Ballast water is essential for the safe operation of a ship, but this water causes significant threats to the environment and the local economy.

Ships carry ballast water to control their stability and trim. The ability of a vessel to load and unload ballast water is essential to the safety of its conduct. 

When a ship loads or unloads cargo or consumes fuel, the resulting changes in displacement and trim must be compensated for by adding or removing ballast water. 

Ballast water is produced between 3,000 to 5,000 million tons, transferred in approximately 85,000 vessels each year.

Table of Contents

Ballast water 

ballast - ballast water
Ballast water, water cycle, and environment (source)

Ballast water is named to seawater collected and stored on ships’ tanks to guarantee that the vessel does not lose stability when it is too light. 

It is therefore used on ships that have just unloaded their cargo. Without capturing this water, the vessel runs severe risks of sinking, breaking up, and being unable to maneuver.

With the use of ballast water, there is compensation. Ballast water starts to play the role of the cargo that was previously present there. 

Typically, the ships that use a tremendous amount of ballast water are tanks and bulk carriers, which transport bulk goods. The capacity of the ballast water tanks could be millions of liters on a large ship. 

Ballast water is drawn through openings at or near the bottom of a ship’s hull; it is pumped by pipes connected to ballast pumps located in the lower engine compartment of the vessel. 

Without these manipulations of ballast water, ships cannot navigate in complete safety: adding or removing ballast water makes it possible to control stability and trim, reduces stress to the hull, facilitates or permits maneuvering, and reduces roll and pitch. 

Water pumped from ballast tanks must inevitably be discharged when the ship is loaded with cargo.

The loading and unloading of ballast water are often done in port during cargo handling operations, but it can also occur in transit over open waters or injunction channels. For this reason, ballast water becomes a route for the introduction of invasive species. 


Before 1870, the vessels used solid ballast such as sandbags, rocks, iron blocks. The ships were loaded with stones as ballast for balancing their loads on water. 

With the gradual increase in the number and size of ships built in steel, it became common to use water, usually salty, as ballast, increasing the problem of the transfer of organisms from one place to another in parallel with the enormous increase in the volume of goods transported by sea. 

Logically, the problem is more significant in areas and countries that export large cargo volumes, such as oil tankers or bulk cargo ships. 

When they arrive in their port, the ships load or unload the ballast water transporting with them the alien species, sediments, sewage, and other contaminants. 

Transfer and introduction of exogenous organisms

The involuntary introduction of alien aquatic organisms into various sea areas has led to the settlement of many species far from their native regions, with a potential threat to the environment and the economy of the areas that receive them.

From the early 90s, the transportation of exogenous organisms has been recorded. Such as:

I. Algae

algae - ballast water
Textures and Patterns of an Algae (source)

The antecedents of the first invasions are centered in Odontella Sinensis, an Asian plankton alga that reproduces with extreme ease. The species invaded Del Norte county in 1903. 

The alga Undaria Pinnatifida has also caused significant invasions. Popularly known as alga Wakame, it is annual and has a rhythm of excessive growth, which reaches sizes between one and three meters. 

It is also very prolific since the number of spores it releases can even reach a hundred million.

II. Zebra Mussels and Chinese Clam

Clam - ballast water
Clams washed up on the beach (source)

The Zebra mussel colonized London docks in the 1920s, introduced by river navigation, and from there, it spread little by little throughout the continent. 

In 1988, it was first seen in North America, in a small lake in Detroit, a density of 200 species per square meter. 

It then penetrated various North American rivers so that the zebra mussel has infested about 40% of the internal channels, requiring an investment of almost $ 1 billion in control measures between 1989 and 2000.

III. Jellyfish, crabs, and starfish

Crabs - ballast water
Red crabs scaling a cliff at Ethel Beach (source)

The jellyfish is native to the western coasts of the American continent. Due to the introduction of this jellyfish in the Black Sea, where it has reached the density of 1kg of biomass per cubic meters, fishing in the former Soviet Union has fallen sharply from 250,000 to 30,000 tons per year. 

In Turkey, American jellyfish exhausted the indigenous action of plankton to such an extent that it contributed to the collapse of the fishing industry.

The Chinese Mitten crab has been introduced in Western Europe, the Baltic Sea, and the East coast of North America.

It undertakes mass migrations to reproduce. It buries itself on the banks of rivers and dikes, causing erosion and sediment. 

The European Green Crab is native to the European Atlantic Coast. It has been introduced in South Australia, South Africa, the United States, and Japan. 

It competed with the indigenous crabs, displaced them, and became dominant in the invaded areas. It consumes and depletes a wide range of prey species.

Another recent intruder is the starfish, native to the North Pacific areas like China, Korea, Japan, and Russia. 

It has a diameter of fifty centimeters, and it reproduces extremely quickly since larger adult females can produce up to 19 million eggs between June and September. 

The larvae are capable of staying more than ninety days in the water. It feeds on many mollusks to cause severe alterations to the ecosystem. 

IV. Goby Fish

Gobies are incredibly aggressive fish that compete fiercely with other species for the most appropriate places to spawn.

Its accidental introduction through ballast water into the Great Lakes in 1990 has resulted in a severe environmental, economic and social problem, especially in Lake Superior.

It appeared in 1995, causing enormous damage to fisheries and substantial economic losses.

Risks of Ballast Water

Ballast waters, used in maritime navigation to provide stability to ships and achieve safety and efficient transportation constitute a real threat to marine ecosystems.

They are discharged when ships arrive at another port, generally distant from the origin waters, to carry out loading tasks.

It is common for ballast water to be the primary vector for spreading viruses and bacteria, carrying spores of fungi, small invertebrates, algae, eggs, cysts, and larvae of various species.

They also have other foreign organisms that can thrive in different ecosystems threatening native species and human health.

Some of the life-threatening risks that the ballast water pose are as follows:

1. Carrier of Pathogens

Ballast water can cause environmental and public health problems since it can contain sewage and toxic materials, in addition to endemic animal and plant species. 

They do not have natural predators, so they can reproduce quickly and compete with native species. 

Bacilli or other pathogenic organisms can also be carried from one region to another along with ballast water discharged into the sea.

2. Spread of Contaminants

As the marine traffic of cargo ships is significant, including on international routes, this water can spread contaminants around the world. Around 10 billion tons of ballast water are moved per year worldwide.

In 2001, the National Health Surveillance Agency of Brazil started a study that detected marine bacteria in 71% of ballast water samples from ships in five ports, including bacilli of Vibrio Cholerae O1.

The bacteria that cause human Cholera; survive up to 26 days in seawater, 19 days in fresh water, and 12 days in sewage.

The presence of these organisms can compromise ecosystems and human life if they reach the beaches.

In addition to these vibrios, intestinal enterococci and Escherichia coli have already been found in the ballast water sample.

3. Risk of Bioinvasion

The bioinvasion process can negatively affect the local fauna due to biodiversity loss and ecological imbalance. 

For example, in Brazil, one of the most famous cases of an invasive species is the golden mussel from South America. 

This species is originally from Asia; they were seen first in Argentina, increasing at the mouth of the Rio da Prata until reaching the Paraguay and Parana rivers. 

The golden mussel was registered in Brazil for the first time in the Rio Grande do Sul, reaching the lake of Itaipu and even affecting the maintenance routines of the Itaipu Plant, which is required to have its turbines stopped periodically to remove the mussel.

Australia also complained that the red algae from China had entered there, which was very dangerous.

In 1984 the Oceanographic Museum of Monaco introduced the killer algae to the French shores of the Mediterranean in a bumpy tank cleaning process. 

Then the disaster begins: the French Riviera, the Italian coasts, and the Spanish islands are invaded by a new species that sweeps everything in its path. Later, the fatal organism spreads to places as remote as Croatia.

4. Cause of Environmental Imbalance

Ballast water taken from one water discharged into other waters has led to the conquest of alien aquatic life species. 

The ballast water intake into the ballast tank is responsible for transferring species that harm the environment and the economy—for example, zebra mussels in the Great Lakes of the United States and Canada.

These alien creatures arriving on the ship can then upset the balance of these waters. 

Toxic algae species, for example, can alter entire marine ecosystems by displacing native species and disrupting food chains. 

It can also cause economic damage by adversely affecting local fisheries, but we can’t ignore the health consequences it brings with it.

5. Adverse effects on Human Health

human health - ballast water
Human health exposed to various pathogens (source)

A serious problem is caused by the bacterium Vibrio Cholerae, responsible for cholera disease in human health.

Cholera causes about 120,000 deaths a year, and in Africa, there are 79 million people at risk of suffering from Cholera. 

Between 1991 and 1992, the five freighters docked in the United States, specifically in the Gulf of Mexico, contained Vibrio Cholerae in their ballast water.

And some cholera epidemics seem directly associated with ballast water. For example, an epidemic appeared simultaneously in three ports distanced from each other. 

In Peru in 1991, later spreading throughout South America, having affected more than a million people and causing the death of some ten thousand in 1994. 


Numerous rules and regulations have been formed, and a ballast water management system has been introduced, but they are not followed as they should be.

It is unnecessary that ballast water only carries harmful organisms and pests but can cause severe damage to their new settlement.

Some invaders have affected natural flora and fauna in many places competing for food, habitat, and other resources. 

The worst consequence is the displacement of a native species by an exotic invader. It can cause the extinction of that species and that of other organisms. 

The situation is serious because exotic marine species and organisms transferred cannot be cleaned by artificial physical means, nor absorbed or eliminated naturally by the oceans. They are almost impossible to eradicate through any system and cause severe damage.

(Last Updated on December 9, 2021 by Sadrish Dabadi)

Ankur Pradhan holds a bachelor’s degree in education and health and three years of content writing experience. Addicted to online creative writing, she puts some of what she feels inside her stormy heart on paper. She loves nature, so she is trying to motivate people to switch to alternative energy sources through her articles.