1. Ships Ballast Why the zebra mussel is in Minnesota

2. The Need for Ballast  Ballast is used in boats to provide stability  Ballast can be people, weights in the bottom of the boat and keels.  Ballast is used in boats to provide stability  Ballast can be people, weights in the bottom of the boat and keels.

3. Human ballast  The people on their sailboats provide ballast to prevent their sailboat from tipping over.  The farther out they can hang the faster the sailboat can go without tipping over.  The people on their sailboats provide ballast to prevent their sailboat from tipping over.  The farther out they can hang the faster the sailboat can go without tipping over.

4. Cargo Ships  On cargo vessels water ballast is added to tanks in the ship.  This helps the ship travel at the proper depth.  This improves propeller immersion, steering and helps to control trim and draft.  On cargo vessels water ballast is added to tanks in the ship.  This helps the ship travel at the proper depth.  This improves propeller immersion, steering and helps to control trim and draft.

5. Ballast Tanks  The tanks are located near the bottom of the ship.  Because water is not very heavy a large ship may need to pump in a large amount of water to be stable  The tanks are located near the bottom of the ship.  Because water is not very heavy a large ship may need to pump in a large amount of water to be stable

6. Without Ballast a ship can be in trouble  This ships ballast tank and pump malfunctioned.  Too much water was pumped out of a nearly empty ship in fresh water.  This ships ballast tank and pump malfunctioned.  Too much water was pumped out of a nearly empty ship in fresh water.

7. How it works

8. A Ship discharging ballast in Duluth

9. All kinds of organisms can stay alive in ballast water and be discharged in a new place.

10. The Caspian shrimp is one of over 20 foreign species that have thrived in Lake Superior.

11. Eurasian Ruffe - first discovered in 1980. Tends to crowd out more desirable fish species.

12. Efforts are being made to inspect and sterilize the ballast water.

13. In the Ballast free ship water is constantly streaming through the ship, so no invader can make it to the destination port.