Benthic Macroinvertebrate

SurveyHonors Biology 13-14

Benthic Macroinvertebrates• Bottom-dwelling, spineless

animals• Some species are very pollution

tolerant while others are not• Species are classified/sorted by

group depending upon their pollution tolerance (group 1 = intolerant, group 4 = very tolerant• Depending upon the diversity of

macroinvertebrates, one may indirectly assess the river’s health re: nitrogen and phosphorus pollution

Sampling Benthic Macroinvertebrates• Working as a team, send two people into the water source in waders: one with

a benthic collection net and the other with a large sampling pan• Place the collection net on the bottom of the river/pond with the current

running into the net (if applicable). Gently kick up materials towards the net, allowing the current to sweep the detritus and macroinvertebrates into the net.• Empty the net into the collection pan. Repeat steps 2-3 until the collection pan

is full.• Transfer the collection pan to the bank of the river/pond.• Using the attached guide to benthic macroinvertebrates and the data sheet,

record and classify any/all macroinvertebrates you find for this water source.• Repeat steps 1-5 for the second water source, using another data sheet

Identify & Record Data

• Identify each different type of species that you find in your sample• You do not record the number

individuals you find (i.e. 45 snails) but rather how many different species you find

Calculating The Benthic Macroinvertebrate Water Quality Index• Each species counts as one taxa• Multiply the # of taxa for each

group by its specific weighting factor• Sum the group scores• Divide the total group score by

the total number of different species/taxa found• The WQI for benthic

macroinvertebrates, unlike the other WQI values is better if the score is LOWER