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Coastal and Continental Morphodynamics laboratory

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The "Coastal and Continental Morphodynamics" laboratory (M2C) is a Joint Research Unit (UMR 6143) created in 1996, under the supervision of the French National Center for Scientific Research (CNRS), the university of Caen Normandie (UNICAEN) and the university of Rouen Normandy (URN). The staff of the laboratory includes 86 persons: 37 researchers, 21 engineers and technicians, 28 PhD students. The research of the M2C laboratory focuses on the characterization and modeling of natural processes dynamics in different compartments along the LAND-SEA continuum, at different scales of time and space. The research is organized into 5 themes:
  • Watershed
  • Estuary
  • Coastal


This research is carried out with an interdisciplinary approach integrating researchers specialized in mechanics, geosciences, oceanography, hydrology, microbiology and ecology of organisms. Our research combines in-situ measurements with numerous dedicated equipment, experimental approaches and numerical moodeling.

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Last publications

Abstract Background Major advances over the past decade in molecular ecology are providing access to soil fungal diversity in forest ecosystems worldwide, but the diverse functions and metabolic capabilities of this microbial community remain largely elusive. We conducted a field survey in montane old-growth broadleaved and conifer forests, to investigate the relationship between soil fungal diversity and functional genetic traits. To assess the extent to which variation in community composition was associated with dominant tree species (oak, spruce, and fir) and environmental variations in the old-growth forests in the Jade Dragon Snow Mountain in Yunnan Province, we applied rDNA metabarcoding. We also assessed fungal gene expression in soil using mRNA sequencing and specifically assessed the expression of genes related to organic matter decomposition and nutrient acquisition in ectomycorrhizal and saprotrophic fungi. Results Our taxonomic profiling revealed striking shifts in the composition of the saprotrophic and ectomycorrhizal guilds among the oak-, fir-, and spruce-dominated forests. The core fungal microbiome comprised only ~ 20% of the total OTUs across all soil samples, although the overlap between conifer-associated communities was substantial. In contrast, seasonality and soil layer explained only a small proportion of the variation in community structure. However, despite their highly variable taxonomic composition, fungal guilds exhibited remarkably similar functional traits for growth-related and core metabolic pathways across forest associations, suggesting ecological redundancy. However, we found that the expression profiles of genes related to polysaccharide and protein degradation and nutrient transport notably varied between and within the fungal guilds, suggesting niche adaptation. Conclusions Overall, our metatranscriptomic analyses revealed the functional potential of soil fungal communities in montane old-growth forests, including a suite of specialized genes and taxa involved in organic matter decomposition. By linking genes to ecological traits, this study provides insights into fungal adaptation strategies to biotic and environmental factors, and sheds light on the importance of understanding functional gene expression patterns in predicting ecosystem functioning.

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The Central English Channel troughs correspond to elongated incisions up to 250 m-deep, at several locations at the bottom of this sea corridor. Depending on their location, they are usually interpreted as part of the submerged quaternary paleovalley network or as resulting from megaflood events. Shedding light on these features, their age, and the processes underlying their development is key for understanding their significance in terms of event geology. The interpretation of a dense grid of high-resolution marine seismic data acquired in the Bay of Seine area reveals that the extensive Quaternary paleovalley and trough network commonly as associated to the "Channel River" system is actually subdivided into at least two superimposed and unrelated incised networks. The overlying network corresponds to fluvial incisions developing during low sea-level conditions of Pleistocene time and connects to the present day fluvial network. The underlying network corresponds to the troughs and appears as a complex, deeper, relatively discontinuous and isolated network. This older network shows unexpected local incision depth up to c.350-400 m-deep and complex sedimentary infill involving several sedimentary processes and environments from fluvial to tidal and shallow-marine. We discuss these observations and their implications for understanding the origin, age and development of the troughs all over the English Channel, from the Dangeard Troughs in the Dover Strait to the Hurd Deep at the western end. We also raise questions about the significance of these large incised features in terms of source-to-sink system of northwestern Europe.

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The suprabenthos includes all bottom-dependent animals (mainly crustaceans, especially peracarids and decapods) that perform daily or seasonal vertical migrations with variable regularity. In the megatidal (tidal range > 8 m) Seine estuary, the suprabenthos of the downstream polyhaline and mesohaline zones have been well described, while this biological compartment have been neglected in the more upstream, oligohaline and freshwater zones. Seasonal sampling of the upstream part of the Seine estuary was conducted between 2019 and 2021 to investigate for the first time the abiotic factors influencing the structure and pattern of the suprabenthos sensu stricto in this part of the estuary. Two suprabenthic communities were distinguished, showing a contrasted spatio-temporal pattern in relation to environmental variables such as salinity, turbidity, water temperature and river discharge. The suprabenthos was characterized by a few numbers of species (13 in total), and was dominated by mysids (which represents 97.5% of total abundance), amphipods and decapods, which resulted in a low diversity of both communities. Species richness, abundance and biomass were the highest during summer at the most downstream stations. Some non-suprabenthic sensu stricto species (planktonic larvae, Teleostei) were also recorded, with major implications concerning the estuarine functions (spawning, nursery and foraging areas, etc.). The recruitment periods of some species are also discussed.

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Artificial Reefs (ARs) are commonly cited as a tool used for increasing fishery production and reinstating ecosystem functionalities. The assessment of ARs deployment is mostly based on analysis of the evolution of fish communities. Recently, studies have focused on trophic modelling to understand the functioning of such ecosystems in a more holistic approach. Trophic models are able to address this concern by describing the interaction between species at different trophic levels and based on the quantification of energy and matter flows through ecosystems. These models allow the application of numerical methods-also called Ecological Network Analysis (ENA)-to characterize emergent properties of the ecosystem. Usually, ENA indices are proposed as indicators of ecosystem health as they are sensitive to different impacts on marine ecosystems. In the present study, the Ecopath software is used to build an ecosystem model composed of 23 compartments, from detritus and phytoplankton to mammals, to describe the situation ''before'' and ''after'' the deployment of ARs in the south of the Bay of Biscay along the Landes coast. In addition, ENA indices are calculated for two periods, ''before'' and ''after'' the deployment of artificial reefs, to compare network functioning and the overall properties of the structural trophic network. Our results show little structural change in the ecosystem, with a rearrangement of the trophic levels and a simultaneous increase in biomass and system maturity. These preliminary results evidently need to be confronted with other environmental factors such as, for instance, substrate composition, proximity to natural reefs and larval supply. Nonetheless, we consider that the maturity index could be used as a new indicator to assess the evolution of ARs with specific management objectives.

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Geomorphological evidence provides significant information on the processes that govern lateral propagation of a growing active anticline. Within actively developing fold-and-thrust belts evidence can be recorded in Quaternary landforms and the drainage network. In the Kuqa fold-and-thrust belt (KFTB), located in the southern foothills of the Tian Shan mountains, we investigate the topographic and fluvial geomorphic records of the eastern part of the Qiulitage and of the Yakeng anticlines. In this study, using a morphometric approach, including the analysis of anomalies in the spatial patterns of river channels, topographic profiles along anticline crests, and the geometry of wind gaps, we speculate on the lateral propagation of these folds. We extract the drainage network related to the growth of the Yakeng and Qiulitage folds from the beginning onset of the folding (5.5 Ma ago) to its acceleration in the Late Quaternary. We examine 15 rivers and their catchments crossing the eastern segment of Qiulitage and the Yakeng anticlines. Our results demonstrate how the ridges along the eastern segment of Qiulitage and Yakeng folds feature (1) an anticline ridge with decreasing relief from the topographic crest to the plunging ends of the ridges, (2) alternating wind gaps and water gaps from west to east, (3) a drainage system closely controlled by folding and differential uplift, (4) a decrease in drainage basin maturity towards the east only, and (5) fluvial features that provide age constraints. We then document the evolution of the drainage network and provide insights on the growth history of the eastern Kuqa fold-and-thrust belt from its nucleation to its growth acceleration. The connections between the topography and the drainage allow us to present an integrated model that could explain their lateral and vertical fold growth along the two folds along their leading edges.

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A prediction model for the turbulent kinetic energy (TKE) induced by tidal-currents is proposed as a function of the barotropic velocity only, along with a robust method evaluating the different parameters involved using Acoustic Doppler Current Profiler (ADCP) measurements from Alderney Race. We find that the model is able to reproduce correctly the TKE profiles with coefficients of correlation on average higher than 0.90 and normalised root-mean-square errors (NRMSE) less than 14%. Different profiles are also tested for the mean velocity, no satisfactory prediction model is found but we are able to have decent estimates of the velocity shear and friction velocity. Two applications are then carried out. First the turbulent budget terms are estimated and discussed. We identify the turbulent production and dissipation of TKE as the most important mechanisms, then we discuss the validity of several theoretical results derived for isotropic turbulence for this application. A strong departure for the estimation of the turbulent dissipation is notably found and explained by the turbulent anisotropy. At last the prediction model for the TKE is used to infer the wave-induced TKE. We show the importance of removing the tidal component, waves can have a strong influence down to mid-depth.

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Offshore Wind Farm (OWF) foundations are considered to have a potential impact on the larval dispersion of benthic species. This study focused on OWFs’ impacts on larval dispersion, considering factors such as the foundation type, flow velocity, flow direction, and release type using numerical modelling. At the scale of monopile and gravity-based foundations, a combination of two numerical models was used: the Eulerian model (OpenFOAM), solving the 3D Navier–Stokes equations for computing the hydrodynamics, and the Lagrangian model (Ichthyop), solving the advection–diffusion equation for the larval dispersion simulations. The validation model tests were evaluated with experimental data as a first step of the study. Accurate results were achieved, yielding a Turbulent Kinetic Energy (TKE) Root-Mean-Squared Error (RMSE) in the range of 6.82–8.27 ×10−5kg/m·s2 within the refined mesh, with a coefficient of determination (R2) approaching unity. For the second phase, more-realistic simulations were modelled. Those simulations demonstrated turbulent wakes downstream of the foundations and horseshoe vortex formations near the bottom. A larval dispersion was simulated using passive particles’ motion. Vertical flumes in the wake with particles experiencing both upward and downward motions, impacting the fall velocities of the particles, were observed. The influence of gravity-based foundations might lead to a stepping-stone effect with a retention time of up to 9 min, potentially allowing the settlement of competent larvae. In a similar geometry with an angular spring tide velocity, 0.4% of particles were trapped.

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The English Channel is subjected to a high and growing number of anthropogenic disturbances (e.g., fishing, aggregate extraction, dredging, port activity and spoil deposition). It is also a hotspot for future Offshore Wind Farm (OWF) development in France. The DRACCAR project is the first French offshore research platform dedicated to offshore wind energy. The aim of this project is to improve the understanding of the interactions between offshore wind energy and the environment, to optimise the design of wind turbines and to co-construct a permanent observation network of the maritime coasts. Six topics are thus studied: ecosystem approach; marine megafauna; fishery resources, biofouling and benthos; wind; structure behaviour and hydro-sedimentary processes. This poster presents the sampling strategy to collect data on the different ecosystem compartments of the Fécamp offshore platform in the Fécamp OWF site, adopting an ecosystem approach for the implementation of a trophic network analysis. This will allow to understand the reef and/or reserve effect of this offshore structure on a gravel habitat. For that, the collection of data on biological compartments (bacteria, phytoplankton, zooplankton, suprabenthos, soft bottom benthos, hard substrate benthos, algae, demersal fishes) are essential. Seasonal patterns will be studied during 2024 to estimate the contribution of each zoological group, with isotopic analyses and stomach contents on demersal fish. Additionally, steel panels will be installed at different distances from the platform wake with colonization to study the spatio-temporal dynamics of biofouling.

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The sandy estuaries along the English Channel have been silting up for over 10 years. Former geoscientific studies, which assessed sediment stocks, showed that the sedimentary material came from the marine rather than the fluvial part due intense cross-shore dynamics. To understand how the sedimentary material was brought from the coastal sea from estuary, a three-dimensional coupled numerical model was first set up, before simulating hydrosedimentary processes. This study was applied to the bay of the Somme, located in the northern France along the English Channel. This estuarine environment is forced by semi-diurnal tides and ocean waves, that move the predominant fine and coarse sands. The sands moving from coastal ocean, a numerical validation was carried out at coastal, nearshore, and bay sites using several datasets from in-situ field campaigns. Good agreement was found between model and data in the coastal zone regarding to bottom and surface current, sea surface height and mean wave parameters. Vertical profiles of current were also well simulated, especially their modulation by ocean waves. The nearshore simulations reproduced the wave set-up and wave set-down, as well as the cross-shore dynamics with simulated undertow and streaming, and the longshore dynamics showing the longshore current generated by oblique incident ocean waves. Inside the bay, a modulation of the tidal wave is observed, as expected. The water filling and draining of the bay are well represented and follow the tidal phase: the ebb flow drains the bay while the flood flow fills it. These simulations were performed under calm and storm conditions, enabling us to identify the contribution of ocean waves to the hydrodynamics. The next step is to build the hydro-sedimentary model to assess the impact of hydrodynamics on sediment transport and the morphodynamics of the bay.

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International collaboration (co-authors)



M2C lab. in Caen

Morphodynamique Continentale et Côtière
Université de Caen Normandie (Campus 1)
24 rue des Tilleuls
14000 Caen Cedex

M2C lab. in Rouen

Morphodynamique Continentale et Côtière
Université de Rouen Normandie (bâtiment Blondel Nord)
Place Emile Blondel
76821 Mont-Saint-Aignan Cedex