The survival rate of species after discharge depends upon the conditions of the receiving area, with species more likely to gain a foothold when conditions are similar in terms of, for example, salinity and temperature. Studies indicate that typically less than three per cent of the released species actually become established in new regions - but just one predatory fish species could seriously harm the local ecosystem.
In the last decade, the International Maritime Organization has been working through its Member States to tackle the problem. Guidelines for Preventing the Introduction of Unwanted Organisms and Pathogens from Ships' Ballast Waters and Sediment Discharges were initially adopted in1991 and IMO is now working towards adopting mandatory regulations on the management of ballast water.
Shipping is a crucial element in world trade, transporting more than 90 percent of goods and commodities around the world. Ballasting of ships is a necessary requirement for their safe operation when sailing empty to pick up a cargo, or with a light load, and it has been recognised that currently the only effective way to stop the spread of unwanted organisms is to prevent them being dumped in foreign ports.
The early invaders
Before the introduction of stee- hulled vessels in the late nineteenth century, when ships began using sea water for ballasting, sand, stone, bricks and even iron were used as ballast.
This ballast was essentially benign. But when ships began to take on board thousands of tonnes of sea water in far off ports to ballast their ships, local life forms were unwittingly scooped up, to be transported to new locations across the oceans. Increasing speed of ships probably also helped these species to survive their journeys, ready to reinstate themselves in new seas - where their natural predators may not exist.
Scientists first recognised the signs of an alien species introduction after a mass occurrence of the Asian phytoplankton algae Odontella (Biddulphia sinensis) in the North Sea in 1903.
But it was not until the 1970s that they began reviewing the problem in detail.
By then, the potential for ships to pollute the marine environment was a global issue -especially following the Torrey Canyon oil tanker disaster of 1967, which acted as a catalyst for IMO to act in drafting regulations to deal with oil pollution by ships.
In 1973, IMO convened a Conference to adopt a new international convention which would address all aspects of marine pollution by ships - the International Convention for the Prevention of Pollution from Ships. (The Convention, and its Protocol adopted in 1978, is known as MARPOL 73/78. It initially consisted of five annexes dealing with oil, chemicals, goods in packaged form, sewage and garbage. In 1997, an annex on air pollution was added.)
At the 1973 Conference, the ballast water problem was raised, specifically in the context of the transport of pathogens harmful to humans. The conference adopted a Resolution, which noted that "ballast water taken in waters which may contain bacteria of epidemic diseases, may, when discharged, cause a danger of spreading of the epidemic diseases to other countries". The Resolution requested IMO and the World Health Organization to "initiate studies on that problem on the basis of any evidence and proposals which may be submitted by governments".
Meanwhile, scientists were assessing the problem. In 1976, a German scientist, Professor H. Rosenthal, published a study reviewing the state of knowledge and risks associated with the transplantation of non-indigenous species to fisheries and aquaculture through ballast water. He concluded that modern fish farms near main shipping routes were at high risk of disease transfer from ballast water.
In the next decade, more and more alien species were being introduced - and being noticed -around the world. In the late 1980s, Canada and Australia were among countries experiencing particular problems with unwanted species, and they brought their concerns to the attention of IMO's Marine Environment Protection Committee (MEPC).
Ballast water guidelines 1991
In 1990, the MEPC at its 31st session set up a working group on ballast water, which developed guidelines on addressing the problem of alien species. An MEPC Resolution - MEPC 50 (31), Guidelines for Preventing the Introduction of Unwanted Organisms and Pathogens from Ships' Ballast Waters and Sediment Discharges - was adopted in 1991.
The Guidelines were aimed at providing Administrations and port State authorities with information on procedures to minimize the risk from the introduction of unwanted aquatic organisms form ships' ballast water and sediment.
