What's in water: freshwater invertebrates

Enter experiment
Subject Env Bio Chem

An investigation into river quality using freshwater invertebrates.

Background and nature of the task
This activity is one of five activities that form part of a virtual environmental field trip to the River Teign in the county of Devon, South West England. The activities can be studied separately or together. Further information can be found in the file at the bottom of this description.

The activity involves an investigation into the invertebrates that can be found in the River Teign. It starts with a short video introduction to the types of invertebrates that inhabit freshwater, and their value as indicators of river quality. The video sequence includes a demonstration of a method for sampling them, and some information on the effects that different environmental variables, such as turbulence or organic pollution, can have on the invertebrate community. The introduction is then followed by three exercises. The first requires you to identify some common freshwater invertebrates by means of a dichotomous, or branching key. The second involves plotting graphs of some environmental data taken from a section of the River Teign that is affected by sewage effluent, and then using the graphs to answer some questions. Thirdly, you are shown some invertebrate sampling data from the same section of the river, and taken through a method for using these data to assess the effect of the effluent on the quality of the river water.

When you have completed this activity, you should be able to:

  • know the meaning of the terms kick sample, biotic index, BMWP index BOD;
  • recognize a selection of common types of freshwater invertebrates
  • carry out an investigation of freshwater invertebrates using the ‘kick sample’ method;
  • use a dichotomous key;
  • plot line graphs using a spreadsheet package;
  • calculate a BMWP index of water quality.

This activity will take you approximately 1 hour to complete.

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