"Many years ago, a Stuttgart zoo imported a lush, bright green seaweed for its aquarium. Caulerpa taxifolia was cultivated in the zoo and exposed, for years, to chemicals and ultraviolet light. Eventually a sample of it found its way to the Oceanographic Museum in Monaco, then headed by Jacques Cousteau. Fifteen years ago, while cleaning its tanks, that museum dumped the pretty green plant into the Mediterranean." "This supposedly benign little plant...