MIT Sea Grant Center for Coastal Resources

Ballast Water

Ballast Water DischargeBallast Water Release. Courtesy of L. David Smith

What is Ballast Water?

In order to maintain stability during transit along coasts and on the open ocean, ships fill their ballast tanks with water. Large ships often carry millions of gallons of ballast water. This water is taken from coastal port areas and transported with the ship to the next port of call where the water may be discharged or exchanged.

What are the Problems with Ballast Water?

Coastal port areas are home to a wide variety of organisms that live in the water and bottom sediments. As a ship loads ballast it also loads many of the organisms living in that port. These organisms range in size and phyla, from microscopic plants and animals to mussels, crabs, and even schools of fish!

The ballast water of shipping vessels has been a primary method of alien species introduction throughout the world. Scientists estimate that as many as 3,000 alien species per day are transported in ships around the world, however, not all transported species survive the trip and their new home. Some of the species that do survive the trip are able to thrive in their new environment. These bioinvaders can cause disruptions in the natural ecosystem, economic troubles, and even carry human diseases.

What can we do about this problem?

Most of the current strategies to deal with the problems posed by ballast water focus on minimizing transport and recommend exchanges where ships discharge and refill their ballast tanks in the open ocean. The United Nations International Maritime Organization and the United States government recommend open ocean ballast water exchange; however, very few countries have adopted this recommendation as law.

If you are concerned about the problems with ballast water release, contact your state and federal representatives to draw their attention to this problem and ask them to look into measures that control the release of exotic organisms from ballast water.

Ballast Water Fact Sheet (link)

Ballast Water Treatment Options (PDF - 528KB)

National Ballast Survey
(PDF - 128KB)

Ballast Water References (link)


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  this page last updated on: 12 April, 2006