A Case Study of Efficacy of Freshwater Immersion in Controlling Introduction of Alien Marine Fouling Communities: The USS Missouri

摘要

The historically significant battleship USS Missouri was recentlydecommissioned and moved from Bremerton, Washington, to Hawai'i to becomea memorial museum at Pearl Harbor, O'ahu, Hawai'i. Dry-docking wascompleted in January 1993, and since that time the vessel has been part of theinactive fleet. In this 5-yr period, a dense growth of fouling organisms had developedon the outer surfaces of the hull. Out of concern that the fouled hullcould become a source for the introduction of alien aquatic nuisance species toHawaiian waters, an evaluation of the fouling community was conducted. Inthis study we found 116 taxa among 12 phyla in 10 samples scraped fromthe vessel's hull. Seventy-six species were identified: 11 known from Hawaiianwaters, 17 with known temperate-boreal distributions, and the remaining 48known only from the Pacific Northwest. Forty percent of the taxa in this foulingcommunity were not identified to species, so there remained some potentialfor alien species introduction. As a precaution to prevent accidental introductions,the ship was moved from Bremerton to the Columbia River in Oregonfor a 9~day sojourn in freshwater before its transoceanic crossing to Pearl Harbor.Inspection of the vessel's hull upon arrival in Pearl Harbor revealed morethan 90% of the hull to be completely clear of any fouling organisms. Only 11species were found to be alive: 3 species probably recruited to the hull on thetransoceanic crossing that may routinely arrive in Hawaiian waters, 4 speciesalready present in Hawai'i, 3 Pacific Northwest species that appeared to beclose to death on their arrival in Hawai'i, and 2 euryhaline amphipod speciesprobably recruited to the hull while in the Columbia River. The amphipodswere not reproductive and brooding young, suggesting that these species wouldnot be successful colonists. A final inspection and sampling of the hull 83 daysafter arriving at Pearl Harbor failed to find live or dead Columbia River amphipodsnor were the three Pacific Northwest species alive. Freshwater exposurefor 9 days coupled with increased water temperatures during the journey toHawai'i appear to be an extremely effective means of eliminating the temperatemarine fouling community. This action substantially reduced the probabilitythat an alien species would be introduced with the arrival of this historicvessel in Hawai'i.