The Observer, May 2008
Marine hitchikers outside ballast tanks also a problem
By Lisa Ka'aihue, Director of Administration
The citizens’ council has long studied the threat of marine invasive species reaching Alaska waters via by the ballast water of crude oil tankers.
Now the council is shifting its focus to the organisms that catch rides from port to port by attaching themselves to vessel hulls, a phenomenon known as hull fouling or biofouling.
In addition to organisms such as barnacles and mussels that attach themselves to hulls, non-attached organisms may travel with ships as well. They may shelter in the nooks and crannies created by a colony of attached organisms. Or they may travel in the vessel’s sea chest, where they are protected from being washed away as the ship moves through the water.
Sea chests are compartments on the sides of ships that house seawater intake lines used for ballast, engine cooling, and fire suppression. Despite the fact that sea chest intakes are equipped with strainers, whole live crabs and lobsters have been found inside.
The council does not know the risks to our waters posed by hull fouling. What is known is that, once organisms become established on the bottoms of vessels, the risk of transporting invasive nonnative species increases, as does the potential for catastrophic effects on native ecosystems.
Vessel owners are constantly fighting the establishment of biofouling communities on their hulls, as such communities create extra drag, slow down the ship, and increase fuel consumption. Many anti-fouling paints have been used on hulls. One of the most effective was a highly toxic paint called tributyl tin. However, it was banned because it tended to leach into seawater and harm native marine life. Newer anti-fouling paints are less toxic, but also less effective.
Hull fouling has only recently emerged as a topic of concern. Researchers around the world are acknowledging that hull fouling may be even more important than ballast water as a pathway for the transport of invasive species, but the problem is not yet well understood, particularly in the United States. It has been reported that 74 percent of the aquatic invasive species that arrived in Hawaii did so because of biofouling.
The council, in partnership with the U.S. Fish and Wildlife Service, is embarking on a project to describe biofouling communities on the major classes of vessels that operate in Prince William Sound, including oil tankers, barges, ferries and cruise ships.
Tactics for combating hull fouling without the use of highly toxic paints could include such measures as limiting the amount of time a vessel is in port and requiring periodic out-of-water cleaning.
As a first step, the council chose the University of Washington to conduct research for this project. The team includes Russell Herwig, Jeffery Cordell, David Lawrence and Gregory Jensen. Over the next year, they will develop hull sampling methods, and take samples from various vessels, with a focus on oil tankers. They will identify the organisms the find and report the results to the Council. This study will provide important information on which vessels in which trade may pose the greatest risk of introducing invasive species via their hulls.
For more information on hull fouling, visit the University of California’s West Coast Ballast Outreach Project hull fouling web page.