Download Projects on Eutrophication - teacher notes

Investigations into Eutrophication
Introduction
Eutrophication is the growth of algae or other aquatic plants in water as a result of minerals in the
water. These minerals often come from the breakdown of organic matter.
Possible Investigations
You could try setting up a range of solutions with increasing amounts of minerals and follow the
growth of aquatic plants in glass containers on a sunny windowsill.
1) A very simple experiment would be to use a range of solutions of "Baby Bio" ranging from very
dilute to stronger than the bottle advises.
2) Alternatively, you could use a solution of basic salts (you can obtain "Sachs water culture
solutions" as tablets from laboratory suppliers) containing everything except Nitrogen (though you
could investigate the effect of other mineral elements instead). You could then add different
amounts of ammonium nitrate (NH4NO3) as this supplies nitrogen without any other extra mineral
nutrients like potasiium for instance.
3) You could seed your solutions with a suitable water plant. Lemna (duckweed) would be
suitable and you can monitor the growth of this by counting the number of fronds and even
calculate the "doubling time". You will find more information about this on our website (use the
search facility).
4) Alternatively, you could wait for algae to arrive in your dishes (in dust) and follow the growth by
measuring the optical density of the solution in a colorimeter.
Students should remember to include repeats (replicates) of your experiment so that any "odd"
results are evened out. For example, some dishes may get algae growing in them whilst others
do not because the right dust did not happen to land there until later in the experiment.
Acknowledgements
Roger Delpech, John Hewitson, Charles Hill and Ottoline Leyser
Science & Plants for Schools: www.saps.org.uk
Investigations into Eutrophication: p. 1
This document may be photocopied for educational use in any institution taking part in the SAPS programme.
It may not be photocopied for any other purpose. Revised 2011.