1. Chapter 7 section 1
Aquatic Ecosystems

2. Aquatic Ecosystems
types of organisms are determined by water’s salinity
divided into freshwater and marine ecosystems.
freshwater- include ponds, lakes, streams, rivers, and wetlands.
Wetlands- areas of land that are sometimes under water or whose soil contains a great deal of moisture.

3. Characteristics of Aquatic Ecosystems
temperature, sunlight, oxygen, and nutrients determine which organisms live in the water.
contain organisms that are grouped by their location
Three groups include: plankton, nekton, and benthos.

4. Characteristics of Aquatic Ecosystems
Plankton
mostly microscopic organisms
float or drift freely in the water
can be microscopic animals called zooplankton or microscopic plants called phytoplankton.
Nekton
swim actively in open water, independent of currents.
Benthos
bottom-dwelling organisms of the sea or ocean and are often attached to hard surfaces.
Decomposers are also aquatic organisms.

5. Freshwater Ecocsystems
Lakes, ponds, and wetlands
form naturally where groundwater reaches the Earth’s surface.
Humans create lakes by damming flowing rivers and streams to use them for power, irrigation, water storage, and recreation.
can be structured into horizontal and vertical zones.
organisms present depend on the amount of sunlight available.

6. Life in a Lake littoral zone - shallow zone
light reaches the bottom and nurtures plants
aquatic life is diverse and abundant.
benthic zone
near the bottom of a pond, lake
too little light for photosynthesis
inhabited by decomposers, bacteria, insect larvae, dead and decaying organisms and clams.

7. A Lake Ecosystem

8. How Nutrients Affect Lakes
Eutrophication
an increase in the amount of nutrients, such as nitrates, in an aquatic ecosystem.
as plants and algae grow, bacteria feeding on the decaying organisms grows.
bacteria use oxygen dissolved in the lake
reduced amounts of oxygen kills other organisms
caused by runoff that can carry sewage, fertilizers, or animal wastes from land

9. Freshwater Wetlands
areas of land covered with fresh water for part of the year.
Two main types:
Marshes
contain nonwoody plants.
Swamps
dominated by woody plants
Most are in the southeastern United States, the largest in the Florida Everglades.

10. Freshwater Wetlands

11. Function of Freshwater Wetlands
act like filters or sponges that absorb and remove pollutants from the water.
control flooding by absorbing extra water when rivers overflow.
provide a home for native and migratory wildlife
feeding and spawning for many freshwater game fish.

12. Marshes
Freshwater marshes tend to occur on low, flat lands and have little water movement.
In shallow waters, plants root themselves in the rich bottom sediments while their leaves stick out about the surface of the water year-round.
There are several kinds of marshes, each of which is characterized by its salinity. Brackish marshes have slightly salty water, while salt marshes contain saltier water.

13. Human Impact on Wetlands
previously considered wastelands that provide breeding grounds for insects.
many have been drained, filled, and cleared for farms or residential and commercial development.
now the law and the federal government protect many wetlands while most states now prohibit the destruction of certain wetlands.

14. Rivers At headwaters (beginning) Flowing downstream
usually cold and full of oxygen
run swiftly through a shallow riverbed.
Flowing downstream
broaden, become warmer, wider, slower, and decrease in oxygen.
Change with the land and the climate through which they flow

15. Rivers in Danger Industries use river water in manufacturing processes
receptacles for wastes
People
-dispose of their sewage and garbage.
Result
-kills river organisms and makes river fish inedible
-runoff from the land puts pesticides and other poisons into rivers and coats riverbeds with toxic sediments.