Ballast water discharge and the environment

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A cargo ship discharging ballast water into the sea.
Diagram showing the water pollution of the seas from untreated ballast water discharges

Ballast water discharges by ships can have a negative impact on the marine environment.

Cruise ships, large tankers, and bulk cargo carriers use a huge amount of ballast water, which is often taken on in the coastal waters in one region after ships discharge wastewater or unload cargo, and discharged at the next port of call, wherever more cargo is loaded. Ballast water discharge typically contains a variety of biological materials, including plants, animals, viruses, and bacteria. These materials often include non-native, nuisance, exotic species that can cause extensive ecological and economic damage to aquatic ecosystems, along with serious human health issues including death.

Problematic species[edit]

There are hundreds of organisms carried in ballast water that cause problematic ecological effects outside of their natural range. The International Maritime Organization list the ten most unwanted species as:[1]

Ballast water issues by country[edit]

New Zealand[edit]

The ballast tanks in New Zealand carry animals and plants that kill ecosystems. Ballast tanks are only used in cargo ships there. Ballast water is controlled under the Biosecurity Act 1993 in New Zealand.


A form of cholera, Vibrio cholerae, previously reported only in Bangladesh apparently arrived via ballast water in Peru in 1991, killing more than 10,000 people over the following three years.[2]

United States[edit]

The zebra mussel, native to the Caspian and Black Seas arrived in Lake St. Clair in the ballast water of a transatlantic freighter in 1988 and within 10 years spread to all of the five neighbouring Great Lakes. The economic cost of this introduction has been estimated by the U.S. Fish and Wildlife Service at about $5 billion.

Ballast water discharges are believed to be the leading source of invasive species in U.S. marine waters, thus posing public health and environmental risks, as well as significant economic cost to industries such as water and power utilities, commercial and recreational fisheries, agriculture, and tourism.[3] Studies suggest that the economic cost just from introduction of pest mollusks (zebra mussels, the Asian clam, and others) to U.S. aquatic ecosystems is more than $6 billion per year.[4]

Congress passed the National Invasive Species Act in 1996 in order to regulate ballast water discharges.[5] The Coast Guard issued ballast water regulations in 2012.[6] Under the authority of the Clean Water Act, the Environmental Protection Agency published its latest Vessel General Permit in 2013. The permit sets numeric ballast water discharge limits for commercial vessels 79 feet (24 m) in length or greater.[7] EPA issued a separate permit for smaller commercial vessels in 2014.[8][9]


Among 818 ports in the Pacific region, Singapore along accounts for an estimated of 26% of cross-region (long range) species exchange. Via targeted ballast management on Singapore and a few other "influential" ports, cross-region species exchange to/from the Pacific region can be combinatorially reduced.[10]

See also[edit]


  1. ^ "International Convention for the Control and Management of Ships' Ballast Water and Sediments". International Maritime Organization. Retrieved 2009-07-11. [dead link]
  2. ^ Living Beyond Our Means: Millennium Ecosystem Assessment, 2005. Statement from the Board
  3. ^ Statement of Catherine Hazlewood, The Ocean Conservancy, “Ballast Water Management: New International Standards and NISA Reauthorization,” Hearing, House Transportation and Infrastructure Subcommittee on Water Resources and Environment, 108th Cong., 2nd sess., March 25, 2004.
  4. ^ David Pimentel, Lori Lach, Rodolfo Zuniga, and Doug Morrison, “Environmental and Economic Costs Associated with Non-indigenous Species in the United States,” presented at AAAS Conference, Anaheim, CA, January 24, 1999.
  5. ^ Pub. L. 104-332. October 26, 1996.
  6. ^ U.S. Coast Guard, Washington, D.C. "Standards for Living Organisms in Ships’ Ballast Water Discharged in U.S. Waters." Federal Register, 77 FR 17254, 2012-03-23.
  7. ^ U.S. Environmental Protection Agency (EPA), Washington, D.C. (2013) "Vessel General Permit."
  8. ^ EPA (2014-09-10). "Final National Pollutant Discharge Elimination System (NPDES) Small Vessel General Permit for Discharges Incidental to the Normal Operation of Vessels Less Than 79 Feet." Federal Register. 79 FR 53702.
  9. ^ "Small Vessel General Permit". NPDES: Vessel Discharges. EPA. 2015-01-09. Retrieved 2015-07-19. 
  10. ^ Xu, Jian; Wickramarathne, Thanuka L.; Chawla, Nitesh V.; Grey, Erin K.; Steinhaeuser, Karsten; Keller, Reuben P.; Drake, John M.; Lodge, David M. (2014). "Improving management of aquatic invasions by integrating shipping network, ecological, and environmental data". pp. 1699–1708. doi:10.1145/2623330.2623364. 

External links[edit]