Marine Pollution from Ship's Ballast Water

Discharge of ship ballast water results in serious marine pollution that disturbs the marine ecosystem, harms marine species and endangers human health.

Marine pollution from ship ballast water is one of the greatest threats to ocean life. With the rapid increase in marine pollution, the International Maritime Organization (IMO) has framed special regulations to monitor the quality of ballast water discarded from ships around the world. Unlike other sources of marine pollution, ballast water pollution does not pose a grave threat to humans, but is still a serious ecological and health issue for marine plants and animals. The effects of marine pollution from ship’s ballast water on marine life are long lasting and difficult to control.

Ship Ballast Water Affecting Marine Life

Ballast water is carried by ships in their dedicated ballast tanks to ensure stability and balance. An unloaded ship is subjected to heavy rolling and pitching and thus requires more ballast, which provides, in return, balance and structural integrity. When a ship takes in ballast from one region, it not only takes in sea water but also native marine organisms as well.
The ship then travels to some other part of the world and discharges its ballast during cargo loading or unloading. In this way, aquatic species such as fishes, bacteria, micro-algae, and aquatic plants and animals in different life cycle stages are transported from one water region to another. When this happens, either the marine organisms that are transferred with the ballast water or the ones living in the region where the ballast is discharged become vulnerable as a result of introduction of alien species.
Introduced invasive organisms can take over areas already occupied by other species, leading to eradication of the endemic species. They can also spread diseases, or introduce new genetic materials which not only induce mutation in native marine organisms but also jeopardize their natural abilities.

Ship Ballast Water Affecting Human Life

Some species introduced to new places in ballast water contaminate filter feeding shellfish, making them toxic and inedible. Consumption of these contaminated shellfish by humans can cause severe health problems and even death. Moreover, harmful microorganisms of various types can become more virulent as a result of contact with other organisms in ballast water.
Apart from introducing invasive species, ballast water from ships is responsible for sea water pollution. The ship ballast tanks are often rusted from inside which ultimately leads to contamination of the sea water taken in as ballast. Sometimes leakage of bilge or from an oil line can also lead to discharge of oil and other impurities into the ballast water making it impure. If oil is discharged with the ballast water it can cause severe harm to marine plants and animals and also to human life in coastal regions.
Ballast tanks are also coated with paints made of toxic chemicals which, on contact with water, release poisonous substances that can disturb the growth of marine organisms by altering their hormonal cycle. Effects include birth defects, damaged immune systems, and genetic disorders. If these diseased organisms get into the human food chain in seafood, they can cause adverse health conditions and even fatal diseases.
Thus, though marine pollution by ballast water might account for only a small percentage of the global pollution that can affect humans, it still poses a serious threat to the marine organisms and the ecosystem as a whole.

References

Dobbs, Fred C. and Andrew Rogerson. June, 2005 "Ridding Ships' Ballast Water of Microorganisms." Environmental Science and Technology. Pubs.acs.org, Accessed July 16 2010

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