About

Cédric G. Fichot is an Associate Professor and the Director of the Center for Remote Sensing at Boston University. He is a marine scientist specializing in estuarine and coastal biogeochemistry and water quality. His research is interdisciplinary, combining marine optics, remote sensing, organic geochemistry, and photochemistry to enhance the understanding of interactions between terrestrial and marine environments and their perturbations caused by climate change and human activities. His work involves a combination of field work, laboratory analyses and experiments, remote sensing data and image analysis, and modeling. His research topics include environmental and biogeochemical change in the Arctic Ocean, climate- and human-driven changes in estuarine and coastal biogeochemistry and water quality, remote sensing of aquatic biogeochemical properties, impacts of UV radiation and photochemical processes on biogeochemical cycles, and the fate of land-derived carbon and contaminants in marine environments. Fichot holds a PhD in Marine Science from the University of South Carolina and an MS in Oceanography from Dalhousie University. He is actively involved in teaching courses related to remote sensing and aquatic optics.

Research topics

• Environmental science
• Geology
• Ecology
• Computer Science
• Remote sensing
• Oceanography
• Geography
• Geomorphology
• Chemistry
• Atmospheric sciences
• Physics
• Environmental chemistry
• Cartography
• Computer vision
• Meteorology

Selected publications

• A Mass-Produced Microplastic Antioxidant Degrades Rapidly under UV and Produces More Toxic Products via Nonphotolytic Processes

  Environmental Science & Technology Letters · 2026-04-22

  article

  Plastic additives are emerging contaminants in aquatic environments, making it critical to understand their persistence in plastics and surrounding waters. In this work, we conducted dual-phase monitoring of antioxidant additive octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1076, I-1076) in a system where low-density polyethylene (LDPE) microplastic films were suspended in pure water and exposed to ultraviolet (UV) radiation (295–365 nm). Over 240 days of exposure, I-1076 concentrations in the plastic phase decreased exponentially, with a half-life of 20.2 days, about 5 times shorter than in the dark control (99.2 days). In contrast, I-1076 concentrations in the aqueous phase remained low and nearly constant in both light and darkness, suggesting slow I-1076 leaching and/or transformation of I-1076 in the water outpacing leaching. Two degradation products were identified: 7,9-di-tert-butyl-1-oxaspiro[4,5]deca-6,9-diene-2,8-dione and 2,6-di-tert-butyl-1,4-benzoquinone. They both predominantly formed under dark conditions, suggesting nonphotochemical oxidative degradation as the primary pathway. Extrapolation to environmental UV conditions suggests that most I-1076 in waterborne LDPE microplastics is degraded before reaching the open ocean, limiting its ecological risks primarily to inland and coastal waters. However, the formation of secondary products may pose indirect toxicological risks. These results underscore the importance of quantifying plastic additives in both the plastic and aqueous phases to understand their fate and ecotoxicological impacts.

  PublisherDOI

• Evidence for Mud as Flocculated Bed‐Material Load Versus Washload in a River Delta

  Journal of Geophysical Research Earth Surface · 2025-07-31 · 3 citations

  article

  Abstract Mud dominates the particulate load of sediment and organic carbon from continents to oceans, but mud concentration and transport rate remain notoriously difficult to predict. In rivers, mud is thought to be transported as washload—particles so small that they are absent from the riverbed, washed through the river like passive tracers, and controlled by external inputs rather than local sediment entrainment from the bed. However, freshwater flocculation in rivers can aggregate mud grains into larger particles that behave hydrodynamically more like sand. If correct, this finding opens the door to describe mud transport as bed‐material load—particles in dynamic interchange between the bed and water column—for which robust theory exists. Here we present evidence that mud behaves as flocculated bed‐material load rather than washload in the freshwater Wax Lake Delta (WLD), a major distributary of the Mississippi River Delta. Grain size‐specific concentration‐depth profiles indicate that mud is flocculated in WLD. In situ turbidity sensors, airborne hyperspectral imaging (AVIRIS‐NG), and concentration‐depth profiles show that mud concentration varies temporally and spatially in response to shear stress variations, consistent with bed‐material load dynamics. Furthermore, mud exists in the channel bed (median 14% mud by volume) and dominates the bed on deltaic islands (median 90%). Bed‐material entrainment theory explains observed near‐bed mud concentrations using a formulation that accounts for floc growth and densification near the bed. Together, these findings support a unified treatment of sand and flocculated mud as bed‐material load in lowland rivers and deltas.

  PublisherDOI

• Great Slave Lake as a modulator of dissolved organic carbon fluxes from the Mackenzie River watershed to the Arctic Ocean

  2025-07-30

  preprintOpen accessSenior author

  Understanding dissolved organic carbon (DOC) fluxes in boreal freshwater systems is critical for constraining global carbon budgets and anticipating climate impacts. This study provides a multi-decadal (2000–2022) assessment of DOC fluxes in the Upper Mackenzie River watershed, focusing on Great Slave Lake (GSL)—a key hydrological node in North America’s largest Arctic-draining river system. Using field observations, remote sensing, and hydrological modeling, we estimated DOC fluxes into and out of GSL and calculated a lake-wide DOC budget. Results reveal strong spatial heterogeneity in DOC fluxes among tributaries, primarily driven by discharge and terrain characteristics such as wetland extent, slope, and soil organic carbon content. Wetland-rich, low-relief basins delivered the highest DOC concentrations, while Canadian Shield rivers contributed the lowest. Daily DOC concentrations were estimated with reasonable accuracy (±14%) from watershed attributes and discharge. The Slave River accounted for ~70% of total DOC input to GSL, followed by the Hay River (~10%). GSL removed >30% of the incoming DOC, highlighting its role as a net DOC sink and modulator of DOC fluxes to the Arctic Ocean. This regulatory function helps explain the lower DOC concentrations and distinct chemical composition of the Mackenzie River relative to major Siberian rivers, which lack large lake influences. By altering DOC concentrations and composition, GSL can influence Arctic-Ocean ecosystems and the long-term fate of terrigenous DOC. As boreal warm seasons intensify, GSL’s modulatory role will likely become increasingly important. These findings underscore the importance of incorporating lake-specific processes into assessments of northern freshwater carbon dynamics.

  PublisherOA PDFDOI

• Delta-X: An airborne remote sensing framework to calibrate hydrodynamic and ecogeomorphic processes responsible for land building in coastal deltas

  Remote Sensing of Environment · 2025-12-26 · 4 citations

  articleOpen access

  Coastal river deltas are highly dynamic regions with hydrological processes that vary on hourly, daily, and seasonal timescales. Soil formation in deltas relies on the balance between mineral sediment deposition, erosion, and organic matter production, which are intricately controlled by vegetation and hydrodynamic conditions. The spatial complexity and rapid variations in flow, particularly due to tides, present a major challenge to spaceborne remote sensing achieving the required spatial resolution and temporal sampling. Here, we present an airborne remote sensing and in situ framework that measures parameters that are critical to calibrate and validate hydrodynamic, sediment transport, morphodynamic, and ecogeomorphic models. We discuss the measurements and models within the context of the NASA Earth Venture-Suborbital Delta-X mission, which implemented the framework in two deltaic regions of the Mississippi River Delta with contrasting hydrological regimes, namely the Atchafalaya (i.e., active, river-dominated) and Terrebonne (inactive, river-abandoned) basins that are undergoing land gain and land loss, respectively. The Delta-X framework uses two airborne radar instruments to monitor hydrodynamic processes, measuring water surface level and slope within channels, and tide-induced water level change within wetlands. In addition, an airborne imaging spectrometer provides estimates of suspended sediment concentrations in open water as well as vegetation type and aboveground biomass. We also discuss how the data are used to calibrate and validate the models that estimate sediment deposition and organic soil production, which build land to offset subsidence and sea level rise.

  PublisherDOI

• Seasonal Sea‐Level Variability Regulates Salt‐Marsh Edge Retreat

  Journal of Geophysical Research Earth Surface · 2025-09-27

  article

  Abstract Seasonal variations in salt marsh edge retreat are often attributed to fluctuations in nearshore wave forcing. This study, conducted along the central coast of Jiangsu, China, demonstrates that monsoon‐driven seasonal sea‐level variability, rather than offshore wave conditions, exerts the primary control on retreat rates. UAV and GNSS‐RTK surveys from 2020 to 2022 reveal accelerated marsh edge retreat during summer–autumn, coinciding with elevated sea levels. Idealized wave modeling shows that higher sea levels reduce energy dissipation across nearby tidal flats, facilitating greater wave energy transmission to the marsh edge. Field observations further show seasonal changes in tidal flat elevation, with erosion in summer–autumn and deposition in winter–spring. These morphological changes appear to result from sea‐level‐driven variations in nearshore wave forcing, where enhanced summer wave action erodes the tidal flat, increasing water depth and further reducing dissipation, thereby reinforcing wave energy transmission to the marsh edge. These findings highlight the dominant role of seasonal sea‐level variability in driving lateral marsh retreat, while suggesting that tidal flat morphological adjustments may amplify the seasonal erosion response by reinforcing nearshore hydrodynamic contrasts.

  PublisherDOI

• Optical and biomarker indicators reveal contrasting saltmarsh and riverine contributions of terrigenous dissolved organic carbon

  Limnology and Oceanography · 2025-12-12 · 1 citations

  articleOpen accessSenior authorCorresponding

  Abstract Dissolved organic carbon (DOC) in the coastal ocean originates from multiple sources that differ in composition and reactivity, influencing their fates in the ocean. The diffuse export of coastal marsh‐derived DOC remains poorly quantified, creating uncertainties in ocean carbon budgets. A major challenge is identifying marsh‐derived DOC within heterogeneous mixtures in coastal waters. Here, we introduce a new multivariate framework to partition terrigenous DOC (tDOC) into saltmarsh‐derived and riverine fractions in nearshore and coastal waters, focusing on the northern Gulf of Mexico. The approach integrates ratios of cinnamyl (C), vanillyl (V), and p ‐hydroxyphenyl (P) dissolved lignin phenols (C/V and P/V) with salinity and other compositional indicators of tDOC (spectral slope coefficient, S 275–295 , and carbon‐normalized yield of lignin phenols carbon, TDLP 9 ‐C) to quantify DOC contributions from riverine, marsh, and marine sources. Implementation of the source framework revealed that nearshore tDOC was dominated by riverine inputs near the Mississippi and Atchafalaya river deltas, whereas saltmarsh‐derived tDOC was prevalent near the marsh‐dominated Terrebonne Bay. Offshore, tDOC comprised a small but non‐negligible fraction (< 20%) of the DOC pool, with ~ 90% derived from rivers, and ~ 10% from saltmarshes on average. This study provides a novel framework for quantifying the contributions of marsh‐derived and riverine DOC in coastal waters, advancing understanding of their roles in coastal carbon budgets.

  PublisherOA PDFDOI

• Decoding the Drivers of DOC: Coupled Solar–Microbial Exposure System For Optical and Chemical Analysis of Dissolved Organic Carbon Concentration and Composition

  Abstracts with programs - Geological Society of America · 2025-01-01

  articleSenior author
  PublisherDOI

• Capturing the Dynamics of Dissolved Organic Carbon (DOC) in Tidal Saltmarsh Estuaries Using Remote‐Sensing‐Informed Models

  Journal of Geophysical Research Biogeosciences · 2024-10-01 · 8 citations

  articleSenior authorCorresponding

  Abstract 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 useable 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 (WL), and a marsh enhanced vegetation index 2 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 ±16% 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.

  PublisherDOI

• Coupling numerical models of deltaic wetlands with AirSWOT, UAVSAR, and AVIRIS-NG remote sensing data

  Biogeosciences · 2024-01-16 · 8 citations

  articleOpen access

  Abstract. Coastal marsh survival relies on the ability to increase elevation and offset sea level rise. It is therefore important to realistically model sediment fluxes between marshes, tidal channels, and bays as sediment availability controls accretion. Traditionally, numerical models have been calibrated and validated using in situ measurements at a few locations within the domain of interest. These datasets typically provide temporal information but lack spatial variability. This paper explores the potential of coupling numerical models with high-resolution remote sensing imagery. Products from three sensors from the NASA Delta-X airborne mission are used. Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) provides vertical water level change on the marshland and was used to adjust the bathymetry and calibrate water fluxes over the marsh. AirSWOT yields water surface elevation within bays, lakes, and channels, and was used to calibrate the Chezy bottom friction coefficient. Finally, imagery from AVIRIS-NG provides maps of total suspended solids (TSS) concentration that were used to calibrate sediment parameters of settling velocity and critical shear stress for erosion. Three numerical models were developed at different locations along coastal Louisiana using Delft3D. The coupling enabled a spatial evaluation of model performance that was not possible using simple point measurements. Overall, the study shows that calibration of numerical models and their general performance will greatly benefit from remote sensing.

  PublisherDOI

• Validating floc settling velocity models in rivers and freshwater wetlands

  2024-02-27 · 2 citations

  preprintOpen accessCorresponding

  Abstract. Flocculation controls mud sedimentation and organic carbon burial rates by increasing mud settling velocity. Floc settling velocity can be predicted using a semi-empirical model that depends on turbulence, sediment concentration, and geochemical variables or an explicit Stokes law-type model that depends on floc diameter, permeability, and fractal properties. However, validation of the semi-empirical and explicit models with direct field measurements is lacking. We employed a camera, in situ particle sizing, and analysis of grain size-specific suspended sediment concentration profiles to measure flocs in the freshwater channels and wetlands of Wax Lake Delta, Louisiana. Sediment finer than ~20 to 50 μm flocculates with median floc diameter of 30 to 90 μm, bulk solid fraction of 0.05 to 0.3, and floc settling velocity of ~0.1 to 1 mm s-1, with little variation along depth. These values are consistent with the semi-empirical model, which indicates that turbulence limits variation in floc settling velocity on flood-to-seasonal time scales. In the explicit model, the effective primary particle diameter, commonly assumed to be the median primary particle diameter, differs by a factor of ~2 to 6 smaller than the median and can be better described using a simple fractal theory. Flow through the floc increases settling velocity by a factor of ~2 and can be explained by parameterizing flocs as effectively permeable clusters of primary particles. Our results provide the first full field validation of effective primary particle diameter and floc permeability theories, which improve floc settling velocity predictions of the explicit model.

  PublisherOA PDFDOI

Frequent coauthors

• Eva Ortega‐Retuerta

  Centre National de la Recherche Scientifique

  20 shared

• Ronald Benner

  University of South Carolina

  18 shared

• Yuan Shen

  Northeast Forestry University

  17 shared

• Sauveur Belviso

  Centre National de la Recherche Scientifique

  17 shared

• Philippe Peylin

  Commissariat à l'Énergie Atomique et aux Énergies Alternatives

  16 shared

• Joshua P. Harringmeyer

  Boston University

  15 shared

• Karl Kaiser

  Texas A&M University at Galveston

  14 shared

• Fabien Joux

  Laboratoire d'Océanographie Microbienne

  14 shared

Labs

• Aquatic Photo-biogeochemistry & Remote Sensing LabPI

Education

• Ph.D, Marine Science Program

  University of South Carolina

  2013

• M.S., Department of Oceanography

  Dalhousie University

  2004

• B.S., Marine and Environmental Systems

  Florida Institute of Technology

  2000