Environmental Hazards and Critical Management of Ballast Water of Ships on Aquatic Ecosystems

Ballast water is held in tanks and/or cargo holds of ships to provide stability and maneuverability during a voyage when ships are not carrying cargo require more stability due to rough seas. Ballast water maybe either fresh or saline. Aquatic species arrive through a variety of mechanisms unintentionally when attached to vessel hulls or carried in vessel ballast water and intentionally when imported for aquaria display، as live seafood for human consumption، or as a transplant to increase sport fishing opportunities. Ballast water is an important way of transferring aquatic nuisance species (ANS) all over the world. ANS include algae، shellfish، developing larvae، eggs and other microorganisms. Due to the lack of natural predators in the new environment، they are often able to thrive and outgrow the native species. This domination can cause massive ecological، economic، and public health problems such as degradation of habitat، alteration of water quality، blockage of flow in drainage and irrigation canals، or even transition of diseases to humans. The International Maritime Organization (IMO) regards the introduction of harmful aquatic organisms and pathogens to new environments via ballast water، as one of the four greatest threats to the world’s oceans. At least one foreign marine species is introduced into a new environment every nine weeks. In this paper the ballast water management methods is explained under three categories، the exchange، the treatment and the isolation of the ballast water. The advantages and disadvantages of these methods are also discussed.