Pakistan & Gulf Economist

Ballast water: a source of biological pollution

Nature has a beautiful way of maintaining balance through food chain, ensuing in a stable ecosystem. A non-native organism, that does not have a well-defined place within the food chain, interrupts the existing ecosystem. Marine life is facing this kind of disaster due to invasion of foreign organisms through ballast water.

The world’s oceans are threatened by marine pollution, overfishing, and physical destruction. As if it is not enough, they are also at risk from non-native, marine species migrating beyond their natural boundaries and are dispersed around the world via shipping.

Approximately two-thirds of traded goods worldwide are transported by ship. Large tanks in ships are filled and emptied with seawater in order to ensure the ship’s buoyancy, stability, and maneuverability when the ship is loaded or unloaded. This ballast water in tanks is responsible for transporting thousands of specimens of native marine organisms including bacteria, small invertebrates, eggs, cysts, and larvae of various organisms.

It is estimated that almost 10 billion tonnes of ballast water are transported worldwide, with an average of 7,000 species per hour being transported per anum. This biological pollution is considered a second potential threat to natural biodiversity after habitat loss. The introduction of exotic species in the port area is currently a major environmental problem in various parts of the world and was first reported by the International Maritime Organization (IMO) in 1973 during the establishment of the international convention for the Prevention of Pollution from Ships- MARPOL 73/78.


Untreated ballast water releases species from one ecosystem to another. If the conditions of the new ecosystems are favorable. The species will thrive and become an invasive aquatic life form. They damage biodiversity and impact economic enterprises like agriculture, forestry, and fisheries. In the last two centuries, thousands of alien species have established in different parts of the world. Zebra mussel, green crab, and goby are examples of aquatic invasions through ballast water.

In North America, the introduced European Zebra Mussel has infested more than 40% of internal waterways and has cost more than US$5 billion in control measures. The invasion of species to non-native places has resulted in economic losses. The fishing industry has suffered the most as a result of species infestation in nonnative areas, where commercial fishing stocks have been damaged depleted. Near the Black Sea, six countries have been affected by the Atlantic comb jelly. It has wiped out the zooplankton from the black sea, which has wiped out the region’s anchovy fishes. Similarly, the toxic red tide has closed clam and mussel farms and fisheries. These two invasive species were introduced by ballast water. The states of Oregon and Washington have estimated annual fishery revenue of $44 million and are vulnerable to purple clams and green crabs. When consumed by humans, these contaminated shell ballast water fish can cause paralysis and even death. Hundreds of examples of major ecological, economic and human health impacts have been witnessed across the globe. It is even feared that cholera may be transported in ballast water. In many cases, ballast water is responsible for spreading various diseases, including cholera.

The golden mussel had never seen off the coast of Argentina, so when it was first discovered, it raised question as to how it got here. An investigation revealed that they were transferred through the ballast water of ships traveling between Hong Kong and Argentina. These golden mussels are commonly found in warm waters of Hong Kong harbor. The golden mussel altered the Amazon’s ecosystem. The golden mussel also destroys the infrastructure as it rapidly reproduces and clogs the city and industrial waterway, causing loss of billions of dollars in loss every year.

Invasive species can be added to the new marine environment in various manners but the most common and lethal is through ballast water. Other forms of transportation of such species are through the fouled bottom of ships where adult, mature species can easily find their way into the new environment where they replicate faster because of conducive water temperature, abundance of food, and nonexistence predators. Other methods include agriculture and manmade means, which provide basic nurturing conditions for such species to grow.

In the case of Pakistan, there is a lack of reliable data on indigenous marine flora and fauna that identifies the invasive species. Also, no research has ever been carried out to examine their impact on the ecosystem. But in general, the conditions are grave in Pakistan. So before the conditions worsen we need to address this issue because aquatic invasions are virtually irreversible and, once the newcomers are settled in the habitat, their impact may increase in severity over time.

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