Executive Summary
Benthic Macroinvertebrate Exploration in the Rumford River

Qualters Middle School
Mark DeGirolamo

The students of Qualters Middle School performed a study called “Benthic Macroinvertebrate Exploration in the Rumford River”. The study was conducted on October 16, 2007 in Mansfield, Massachusetts. The study location consisted of one site located at 143 Chauncy Street.

The purpose of this study was to introduce benthic macroinvertebrates and their role as indicators for evaluating stream water quality. Students utilized state of the art methods and techniques during all aspects of this study.

The Rumford River is listed on the Environmental Protection Agencies (EPA) National Priority List (NPL). The river was polluted with dioxins, furans and phenols by a wood treating company from 1953-1993. The amounts of pollutants and the frequency of their release are not known. As part of an EPA ecological study, benthic macroinvertebrates were studied and found to not be at a substantial risk of harm. The “Benthic Macroinvertebrate Exploration in the Rumford River” study was performed to compare our results with those found in the EPA study of 2005.

Benthic macroinvertebrates were collected utilizing the “kick net” method. A total of four samples were collected at the site. Each of which consisted of two low-flow and two high-flow sub-samples to ensure an accurate and diverse collection. Physical habitat data was also collected to document specific habitat information at the site. This data was evaluated against the types of organisms found to see if there were any discrepancies between habitat and macroinvertebrates within the stream study location. All physical habitat data was recorded utilizing the “Stream Biomonitoring: Physical Habitat Data Field Sheet” which was modified from CABIN.

Benthic macroinvertebrates were then identified to the “order” level. This was accomplished by viewing the specimens under stereomicroscopes. Dichotomous keys found in the “Living Waters: Using Benthic Macroinvertebrates and Habitat to Assess Your River’s Health. River Watch, A Program of River Network, 1997 and Aquatic Entomology: The Fishermen’s and Ecologist’s Illustrated Guide to Insects and Their Relatives. McCafferty, Patrick, W. 1998.” were utilized for the identification piece of the project. Order level data was recorded on the “Stream Biomonitoring: Level 1 Major Group Biotic Index” data sheet.

Necessary calculations were performed to indicate the overall Major Group Biotic Index (MGBI). The calculations are as follows: average count, average organism density and group percent. These calculations were performed on an excel spreadsheet. The MGBI was then compared to the Hilsenhoff Biotic Index (HBI) to give a water quality rating. The calculated MGBI for the sample location was 5.43. This value falls between the HBI range of 5.01-5.75, which indicates a “fair” water quality rating.

The 10 Max Biotic Index (10 Max MGBI) was also calculated to reduce the weighting effect of major groups containing large numbers. The calculated 10 Max MGBI for the sample location was 4.59. This value falls between the HBI range of 4.26-5.00, which indicates a “good” water quality rating.

The “Benthic Macroinvertebrate Exploration in the Rumford River” sampling program detailed a diverse macroinvertebrate community. It also showed that the Rumford River appears to be in fair condition as indicated by the macroinvertebrate community. Our data appears to support the findings from the above-mentioned 2005 EPA report.

Please see the PowerPoint Presentation for details.