EKOSISTEM AIR TAWAR Freshwater ecosystems SUMBER: ecosystems.ppt

EKOSISTEM AIR TAWARFreshwater ecosystems

SUMBER: https://apesatpvhs.wikispaces.com/file/view/Freshwater+ecosystems.ppt

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


Kinds of freshwater habitats

• Rivers, streams– Flowing freshwater– Source: where it starts– Mouth: where it ends

• Lakes, ponds

• Wetlands


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


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.


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


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



Parts of a lake


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



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


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."


Wetlands

• May be fresh or brackish• Freshwater types include:– Marsh– Swamp– Bog– Fen


Marsh

1. Most common freshwater wetland in U.S.

2. Occur along streams or in depressions3. Characterized by organic, wet soils and

non-woody (i.e., no trees) vegetation.


Swamp

Wetland dominated by woody plants


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.


What good are wetlands?

• Reduce flooding by acting like sponges



• 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.



• Protect shorelines from erosion

• Erosion in this case came from grazing animals


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EKOSISTEM AIR TAWAR Freshwater ecosystems SUMBER: ecosystems.ppt