Rapid Bioassessment Protocol
The Rapid Bioassessment Protocol procedure used by the Bureau is based
on the USEPA's Rapid Bioassessment Protocols for use in Streams and Wadeable Rivers (EPA 841-B-99-002 Nov. 1999). The procedure involves the use of a net in sampling of stream bottoms to collect insects, mollusks, crustaceans, and worms that are collectively referred to as "macroinvertebrates". Benthic macroinvertebrates are bottom-dwelling invertebrate organisms easily viewed with the naked eye. Samples are collected using a multi-habitat sampling approach, concentrated on the most productive habitat of the stream, the riffle/run areas (when available), using a 600 - 900 um mesh surber sampler or D-framed net. On streams without riffles (primarily in the Coastal Plain), woody snags, banks, and macrophytes are
the principle habitats sampled. The samples are preserved with formalin
or alcohol, labeled, and transported to the laboratory for sorting and
identification. In the laboratory, samples are rinsed through a sieve
with water to remove preservative. Sorting is performed by evenly dispersing the sample in a gridded pan, then removing organisms from randomly selected grids until
at least a 100 organism sub-sample is obtained. The sub-sample organisms
are then identified to the lowest pratical taxonomic level with the aid of a microscope
and appropriate taxonomic keys.
The data analysis scheme uses five (5) biometrics to calculate the New
Jersey Impairment Score (NJIS). Biometrics are predictable measures of
the benthic community's response to stresses, such as changes in water
quality or habitat degradation. Each biometric measures a different component
of community structure and has a different range of sensitivity to pollution
stress. Deficiency of any one biometric will not invalidate the entire
approach (see Table 1). The following biometrics,
based on family-level taxonomy, are used in assessing a NJIS score:
Taxa Richness
Total numbers of families present in the sub-sample. This metric is calculated by simply totaling each different family name in the subsample. This parameter will become reduced in response to stress.
% Contribution of the Dominant Family (%CDF)
Percentage of the total number of the sub-sample organisms in the numerically dominant family. To calcualte this metric, find the family with the greatest number of individuals and take that percent of the total. This parameter is an indication of community balance and will increase in response to stress.
E+P+T
Total number of families present belonging to the orders Ephemeroptera, Plecoptera, and Trichoptera, commonly known as mayflies, stoneflies, and caddisflies. This metric summarizes the taxa richness within the insect groups that are generally considered pollution sensitive. To calculate this metric, add up each EPT family in the subsample. the This parameter will become reduced in response to stress.
%EPT
Percentage of the total number of organisms in the sub-sample belonging to the EPT orders. This parameter will also become reduced in response to stress.
Modified Family Biotic Index (FBI)
A weighted sum of the Family Tolerance Values (FTV), based on Hilsenhoff's scale of 0 being the most pollution intolerant and 10 being the most pollution tolerant. This parameter will increase in response to stress. To calculate this metric, use the FBI calculation below:
where:
xi=number of individuals within a family
ti=tolerance value of a family
n=total number of organisms within the subsample (100)
Habitat Assessment
A generic habitat assessment, as mentiond in USEPA's document, is also performed at each site. Each assessment is based on visual observations and can be separated into 2 basic approaches--one designed for high-gradient streams and one designed for low-gradient streams. High-gradient or riffle/run prevalent streams are those in moderate to high gradient landscapes. Natural high-gradient streams have substrates primarily composed of coarse sediment particles (i.e., gravel or larger) or frequent coarse particulate aggregations along stream reaches. Low-gradient or glide/pool prevalent streams are those in low to moderate gradient landscapes. Natural low-gradient streams have substrates of fine sediment or infrequent aggregations of more coarse (gravel or larger) sediment particles along stream reaches. The entire sampling reach is evaluated for each parameter. A final habitat assessment of optimal, suboptimal, marginal, or poor, is achieved by tallying the scores (see Table 4).
NOTES:
Based on the NJIS, a biological assessment of the stream is determined;
non-impaired, moderately impaired, or severely impaired (see
Table 1). RBP is only one tool used in the assessment of streams and
rivers. Other biological and chemical testing, and stream habitat assessments (see Table 4)
may be needed to further evaluate the condition of the stream.
