The northeast Pacific coastal temperate rainforest (NPCTR) of British Columbia produces large fluxes of freshwater and dissolved organic matter (DOM) to nearshore marine waters. Regionally, these land-ocean linkages provide important DOM contributions to marine ecosystems but current understanding is based largely on freshwater studies of relatively small watersheds, with little attention given to the role of DOM export from large rivers and estuarine processes. We examine freshwater-ocean linkages of DOM exported from a large river (Skeena River) within the NPCTR. We examine dissolved organic carbon concentration and DOM composition using fluorescence spectroscopy and ultra-high resolution Fourier-transform ion cyclotron resonance mass spectrometry. Seasonality is an important control over riverine DOM export, and we observe non-conservative land-ocean mixing behavior with changes across salinity in optical properties and molecular-level metrics, including biological index, modified aromaticity index, heteroatom class, and the relative abundance of highly unsaturated and phenolic, aliphatic and peptide-like compounds. We also investigate source-specific marker formulae to identify and trace unique and dynamic DOM contributions across the land-to-ocean continuum.

Primary Presenter: Allison Oliver, Skeena Fisheries Commission (allisonoliver@skeenafisheries.ca)

Authors:

Allison Oliver, Skeena Fisheries Commission  (allisonoliver@skeenafisheries.ca)

Megan Behnke, Alaska Coastal Rainforest Center, University of Alaska Southeast  (mibehnke@alaska.edu)

Amy Holt, National High Magnetic Field Laboratory Geochemistry Group and Department of Earth, Ocean, and Atmospheric Science, Florida State University  (adholt@fsu.edu)

Amy McKenna, Ion Cyclotron Resonance Facility, National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL; Department of Soil & Crop Sciences, Colorado State University, Fort Collins, CO  (mckenna@magnet.fsu.edu)

Robert Spencer,  National High Magnetic Field Laboratory Geochemistry Group and Department of Earth, Ocean, and Atmospheric Science, Florida State University  (rgspencer@fsu.edu)