Lab Notes

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12 Apr 2012
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Lab 1: Eutrophication
Null Hypothesis: Fertilizers (phosphorus and nitrate) will have no effect on the
system
Eutrophication results from continuous pollution in the form of agricultural
run-off or sewage outflows (human or animal)
Fertilizers and sewage outflows are high in nitrogen and phosphorus
essential for plant growth in terrestrial and aquatic environments
These nutrients are typically in low concentrations and limit the numbers of
algae and aquatic plants
When concentrations are increased to high levels, primary production can
explode, resulting in eutrophication
Nitrogen eutrophication inshore marine waters
Phosphorus eutrophication freshwater systems
Algal bloom first stage of eutrophication appears as a thick green film
near the surface of the water occurs when algal populations experience
exponential growth in response to heavy nutrient loading
oPrevents sunlight from reaching other algae and aquatic plants below
the surface, causing them to die
oPopulations of organisms that feed on algae also increase in number
The bloom prevents algae and aquatic plants below the surface from receiving
sunlight, causing them to die
Algal cells are short-lived lots of dead matter is produced when they die
The large amounts of dead plant and animal material are decomposed by
heterotrophic organisms (mainly bacteria), which use oxygen and produce
CO2 while feeding on plant material
High rates of decomposition result in low oxygen and high CO2
oBoth are detrimental to aquatic organisms that require oxygen to
survive
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The end result of eutrophication is typically a large number of dead
organisms, mostly fish
The death of aquatic plants also results in habitat loss for invertebrates and
fish
When oxygen levels are high, green algae are more common (Phylum
Chlorophyta)
When oxygen levels decrease, blue-green algae are more common; they are
more tolerant to lower oxygen (Phylum cyanobacteria)
Cyanobacteria carry out photosynthesis and require water, nitrogen gas,
oxygen, some mineral elements, light, and carbon dioxide to survive
oThey produce a lot of toxic compounds, which contribute to fish
mortality
Experimental Protocol
Three treatments: no fertilizer, moderate fertilizer, high fertilizer on an aquatic
environment containing phyloplankton and Salvinia
Control contains only tap water
High treatment 10 times the amount of fertilizer applied to moderate
Add 500mL of the appropriate treatment every week since evaporation of
water in the pails is high and to simulate a eutrophic system where the input of
nutrients occurs over time
Phyloplankton
Microscopic, single-celled aquatic organisms that form filaments or multi-celled
colonies
Photo-autotrophs use light energy to make macromolecules from simple
precursors
oLight = primary source of energy
Major nutrients Carbon, Nitrogen, Phosphorus (also combined with Oxygen
and Hydrogen) form the basis of energy metabolism
Short-lived new cells multiply, old cells die
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Salvinia molesta
Record growth by estimating the percent coverage of leaves over the water
surface
Free-floating water fern
A serious weed throughout the tropics
Entirely asexual; never reproduces from seeds or spores
oNew plants bud off from the parent plant
oA single pair of leaves, which can be carried by wind is all that’s
required to being a new colony
oCan double in size every few days under ideal conditions
Controlled by biological, chemical, and physical means
oUse a black weevil to control infestations of S. molesta
Water Quality Parameters
Conductivity
Estimates the total amount of dissolved ions in water; measured in
(microSiemens(uS)/cm)
Also an indirect measure of salinity in water, detecting chloride ions from salt
(NaCl)
Distilling removes the many ions found in tap water
Sources of pollutants that may increase conductivity:
oWastewater from sewage treatment plants and septic systems
oUrban run-off from roads (especially road salt)
oAgricultural run-off (water draining agricultural fields has extremely high
levels of dissolved salts from fertilizers and pesticides)
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