Poster Presentation Society for Freshwater Science 2025 Annual Meeting

Evaluation of macroinvertebrate drift and emergence in response to metals exposure: accounting for emigration using stream mesocosms  (117559)

Christopher J Kotalik 1 , Pete Cadmus 2 , David M Walters 1 , William H Clements 3
  1. U.S. Geological Survey, Columbia Environmental Research Center, COLUMBIA, MISSOURI, United States
  2. Colorado Parks and Wildlife, Fort Collins, CO
  3. Department of Fish, Wildlife, and Conservation Biology , Colorado State University, Fort Collins , CO

Larval drift and adult emergence by macroinvertebrates are essential “movements” for dispersal and colonization in streams and rivers; however, contaminant exposure can alter these ecologically important processes. We exposed naturally occurring stream benthic communities to two trace metal (Cu, Zn) exposure regimes, a continuous exposure, and a pulse exposure that was intermittently implemented over the 10-day experiment. We measured aquatic insect drift and emergence daily and collected benthic invertebrates at the end of the experiments. We observed significant changes in timing of emergence, with both stimulated and delayed emergence, which was taxa dependent and varied between exposure regimes. Larval drift increased with metals exposure, with greater drift abundance associated with the continuous exposure compared to the pulse exposure. Assessment of benthic community composition at the end of the experiments showed differences among treatments, including significantly reduced abundance of mayflies and caddisflies due to emigration. Altered drift and emergence has important implications for invertebrate population dynamics and for the animals (e.g., fish, birds, spiders) that depend on invertebrate prey resources. By accounting for macroinvertebrate emigration, we can better estimate how aquatic invertebrates and linked food webs are affected by contaminant exposure.