AKA "The Green Invader" AKA "The astroturf
of the Mediterranean."
This fast-growing green tropical alga used to decorate saltwater aquariums is best known for escaping the Oceanographic Museum of Monaco in 1984 into the open Mediterranean. From an initial patch of about one square meter, the algae spread to cover about 2.5 acres (one hectare) of ocean floor in just five years. In shallow waters, up to 35 meters, it tends to cover 100 percent of the sea floor, on rock, sand, mud, or undersea meadow. Having no natural predators in the Mediterranean, caulerpa algae now have spread throughout the northern coastline, harming tourism, destroying recreational diving, overgrowing native sea plants, tangling net fishing operations, and influencing fish populations (the algae contain a toxin that can interfere with the eggs of some marine animals and kill off some microscopic organisms).
Marine biologists have identified the first North American sample of the species several weeks ago in eelgrass beds in a coastal lagoon about 20 miles (32 km) north of San Diego, California. (Though the importation of caulerpa was banned in 1999, the most likely source of the California infestation is someone dumping their fish tank down a storm drain).