1. Happy Wednesday! – 10/26
What is the role of decomposers in an ecosystem?
A They recycle oxygen back into the ecosystem.
B They recycle energy from dead organisms back to the ecosystem.
C They absorb energy from sunlight to pass on to other organisms.
D They obtain and use the energy that remains in living organisms.

2. Chapter 7: Aquatic Ecosystems
Section 1 – Freshwater Ecosystems

3. Introduction
The types of organisms in an aquatic ecosystem are mainly determined by the water’s salinity (amount of dissolved salts).
Aquatic ecosystems divided into freshwater ecosystems and marine ecosystems.

4. Characteristics of Aquatic Ecosystems
Factors such as temperature, sunlight, oxygen, and nutrients determine which organisms live in which areas of the water.

5. Characteristics of Aquatic Ecosystems
3 groups of aquatic organisms:
1. Plankton – organisms that float near the surface of the water a. Phytoplankton – microscopic plants
b. Zooplankton – microscopic animals

6. Characteristics of Aquatic Ecosystems
3 groups of aquatic organisms:
2. Nekton – free-swimming organisms Ex. Fish, turtles, and
whales

7. Characteristics of Aquatic Ecosystems
3 groups of aquatic organisms:
3. Benthos – bottom-dwelling organisms Ex. Mussels, worms,
and barnacles
- Many bottom-dwellers live attached to rocks.

8. Lakes and Ponds
Lakes, ponds, and wetlands can form naturally where groundwater reaches the Earth’s surface.
Humans intentionally create artificial lakes by damming flowing rivers and streams to use them for power, irrigation, water storage, and recreation.

9. Life in a Lake
Lakes and ponds can be structured into horizontal and vertical zones.
Littoral zone – nutrient-rich layer near the shore with abundant, diverse aquatic life
Ex. Cattails, Reeds, Pond lillies, Algae
Benthic zone – bottom of a pond or lake with dead and decaying organisms
Ex. Decomposers, Insect larvae, Clams

10. How Nutrients Affect Lakes
Eutrophication is an increase in the amount of nutrients in an aquatic ecosystem.
A lake that has a large amount of plant growth due to nutrients is known as a eutrophic lake.

11. How Nutrients Affect Lakes
As plants and algae increase, the number of bacteria increase.
Bacteria drain the oxygen from the lake, and now organisms who need the oxygen die.

12. How Nutrients Affect Lakes
Eutrophication can be accelerated by runoff.
Runoff is precipitation that can carry sewage, fertilizers, or animal wastes from land into bodies of water.

13. Happy Halloween! – 10/31
Which of the following processes describes an increase in the amount of nutrients in an aquatic ecosystem?
A Oligotrophication
B Eutrophication
C Autotrophication
D Heterotrophication

14. Freshwater Wetlands
Freshwater wetlands are areas of land that are covered with fresh water for at least part of the year.
2 main types are marshes and swamps.

15. Freshwater Wetlands
Wetlands perform several important environmental functions:
Trapping and filtering sediments, nutrients, and pollutants
Reducing likelihood of a flood
Buffering shorelines against erosion
Providing habitat for rare, threatened, ad endangered plants and animals

16. Marshes Located in southeastern United States
Florida Everglades is largest freshwater marsh in US.

17. Marshes Occur on low, flat land and have little water movement
Benthic zones are nutrient rich and contain plants, numerous decomposers, and scavengers.
Attract migratory birds

18. Swamps Occur on flat, poorly drained land, often near streams
Dominated by woody shrubs or water-loving trees

19. Swamps Mangrove swamps occur in warm climates near ocean.
Freshwater swamps are ideal habitat for many amphibians.
Swamps attract wood ducks and reptiles like American alligator.

20. Human Impact on Wetlands
Wetlands were previously considered to be wastelands.
Many have been drained, filled, and cleared for farms or residential and commercial development.
Law and the federal government protect many wetlands.

21. Rivers Many rivers originate from snow melt in mountains.
At its headwaters, a river is usually cold and full of oxygen and runs swiftly through a shallow riverbed.
As a river flows down a mountain, a river may broaden, become warmer, wider, and slower and decrease in oxygen.

22. Life in a River
In headwaters mosses anchor themselves to rocks by using rootlike structures called rhizoids.
Trout and minnows are adapted to cold, oxygen-rich headwaters.

23. Life in a River
Farther downstream, plankton can float in the warmer, calmer waters.
Fish such as catfish and carp also live in the calmer waters.

24. Rivers in Danger
Industries use river water in manufacturing processes and as receptacles for waste.
People have used rivers to dispose of their sewage and garbage.

25. Rivers in Danger
These practices have polluted rivers with toxins, which have killed river organisms and made river fish inedible.
Runoff from the land puts pesticides and other poisons into rivers.