Teacher's notes

The main objectives of this lesson is to illustrate the usefulness of indicator species and to show how this is particularly helpful if the species are used to calculate a biotic index.  There are three activites but not all of them need to be covered. However the first two could be set for homework if the class does the field work lab. Alternatively the third activity might be left out, as the theory is well covered in the other two activities.

The first activity tries to suggest that the capacity to absorb oxygen in benthic macro-invertebrates varies between different benthic species, and for this reason they are more or less tolerant of low oxygen levels which typically follow pollution by organic material.

  Washington state - kick sampling methodology video is quite long but thorough.

The second activity shows how this could work in practice using simple images of invertebrate samples and three options of biotic index.  There are actually many different types.

Model answers for activity 2 - Biotic index can be found here: River pollution biotic index - model answers  (Teacher can control student access to this page)

The third activity can take students outside in a simple investigation of lichens on trees to estimate sulfur dioxide concentration. This simplified table may be helpful.
 

Lichens and estimates of Sulfur dioxide pollution

This scale is adapted from the 'Hawksworth & Rose' zone scale. (http://www.air-quality.org.uk/19.php)
It can be used for the estimation of sulphur dioxide levels using lichens growing tree bark