As anyone with a boat knows, many sorts of marine life can attach themselves to a hull below the waterline (right: barnacles on a ship's hull). On a large ship, the weight of such hitchhikers—everything from algae to barnacles to small colonies of coral—can weigh as much as 10 tons, says marine ecologist Susan Williams of the University of California, Davis, Bodega Marine Laboratory in Bodega Bay. The costs of these hull-fouling stowaways are substantial: According to one study, the U.S. shipping industry spends more than $36 billion each year in added fuel costs to overcome the drag induced by clinging marine life or for anti-fouling paint that prevents that life from hitching a ride in the first place. And that figure doesn’t include the cost
In the future, those costs could rise substantially, says Williams. In lab tests for which seawater was warmed 3.5°C above today’s average—a scenario that represents water temperatures expected in the year 2100—organisms in a typical community of hull-clinging creatures grew twice as fast as they do under today’s conditions. They not only grow more quickly in the warmer water but also grew to form thicker layers.
As a result, maintenance will likely be required more often in the future, boosting operational costs even further. In fact, recent warming may already have increased the need for routine hull scraping, says Williams. Ten years ago, boat owners in the marina where she lives typically scraped their boats only once every 3 months. Now, she notes, they need to perform such maintenance on a monthly basis.
See the complete coverage of the 2011 AAAS annual meeting in Washington, D.C.
Science Magazine,"A Warming World Could Add Billions to Shipping Costs ",accessed February 21, 2011