Importance and Issues
Benthic macroinvertebrates are a vital component of healthy stream ecosystems. Advantages of using benthic macroinvertebrates assemblages to monitor streams include:
- They are good indicators of local conditions because most benthic species are either sessile or have limited migration patterns through their aquatic phases.
- They exhibit wide variation in tolerance among species and life stages to environmental stresses.
- Many species have long life cycles relative to other groups which allows inference regarding temporal trends.
- Sampling benthic macroinvertebrate assemblages is relatively easy and inexpensive, and has minimal effects on resident biota.
In addition, because benthic macroinvertebrates have been by far the most commonly used group for biological monitoring of aquatic habitats in North America, a large suite of benthic macroinvertebrate summary metrics have been evaluated with respect to natural variation and responses to numerous sources of degradation.
An independent review by scientists and park managers indicated that, out of 43 potential vital signs for Shenandoah, macroinvertebrate communities ranked as the most significant based on combined ecological, management, and policy interests.
Staff at this park have sampled benthic macroinvertebrates for more than 25 years, initially in response to gypsy moth defoliation. However, this data is also being used to monitor other impacts such as trail and road erosion, road salt contamination, wastewater treatment plant effluent, and stream water acidification due to acid deposition.
This long term data set has proven to be highly beneficial for establishing and assessing environmental monitoring thresholds (and baselines) and for characterizing the influence of sampling protocols on monitoring results. In the Blue Ridge section of the Mid-Atlantic Network, approximately 240 known taxa of benthic macroinvertebrates have been documented.
Document status and trends of benthic macroinvertebrate communities at sites across the park representing geologic and elevational strata by means of metrics that reflect abundance, richness, evenness, environmental requirements, ecological roles, and responses to various potential stressors.
Relate measures of habitat condition (both instream and riparian) and water quality at the sampling sites to ecological health (i.e. status and trends) of benthic communities.
Relate the ecological health of benthic macroinvertebrate communities at individual sample sites to thresholds of ecological health.
Provide additional ecological information to supplement data from the fish monitoring protocol and to inform fish, especially brook trout, conservation and management.