ESU 7:  Water Quality Research Project

Stream
Macroinvertebrates

A key for identifying the major groups of insects, crustaceans and other organisms found in Nebraska streams.

INTRODUCTION

It has been found that the relative condition of a habitat can often be determined by the species of animals, especially the smaller fauna, that are found in that habitat. This is especially true of bodies of water. Many species are highly sensitive to pollutants while others will die or leave if oxygen levels fall or suspended particulate matter increases beyond a certain level. These species are called "indicator species" because their absence or presence indicates that there may be a problem with pollutants, silt, etc.

The objective of this project is to form a base profile of the indicator species that are present in the stream that your class is sampling. This will give you a rough idea of the the stream's water quality. Any change in the make-up of indicator species in the stream during future sampling would then signal a possible change in the condition of the habitat. In order to get as complete a sample as possible, a certain protocol should be followed at each sampling.

PROTOCOL FOR SAMPLING

EQUIPMENT AND MATERIAL

MACROINVERTEBRATE KEY

A typical field trip: Lost Creek, October 10, 2000.

RECORDING SAMPLES OF MACROINVERTEBRATE SURVEY
adapted from Izaak Walton League's SAVE OUR STREAMS Program

Tabulate the presence of a particular type of organism using an "x" in the box next to its name. Then, add up the number of "x"s in each column and multiply by the indicated index value. The following columns are divided based on the organism's sensitivity to pollution.

(Make copies of form below for student use)

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Date:_________________          Area of Stream:____________________

Indicate presence with an "x"

Sensitive

Indicate presence with an "x"

Somewhat sensitive

Indicate presence with an "x"

Tolerant

  caddisfly larva   beetle larva   aquatic worms
  hellgrammite   clams   pouch (& other) snails
  mayfly nymph   crane fly larva   leeches
  gilled snails   crayfish   midge larva
  riffle beetle adult   damselfly nymph    
  stonefly nymph   dragonfly nymph    
  water penny larva   scuds    
      sowbugs    
      fishfly larva    
      alderfly larva    
      blackfly larva    
      atherix    
___ # different organism types times 3 = ______   ___ # different organism types times 2 = ______   ___ # different organism types times 1 = ______

Now add together the three index values = ________Total index
Compare this total index value to the following numbers to determine the water quality of your stream. Good water quality is indicated by a variety of different kinds of organisms, with no one kind making up the majority of the sample.

WATER QUALITY RATING

Excellent (>22)
Good (17-22)
Fair (11-16)
Poor (<11)

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