage Seward Env Sim Volume Age Prince William Sound Nikiski Afognak Valdez Red Dog Ketchikan Hydaburg Dutch Harbour No Change Klawock Hawk Inlet Skagway Drift River Terminal Tolstoi Bay