A killer seaweed threatens local sea life in the Mediterranean. By Mark Little.
It spreads silently, occupying acres overnight, before anyone notices. Once it lays claim to its territory, crowding out the local life forms, there is little that can be done to eliminate it. Having found a perfect home in a completely new environment where it has no natural enemies to check its inexorable expansion, there’s no stopping it...
Fortunately for us humans, Caulerpa taxifolia doesn’t eat people. A good thing, too, for it has made a new home in the Mediterranean waters off the beaches where tourists frolic in their millions.
Caulerpa taxifolia does not come from another planet. It is a type of seaweed which is native to the warm waters of the Pacific, and is yet one more example of what can happen when a plant or animal species is introduced, whether by human design or accident, to an environment to which it does not belong (see more examples).
In the case of the killer seaweed, apparently it arrived as part of an exhibit at the famous oceanographic institute of Monaco. Some of the seaweed was accidentally flushed down a drainpipe into the Med, where it mutated to adapt to local conditions and thrived. First reported in the 1984 in the waters off southern France, by 1993 it had reached the Catalan coast and the Balearics in its continuous advance southwards along the Spanish coast. In 1995 it had established colonies off Croatia, in the Adriatic. The seaweed, whose fronds are shaped somewhat like those of a Boston fern, kills up to 95 percent of the local plant life and crowds out shellfish. It is toxic (a mouse fed with the weed will die within hours) and local fish will not feed off it. It spreads as sea currents carry it to fresh underwater fields, or it hitches a ride on the anchors of yachts. Authorities have been able to do nothing to exterminate it. According to one Greenpeace study, by 1995 the algae had colonized nearly 4,000 acres of seabed, and the ecology organization reckoned that the rate of growth would accelerate as it reached warmer waters off southern Spain. Indeed, by 1999 it was reckoned to have spread over some 11,500 acres.
More invaders from inner space: cocky ducks, monster catfish, and more
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