1. The Great Lakes

2. Watershed
A watershed is a geographic area that includes all of the land and waterways that drain into a body of water. Sometimes a watershed is called a drainage Basin.

3. Food Chain and Food Web
The definition of food chain is a series of plants and animals, each of which depends on the one below it for food. A food chain usually forms part of a much larger food web.
The definition of food web is all of the feeding relationships within an ecosystem. Each living thing in a food web provides food energy to other living things within that ecosystem.

4. Great Lakes Food Chains and Webs

5. Pollution

6. Point and Nonpoint Pollution
Point-source pollution is water pollution from a single place, such as discharge pipe at a plant that treats sewage.
Non-point source pollution is pollution that does not come from a single location, but rather from many sources such as runoff from farms.

7. Point source and Non-point source Pollution

8. Non-point pollution
This silt-laden runoff from a residential area contains not only soil and clay particles from nearby construction, but also is likely to contain small amounts of lawn chemicals, oil, grease, gasoline, and even residues from recent highway de-icing. These are all examples of pollutants released from nonpoint sources.

9. Atmospheric Pollution
Atmospheric pollution Atmospheric pollution (or air deposition) is another form of nonpoint source pollution, though instead of polluting via runoff, the pollution falls from the sky. As water moves through the hydrologic cycle, it falls as rain or snow and then evaporates into the air from land and surface water. Pollutants emitted into the air, such as through smoke stacks, follow this same path, and can be carried through the atmosphere and deposited into waterways hundreds of miles away from its source. Acid rain is the most well-known form of atmospheric pollution. The major sources of atmospheric pollution include coal- burning energy plants and waste incinerators. The combustion of fossil fuels and waste (such as from hospitals) produces large amounts of mercury in the air, a toxic chemical that is fatal to humans and animals in large quantities. Phosphorus and polychlorinated biphenyls (PCBs) are also transported to waterways via air deposition.

10. DDT and PCBs
PCBs are synthetic (human-made) chemicals first produced in the late 1920s.  They were used as cooling fluids in electrical equipment and machinery because of their durability and resistance to fire.
DDT was developed as an insecticide in the 1940s, and was widely used during World War II to combat insect-borne diseases.
DDT’s effectiveness, persistence, and low cost made it popular for agricultural and commercial uses. More than a billion pounds were used in the U.S. over a 30-year period.

11. Animals hurt by pollution