2023 Early Hearing Detection & Intervention Conference

March 5-7, 2023 • Cincinnati, OH

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6/05/2017 | 3:30 PM - 3:45 PM | PARTITIONING THE ROLE OF BIOLOGY AND SEASONALITY IN DIEL SOLUTE SIGNALS FROM TWO RIVER NETWORKS OF CONTRASTING LAND USE | 306A

PARTITIONING THE ROLE OF BIOLOGY AND SEASONALITY IN DIEL SOLUTE SIGNALS FROM TWO RIVER NETWORKS OF CONTRASTING LAND USE

Quantifying the relative role of nitrogen (N) uptake processes at the stream network scale is challenging, but empirical data are needed to refine models of N transport and retention in lotic ecosystems. Recently, open-channel methods have facilitated measurements of reach-scale metabolism and denitrification, allowing for partitioning of biological N removal into assimilatory vs. dissimilatory processes. We compared diel signals of dissolved solutes and gasses across seasons in a tributary and mainstem reach in two watersheds of contrasting land use: the Manistee (MI; 83% forested) and Tippecanoe (IN; 82% agricultural). We estimated metabolism and assimilatory N uptake using continuous measurements of dissolved oxygen and NO₃-N. During these 36-hour sampling campaigns, we collected dissolved N₂ samples to estimate reach-scale denitrification using membrane-inlet mass spectrometry. In summer, assimilatory uptake dominated NO₃-N removal in the agricultural Tippecanoe during peak macrophyte growth, while denitrification drove NO₃-N removal in the forested Manistee. After macrophyte senescence, denitrification controlled NO₃-N removal in the Tippecanoe. Diel measurements of dissolved gasses and solutes in these two contrasting systems strengthen the temporal, spatial, and seasonal context of N dynamics in stream networks.

C27 Landuse and Non-Point source Impacts
C06 Large River Ecology
C10 Biogeochemistry

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Presenters/Authors

Martha M. Dee (), University of Notre Dame, mdee@nd.edu;