Ballast Water OrganismsBy Cynthia Kirk
This is the VOA Special English ENVIRONMENT REPORT.
Scientists are concerned about possible diseases that can be spread from the ballast water of ships. Ballast water is held in tanks or in cargo areas of ships. It helps keep the ship floating when the ship is not carrying enough heavy cargo.
It is used to keep the ship balanced when it is sailing in the open ocean. Large ships usually carry millions of tons of ballast water. The ship later releases the water at ports of call. Almost ninety-million tons of foreign ballast water are released into ports in the United States each year.
Ballast water can contain millions of large and small organisms. Some of these organisms may threaten life in the oceans or may be harmful to human health. American scientists are examining the ballast water of ships to find better ways to deal with the possible environmental risks.
Ballast water often comes from polluted coastal areas. It can contain thousands of millions of living organisms. Some of them are harmless. But the water may also contain harmful species that could invade areas where they are released. Scientists say these invaders can destroy native species or carry diseases and parasites that can infect local populations.
Scientists in the United States say small organisms in ballast water such as bacteria are an even bigger environmental threat. They studied samples of ballast water from fifteen ships in the Chesapeake Bay near the states of Virginia and Maryland. The ships were mainly from Europe and the Mediterranean Sea. They found that the ballast water contained large amounts of bacteria and suspected viruses. They also found bacteria that cause the disease cholera.
Some scientists and environmentalists are calling for stronger restrictions on dumping ballast water to control the invasion of foreign species. They say ships should be required to dump the water far out at sea and away from coastal areas.
Some countries are developing ways to control the escape of invasive species in the water. And the shipping industry has been developing new technologies to destroy them before reaching port. But experts say microorganisms are difficult to control. This is because of their extremely small size, resistance to extreme temperatures and ability to change in the environment.
This VOA Special English ENVIRONMENT REPORT was written by Cynthia Kirk.