1. Impacting the Environment
Photo by Felix Andrews
Impacting the Environment

2.
Toxic substances are often introduced into the environment as a result of human activities. Mercury, pesticides, and other pollutants can disrupt the stability of ecosystems and affect entire populations of organisms.

3. These pollutants are often originally found in terrestrial ecosystems, but freshwater runoff carries these pollutants into the water supply of the ecosystem after it rains or as a result of irrigation.

4. Biological Magnification
Runoff carries the mercury and pesticides into the water supply of an ecosystem. Because of this, the greatest effects of this pollution are often seen in aquatic ecosystems: both freshwater and marine.

5. Biological Magnification
The pollutants build up in the fat tissues of animals causing the concentrations of toxins to increase up the food chain. This process is called biological magnification.
Notice that this is opposite to the
way energy and biomass move through the food chain!

6. Predatory birds are often at the top of aquatic food chains, and certain toxins can keep these animals from reproducing properly.

7. Watch the short video over Biological Magnification

8. Photo by Felix Andrews
Photo by Sasha Trubetskoy
Fertilizers are another product humans introduce to ecosystems that can disrupt ecosystem stability. When nitrogen and other nutrients are added to a body of water, it is called eutrophication.

9. Fertilizers are used by farmers to increase their crop yields, but these fertilizers enter the water supply of the ecosystem through freshwater runoff as a result of rain and irrigation.

10. Photo by Felix Andrews
Photo by Sasha Trubetskoy
The addition of nutrients like nitrogen and phosphates allows algae to grow much more rapidly than normal. This rapid growth of algae is called an algal bloom, and algal blooms can have a negative effect on the ecosystem.

11. Algal Bloom
As algae grow rapidly, they begin to reduce the amount of dissolved oxygen that is available in the water. This creates a hypoxic zone which is an area with lower than normal oxygen levels causing fish to die in large numbers.
Fish die due to depleted oxygen levels in the water
Algae use up the oxygen in the water as they rapidly grow.
Photo from Maryland Department of the Environment

12. Algal Bloom
Algae growing on the surface can block light from reaching aquatic plants. Without light, these plants cannot perform photosynthesis and die as a result of the algal bloom.
Photo by Felix Andrews
Photo by Sasha Trubetskoy

13. Keeping nitrogen levels in check prevents the overgrowth of algae!
Algal Bloom
By reducing the overuse of fertilizers, humans can help prevent the disruption of ecosystems that occurs when excess amounts of nitrogen and other nutrients are added to the water supply.
Keeping nitrogen levels in check prevents the overgrowth of algae!
Photo by Sasha Trubetskoy

14. Deforestation
Deforestation is the removal of forest for other uses, and it reduces populations by removing habitats and reducing the biomass of ecosystems.

15. Deforestation
Rainforests are the most diverse ecosystems in the world, and they are being removed at an alarming rate. Deforestation reduces biodiversity by causing mass extinctions.
Photo by Adam J.W.C.

16. Deforestation
Deforestation also leads to more carbon dioxide in the atmosphere as terrestrial producers are destroyed and can no longer absorb CO2.