Document: MIC-3-71-9

Linking shallow groundwater invertebrate assemblages with stream ecosystem processes in Grand Teton National Park, Wyoming.

MARSHALL, M.C.* ¹, R.O.HALL ¹ and J.L.TANK ²

University of Wyoming, Laramie WY 82072 ¹
University of Illinois, Urbana, IL 61801 ²

Abstract:
Shallow groundwater (hyporheic) invertebrate samples and stream ecosystem parameters were compared in seven streams (discharge from 12 to 231 L/s) in Grand Teton National Park, Wyoming. Conservative and non-conservative solute injections were used to measure transient storage zone size (time water spends in storage relative to time it spends in main channel; TSZ) and turnover time (average time a water molecule spends in the TSZ). Diel upstream and downstream oxygen measurements with an inert gas tracer addition were used to estimate community respiration (CR). Hyporheic invertebrates were sampled with a standpipe and diaphragm pump (density from 10 to 155 individuals/L). Among the 7 streams, CR ranged from 0.97 to 8.77 mg O₂/m² day, turnover time from 8.8 to 31.8 min and TSZ from 0.045 to 0.295 (min/min). In riffle heads, average mayfly size and oligochaete density were each significantly positively correlated with turnover time (r²=0.93 and r²=0.68, respectively). Increasing TSZ was the best predictor of both small mayfly density (r²=0.54) and stonefly size (r²=0.50), suggesting some invertebrates have a preference for streams with larger subsurface volume. Ostracod density and diptera biomass both increase with increasing CR (r²=0.53 and r²=0.56, respectively), suggesting these subsurface invertebrates may play an important role in stream metabolism. These trends lend support for the connection between streams and groundwater and suggest that whole-stream hydraulic and metabolic measurements might be useful in predicting attributes of some hyporheic invertebrate assemblages.

Keywords: invertebrate, hyporheic, whole-stream metabolism

This abstract is being presented at: 10:30 AM in session:
Poster Session #9: Fish, Lakes, Streams and Wetlands.