Chesapeake Bay Basin-Wide Index of Biotic Integrity

Track 2C: Gaining Insights from Invertebrate Organisms
Thursday, October 12, 2017, 2:00 pm – 3:10 pm

Zachary M. Smith
Aquatic Ecologist
Interstate Commission of the Potomac River Basin

Federal, State, and non-profit programs independently collect benthic macroinvertebrates across the ~167,000 km2 Chesapeake Bay basin to assess water quality. These programs cannot evaluate wadeable stream conditions across the entire Chesapeake Bay basin. Benthic macroinvertebrate data collected by 29 programs were assimilated into a single database and used to develop the Chessie BIBI. Indices developed at the family-level were generally comparable to genus-level indices. A single Chesapeake-wide index was biased by natural environmental factors, but indices developed for two large geographic areas (i.e., regions) and twelve small geographic areas (i.e., bioregions) could detect the defined disturbance gradient. Region indices provided the best results for evaluating stream condition as a whole within the basin because index scores could be directly compared over large swaths of the basin. Bioregion indices were developed for smaller geographic areas with homogeneous environmental conditions, and thus, are likely more sensitive to local environmental changes. Ultimately, using the Region and Bioregion indices in conjunction provides a more robust review of stream condition.