teach.GLIN.net
GLIN Daily News About GLIN
AboutEnvironmentHistory/CultureGeographyPollutionCareers/BusinessTeachers' Corner
water photo
What's New?

Anglers enlisted in water fight
Great Lakes Echo (6/29)
A recent study by researchers at Cornell University, in N.Y., revealed that anglers in the Great Lakes region are aware of and concerned about the threat of aquatic invasive species (AIS).

Lake State opens Sea Grant office
Sault Ste. Marie Evening News (6/29)
Lake Superior State University officially welcomed its new Michigan Sea Grant office to campus with a ribbon cutting ceremony Monday morning.

Stone Lab hosts series of experts to discuss lake
Port Clinton News Herald (6/28)
In Ohio, people looking to learn more about the issues facing Lake Erie will have several opportunities this summer to hear firsthand from the experts in the field who deal with those issues every day.

Goal of UWM habitat study is to help restore fisheries in river
Milwaukee Journal Sentinel (6/25)
Led by University of Wisconsin-Milwaukee's School of Freshwater Sciences, a habitat study's goal is to identify habitat that supports estuary fish and recommend strategies to protect, encourage and connect these habitats in harbor revitalization and habitat restoration plans.

Funding milestone reached for Aquatic Research Lab expansion
The Sault Ste. Marie Evening News (6/13)
Both houses of Michiganís legislature have approved nearly $9 million in funding for an expansion of Lake Superior State Universityís successful Aquatic Research Lab (ARL).

Students dive, document Sheboygan shipwreck
Sheboygan Press (6/13)
A team of budding nautical archaeologists from East Carolina University dove below the waves of Lake Michigan to discover what treasures lay hidden on the sandy bottom.

TEACH Calendar of Events
What's going on in your neighborhood this month? Meet other people and learn together at recreational and educational events! Our new dynamic calendar is updated daily with current educational events.
TEACH Invasive Species

4 | How do invasive species get here?

Ballast transport
Ballast water is fresh or saltwater (sometimes containing sediments) held in tanks and cargo holds of ships. Ballast water is pumped onto ships at different ports of call to add weight to ships that may be carrying little or no cargo. These ships are considered to have "ballast on board" (BOB). Ballast water release. Click to see larger image.The added weight of the ballast water causes the vessel to sit lower in the lakes or ocean, thus providing stability and maneuverability during voyage and clearance under structures, such as bridges, in waterways. Even ships that have "no ballast on board" (NOBOB) may have water and sediments that could not be completely pumped out of the ballast tanks.

Once NOBOB and BOB ships arrive in another port of call, the water held in ballast tanks is discharged, exchanged or water is added. This ballast exchange may occur at multiple ports of call during a vessel's long journey. Larger vessels often carry millions of gallons of ballast water and, with more than 80 percent of the world's commodities carried on ships, that is a lot of water traveling around the globe every year!

But it is not only water or sediments that goes into ballast tanks. When ballast water is pumped into the ship at a port, it includes organisms found in that port. These organisms range in size from microscopic phytoplankton and zooplankton to crabs and fish. According to MIT Sea Grant, it is estimated that as many as 3,000 exotic species are carried in ships' ballast every day around the globe.

Those organisms that survive the trip are ultimately released when the ballast water is discharged at the final port destination. In many cases, the nonindigenous species are not kept in check by the indigenous predators and competitors they might find in their native waters. Therefore, they have a very good chance of increasing their population and out-competing native organisms for food and space. Though not all species brought in ballast water have disastrous effects on the Great Lakes (or even survive the trip), zebra mussels are a good example of the ecological and economic damage ballast-borne invasive species can cause.

Other routes of invasion
Although ballast water is considered the primary pathway of invasion into the Great Lakes, nonindigenous species have been introduced to the lakes in the following ways:
  • removal of physical barriers during the building of canals (such as the Chicago Sanitary and Ship Canal)
  • accidental introduction or unintential release of organisms through aquaculture ("fish farming"), the aquarium trade, or the use of exotic bait for fishing
  • through the stocking of sport fish

Graphic: Ballast water release. Courtesy L. David Smith/MIT Sea Grant.

1 | 2 | 3 | 4 | 5 | 6 | 7   Next page