1. Freshwater ecosystems
Kinds
Characteristics
Threats

2. Aquatic ecosystems
Key distinction: salinity = salt content of the water
Measured in parts per thousand (ppt)
1 gm of salt in 1000 gms water = 1 ppt
FRESH usually < 0.5 ppt
OCEANS average 35 ppt
0.5 to 17 ppt is called BRACKISH

3. Kinds of freshwater habitats
Rivers, streams
Flowing freshwater
Source: where it starts
Mouth: where it ends
Lakes, ponds
Wetlands

4. All freshwater ecosystems
Just a fraction of the Earth’s water
.01% = one one-hundredth of one percent
Occupy less than 1 percent of the Earth’s surface

5. Rivers and streams
More than 3.5 million miles of rivers and streams (including intermittent streams)
Just the U.S.! More than 140 times around the Earth.
The miles of rivers and streams in the United States is equivalent to more than 140 times the circumference of the earth – 140 trips around the equator.
Identify some of the regional rivers and streams known by the students.

6. Rivers from start to finish
Source = Headwaters
Can be:
Snowmelt
Spring
Even a lake
Water is colder, clearer, more highly oxygenated
Organisms include trout, mayflies
Mouth: where the river ends
Usually the ocean or another river, or lake
River widens and slows, getting warmer, siltier.
Middle is most diverse, lots of plants
Near mouth, increased sediment limits light and plants, water is warmest

7. What are some of the differences?
Trout stream, NW NJ Mississippi R. Greenville, MS

8. Mouth
Mississippi River
delta

9. Lakes and ponds What’s the difference? Ponds typically smaller
May be seasonal—that is, dry up part of the year
Lakes exist hundreds or thousands of years
But, even lakes can fill in or dry up

11. Parts of a lake

12. Parts of a lake Littoral zone: near shore
Nutrient rich, lots of plant and animal life
Warm
Limnetic zone: near surface, open water
Lots of light
Lots of plankton
Profundal zone: deeper, little light
Benthic zone: the bottom, little light, low oxygen

14. Eutrophication
If nutrients increase too much in a lake, pond, or ocean, excessive plant growth results
Phosphorus
Nitrogen
NOT GOOD: why?
As plants decay, decomposing bacteria use oxygen dissolved in the lake to do their jobs.
Dissolved oxygen goes down

15. Wetlands
CA OR AK

16. Wetlands: what are they?
For regulatory purposes under the Clean Water Act, the term wetlands means "those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas."

17. Wetlands May be fresh or brackish Freshwater types include: Marsh
Swamp
Bog
Fen

18. Marsh Most common freshwater wetland in U.S.
Occur along streams or in depressions
Characterized by organic, wet soils and non-woody (i.e., no trees) vegetation.

19. Swamp
Wetland dominated by woody plants
Common in SE U.S.

20. New Jersey wetlands
About 916,000 acres, or 19% of New Jersey, is wetlands, which seems like a lot; but the bad news is that about 40% of the original 1,500,000 acres has been lost to dredging and filling, dams, farming, development and highways.

21. NJ wetlands

22. What good are wetlands?
Reduce flooding by acting like sponges

24. What good are wetlands? Help clean water by acting like a filter
The plants and slow water flow in a wetland help remove pollutants, leaving water cleaner downstream in a lake or river.
Too much pollution can leave a wetland toxic to visiting animals, such as many birds.

25. What good are wetlands? Protect shorelines from erosion
Erosion in this case came from grazing animals