Asian Kelp (Undaria pinnatifida)
Better known as wakame, this edible seaweed is commonly used in Japanese and Korean cuisine. While native to cold-water coastal areas of Japan, Korea, and China, it has found its way to New Zealand, France, Great Britain, Spain, Italy, Argentina, Australia, Mexico and the US, where aggressive measures are underway to remove the plant from harbours on the western seaboard. The kelp was discovered in San Francisco Bay in May 2009.
Cholera (Vibrio cholera)
Port areas near the mouths of rivers are prime breeding ground for cholera bacteria, especially in countries where sanitation is poor and water has been heavily polluted with raw sewage. V. cholera bacteria attach to the surfaces of planktonic animals such as copepods (a type of small crustacean) and other zooplankton, particularly in tropical countries, as well as to shellfish and aquatic plants. By attaching themselves to waterborne microscopic organisms, the bacteria can enter ballast water and be transmitted to new areas around the world. If ingested in drinking water, strains O1 and O139 of the bacteria can cause cholera in humans.
European Green Crab (Carcinus maenas)
Another species colonising Australia is the European green crab, which has found its way from its original habitat in the north-east Atlantic Ocean and Baltic Sea to the Antipodes, South Africa, South America and both the Atlantic and Pacific coasts of North America. The green crab is a carnivore that preys upon clams, mussels, oysters, and gastropods. Its introduction to the US in the 1950s has cost the American fishing industry millions of dollars because the green crab preys on scallops and other commercially important shellfish. Aside from preying on native species, the European green crab is able to outcompete them for food, and can reproduce in high volumes. Research suggests that the green crab’s colonisation of estuaries in Washington, Oregon and British Columbia was facilitated by the El Niño storms of 1997 and 1998.
North Pacific Seastar (Asterias amurensis)
Native to Japan, North China, Korea and far eastern Russia, this starfish is capable of tolerating many temperatures and wide ranges of water salinities and is often found in estuaries and intertidal zones. Spawning between July and October, the female is capable of carrying up to 20 million eggs, which hatch and live as planktonic larvae for up to 180 days. The species has since been introduced to south-eastern Australia and Tasmania, most probably after having been carried as larvae in ballast water. The port of Melbourne is Australia’s biggest container port, handling many vessels inbound from the Far East. It is in Australia that North Pacific seastars are doing most damage. The creatures eat the eggs of the endangered handfish.