World's coastal waters riddled with invasive species

Eighty-four percent of the world's coasts are being colonized by foreign aquatic species, according to a Nature Conservancy study.

San Francisco Bay is the most invaded aquatic region on Earth, the study finds, with 85 invasive species in its waters, 66 percent of them considered harmful. More than half of San Francisco Bay fish and most of its bottom-dwelling organisms are not native to the Bay, and new invaders are constantly being introduced. Invasive species are non-native species that have been introduced into a new landscape, freshwater system or ocean region. Because this new area often lacks natural competitors and predators, the invaders tend to displace native plants and animals, disrupt food webs, and alter fundamental natural environmental processes. 'The scale of this problem is vast,' said Jennifer Molnar, conservation scientist at The Nature Conservancy and lead author of the study, 'Assessing the Global Threat of Invasive Species to Marine Biodiversity. 'Every day, thousands of vessels cross our oceans with invasive species hitchhiking on their hulls,' Molnar said. 'Because of this, as many as 10,000 species are estimated to be in transit at any one time.' Throughout the world's oceans, aquatic alien invasive damage economies by diminishing fisheries, fouling ships' hulls, and clogging intake pipes.

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