The Macro-invertebrate Representation Score is a method of biological monitoring (adapted from Water Quality Monitoring Handbook, Bill MacIntyre, 1994). The relationship between the composition of benthic invertebrates and water quality has been recognised for a long time. This relationship is based on "the fact that every organism has a certain range of physical and chemical conditions in which it can survive." (Mitchell and Stapp, Field Manual for Water Quality Monitoring, p. 116). Some organisms have a wide tolerance range while others can only tolerate a limited range of conditions.
In 1978 the Biological Monitoring Working Party (BMWP) proposed a system for Great Britain that used identified freshwater invertebrates and matched them with their ability to tolerate pollution. The system they proposed is called Macroinvertebrate Community Index (MCI). A modified (1-4) form of the MCI is used in the Manitoba Waterways Project.
The system allocates a score from 1 to 4 to families of freshwater invertebrates according to their ability to tolerate pollution. Families (in taxonomic terms - those words that end in 'ae') that were pollution intolerant gained a lower score (1) than those that were able to tolerate a higher degree of polution (4).
The scores for some of Manitoba's freshwater taxonomic groups can be found by clicking the link below. On your data submission, list the names of the organisms found and their group score (ie. group 1, 2, 3, or 4).
Macro-invertebrate Representation Scoring
There is a variety of equipment and methods for sampling the benthic macroinvertebrates. Most samples are taken at gravel or strong ripples (fast flowing, shallow water with broken surface) although other stream areas (rapids, pool, and margins) can be used as well.
***In all sampling situations a sieve/screen is used to collect the organism DOWNSTREAM from the disturbance of the substrate UPSTREAM.***
Once collected in the sieve/screen, transfer the organisms to a bucket filled with the stream water for identification at a later time. Return all organisms to their habitat after identification.
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