Biological monitoring is used as an indicator of water quality and uses different categories of pollution tolerances that characterize different species of macroinvertebrates. Monitoring is done twice per year: once in the late winter/early spring and once in the late summer/early autumn before the leaves fall. During these times the macroinvertebrates are largest at these times of the year, and easiest to identify. 

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Benthic Macroinvertebrates Benthic refers to the  bottom of the stream, macro means large, or visible to the naked eye, invertebrates are organisms without a backbone. Therefore, benthic macroinvertebrates are organisms that lack a backbone, are visible without magnification, and live on the stream bottom. Click here to view images and learn more, https://www.mostreamteam.org/macroinvertebrates.
 
The Stream Team program uses a net, magnifying lens, forceps, and a sorting tray to identify, count, and record macroinvertebrates on a biological monitoring data sheet. This data sheet provides a water quality rating based on the kinds and diversity of "macros" collected and analyzed.