Variability and degradation of colored dissolved organic matter along the Yukon River-plume-coastal ocean continuum

Brice Grunert1, Maria Tzortziou1, Alana Menendez2, Patrick Neale3, Peter J Hernes4, Antonio Mannino5 and Robert G Spencer6, (1)CUNY City College of New York, Earth and Atmospheric Sciences, New York, NY, United States, (2)CUNY City College of New York, New York, NY, United States, (3)Smithsonian Environmental Research Center Edgewater, Edgewater, MD, United States, (4)University of California Davis, Davis, CA, United States, (5)NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Greenbelt, United States, (6)Florida State University, Tallahassee, United States
The Arctic Ocean receives ~15% of global riverine discharge despite accounting for ~1% of global ocean volume. Thus, processes occurring along the land-ocean continuum play a disproportionate role in the biogeochemistry and optical properties of the Arctic Ocean and connected marginal seas. Elevated levels of colored dissolved organic matter (CDOM), in particular, highlight unique carbon cycling in these systems and pose a challenge for Arctic and sub-Arctic ocean color remote sensing. The rapid changes occurring in these systems due to a warming climate also pose significant challenges in developing an algorithm, as variability and anticipated change in CDOM absorption is not well characterized. We present results from a recent (2019) field campaign in the Yukon River delta and coastal ocean waters during peak spring discharge, showing clear variability in CDOM optical properties from river to plume to coastal ocean waters. Further, we present results from photo-, size-specific microbial and photo+microbial degradation experiments conducted on a sub-set of these stations, showing the relative role of these primary drivers of CDOM variability along the river-plume-ocean continuum. Rates from individual and combined degradation pathways and the relative role of unique size classes of bacteria on CDOM quantity and spectral quality are presented, while links between kinetics and parameterized spectral degradation (derivative analysis and Gaussian decomposition) provide a pathway for linking changes in CDOM to optically-distinct compound classes.