Cédric G. Fichot

Boston University | BU · Department of Earth & Environment

Continental runoff is a major source of freshwater, nutrients and terrigenous material to the Arctic Ocean. As such, it influences water column stratification, light attenuation, surface heating, gas exchange, biological productivity and carbon sequestration. Increasing river discharge and thawing permafrost suggest that the impacts of continental...

[1] The mineralization of terrigenous dissolved organic carbon (tDOC) discharged by rivers can impact nutrient and trace metal cycling, biological productivity, net ecosystem metabolism, and air-sea CO2 exchange in ocean margins. However, the extreme heterogeneity of river-influenced ocean margins represents a major challenge for quantitative asses...

Lake surface water temperature Thermal front Thermal bar Lake stratification A B S T R A C T Most large temperate lakes experience overturning every spring and fall as surface water moves past 4 °C, the temperature of maximum density for freshwater. These semiannual, lake-wide overturning events play an important role regulating the thermal structu...

Flocculation controls mud sedimentation and organic carbon burial rates by increasing mud settling velocity. However, calibration and validation of floc settling velocity models in freshwater are lacking. We used a camera, in situ laser diffraction particle sizing, and suspended sediment concentration–depth profiles to measure flocs in Wax Lake Del...

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...

Measurements of dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) concentrations are used to characterize the dissolved organic matter (DOM) pool and are important components of biogeochemical cycling in the coastal ocean. Here, we present the first edition of a global database (CoastDOM v1; available at 10.1594/PANGAEA.964012, L...

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...

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 l...

In hydrological optics, “optical closure” means consistency between the apparent optical properties (AOPs) determined from radiometric measurements and those derived from radiative transfer modelling based on concurrently measured inherent optical properties (IOPs) and boundary conditions (sea and sky states). Good optical closure not only provides...

Inland and coastal waters provide key ecosystem services and are closely linked to human well-being. In this study, we propose a semi-analytical method, which can be applied to Sentinel-2 MultiSpectral Instrument (MSI) images to retrieve high spatial-resolution total suspended solids (TSS) concentration in a broad spectrum of aquatic ecosystems ran...

The measurements of dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) are used to characterize the dissolved organic matter (DOM) pool and are important components of biogeochemical cycling in the coastal ocean. Here, we present the first edition of a global database (CoastDOM v1; available at https://figshare.com/s/512289eb43c4f...

Total suspended solids (TSS) can be a useful indicator of environmental change in nearshore coastal environments. Understanding the mechanisms of TSS variations in response to environmental drivers is of broad interest for ecology and geomorphology. The Yellow River Delta (YRD) in China is a fragile coastal region that has been affected by human ac...

In hydrological optics, "optical closure" means consistency between the apparent optical properties (AOPs) determined from radiometric measurements and those derived from radiative transfer modelling based on concurrently measured Inherent optical properties (IOPs) and boundary conditions (sea and sky states). Good optical closure not only provides...

In hydrological optics, "optical closure" means consistency between the apparent optical properties (AOPs) determined from radiometric measurements and those derived from radiative transfer modelling based on concurrently measured Inherent optical properties (IOPs) and boundary conditions (sea and sky states). Good optical closure not only provides...

Coastal marsh survival relies upon to their ability to increase their elevation and offset sea level rise. It is therefore fundamental to realistically model the sediment fluxes between marshes, tidal channels and bays. Traditionally, numerical models have been calibrated and validated using in-situ measurements located in few locations within the...

The ocean plays a central role in modulating the Earth’s carbon cycle. Monitoring how the ocean carbon cycle is changing is fundamental to managing climate change. Satellite remote sensing is currently our best tool for viewing the ocean surface globally and systematically, at high spatial and temporal resolutions, and the past few decades have see...

The development of algorithms for remote sensing of water quality (RSWQ) requires a large amount of in situ data to account for the bio-geo-optical diversity of inland and coastal waters. The GLObal Reflectance community dataset for Imaging and optical sensing of Aquatic environments (GLORIA) includes 7,572 curated hyperspectral remote sensing refl...

Future global Visible Shortwave Infrared Imaging Spectrometers, such as the Surface Biology and Geology (SBG) mission, will regularly cover the Earth's entire terrestrial land area. These missions need high fidelity atmospheric correction to produce consistent maps of terrestrial and aquatic ecosystem traits. However, estimation of surface reflecta...

Global spectroscopic missions, such as NASA’s Surface Biology and Geology, will observe coastal environments and must account for the optical properties of both land and sea. Specifically, they must consider reflectance effects that arise from interactions between surface structures and variable observing geometries that are unique to terrestrial a...

You can learn a lot about rivers, lakes, estuaries, and oceans by looking down at them from the sky. Scientists use a technique called remote sensing to measure the amount of light or heat energy reflected and emitted from the Earth. Sensors can be on satellites or mounted on airplanes, helicopters, or drones. Scientists use this information to map...

Seagrass meadows worldwide provide valuable ecosystem services but have experienced sharp declines in recent decades. This rapid loss has prompted numerous restoration efforts with variable levels of success, often depending on the suitability of the restoration sites. The selection of sites can be guided by simple habitat suitability models driven...

High inflows of freshwater from the Mississippi and Atchafalaya rivers into the northern Gulf of Mexico during spring contribute to strong physical and biogeochemical gradients which, in turn, influence phytoplankton community composition across the river plume–ocean mixing zone. Spectral features representative of bio-optical signatures of phytopl...

Ultraviolet (UV)-visible imaging spectroscopy is an emerging and highly anticipated technology, expected to improve the remote sensing of coastal waters and expand its range of applications. Upcoming NASA satellite missions including PACE and GLIMR will feature imaging spectrometers capable of measuring hyperspectral remote-sensing reflectance (R r...

Total suspended solids (TSS) concentration is an important biogeochemical parameter for water quality management and sediment-transport studies. In this study, we propose a novel semi-analytical method for estimating TSS in clear to extremely turbid waters from remote-sensing reflectance (Rrs). The proposed method includes three sub-algorithms used...

The MALINA oceanographic campaign was conducted during summer 2009 to investigate the carbon stocks and the processes controlling the carbon fluxes in the Mackenzie River estuary and the Beaufort Sea. During the campaign, an extensive suite of physical, chemical and biological variables were measured across seven shelf–basin transects (south–north)...

River networks are important water carriers that provide a multitude of ecosystem services, including freshwater for agriculture, drinking water for cities, and recreational activities. Accurate mapping of river networks from remote-sensing images is important for the study of these systems. Unfortunately, the delineation of river networks is chall...

The elemental stoichiometry of particulate organic carbon (C), nitrogen (N), and phosphorus (P) connects the C fluxes of biological production to the availability of the limiting nutrients in the ocean. It also influences the marine food-web by modulating zooplankton’s feeding behavior and organic matter decomposition by bacteria. Despite its impor...

The photobleaching of chromophoric dissolved organic matter (CDOM) is considered an important loss process for CDOM absorption in sunlit natural waters, where it can regulate the biota's exposure to sunlight, surface solar heating, and dissolved organic matter dynamics. Despite its importance, this sink remains poorly quantified, primarily because...

The MALINA oceanographic campaign was conducted during summer 2009 to investigate the carbon stocks and the processes controlling the carbon Fluxes in the Mackenzie River estuary and the Beaufort Sea. During the campaign, an extensive suite of physical, chemical and biological variables was measured across seven shelf–basin transects (south-north)...

The elemental stoichiometry of particulate organic carbon (C), nitrogen (N), and phosphorus (P) connects the C fluxes of biological production to the availability of the limiting nutrients in the ocean. It also influences the marine food-web by modulating the feeding behavior of zooplankton and the decomposition of organic matter by bacteria and vi...

Rapid water level rise due to climate change has the potential to remobilize loose sediments along shorelines and increase the turbidity of nearshore waters, thereby impacting water quality and aquatic‐ecosystem health. Siling Lake is one of the largest and most rapidly expanding lakes on the Tibetan Plateau. Between 2000 and 2017, this lake experi...

Although methanogenesis is considered a strictly anaerobic process, oxygen‐replete surface open‐ocean waters are usually supersaturated with methane (CH4 ), a phenomenon termed the oceanic methane paradox. Here, we report that abiotic methane photoproduction from chromophoric dissolved organic matter (CDOM) significantly contributes to this paradox....

One of the challenging tasks in modern aquatic remote sensing is the retrieval of near-surface concentrations of Total Suspended Solids (TSS). This study aims to present a Statistical, inherent Optical property (IOP) -based, and muLti-conditional Inversion proceDure (SOLID) for enhanced retrievals of satellite-derived TSS under a wide range of in-w...

Advances in Earth Observation technologies, particularly hyperspectral remote sensing, can fill important gaps in the information needed about shallow coastal habitats, which are among the most productive ecosystems of the world oceans (e.g. eelgrass meadows, kelp forests, etc). The main objectives of this project were 1) to test the new WaterSAT I...

Semi-analytical Radiative Transfer Model for shallow water under development

The deposition of suspended sediment is an important process that helps wetlands accrete surface material and maintain elevation in the face of sea level rise. Optical remote sensing is often employed to map total suspended solids (TSS), though algorithms typically have limited transferability in space and time due to variability in water constitue...

Coastal ecosystem studies using remote visible/infrared spectroscopy typically invert an atmospheric model to estimate the water-leaving reflectance signal. This inversion is challenging due to the confounding effects of turbid backscatter, atmospheric aerosols, and sun glint. Simultaneous estimation of the surface and atmosphere can resolve the am...

Recent climate change is causing most lakes on the Tibetan Plateau to grow at an unprecedented rate. Changes in the physical properties and water storage of the lakes are now relatively well documented. Yet the impacts on their water quality remain poorly understood. Turbidity is a well-established optical water-quality indicator related to suspend...

For the past decade, observations of carbonyl sulfide (OCS or COS) have been investigated as a proxy for carbon uptake by plants. OCS is destroyed by enzymes that interact with CO2 during photosynthesis, namely carbonic anhydrase (CA) and RuBisCO, where CA is the more important one. The majority of sources of OCS to the atmosphere are geographicall...

Short timescale observations are valuable for understanding microbial ecological processes. We assessed dynamics in relative abundance and potential activities by sequencing the small sub-unit ribosomal RNA gene (rRNA gene) and rRNA molecules (rRNA) of Bacteria, Archaea, and Eukaryota once to twice daily between March 2014 and May 2014 from the sur...

Short time-scale observations are valuable for understanding microbial ecological processes. We assessed dynamics in relative abundance and potential activities by sequencing the small sub-unit ribosomal RNA gene (rDNA) and rRNA molecules (rRNA), of Bacteria, Archaea and Eukaryotes once to twice-daily between March and May in the surface ocean off...

Dissolved organic carbon, DOC, and the colored component of dissolved organic matter, CDOM, are key indicators of coastal water quality and biogeochemical state. Yet applications of space-based remote sensing to monitoring of CDOM variability across estuarine ecosystems and assessment of DOC exchanges along highly dynamic terrestrial-aquatic interf...

Rapid environmental changes in the Arctic Ocean affect plankton productivity and the bioavailability of dissolved organic matter (DOM) that supports microbial food webs. We report concentrations of dissolved organic carbon (DOC) and yields of amino acids (indicators of labile DOM) in surface waters across major Arctic margins. Concentrations of DOC...

In this study, we examine the capabilities of the Landsat 8 Operational Land Imager (OLI), Thermal Infrared Sensor (TIRS), and Aqua Moderate resolution Imaging Spectroradiometer (MODIS) for monitoring the environmental impact of the 2015 Hyperion Treatment Plant (HTP) wastewater diversion in Santa Monica Bay, California. From 21 September−2 Novembe...

For the past decade, observations of carbonyl sulfide (OCS or COS) have been investigated as a proxy for carbon uptake by plants. OCS is destroyed by enzymes that interact with CO2 during photosynthesis, namely carbonic anhydrase (CA) and RuBisCO, where CA is the more important. The majority of sources of OCS to the atmosphere are geographically se...

Dissolved lignin phenols and optical properties of dissolved organic matter (DOM) were measured to investigate the sources and transformations of terrigenous DOM (tDOM) in Otsuchi Bay, Japan. Three rivers discharge into the bay, and relatively high values of syringyl:vanillyl phenols (0.73 ± 0.07) and cinnamyl:vanillyl phenols (0.33 ± 0.10) indicat...

Concentrations of dissolved organic carbon (DOC) and major biochemicals (amino acids and carbohydrates) were measured during five cruises (2009-2010) to the Louisiana margin in the northern Gulf of Mexico. Concentrations of amino acids and carbohydrates were elevated at mid-salinities and were indicative of plankton production of dissolved organic...

Dissolved lignin is a well-established biomarker of terrigenous dissolved organic matter (DOM) in the ocean, and a chromophoric component of DOM. Although evidence suggests there is a strong linkage between lignin concentrations and chromophoric dissolved organic matter (CDOM) absorption coefficients in coastal waters, the characteristics of this l...

Dissolved lignin is a well-established biomarker of terrigenous dissolved organic matter (DOM) in the ocean, and a chromophoric component of DOM. Although evidence suggests there is a strong linkage between lignin concentrations and chromophoric dissolved organic matter (CDOM) absorption coefficients in coastal waters, the characteristics of this l...

The San Francisco Bay-Delta Estuary watershed is a major source of freshwater for California and a profoundly human-impacted environment. The water quality monitoring that is critical to the management of this important water resource and ecosystem relies primarily on a system of fixed water-quality monitoring stations, but the limited spatial cove...

Excitation emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) is commonly used to investigate the dynamics of dissolved organic matter (DOM). However, a lack of direct comparisons with known biomolecules makes it difficult to substantiate the molecular composition of specific fluorescent components. Here...

Abstract. The global budget of tropospheric carbonyl sulfide (OCS) is believed to be at equilibrium because background air concentrations have remained roughly stable over at least the last decade. Since the uptake of OCS by leaves (associated with photosynthesis) and soils have been revised significantly upwards recently, an equilibrated budget ca...

The Portable Remote Imaging Spectrometer is a recently developed pushbroom imaging spectrometer airborne sensor designed to address the needs of coastal ocean science. We present here selected results from recent PRISM campaigns in Florida and California using the Twin Otter aircraft at a maximum altitude of ~20 kft. We also present a summary of im...

The global budget of tropospheric carbonyl sulfide (OCS) is believed to be at equilibrium because background air concentrations have remained roughly stable over at least the last decade. Since the uptakes of OCS by leaves (associated to photosynthesis) and soils have been revised significantly upwards recently, an equilibrated budget can only be o...