Generally, ballast water is water carried in ships' ballast tanks to improve stability, balance and trim. It is taken up or discharged when cargo is unloaded or loaded, or when a ship needs extra stability in foul weather. When ships take on ballast water, plants and animals that live in the ocean are also picked.
In this article we will try to give some small background to the ballast water management which is becoming an issue of higher and higher importance to the protection of the marine environment. International shipping has been identified as one of the key pathways for the movement of species between different eco systems. Organisms and pathogens found in the ballast water and sediments in ballast tanks have significant economic and ecological impact on marine biodiversity in many regions.
They can also potentially pose a serious threat to human health from the spread of diseases and species harmful to humans. Unlike some forms of ship-sourced environmental harm, the problem arises from the activity inherent to ship's operation. Currently, there is no entirely satisfactory means of preventing the transfer of species in ballast water.