Freshwater Ecosystems Notes
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Transcript of Freshwater Ecosystems Notes
Freshwater Ecosystems Notes
The study of fresh bodies of water
Lentic: standing water (lakes and ponds)
Lotic: flowing water (streams and rivers)
Limnology
How might they be different?
Lentic vs Lotic
Glacial erosion and deposition - movement of glaciers eroded land (Great Lakes)
Deposition of silt, driftwood, and other debris in slow-flowing streams- cuts off a meander and forms a crescent shape or oxbow lake.
Formation of lakes and ponds:
Shifts in the Earth’s crust- tectonic movement; valleys and craters fill with water
Nongeological activity: manmade dams, log jams, strip mining (all lakes in TX except one, which one???)
Formation of lakes cont.
High specific heat of water make aquatic environment temperatures more stable than terrestrial
Epilimnion: surface water, small temperature change
Metalimnion: middle mass of water with a rapid temperature decline (1°C/ meter)Thermocline: temperature gradient found in metalimnion
Hypolimnion: deep cold layer cutoff from air; most dense
Physical Characteristics
Summer- large thermocline. Why? Winter- Surface water loses heat to
atmosphere therefore thermocline decreases
Overturn: surface water temp. decreases and causes water to mix and stir up nutrients and dissolved oxygen because of density changes (Fall and Spring)
Seasonal Fluctuations
Enters the water by absorption from the atmosphere and by photosynthesis
The amount of oxygen and other gases water can hold depends upon pressure and temperature
As temperature increases- solubility of dissolved oxygen decreases
As pressure increase- solubility of DO increases
Dissolved Oxygen (D.O.)
Water loses oxygen through increased temperature, increased respiration of aquatic life, and aerobic decomposition
During the summer, oxygen may become stratified in lakes and ponds
The quantity of oxygen decreases with depth because of decomposition in the bottom sediments
During Spring and Fall overturn- water circulation (churning) replenishes oxygen in the bottom
In winter- DO decreases slightly with depth; DO is more stable because cold water can hold more DO than warm water
The depth to which light penetrates is limited by turbidity of the water and the absorption of light rays
Trophogenic zone- layer through which light can penetrate and where photosynthesis occurs (photic zone)
Tropholytic zone- layer through which light cannot pass through and where decomposition occurs
Compensation level-where photosynthesis ends and decomposition begins
Sunlight
1. Littoral zone- (horizontal) shallow water zone where light penetrates the bottom
emergents- plants whose roots are underwater and stems and leaves are above water. Live in the littoral zone.
submergents-completely below water
Trophogenic Zone: separated into two zones
2. Limnetic Zone -Open water zone where photosynthesis occurs
Plankton- suspended/floating organism Phytoplankton- photosynthetic plankton;
algae Zooplankton- animal-like plankton;
rotifer Nekton-free swimming organisms
Is carried out in the limnetic zone by phytoplankton (ALGAE) and in the littoral zone by macrophytes- large aquatic plants (emergents and submergents)
6CO2 + 6H2O + light C6H12O6 + 6O2
(photosynthetic equation)
Primary Production
Drawing: Lentic Ecosystem in mid-summer1)Title your paper Lentic Ecosystem- mid-summer
2) Draw a cross section of a lake on your paper (this should take up a considerable amount of room on your paper).
3) Use your Freshwater Ecosystem Notes and laptop to label following on the cross section of a lake:
4) Use your freshwater Ecosystem Notes and laptop and draw in examples in their proper places of the following the cross section of a lake:
Littoral Zone, Limnetic Zone, Trophogenic Zone, Tropholytic Zone, Compensation Depth
Epilimnion, Metalimnion, Hypolimnion, Thermocline, Benthic Zone
sun, sun rays, emergents, submergents, algae, and fish.
Label where decomposition and photosynthesis are occurring.
1. Rainwater runs off - dissolves and carries nutrients into lakes.
2. Water carries with it silt, clay, organic matter, and nutrients in solution to enrich the aquatic ecosystem
3. Human activities including road building, logging, mining, construction, and agriculture add to the amount of silt and organic matter
Nutrients
Eutrophication- nutrient enrichment of an aquatic ecosystem
Oligotrophication- nutrient poor aquatic ecosystem
Nutrient status cont.
Deeper, steep sides Poorly developed littoral zone Blue-green water, clear High in DO Poor in phosphorous, nitrogen, and calcium Few organisms but a high diversity Very little organic matter
Oligotrophic System
Oligotrophic
Shallow Rich in organic matter and nutrients DO depletion in hypolimnion during summer
due to decomposition Eventually will turn into a bog or marsh Lots of organisms, low diversity
Eutrophic Systems
Eutrophic
Eutrophic vs Oligotrophic
For a healthy ecosystem you want a balance between eutrophic and oligotrophic.
There needs to be enough nutrients for organisms to grow and reproduce.
Flowing Water Habitats Creeks, streams, and rivers
The flow of the water influences the lives of the organisms inhabiting the waters and the physical characteristics of the stream.
Lotic Ecosystems
http://www.scienceclarified.com/landforms/images/ueol_03_img0108.jpg
Headwaters: streams that join together and form a river
Near headwaters river usually flow fast and currents are swift
Rocky bottom Higher levels of D.O. due to flow and
temperature of the water.
How a Stream/ River Begins
Velocity decreases River gets wider and wider Meanders become common (curves) Pools: where water is deeper and slows
down, filled with fine sediments Riffles: faster, shallower with rocky bottom Run: fast flowing water, deeper water
Middle of a River
How a Meander Forms
The meandering Tigre River, Argentina . PHOTOGRAPH REPRODUCED BY PERMISSION OF THE CORBIS CORPORATION Read more: http://www.scienceclarified.com/landforms/Ocean-Basins-to-Volcanoes/Stream-and-River.html#ixzz1147UMeyX
http://www.geographyhigh.connectfree.co.uk/s3riversgeoghigh26f.gif
http://belmont.sd62.bc.ca/teacher/geology12/photos/erosion-water/Meander_processes.jpg
Flat stretches of land on either side of a slow moving river
During storms, rivers overflow and flood these areas
When water recedes deposits of rich sediment are left behind ; fertile land
Flood Plains
Less oxygen
Warmer temperature
Communities of catfish, algae, turtles, dragonflies and other organisms that can live in lower DO.
Slower Water
Usually empties into an ocean or a lake. Water slows even more Sediment is deposited and creates new land
called a delta. Where a river meets an ocean, freshwater
mixes with salt water, an estuary is formed.
Estuaries are important nurseries for lots of aquatic organisms.
Mouth
http://farm3.static.flickr.com/2117/2279411722_17c2675fb1.jpg
Lotic Ecology In temperate regions, leaves and other
plant parts (Coarse particulate organic matter or CPOM) are the main source of energy available to the stream ecosystem.
Headwaters: more CPOMBenthic invertebrates: shredders and
collectorsFish: trout (colder more oxygenated water)
Near headwaters: high O2, colder temperatures, CPOM
Further downstream: lower O2, warmer temperatures, FPOM
Affects which species flourish in a given area
Lotic Ecology
Lotic Ecology: headwaters
Down stream: Fine particulate organic matter (FPOM) washed down from headwaters
Algae (both filamentous and planktonic) and plants are more common because of slower water and more sunlight.
Few shredders, more collectors and grazers.
Fish: Carp and catfish, tolerate lower D.O. and warmer temperatures.
Lotic Ecology
Lotic Ecology: downstream