Background

Impacts to water quality are so diverse and variable in duration that chemical monitoring alone may fail to detect many of them. Effective monitoring of NCRN water resources should address several vital signs for a more comprehensive assessment than can be gained from any single measure. Stream health should reflect the health of the entire food web, not just one component, yet most assessment methods use either fish or benthic macroinvertebrates and assume that this component represents overall system condition. However, different components may not equally reflect the presence or magnitude of stressors in the system. Therefore a number of measures should be employed to obtain a more comprehensive assessment. Information on water chemistry, physical habitat, and the aquatic community indicate much about the condition of a stream and its watershed. This is the basis of monitoring techniques such as the Index of Biotic Integrity (IBI). IBIs have been very successful at assessing the condition of aquatic resources and have been developed for the region's fish and benthic macroinvertebrate assemblages to assess current ecological conditions throughout the Potomac River watershed. Resident biota (fish and benthic macroinvertebrates) are sensitive to low-level chemical, physical, and biological disturbances and therefore function as continuous monitors of system integrity. Quantitative assessment of biotic assemblages based on ecological principles is more likely to identify human impacts than chemical or physical habitat monitoring alone because aquatic organisms integrate more anthropogenic factors that potentially influence aquatic systems.

Objectives

• Determine current conditions and track long-term trends in water resource condition measured by benthic macroinvertebrates.
• Determine trends in species composition and functional groups of benthic invertebrates.

Measures

Benthic macroinvertebrates are collected in a variety of habitats including riffle area, gravel, broken peat, or clay lumps in a run area; snags or logs that create a partial dam or are in run habitat; undercut banks and associated root mats; and SAV and detrital/sand areas in moving water with a "D" net to provide a semi-quantitative description of the community composition at each sampling site. Sampling is conducted during the spring index period. Benthic community data are collected primarily for the purpose of calculating Maryland DNR's Benthic Index of Biotic Integrity (BIBI) for Maryland streams (Stribling et al. 1998) although the component metrics that make up the index are also valuable for assessing temporal trends. The benthic macroinvertebrates are identified to genus, or lowest practicable taxon, in the laboratory.

Status

NCRN has contracted out sampling based on the Maryland Biological Stream Survey (MBSS). The MBSS was developed and tested to provide estimates of the condition of non-tidal first through fourth order streams and rivers of Maryland on a watershed as well as a statewide scale. Overall, 36 streams are sampled on a 6-year rotating panel of 6 streams per year.

Contacts
Jim Pieper, NCRN Hydrologist
202.342.1443 ext. 227

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