Using Insect Emergence to Understand Aquatic-Terrestrial Connectivity in Restored Systems
Emily Jones
Beaver Creek Hydrology
Lexington, KY
Authors: Emily Jones, Leslie J. White, PhD, Jesse Robinson, PhD, Mike Croasdaile, PhD, Amy Braccia, PhD
aRegulatory evaluation of stream restoration success relies heavily on in-stream indicators such as habitat condition, geomorphic stability, and larval macroinvertebrate indices. While these metrics are well established, they capture only a portion of stream function and do not directly assess whether restored systems are achieving ecological connectivity beyond the channel. Aquatic insect emergence represents a measurable linkage between aquatic and terrestrial ecosystems and provides a functional indicator of biological production, energy transfer, and habitat uplift largely absent from current regulatory frameworks.
We present a case study that compared aquatic insect emergence from a restored headwater system and an unmanaged, degraded headwater stream by quantifying emergence abundance, biomass, and community assemblage. Two habitat types were sampled from the restored system – free-flowing lotic sections and a damned beaver pool. Only one habitat was available for sampling at the unrestored system – free-flowing lotic. While the restored and unrestored systems had similar biomass (mg AFDM/m2/day), the restored system exhibited greater emergence abundance (individuals/m2/day) compared to the unrestored system. Additionally, morphospecies were identified and compared between systems and habitats sampled.
Results suggest stream restoration translates into measurable increases in aquatic insect abundance and export to adjacent terrestrial systems. Emergence also exhibited strong seasonality. The restored system had measurable emergence year-round while the unrestored system did not contribute meaningfully to aquatic insect emergence during the summer months. Incorporating emergence-based metrics into post-construction monitoring provides regulators and practitioners with a functional measure of ecological uplift that complements existing performance standards. Emergence studies offer a tool for assessing restoration success, supporting credit release decisions, and improving understanding of the broader ecological benefits generated by headwater stream restoration.
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