Download File - Bowie Aquatic Science

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The study of fresh bodies of water
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Lentic: standing water (lakes and ponds)
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Lotic: flowing water (streams and rivers)
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How might they be different?
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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.
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Geologic activity- tectonic movement; valleys
and craters fill with water
Manmade: dams, log jams, strip mining (all
lakes in TX except one, which one???)
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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
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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)
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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
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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
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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
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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
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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
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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)
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1)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: Littoral Zone, Limnetic
Zone, Trophogenic Zone, Tropholytic Zone, Compensation
Depth, Epilimnion, Metalimnion, Hypolimnion, Thermocline,
Benthic Zone, Profundal Zone
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: sun, sun rays, emergents, submergents, algae,
and fish. Label where decomposition and photosynthesis are
occurring.