1. Human Impact on Aquatic Ecosystems

2. 1. 40% of the world's oceans are heavily impacted by human activities
2. The areas with the least impact are near the poles

3. Major Threats to Marine Systems from Human Activities
Coastal development – destroys and pollutes coastal habitats
Runoff from agricultural and urban sources such as sediment from soil erosion, fertilizer, pesticides, livestock waste
Pollution from ships and oil spills
Overfishing of commercial fish species
Using fish trawlers (dragging weighted nets across ocean floor) which degrades and destroys habitat
Introducing invasive species
Human induced climate change

4. Dissolved Oxygen verses Biochemical Oxygen Demand
1. Oxygen is measured in its dissolved form as dissolved oxygen (DO). If more oxygen is consumed than is produced, dissolved oxygen levels decline and some sensitive animals may move away, weaken, or die.
2. Biochemical oxygen demand, or BOD, measures the amount of oxygen consumed by microorganisms in decomposing organic matter in stream water.
3. BOD directly affects the amount of dissolved oxygen in rivers and streams. The greater the BOD, the more rapidly oxygen is depleted in the stream. This means less oxygen is available to higher forms of aquatic life.

5. Zone of Hypoxia
Forms from nutrient overload of N & P from fertilizer runoff (inorganic or livestock waste) in streams which empty into rivers which empty into the ocean

6. Hypoxia Facts
1.7 million tons of nutrients are delivered to the Gulf of Mexico each year
41% of continental US drains into Gulf of Mexico
70% of nutrient load comes from agricultural runoff (surface water runoff form agricultural land) MOST comes from the MIDWEST
12 million people live in urban area along the Mississippi River that dump treated sewage into the Mississippi River

7. Cause of Hypoxia in the Gulf of Mexico
Rivers that empty into the Gulf of Mexico that carry runoff from agriculture and cities contribute to hypoxia in the Gulf of Mexico

8. Habitat Loss Due to Poor Water Quality: Threatens Populations
Algae bloom coats submerged aquatic vegetation (SAV) which reduces their photosynthetic output.
SAV provides food, shelter, & nursery areas for blue crabs
Blue crabs , but are major predators of benthic communities and are prey for many other fish species.

9. Coral Bleaching
Corals expel algae from tissues when stressed; causes corals to turn completely white
Causes of stress include:
Warm water temps
Cold water temps
Lack of light
When coral bleaches, it is not completely dead
Corals can survive a bleaching event, but they are under more stress & are subject to mortality

10. Where Coral Bleaching is Occurring

11. Deepwater Horizon Explosion in Gulf of Mexico (Possible FRQ this year)
million gallons of crude oil leaked into Gulf of Mexico
2. The presence of discharged oil in the environment causes
decreased habitat use in the area
altered migration patterns
altered food availability
disrupted life cycles
Oiled plants die, eliminating the roots that help bind and stabilize soil, leading to erosion.
Some of the oil evaporated into the air as benzene (carcinogen) and hydrogen sulfide (combines with water to form acid rain)

12. How Quickly Oil Traveled

13. The Clean-up
1. Efforts have focused on capping, cutting off, containing, and capturing oil.
2. These collective efforts under water and on the surface of the Gulf were intended to keep the oil from reaching coastal marshes and wetlands
3. Within days there were reports that oil had reached coastal areas and had begun to affect land and wildlife
4. Oiling continued more than 100 days after the explosion: on August 1, 10% of Gulf coast shoreline miles were oiled

14. Freshwater Inland Wetlands: Vital Sponges
Inland wetlands act like natural sponges that absorb and store excess water from storms and provide a variety of wildlife habitats. 14

16. Freshwater Inland Wetlands: Vital Sponges
1. Filter and degrade pollutants
2. Reduce flooding and erosion by absorbing slowly releasing overflows.
3. Help replenish stream flows during dry periods.
4. Help recharge ground aquifers.
5. Provide economic resources and recreation.

17. Cultural Eutrophication
1. Phosphate has been the biggest problem because it accumulates over time.
2. Nitrate is a lesser problem because it denitrifies over time
3. Result can be large fish kills if not controlled

18. Correcting Cultural Eutrophication
1. Try to find the source of nutrients (nitrates and phosphates) and stop them from entering lake
2. Dredge the lake
Dredge: removing sediments and organic debris from the bottom of the lake and disposing of them in a different location.
3. Applying ecosystem herbicides to kill invasive / nuisance plants
4. Aerate the lower levels to give oxygen to decomposers
5. Introduce insects that will feed on plants

19. Introduced / Invasive Species
1. Hydrilla can grow in deep & shallow water
2. Can grow in water that has 7% salinity
3. Slows water flow
4. Clogs irrigation and flood-control canals
5. Crowds out and outcompetes native species such as tapeweed, pondweed, and coontails
1. Zebra Mussels – introduced in Great lakes from Caspian Sea
2. Filter feeders, eat algae
3. Anchor themselves onto native mussel species which prevents native mussels from eating
4. Also clog outlet pipes, preventing drainage of an area & can result in flooding

20. Dams
1. Dams alter the pattern of disturbances that the plants and animals of a river have evolved
Many aquatic animals coordinate their reproductive cycles with annual flood seasons
Floods provide nutrients for the river’s plants & animals
Floods provide shallow backwater areas on vegetated land & shaded riversides which protect young organisms
2. Dams interfere with fish migrations
Many fish species must move upstream and downstream to complete their lifecycles.

21. Largest Hydroelectric Dam in the World
The Three Gorges Dam is the largest hydroelectric dam in the world. It is located in the middle of the tree gorges on the Yangtze River, (CHINA) the third longest in the world.

22. Levees 1. How levees affect ecosystems:
a. limit & redirect surface water flow
b. limit the movements of species, energy, & ecosystem processes such as fire
2. Levees fail in many ways
Breach: When a part of the
levee breaks away, leaving an
opening for water to flow
through
Overtopping: When flood waters
reach a level higher than the
levee crest
Bank erosion
Slope instability
Seepage of water through soils
beneath the levee
Levees

23. Watersheds
A watershed is area of land where all of the water that is under it or drains off of it goes into the same place.
1. What word is used to describe the area around the lowest point of the river?
2. What are two sources of possible pollution shown on the map?
3. Why are wetlands more affected by pollution than other parts of the watershed?
Wetlands
sewage treatment plant, runoff from farm, sediment from construction
They receive pollution from all water sources that drain into them

24. Watershed Divide 1. Label the main river channel on the map.
2. Look at the spot marked by the on the map and on the cross section of the terrain. Notice where the is pointing. Will pollution from the site likely affect the watershed? Why or why not?
Main river channel