Salty streams: Insect biomass and emergence in response to mining-induced salinization in Appalachian headwaters

Freshwater salinization is an emerging concern arising from the interaction of land use and water quality. In central Appalachian headwaters, macroinvertebrate diversity declines following mining-induced salinization, but effects on ecosystem processes remain unclear. Macroinvertebrates are widely used for biomonitoring, but they may have varied responses to stressors dependent upon life stage, suggesting that assessments relying on immatures may not fully characterize the effects of salinization. Our aim is to identify how both macroinvertebrate benthic and emergent adult biomass respond to a sulfate-dominated salinity gradient. This study consists of nine central Appalachian streams representing a salinization gradient (25-1460 µS/cm). We collected benthic riffle samples in August 2019, November 2019, and April 2020. Concurrently, we deployed emergence traps and collected insects for one to three weeks. We used published length-mass regressions to obtain biomass metrics. We predicted that benthic and emergent biomass of salt-sensitive taxa (e.g. Ephemeroptera) would decrease, but total emergent biomass would decrease disproportionately to benthic biomass as late instars and pupae succumb to cumulative stress. Macroinvertebrate biomass and efficacy of emergence as a metric to assess salinization will be presented. Coupled benthic and emergent metrics broaden the scope of ecosystem assessments by quantifying movement of matter across aquatic-terrestrial interfaces.