Rutgers Experiment

Effect of UV Radiation on Phytoplankton



Problem

The ozone layer in the atmosphere is a gas layer that filters the damaging ultraviolet radiation but it is getting thinner and is not able to effectively block the UV radiation.Phytoplankton is the primary producer of the aquatic food web. The question  and concern is: "What effect does the ultraviolet radiation have on the phytoplankton, green algae, Tetraselmis sp.?"
 

Hypothesis

Since ultraviolet radiation can damage DNA and proteins which  are necessary for the growth of and reproduction of the phytoplankton, we hypothesize that exposure to UV radiation will cause green algae (Tetraselmis sp.) to grow more slowly than those with only visible light.

Materials
Plastic bag
Kiddy pool
Phytoplankton (Tetraselmis species)*
f/2 enriched sea water medium*
100ml measuring cylinders
microscope
hemocytometer*
pasteur pipettes and bulbs or disposable transfer pipettes
Lugol's solution
test tubes (glass or plastic)
spectrophotometer*
centrifuge
centrifuge tubes
black Plexiglas boxes*

*Materials Modifications

Procedure

  1. Inoculate two 2000 mL flask full of filtered sea water with Tetraselmis sp.
  2. Pre-expose one flask of Tetraselmis sp. to high levels of incandescent light. Pre-expose the other flask to low levels of incandescent light.
  3. Prepare culture samples by mixing 400 mL of  the Tetraselmis sp. high light exposure sample with 1300 mL of sea water or f/2 sea water media. Repeat with Tetraselmis sp low light pre exposure sample.
  4. Pour 250 mL Tetraselmis sp high light culture into a Whirl Pack Thio (UV transparent plastic) bag labeled with the species and type of  light which it will be exposed. Example: Tetraselmis sp visible light; Tetraselmis sp, visible, UVA; Tetraselmis sp, visible, UVA, UVB. Save the rest of the culture for the initial cell count and initial absorbency (spectrophotometry).
  5. Run two trials for each level (two bags of each).
  6. Place the kiddy pool in a location where it will be exposed to maximum sunlight and maximum length of time in the day.
  7. Put the black Plexiglas boxes in the kitty pool and fill the boxes and the pool with water.
  8. Put  two labeled Whirl Pack Thio bags in each of black boxes. Cover with transparent top and place bags face down in the water.
  9. Measure absorbency (spectrophotometry) and make cell count the third and sixth day of exposure.
  10. Measure the cell count using hemocytometer with a microscope.


Data Collection

Samples
day 1
day 3
day 6
reading [chlor A] [chlor B] ratio[ A]/[B cell count reading [chlor A] [chlor B] ratio [A]/[B] cell count reading [chlor A] [chlor B] ratio [A]/[B] cell count
HL1                              
HL2                              
HL3                              
LL1                          
LL2                              
LL3                              

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The Woodrow Wilson National Fellowship Foundation
CN 5281, Princeton NJ 08543-5281 - Tel:(609)452-7007 - Fax:(609)452-0066
Technical contact: lpt@woodrow.org