Cyanobacteria blooms in Lake Kinnert
can be explained by the effect of thermal stratification. The density of water
depends on temperature: Surface waters are warmer and less dense compared to
bottom waters that are colder and denser. These layers affect the vertical
movement of oxygen and nutrients in water. This process is known as thermal
stratification. Thermal stratification creates conditions which favor the
growth of Cyanobacteria blooms (United
states environmental protection agency, Office of Water EPA 820-S-13-001, 2013,
Impacts of Climate Change on the Occurrence of Harmful Algal Blooms).
Our question is: what is the
correlation between thermal stratification of waters and the vertical movement
of substances in stratified waters?
To help us answer this question
you are asked to perform an experiment demonstrating thermal stratification and
movement of color between the water layers.
For this you will need:
1.Two identical clear, drinking glasses.
2.One teaspoon of freeze-dried coffee.
3.Boiling water and cold water.
4.A square of cardboard, large enough to cover your drinking glasses.
5.Download to your Smartphone the application “Color Analysis”.
The following videos
demonstrate the experiment:
1.Apply white paper behind the glasses in order to
examine the colors correctly.
2.Completely fill in one glass with cold water.
3. Completely fill in the other
glass with boiling water, add one teaspoon of coffee, and mix well.
4. Lay the square of cardboard
carefully onto the top of the glass with the boiling water.
5. Pick up this glass and turn it
6.Put it on top of the glass filled with the cold water.
7.Carefully pull the card out.
8.Take a picture of the lower part of the glass with the cold water using
9.Analyze the colors in the picture you just took using the “Color
10. Perform stages 1-8 again, only this time put
the cold water on top of the boiling water mixed with the coffee.
11.You should now have two values of
blue color level of the dominant color found by the application:
___________ = blue color level of stratified water (hot water on top of
= blue color level of non-stratified water (cold water on top of hot
Notice: Using the
RGB (Red, Green, Blue) color model: Brown is made by combining red and green
only, while White is made by combining red, green and blue colors!