World's Coastal Waters Riddled with Invasive Species - 28 February 2008
WASHINGTON, DC, February 24, 2008 (ENS) - Eighty-four percent of the world's coasts are being colonized by foreign aquatic species, according to a Nature Conservancy study published this week. 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. Chinese mitten crab, Eriocheir sinensis, taken from San Francisco Bay (Photo courtesy California Dept. Fish and Game)
The Chinese mitten crab is one of more than 200 exotic species which have invaded the Delta and San Francisco Bay since the 1850s. These small crabs, which were brought to the San Francisco Bay via ships' ballast water, were first were documented in California in 1992. They reproduce rapidly and have spread throughout the Delta. They may imperil the state's threatened and endangered salmon populations due to the crabs' appetite for juvenile salmon.
"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," published in the journal "Frontiers in Ecology and the Environment."
"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."
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