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