Ballast Water Threat

Ballast water is carried in unladen ships to provide stability. It is taken on board at the port before the voyage begins. Tiny stowaways, in the form of marine organisms, are also taken on board with it. At the ships’ destination, the cargo is loaded and the ballast water, with its stowaway organisms are pumped out. Some of these organisms then establish populations in the surrounding waters. Hundreds of such species of marine organisms are known to have been introduced by ballast water. While some appear benign, others have become pests, threatening to the local marine ecology. Worldwide, marine bioinvasion of a wide spectrum of organisms including plants & animals have been reported.

Seawater that is taken up as ballast by ships contain a gamut of organisms and their propagules.
In the wild their sustenance is controlled by natural events. However, once in the dark ballast chambers, their ambient environment is altered. This leads to alteration of population structure in the seawater.

The introduction of invasive marine species to new environments is a major threat to the world’s oceans. The four diagrams below illustrate how shipping results in unwanted stowaways being transported from one port to another.

Fig. 1: At the source port, Ballast Water is loaded in the ballast tanks after Cargo is discharged, to maintain the balance of the Ship. This results in a lot of unwanted organisms being loaded alongwith.		Fig. 2: The ship with its ballast tanks filled with Ballast Water goes on a voyage to the port (destination) from where it has to pick up Cargo.
		<
Fig. 3: At the destination port, the Ballast Water is discharged so that Cargo can be loaded on to the ship. This results in the unwanted organisms being released in a new marine environment where they pose potential threats.		Fig. 4: Once the Ballast Water is discharged, the ship is loaded with Cargo and continues with its voyage.

Indian Scenario

India’s coastline spanning over 7500 kms and housing 12 major ports may serve as gateways for marine bioinvasion. In addition to introduction of alien species, the threat of its dispersal to neighboring environments poses a serious challenge. The precious coral reefs of Andaman & Nicobar and Lakshadweep islands could be severely threatened by this.

In the Indian scenario, black stripped mussel Mytilopsis sallei has been reported from Mumbai and Visakhapatnam. This species is native of tropical and sub tropical Atlantic waters and is reported to have invaded the Indian waters sometime during 1960's. Green Crab - Carcinus meanas, a native of Europe is also reported from the Indian Ocean (Sri Lanka). The molluscs and crustacean population on which this crab preys upon can be affected. There could be man more such examples and their elucidation is needed.