of Two Methods for Benthic Macroinvertebrate Sampling and Analysis:
Rapid Bioassessment Protocol II vs. West Virginia Save Our Streams
Institute, High View, WV
In recent years, the science of using animals to assess the vitality
of a river ecosystem has gone public. Volunteer monitoring programs,
such as the Isaak Walton League's pioneering Save Our Streams (SOS)
program, have sprouted up around the country. The SOS and other
volunteer methods are similar in general design to the methods used by
professionals, but tailored to the capabilities of non-professionals.
Such programs make the link between causes and effects of pollution
using hands-on, in-stream activities, and make the societal benefits of
clean water immediate and real.
Cacapon Institute (CI) received funding from the WVDNR Non-Game
Program to compare results from WVís volunteer SOS monitoring and the
more scientifically rigorous Rapid Bioassessment Protocol (RBPII) stream
assessment methods used by WVís Division of Environmental Protection (WVDEP).
Both methods assess stream health using benthic macroinvertebrates, the
small animals without backbones (invertebrates) that live on the river
bottom (benthos) and are visible without magnification (macro). Our
study had two primary goals:
The professional RBP data analysis uses the number of different kinds
of organisms to calculate a set of six standard Indices, which can be
used to indicate various attributes of the stream site. These indices
are then combined into the WV Stream Condition Index (WVSCI) Score,
which is used to rate the site. In the SOS method, the streamís
biological health is described using a single numeric indicator, the SOS
score; abundance of organisms does not factor into this rating.
CI modified the standard SOS protocol slightly. Each of the three
samples per site was collected using a timed, two-minute effort, in
order to obtain a catch per unit effort. After handpicking live in the
field, organisms were preserved in alcohol and brought to the lab for
identification to the standard SOS level. We also counted these
organisms, and noted visually distinct "kinds" within each SOS
taxonomic grouping. This allowed us to calculate additional indices
similar to those used in the professional RBPII method.
Some overall conclusions
SOS scores as currently calculated don't provide stream assessment
data comparable to professional RBPII results because they lack
abundance data and thereby lack critical information. As the Virginia
Tech study found, SOS scores tend to overrate sites the RBPII stream
score found to be impaired. However, the SOS method provides a
conservative stream assessment tool Ė although it may miss some
impaired streams, if the SOS score says itís bad, it really is.
The identification level used with the SOS method can provide a
stream assessment comparable to professional methods, based on our
analysis. The main drawback, is that SOS simply categorizes the
organisms using A = 1-9, B = 10-99 and C = 100 or more, and these
"count" categories are then not used in the calculation of the
stream score. Our study indicates that actual counts of the organisms
collected are essential in order to properly weight the importance of
each organism. These counts allow volunteers to calculate variants of
the biological indices used in rapid bioassessment protocols (RBP II),
and also calculate an overall stream index similar to DEP's West
Virginia stream condition index (WVSCI). The indices can be easily
calculated using a computer spreadsheet, developed by Cacapon Institute,
where volunteers enter organism counts and the number of different
"kinds" and the computer does the rest.
Our study also found that the SOS method of fieldpicking live organisms
tends to disproportionately miss some small organisms in specific
groups, like midges and blackflies, when compared to picking preserved
samples in the lab. This difference appears to be of paramount
importance. We believe it is unlikely that field picked samples
analyzed under any method (SOS or professional RBP) will produce results
consistent with laboratory picked samples because certain critical
groups are likely to be seriously underrepresented in field picked
Suggested modifications to WVSOS methodology
to improve validity of volunteer collected data
1. Count the organisms collected by SOS level identification
2. Samples should be preserved in alcohol in the field and picked in
the lab (or on the kitchen counter) under slight magnification with good
lighting. This will eliminate disproportionate "under-picking"
of important groups such as midges and blackflies and will reduce the
overestimation inherant in SOS methods. While this is a separate step
for volunteers, it is actually easier (and more comfortable) than the
current field picking - and more rewarding because the results will have
greater validity and, hopefully, achieve greater acceptance by
3. Note visually different "kinds" of organisms in SOS
level identification categories, to obtain a measure of species
richness, or diversity.
4. Supply an automated spreadsheet for volunteers to enter raw data
and generate a composite metric (based on a number of metrics) similar
to the WV Stream Condition Index, which relates well to the professional
stream quality rating score.
Based on our study, it is possible for non-professional, volunteer
conducted, benthic stream assessments to obtain results that compare
favorably to professional assessments. The proposed method utilizes the
same level of identification skill currently required of SOS volunteers
and the same collection technique. It differs by requiring samples to be
preserved in the field for "picking" under slight
magnification and good lighting at home, in counting the organisms
obtained, and in noting different "kinds" within each of the
current SOS identification categories.
A detailed report on this project in PDF format is
Many thanks to the good folks at WV DEP's Watershed
Assessment Program. This project would not have been possible
without their cooperation.
information, contact Neil Gillies at
Cacapon Institute, #10 Rock
Ford Road, Great Cacapon, WV 2522,