Some case studies
American comb jelly plagues fisheries in the Black Sea
The American ctenophore Mnemniopsis leidyi, an organism originating from the east coast of the Americas, is believed to have been introduced into the Black Sea through ballast water in the 1970s.
The comb jelly (an organism with similarities to a jelly fish) is a voracious predator on zooplankton and fish eggs and larvae and has been largely responsible for the collapse of the anchovy fishing industry in the Black Sea.
As author Neal Ascherson wrote in his book "Black Sea" (Jonathon Cape, London, 1996):
"In the late 1980s, mostly between 1987 and 1988, there took place one of the most devastating biological explosions ever recorded by science. Mnemniopsis, an animal with no known predators to control it, spread suddenly and incontinently through the Black Sea. It fed voraciously on zooplankton, the food of young fish, and on fish larvae. In the Sea of Azov, Mnemniopsis consumed almost the entire zooplankton population, which in 1989 and 1991 collapsed to one-six-hundredth of its normal average. Its total biomass in the Black sea and the Sea of Azov reached 700 million tons of translucent jelly, and its impact was entirely catastrophic. No recorded destruction by human pestilence or locust swarm compares with this damage to fish and their resources..."
Further reading: Opportunistic settlers and the problem of the ctenophore Mnemiopsis leidyi invasion in the Black Sea.
GESAMP Reports and Studies No.58.
IMO/FAO/UNESCO-IOC/WMO/WHO/IAEA/UN/UNEP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP). ISSN 1020-4873; ISBN 92-801-1436-4
Toxic dinoflagellates and other species in Australian waters
Australia receives some 60 million tonnes of ballast water annually and concern over alien species mounted in the 1980s.
In 1990, Australia introduced voluntary guidelines on ballast water for ships calling at Australian ports. This followed particular concern over the introduction of toxic dinoflagellates to Australian waters, representing a real threat to shellfish farming industries on the Tasmanian, Victorian and New South Wales coastline.
Toxic dinoflagellates are a type of algae known to cause paralytic shellfish poisoning in humans. Evidence suggested the toxic dinoflagellate Gymnodinium catenatum became established in Australian waters after arriving in ballast water - the species was already present in waters of Argentina, Japan, Mexico, Portugal, Spain, Venezuela and in Mediterranean sea ports. Toxic dinoflagellates of the species Alexandrium tamarense have a wide distribution and became established in waters off Melbourne.3
Dinoflagellates can reproduce simply by splitting in two, allowing multiplication wherever conditions are favourable. Gymnodium catenatum also has a type of reproduction in which two cells of opposing "gender" come together, which is usually a result of unfavourable conditions. This results in a tough encased spore that can survive different conditions by staying dormant in sediment.
These spores remain viable for 20 to 30 years, germinating into the usual swimming form when conditions are suitable, and entering the food cycle of shellfish causing the shellfish to become toxic to humans.
Farms in Tasmania had been forced to shut down for extensive periods on occasions, as a precautionary measures during plankton blooms (red tides), which generally follow heavy rain.
In the 1990 guidelines, ships were asked to carry certificates attesting that the ballast water was loaded in a place free from toxic dinoflagellates at the time the ballasting took place, to re-ballast at sea in open tropical waters, or to treat the ballast water in hold or in on-shore ballast tanks.
Toxic dinoflagellates were not the only species Australia was, and is, concerned about. In 1990, Australia presented a paper to IMO in which it listed several species found in Australian waters and their suspected origin:
3 Toxic dinoflagellates, introduced by ballast water, have also caused problems to shellfish industries in other parts of the world, including China, India and South Africa.
