2023 Early Hearing Detection & Intervention Conference

March 5-7, 2023 • Cincinnati, OH

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5/20/2019  |   2:45 PM - 3:00 PM   |  SEASONALITY IN FLOW FOOD WEBS: THE IMPORTANCE OF WINTER BASEFLOW IN ALPINE STREAMS   |  250 DE

SEASONALITY IN FLOW FOOD WEBS: THE IMPORTANCE OF WINTER BASEFLOW IN ALPINE STREAMS

Stream basal resources, both autochthonous (i.e., within-system; e.g., biofilm) and allochthonous (i.e., external; e.g., coarse benthic organic matter [CBOM]), support food webs, though their availability varies with environmental characteristics such as the hydrological regime. We sampled biofilm, CBOM, and macroinvertebrates in three catchments for biomass and stable isotopes approximately monthly for over a year. Biofilm showed seasonal trends with high biomass in winter months (Dec-Apr) while CBOM was aseasonal, both temporal patterns similar across catchments. Macroinvertebrate abundance generally tracked instream resources with high abundances in winter months (e.g., 100s of 1 mm individuals per m²), and was dominated by Plecoptera and Ephemeroptera. Preliminary results indicate higher reliance of Heptageniidae grazers on instream resources in winter months (higher ?¹³C values). However, size class distributions remained fairly constant during those winter months (e.g., Heptageniidae: peak 3 mm Oct-Mar). Combining estimates of monthly secondary production with stable isotope data will be needed to identify reliance on and importance of specific basal resources. Hydrological regime drives temporal patterns in basal resources and as a result likely affects flow food webs with winter baseflow critical for early instar growth and thus productivity in Alpine streams.

• Invertebrate
• Isotope
• Secondary Production

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Presenters/Authors

Janine Rüegg (), University of Lausanne, janine.ruegg@unil.ch;

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Tom Battin (), Ecole Polytechnique Fédérale de Lausanne, tom.battin@epfl.ch;

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