Introduction

Benthic macroinvertebrates (BMIs) are animals without backbones that spend at least part of their life cycle in or on the bottom of a body of water. For a number of reasons, macroinvertebrates are well suited to assess the biological condition of water bodies:

BMIs are good indicators of localized conditions. Because many BMIs have limited migration patterns or a sessile mode of existence, they are well-suited for assessing site-specific impacts.
BMIs integrate the effects of short-term environmental variation.
BMI assemblages are made up of many kinds of organisms that vary widely in their tolerance to pollution and other disturbances.
Degraded conditions can often be detected through a cursory examination by an experienced biologist.
Sampling is relatively easy and inexpensive and has minimal effect on the resident community.

For these reasons, BMI sampling is often used for a wide-variety of stream assessment and monitoring applications. Because they’re relatively easy to collect and identify to higher taxonomic levels (insect order, for example), many watershed groups include macroinvertebrate monitoring as both a screening-level approach to assessing stream conditions and as an education/outreach tool to better acquaint citizens with their watershed. Recognizing the need for more information about stream and river conditions in the Deerfield River watershed, the DRWA initiated its own macroinvertebrate monitoring program in 2005. The general approach to our program was to utilize professional-level sampling, laboratory, and analysis protocols to allow our data to be used by the Massachusetts Department of Environmental Protection, Division of Watershed Management (DWM) to use the results of work in their water quality assessment and reporting activities. The details of our approach and protocols are explained in the Background and Program Protocols pages on this site.