Bottom Dwellers

Crane Fly Larvae

Aquatic macroinvertebrates are insect life stages, worms, crustaceans, snails, and clams that spend part or all their lives in the water. They are a major food source for many fish and have important roles processing and recycling nutrients in aquatic ecosystems.

Indexes of Biotic Integrity

Indexes of biotic integrity are analysis tools designed to characterize the status of a macroinvertebrate population relative to a reference or high-quality community.

• “Chessie BIBI” Index for Streams: A multi-metric index for stream macroinvertebrate communities in the Chesapeake Bay watershed’s twelve bioregions.
• Multi-Metric Index for Large Mid-Atlantic Rivers: A multi-metric index for large river macroinvertebrate communities in the Potomac, Susquehanna, and Delaware river basins.
• Potomac Basin-wide Index of Biotic Integrity: The precursor to Chessie BIBI.

Other ICPRB macroinvertebrates projects and reports

• Hydrologic Alteration
• Nutrient Thresholds
• Lower Potomac Mainstem Biological Survey
• Stream Health Outcome

A Potomac Basin-wide Index of Biotic Integrity

Building off earlier efforts, stream macroinvertebrate datasets collected in the Potomac River basin by different jurisdictions were merged and used to identify and calibrate biological indicators of human disturbance. The results confirm that a common suite of bioindicators can be generated from multiple datasets if the merge is done with care. Physiographic regions were most effective at grouping streams into site classes with similar attributes. Common elements from states’ habitat and water quality assessments were used to characterize regional reference and impaired sites.

Potomac B-IBI

From the merged datasets, a Basin-wide Index of Benthic Integrity (B-IBI) was developed that can be used to uniformly evaluate macroinvertebrate conditions in the Potomac’s non-tidal, wadeable streams. The index (aggregated metric scores) accurately identified 95% of impaired sites. A jackknife cross-validation procedure confirmed the accuracy of the B-IBI. The Potomac B-IBI is more useful than state-specific indexes for comparisons across jurisdictional boundaries.

The index can improve the understanding of water quality issues basin-wide and enhance the abilities of water quality managers to make well-informed decisions concerning the basin as a whole.

The Potomac B-IBI index was the precursor to the Chessie BIBI.

• Astin, L. 2006. Data synthesis and bioindicator development for nontidal streams in the interstate Potomac River Basin, USA. Ecological Indicators 6(4):664-685. https://doi.org/10.1016/j.ecolind.2005.08.030.
• Astin, L. 2007. Developing biological indicators from diverse data: The Potomac Basin-wide Index of Benthic Integrity (B-IBI). Ecological Indicators 7(4):895-908. https://doi.org/10.1016/j.ecolind.2006.09.004.

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