ORIGINAL RESEARCH article
Front. Mar. Sci.
Sec. Coastal Ocean Processes
This article is part of the Research TopicApplication of Remote Sensing in Coastal Oceanic Processes Volume IIView all 9 articles
The role of organic matter on Suspended Particulate Matter dynamics in the Rhine Region Of Freshwater Influence
Provisionally accepted
Claire Chassagne1*
Zeinab Safar1Sabine Rijnsburger1
Raúl P. Flores2
Julie Pietrzak1
Alejandro Jose Souza3
Thijs Van Kessel4Alexander R. Horner-Devine5- 1Delft University of Technology, Delft, Netherlands
- 2Universidad Tecnica Federico Santa Maria, Valparaíso, Chile
- 3Cinvestav Unidad Merida, Mérida, Mexico
- 4Deltares, Delft, Netherlands
- 5University of Washington, Seattle, United States
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In this study we investigate the Suspended Particulate Matter (SPM) source and dynamics in terms of resuspension and advection in the mid field region of Rhine Region Of Freshwater Influence (Rhine-ROFI). The freshwater front transports organic matter (such as microalgae strains and other organic matter) from the estuary into the coastal area. In calm weather conditions in autumn, most particles in suspension are of low density and high anisotropy. These particles are recognized as elongated algae strains with some organic matter-clay aggregates (flocs), giving trimodal Particle Size Distributions (PSD). During the neap tides strong salinity stratification and low turbulence result in SPM accumulation at the bed forming a fluff layer. At spring tides a fast switch between stratified and well mixed water column conditions caused by tidal mixing results in resuspension of SPM. During spring tides, the PSD's are multimodal at low bed stress (predominance of microalgae) and monomodal at high bed stress (predominance of mineral sediment). At the storm initiation in autumn, the organic-matter rich fluff layer is depleted in a matter of hours, which is reflected in the change in modality of the PSD's. Once the resuspended material is dominated by the mineral clay fraction, the PSD turns sharply monomodal. During winter monomodal PSD's are recorded during calm weather conditions. The particles in suspension are then relatively spherical flocs of low density. During the winter storm, the fluff layer, which is much thinner than in autumn, is depleted very fast. This study shows the importance of organic matter in the transport of mineral sediment particles in coastal areas. The dynamic composition of the fluff layer of the bed should be accounted for in erosion models.
Keywords: Floc aggregates, Fluff layer, sediment, Particle size distribution (PSD), LISST 100X
Received: 08 Sep 2025; Accepted: 07 Nov 2025.
Copyright: © 2025 Chassagne, Safar, Rijnsburger, Flores, Pietrzak, Souza, Van Kessel and Horner-Devine. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Claire Chassagne, c.chassagne@tudelft.nl
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