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Aquatic Ecology Limnology- study of freshwater ecosystems

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Presentation on theme: "Aquatic Ecology Limnology- study of freshwater ecosystems"— Presentation transcript:

1 Aquatic Ecology Limnology- study of freshwater ecosystems
Lentic- standing water Lotic- moving water

2 Lentic Ecosystems Depressions in land 1-2,000 meters deep
In northern hemispheres, glaciers left behind carved out basins that filled with rain and snow Other causes include: Silt, driftwood and other materials that block the flow of streams Streams that were flat get cut off to create “oxbows”

3 Lentic Ecosystems Craters from extinct volcanoes fill with water

4 Lake Formation Many lakes are formed by one of two mammals
Humans- dam rivers for power, irrigation, digging Beavers- dam streams to form shallow ponds or lakes

5 Lake Layers 3 layers Epilimnion- “upper lake” consists of a free circulating upper layer Metalimnion- also called thermocline or “middle lake” has a rapid decline in temperature (1 degree Celsius for every meter you go down) Hypolimnion- “lower lake” is the deep, colder layer

6 Lake Structure Littoral zone- shallow water zone, light reaches the bottom and it usually has plants Emergents- plants whose roots and stems are in water but upper stems and leaves are out of the water Limnetic or Pelagic zone- open water, and has Plankton- suspended organisms Nekton- free swimming fish

7 Lake Zones Benthic zone- sediment on bottom of lakes and ponds
Photic zone- where light penetrates to the bottom Aphotic zone- under water area where light does not reach Eutrophic- nutrient rich Oligotrophic- nutrient poor Hypertrophic- excessive nutrients

8 Lake Temperatures Summer/Spring
Water is warm on top and cold on bottom

9 Lake Temperatures Fall/winter
Temperature on surface drops and metalimnion sinks Epilimnion increases until all water is the same temperature\ Water circulates oxygen and nutrients Overturn- seasonal mixing of water

10 Water Chemistry Dissolved Oxygen (DO)
Enters the water through the atmosphere and photosynthesis Amount of oxygen the water can hold depends on pressure, temperature, and salinity Cold water holds more oxygen that warm water As atmospheric pressure increases, so does the amount of oxygen in the water Oxygen absorbed by the surface is mixed by turbulence of internal currents Overturn replenishes oxygen in the water

11 Water Chemistry Carbon Dioxide
Carbon dioxide is usually the same concentration as that in the atmosphere

12 Water Chemistry pH A measure of the acidic or basic the water is
On a scale of 1-14 1 is very acidic and 14 is very basic 7 is neutral Freshwater 3-10 Rainwater 5-6 Streams and lakes Limestone under the water causes the pH to increase (or become more basic)

13 Lotic Ecosystems Flowing water (rivers and streams)
Velocity and current decide most things because it cuts channels and affects living organisms Velocity is determined by size, shape, gradient of the channel, roughness of bottom, depth, and precipitation

14 Streams May begin as outlets of ponds or lakes
Flow is determined by the lay of the land if the stream has not been disturbed As water flows, it picks up debris that scrapes the bottom and makes the stream bigger

15 Terms Meander- bends in streams (aka. Sinuosity)
Watershed- body of land where all runoff collects in a common body of water Turbidity- the amount of particles suspended in water prohibiting light to shine through Channel- the stream bed and banks formed by flowing water Flood Plain- a strip of land that is normally dry and flat that is on the sides of a river or stream and is wet during floods.

16 Terms Riparian Zone- the land and vegetation bordering flowing or standing water Riffle- a section of a stream where the water is shallow, fast moving, and is broken into waves by an obstruction Siltation- deposition of fine particles (silt) on the beds of streams or lakes Pools- water that is relatively deep Bankfull Width- where water will stop if it comes out of the stream

17 How can you tell if a stream is healthy?
Stream Quality is determined by Area cover Do things hang over the stream? Embeddedness Are there dirt particles on the bottom? Depth Is the stream shallow or deep? Sediment deposits Are there sediment build ups? Channel flow Does water fill up the channel?

18 Stream quality continued…
Channel Alteration Has concrete, rock, or anything else been added to the stream? Frequency of riffles or bends Does the stream curve or have any white water? Bank stability Are the banks falling into the stream? Vegetative Protection (on the banks) Are there plants growing on the banks? Riparian zone width How big is the area on the bank where plants grow?


20 Stream Chemistry pH A range of 6-9 is ideal for running freshwater fish and bottom dwelling invertebrates Synergistic Effects Happens when two things combine to produce effects greater than their sum Example.) Pollutants can change the pH of a stream

21 Stream Chemistry Dissolved Oxygen (DO)
If dissolved oxygen drops below 5 mg per liter, aquatic life is stressed The lower the concentration, the more stress Levels below 1-2 mg per liter for a few hours result in “fish kills”

22 Stream Chemistry BOD (biochemical oxygen demand)
The amount of oxygen needed for decomposition If there is little oxygen, decomposers that use it will die Too much oxygen causes “gas bubble disease” Rare Oxygen blocks blood vessels Can see bubbles on the fins and the skin


24 Stream Orders Streams join together to form rivers. Each time one stream joins another “order” changes. A first order stream is one that does not have any other stream joining it. A stream can only increase in order if a stream of a similar order joins it. For example, when a first order stream runs into another first order stream, it becomes a second order stream. Likewise, when two second order streams join each other, it becomes a third order stream and so on.

25 Stream Orders Order is not increased when a lower order stream joins one of a larger order. Generally: First through third order streams are usually called headwater streams Fourth through sixth order streams are usually called medium-sized streams Above sixth order, the streams become rivers Lower order streams are usually on steep slopes compared to higher order streams Higher order streams have flood plains

26 A watershed is a section of land where all the water runoff flows into a common basin.

27 Stream Restoration There are many aspects to stream restoration, but some suggestions would be: Decrease the slope of the banks (if it will not compromise or eliminate the riparian zone). This is generally accomplished by using a 3:1 ratio.Stream3 ft.1 ft.Bank Reduces the stress on channel walls from flowing water Becomes more stable Stops erosion and sedimentation Creates a surface for vegetation Stream 3 ft. 1ft. Bank

28 Stream Restoration Stabilize the Stream Banks Riparian Forestation
Plant native vegetation on the stream banks to stop erosion. The roots of the plants will hold the soil onto the banks. Add big structures to the banks like wood, stone, or fabric that will not wash away. Fabric provides a surface to hold planted vegetation. Drive posts into the bank to keep soil from eroding into the stream. Make the channel bigger.

29 Stream Restoration Construct riffles and pools
Adding large rocks and/or other materials from the site to the stream prevents natural areas from being disturbed by trucks hauling rock to the stream. Allows more DO to enter the water Slows the velocity of flowing water Before adding rock to the stream, organic matter must be cleared from the bottom to be sure the rock will be stable. The rock must be lower than the bank.

30 Stream Restoration Cut and Fill
Widening the channel in a particular area to allow water a larger surface to pass over If the channel has been cut very deep, the water will not be able to get into the flood plain. By adding rock to the bottom of the channel, the water level is raised allowing it to reach the flood plain if needed.

31 Stream Restoration Add a waterfall Remove garbage
Create a difference in elevation allowing the water to fall. This will increase DO, slow the flow of the water, and create a habitat for aquatic life. Remove garbage

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