(Standard Operating Procedures for Macroinvertebrate Population Surveys)
During the instructional planning stages, the teacher may wish to read About the Watershed: Instructional Framework, especially parts III. Water and Sediments, V. The Chesapeake Bay Watershed as an Ecological System, VI. Conservation, Restoration, and Stewardship of the Chesapeake Bay Watershed, and VII. Chesapeake Bay Watershed Issues and Trends: Alternatives and Consequences.
Understanding the Project
The stream quality survey, originally designed by the Izaak Walton League of America and revised and updated by the Virginia Save Our Streams Program (VA SOS), allows volunteer monitors to collect data on the health of their local streams. This data, if collected and recorded properly, assists state agencies, local governments, and concerned citizens in improving local environmental conditions related to water quality. This project provides comprehensive instructions for doing a stream survey that contributes to the state effort to manage and protect Virginia's waterways.
Conducting a survey of the macroinvertebrates, organisms large enough to be seen by the unaided eye, allows one to assess the health of the stream. Many stream-dwelling organisms are sensitive to changes in water quality. Their presence, absence, or population changes through time serves as an indicator of environmental conditions.
Conducting the Survey
Macroinvertebrates are easy to find, collect, and identify. By following the instructions below (a summary of the VA SOS Training Session) and filling out the VA SOS Stream Survey (available at http://www.vasos.org/fieldSheetsNewMethod.pdf), one can diagnose a stream's water quality. Remember, the data is most useful when a certified VA SOS monitor is collecting the data.
Monitoring the Stream
Monitoring should be done at one station, defined as a single stretch of stream not more than 100 yards long. If you wish to assess a longer section of a stream, select two monitoring stations at the top and bottom of the stretch, or multiple sites along the length of the stretch at quarter-mile or greater intervals. Be sure to revisit the same station each time so that your results will be comparable. Carefully record the location of your monitoring station on your VA SOS Stream Survey form. If you do not know the latitude and longitude coordinates when you monitor, use an accurate description of the site (e.g., "Site located on north side of Route 660, 1 mile east of Route 607") that enables you or another monitor to return to the same location. The regional coordinator or VA SOS staff will help you identify the coordinates at a later date.
Monitoring should be conducted four times a year for each station you monitor. VA SOS suggests a schedule of January, April, July, and October, though consistency is more important than a specific month. In addition, you may choose to monitor after a significant event that may have a significant impact on the stream, such as a chemical or oil spill, a heavy rain following the spreading of manure or fertilizer on lands nearby, or a flood. Do this no more than twice, for an annual maximum of six surveys. The survey itself is a stream disturbance and too heavy a monitoring cycle can negatively impact macroinvertebrate populations.
If you are monitoring more than one station on a stream, you should begin monitoring at the station furthest downstream and work upstream. This will prevent macroinvertebrates disturbed from your first test from washing downstream and getting caught in your net a second time. Each station should include only the organisms present at that location and not those disturbed from previous tests.