Oral Presentation Freshwater Sciences 2023

Changes in the identity and function of freshwater aquatic invertebrates along a mining-induced salinization gradient. (#86)

Sally Entrekin 1 , Aryanna` James 1 , Erin Hotchkiss 1 , Daniel McLaughlin 1 , Greg Pond 2 , Carl Zipper 1 , Tony Timpano 3 4 , Stephen Schoenholtz 1
  1. Virginia Polytechnic Institute and State University, Blacksburg, VA, United States
  2. Region 3's Office of Monitoring and Assessment, United States Protection Agency, Wheeling, West Virginia, U.S.
  3. Virginia Department of Environmental Quality, Richmond, VA, US
  4. Virginia Department of Environmental Quality, Ri

Freshwater invertebrates (e.g. macroinvertebrates) are diverse and abundant, making them key players in energy transfer and transformation within and around freshwater ecosystems. Respiration, osomoregulation and feeding require adaptations that support the freshwater macroinvertebrate lifestyle; they also pose challenges during environmental change that have consequences for food webs.  In Appalachian headwaters, macroinvertebrate diversity declines following mining-induced salinization, but changes to overall biomass and subsequent insect emergence remain less predictable. Larval biomass may be sustained through compensation by salt-tolerant taxa and changes in food availability. However, late instars and pupae may succumb to cumulative stress (e.g., oxygen deprivation, ion regulation, diet alteration), resulting in decreased emergence and aquatic subsidies to riparia. We predicted that larval and emergent biomass would decouple in response to a sulfate-dominated salinity gradient where emergent biomass would decrease disproportionately to benthic biomass as late instars succumb to stress. We also predicted that benthic and emergent biomass of salt-sensitive taxa and particular traits (e.g. scrapers) would decrease. We sampled benthic macroinvertebrates from the riffles of nine central Appalachian streams representing a salinization gradient (25-1460 µS/cm) in August 2019, November 2019, and April 2020. Concurrently, we deployed emergence traps and collected insects for one to three weeks. We estimated biomass and quantified food resources using natural abundance of carbon and nitrogen stable isotopes in one salinized and one unsalinized stream. Preliminary results suggest that taxonomic (but not trait) identity was different, total benthic and emergence biomass was sustained across the salinity gradient and though mayfly biomass declined. We will present coupled benthic and emergent metrics with food resource assimilation as enhanced assessments of material transfer across aquatic-terrestrial interfaces.