Oral Session 8

Capturing the dynamics of dissolved organic carbon (DOC) in tidal saltmarsh estuaries using remote-sensing-informed models

The fluxes of dissolved organic carbon (DOC) through tidal marsh-influenced estuaries remain poorly quantified and have been identified as a missing component in carbon-cycle models. The extreme variability inherent to these ecosystems of the land-ocean interface challenge our ability to capture DOC-concentration dynamics and to calculate accurate DOC fluxes. In situ discrete and continuous measurements provide high-quality estimates of DOC concentration, but these strategies are constrained spatially and temporally and can be costly to operate. Here, field measurements and high-spatial-resolution remote sensing were used to train and validate a predictive model of DOC-concentration distributions in the Plum Island Estuary (PIE), a mesotidal saltmarsh-influenced estuary in Massachusetts. A large set of field measurements collected between 2017 and 2023 was used to develop and validate an empirical algorithm to retrieve DOC concentration with a +/-15% uncertainty from Sentinel-2 imagery. Implementation on 141 usable images produced a 6-year time series (2017 –2023) of DOC distributions along the thalweg. Analysis of the time series helped identify river discharge, tidal water level, and a marsh enhanced vegetation index 2 (EVI2) as predictors of DOC distribution in the estuary, and facilitated the training and validation of a simple model estimating the distribution. This simple model was able to predict DOC along the PIE thalweg within +/-15% of the in-situ measurements. Implementation for three years (2020-2022) illustrated how this type of remote-sensing-informed models can be coupled with the outputs hydrodynamic models to calculate DOC fluxes in tidal marsh-influenced estuaries and estimate DOC export to the coastal ocean.

*Aylin Tuzcu Kokal, Boston University, USA, https://orcid.org/0000-0003-2786-2033

Joshua Harringmeyer, Boston University, USA, https://orcid.org/0000-0001-8108-0644

Olivia Cronin-Golomb, Boston University, USA, https://orcid.org/0000-0003-2842-158X

Matthew Weiser, Boston University, USA, https://orcid.org/0009-0002-7178-2153

Jiyeong Hong, Boston University, USA, https://orcid.org/0000-0001-9731-0272

Nilotpal Ghosh, Boston University, USA, https://orcid.org/0000-0003-2001-5229

Jaydi Swanson, Boston University, USA

Xiaohui Zhu, Boston University, USA, https://orcid.org/0000-0002-9000-312X

Nebiye Musaoglu, Istanbul Technical University, Turkey, https://orcid.org/0000-0002-8022-8755

Cedric Fichot, Boston University, USA, https://orcid.org/0000-0002-1099-5764

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