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4. Mapping intertidal mudflat gross primary production (GPP) by hyperspectral imagery, coupling with atmospheric CO2 fluxes at varied temporal and spatial scales: from the lab to the ecosystem level, through the seasons

Author

Meleder, Vona, Polsenaere, Pierre, Launeau, Patrick, Jesus, Bruno, Zhang, Meng, Lavaud, Johann, Giraud, Manuel, Rosa, Philippe, Deborde, Jonathan, Geairon, Philippe, Grizon, James, Lamaud, Eric, Bonnefond, Jean-marc, Meleder, Vona, Polsenaere, Pierre, Launeau, Patrick, Jesus, Bruno, Zhang, Meng, Lavaud, Johann, Giraud, Manuel, Rosa, Philippe, Deborde, Jonathan, Geairon, Philippe, Grizon, James, Lamaud, Eric, and Bonnefond, Jean-marc

Published
2024

5. Remote Sensing for Mapping Natura 2000 Habitats in the Brière Marshes: Setting Up a Long-Term Monitoring Strategy to Understand Changes.

Author

Lafitte, Thomas, Robin, Marc, Launeau, Patrick, and Debaine, Françoise

Subjects
REMOTE sensing, INTRODUCED species, RANDOM forest algorithms, INFORMATION storage & retrieval systems, SPATIAL resolution, MULTISPECTRAL imaging
Abstract

On a global scale, wetlands are suffering from a steady decline in surface area and environmental quality. Protecting them is essential and requires a careful spatialisation of their natural habitats. Traditionally, in our study area, species discrimination for floristic mapping has been achieved through on-site field inventories, but this approach is very time-consuming in these difficult-to-access environments. Usually, the resulting maps are also not spatially exhaustive and are not frequently updated. In this paper, we propose to establish a complete map of the study area using remote sensors and set up a long-term and regular observatory of environmental changes to monitor the evolution of a major French wetland. This methodology combines three dataset acquisition technologies, airborne hyperspectral and WorldView-3 multispectral images, supplemented by LiDAR images, which we compared to evaluate the difference in performances. To do so, we applied the Random Forest supervised classification methods using ground reference areas and compared the out-of-bag score (OOB score) as well as the matrix of confusion resulting from each dataset. Thirteen habitats were discriminated at level 4 of the European Nature Information System (EUNIS) typology, at a spatial resolution of around 1.2 m. We first show that a multispectral image with 19 variables produces results which are almost as good as those produced by a hyperspectral image with 58 variables. The experiment with different features also demonstrates that the use of four bands derived from LiDAR datasets can improve the quality of the classification. Invasive alien species Ludwigia grandiflora and Crassula helmsii were also detected without error which is very interesting when applied to these endangered environments. Therefore, since WV-3 images provide very good results and are easier to acquire than airborne hyperspectral data, we propose to use them going forward for the regular observation of the Brière marshes habitat we initiated. [ABSTRACT FROM AUTHOR]

Published
2024
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11. Is an earthquake scenario compatible with the fall of the 'Grand Menhir Brisé' of Locmariaquer (Brittany, France)?

Author

Montabert, Arnaud, Giry, Cédric, Pelenc, Raphaël, Dahou, Amine Ben, Bonnin, Mickaël, Fligiel, Damien, Launeau, Patrick, Perrin, Clément, Cassen, Serge, Lyon-Caen, Hélène, and Mocquet, Antoine

Subjects
EARTHQUAKE intensity, GROUND motion, PALEOSEISMOLOGY, MENHIRS
Abstract

The menhir of Locmariaquer lays in four fragments 200 m north of Locmariaquer (Morbihan, Brittany, France). Several hypotheses have been raised over time to explain its fall. This study discusses a potential earthquake origin and investigates the associated ground motion features. The historical seismicity and the current instrumental seismicity support the concept of an active seismic area. Soil and subsurface characterization highlights a complex site response. Several models of the menhir based on archaeological observations are proposed to simulate the dynamic response of the menhir. A ground motion selection from the European Strong Motion database is used as inputs. An earthquake scenario is compatible with the fall of the menhir. The associated Intensity Measures are discussed. [ABSTRACT FROM AUTHOR]

Published
2023

21. Mapping intertidal mudflat primary production: coupling hyperspectral remote sensing and atmospheric eddy covariance

Author

Méléder, Vona, Polsenaere, Pierre, Launeau, Patrick, Jesus, Bruno, Zhang, Meng, Lavaud, Johann, Giraud, Manuel, Rosa, Philippe, Deborde, Jonathan, Geairon, Philippe, Grizon, James, Lamaud, Eric, Bonnefond, Jean-Marc, Mer, molécules et santé EA 2160 (MMS), Le Mans Université (UM)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Université de Nantes - UFR des Sciences Pharmaceutiques et Biologiques, Université de Nantes (UN)-Université de Nantes (UN), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Bio-Indicateurs Actuels et Fossiles (BIAF), Université d'Angers (UA), LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Interactions Sol Plante Atmosphère (UMR ISPA), Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), and Lamaud, Eric

Subjects
[SDE] Environmental Sciences, [SDE]Environmental Sciences, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2021

22. Easily Implemented Methods of Radiometric Corrections for Hyperspectral–UAV—Application to Guianese Equatorial Mudbanks Colonized by Pioneer Mangroves

Author

Jaud, Marion, primary, Sicot, Guillaume, additional, Brunier, Guillaume, additional, Michaud, Emma, additional, Le Dantec, Nicolas, additional, Ammann, Jérôme, additional, Grandjean, Philippe, additional, Launeau, Patrick, additional, Thouzeau, Gérard, additional, Fleury, Jules, additional, and Delacourt, Christophe, additional

Published
2021
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24. Denitrification by benthic foraminifera and their contribution to N-loss from a fjord environment

Author

Choquel, Constance, Geslin, Emmanuelle, Metzger, Édouard, Filipsson, Helena, Risgaard-Petersen, Nils, Launeau, Patrick, Jauffrais, Thierry, Jesus, Bruno, Mouret, Aurélia, Giraud, Manuel, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Geology [Lund], Lund University [Lund], Aarhus University [Aarhus], Ecologie marine tropicale des océans Pacifique et Indien (ENTROPIE [Nouvelle-Calédonie]), Ifremer - Nouvelle-Calédonie, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD [Nouvelle-Calédonie])-Université de la Nouvelle-Calédonie (UNC), Mer, molécules et santé EA 2160 (MMS), Université de Nantes - UFR des Sciences Pharmaceutiques et Biologiques, Université de Nantes (UN)-Université de Nantes (UN)-Le Mans Université (UM)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN), Institut de Recherche pour le Développement (IRD [Nouvelle-Calédonie])-Ifremer - Nouvelle-Calédonie, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de la Nouvelle-Calédonie (UNC), Le Mans Université (UM)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), and Université de Nantes (UN)-Université de Nantes (UN)-Université de Nantes - UFR des Sciences Pharmaceutiques et Biologiques

Subjects
[SDV]Life Sciences [q-bio], fungi, [SDE]Environmental Sciences, Biochemistry and Molecular Biology, Geology, Oceanography, Hydrology, Water Resources, ComputingMilieux_MISCELLANEOUS
Abstract

Oxygen and nitrate availabilities impact the marine nitrogen cycle at a range of spatial and temporal scales. Here, we demonstrate the impact of denitrifying foraminifera on the nitrogen cycle at two oxygen and nitrate contrasting stations in a fjord environment (Gullmar Fjord, Sweden). Denitrification by benthic foraminifera was determined through the combination of specific density counting per microhabitat and specific nitrate respiration rates obtained through incubation experiments using N2O microsensors. Benthic nitrate removal was calculated from submillimeter chemical gradients extracted from 2D porewater images of the porewater nitrate concentration. These were acquired by combining the DET technique (diffusive equilibrium in thin film) with chemical colorimetry and hyperspectral imagery. Sediments with high nitrate concentrations in the porewater and oxygenated overlying water were dominated by the non-indigenous species (NIS) Nonionella sp. T1. Denitrification by this species could account for 50 %–100 % of the nitrate loss estimated from the nitrate gradients. In contrast sediments below hypoxic bottom waters had low inventories of porewater nitrate, and denitrifying foraminifera were rare. Their contribution to benthic nitrate removal was negligible (< 5 %). Our study showed that benthic foraminifera can be a major contributor to nitrogen mitigation in oxic coastal ecosystems and should be included in ecological and diagenetic models aiming to understand biogeochemical cycles coupled to nitrogen.

Published
2021

25. Easily Implemented Methods of Radiometric Corrections for Hyperspectral–UAV—Application to Guianese Equatorial Mudbanks Colonized by Pioneer Mangroves

Author

Jaud, Marion, Sicot, Guillaume, Brunier, Guillaume, Michaud, Emma, Le Dantec, Nicolas, Ammann, Jérôme, Grandjean, Philippe, Launeau, Patrick, Thouzeau, Gerard, Fleury, Jules, Delacourt, Christophe, Jaud, Marion, Sicot, Guillaume, Brunier, Guillaume, Michaud, Emma, Le Dantec, Nicolas, Ammann, Jérôme, Grandjean, Philippe, Launeau, Patrick, Thouzeau, Gerard, Fleury, Jules, and Delacourt, Christophe

Abstract

Hyper-DRELIO (Hyperspectral DRone for Environmental and LIttoral Observations) is a custom, mini-UAV (unmanned aerial vehicle) platform (<20 kg), equipped with a light push broom hyperspectral sensor combined with a navigation module measuring position and orientation. Because of the particularities of UAV surveys (low flight altitude, small spatial scale, and high resolution), dedicated pre-processing methods have to be developed when reconstructing hyperspectral imagery. This article presents light, easy-implementation, in situ methods, using only two Spectralon® and a field spectrometer, allowing performance of an initial calibration of the sensor in order to correct “vignetting effects” and a field standardization to convert digital numbers (DN) collected by the hyperspectral camera to reflectance, taking into account the time-varying illumination conditions. Radiometric corrections are applied to a subset of a dataset collected above mudflats colonized by pioneer mangroves in French Guiana. The efficiency of the radiometric corrections is assessed by comparing spectra from Hyper-DRELIO imagery to in situ spectrometer measurements above the intertidal benthic biofilm and mangroves. The shapes of the spectra were consistent, and the spectral angle mapper (SAM) distance was 0.039 above the benthic biofilm and 0.159 above the mangroves. These preliminary results provide new perspectives for quantifying and mapping the benthic biofilm and mangroves at the scale of the Guianese intertidal mudbanks system, given their importance in the coastal food webs, biogeochemical cycles, and the sediment stabilization.

Published
2021
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27. Coastal Sand Dunes Monitoring by Low Vegetation Cover Classification and Digital Elevation Model Improvement Using Synchronized Hyperspectral and Full-Waveform LiDAR Remote Sensing

Author

Frati, Giovanni, Launeau, Patrick, Robin, Marc, Giraud, Manuel, Juigner, Martin, Debaine, Françoise, Michon, Cyril, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN), Littoral, Environnement, Télédétection, Géomatique (LETG - Nantes), and Normandie Université (NU)-Normandie Université (NU)-École pratique des hautes études (EPHE)

Subjects
[SPI]Engineering Sciences [physics], hyperspectral, classification, airborne remote sensing, [SDE.MCG]Environmental Sciences/Global Changes, [SDE]Environmental Sciences, low vegetation, dune morphodynamics, lcsh:Q, lcsh:Science, full-waveform LiDAR
Abstract

International audience; Due to the coastal morphodynamic being impacted by climate change there is a need for systematic and large-scale monitoring. The monitoring of sandy dunes in Pays-de-la-Loire (France) requires a simultaneous mapping of (i) its morphology, allowing to assess the sedimentary stocks and (ii) its low vegetation cover, which constitutes a significant proxy of the dune dynamics. The synchronization of hyperspectral imaging (HSI) with full-waveform (FWF) LiDAR is possible with an airborne platform. For a more intimate combination, we aligned the 1064 nm laser beam of a bi-spectral Titan FWF LiDAR with 401 bands and the 15 cm range resolution on the Hyspex VNIR camera with 160 bands and a 4.2 nm spectral resolution, making both types of data follow the same emergence angle. A ray tracing procedure permits to associate the data while keeping the acquisition angles. Stacking multiple shifted FWFs, which are linked to the same pixel, enables reaching a 5 cm range resolution grid. The objectives are (i) to improve the accuracy of the digital terrain models (DTM) obtained from an FWF analysis by calibrating it on dGPS field measurements and correcting it from local deviations induced by vegetation and (ii) in combination with airborne reflectances obtained with PARGE and ATCOR-4 corrections, to implement a supervised hierarchic classification of the main foredune vegetation proxies independently of the acquisition year and the physiological state. The normalization of the FWF LiDAR range to a dry sand reference waveform and the centering on their top canopy echoes allows to isolate Ammophilia arenaria from other vegetation types using two FWF indices, without confusion with slope effects. Fourteen HSI reflectance indices and 19 HSI Spectral Angle Mapping (SAM) indices based on 2017 spectral field measurements performed with the same Hyspex VNIR camera were stacked with both FWF indices into a single co-image for each acquisition year. A simple straightforward hierarchical classification of all 35 pre-classified co-image bands was successfully applied along 20 km, out of the 250 km of coastline acquired from 2017 to 2019, prefiguring its systematic application to the whole 250 km every year.

Published
2020
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30. Methane, pockmarks and Haploops, a biogeochemical connexion

Author

Metzger, Édouard, Champilou, Jean-Baptiste, A, Nicols, Mojtahid, Meryem, Barras, Christine, Baltzer, Agnès, Marine, Reynaud, Nardelli, Maria Pia, Daumeau, A., Beneteau, Eric, Launeau, Patrick, Mouret, Aurélia, baltzer, Agnès, Laboratoire de Planétologie et Géodynamique - Angers (LPG-ANGERS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Bio-Indicateurs Actuels et Fossiles (BIAF), Université d'Angers (UA), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN), and École Centrale de Nantes (ECN)

Subjects
[SDE] Environmental Sciences, [SDE]Environmental Sciences, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2020

37. Fischeries, archeological evidences of the last sea-level rise around the Island of Yeu

Author

Cariou, Elsa, Baltzer, Agnès, Argant, Sébastien, Robert, Laurence, Stéphan, Pierre, Launeau, Patrick, Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN), La Terre Ferme, Littoral, Environnement, Télédétection, Géomatique (LETG - Brest), Université de Nantes (UN)-Université de Nantes (UN)-Université de Caen Normandie (UNICAEN), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN)

Subjects
[SDE]Environmental Sciences, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2019

40. Full-Waveform LiDAR Fast Analysis of a Moderately Turbid Bay in Western France

Author

Launeau, Patrick, Giraud, Manuel, Robin, Marc, Baltzer, Agnes, Launeau, Patrick, Giraud, Manuel, Robin, Marc, and Baltzer, Agnes

Abstract

In shoreline monitoring, only topo-bathymetric light detection and ranging (LiDAR) can map large corridors from aerial dunes to sandbanks in shallow water. Increasing turbidity masking the formation of 532 nm laser beam echoes on the sea bed makes this challenging. Full-waveform recording all the laser beam damping functions, a turbid water column can be seen as an accumulation of layers forming a single continuum and a distinction can be made between signals ending at the bottom down to a depth of 10 m. In practice full-waveforms are converted by laser beam tracing an image cube with a grid of 1-m-wide pixels and a 0.15 m range resolution storing the mean intensities returned along incident angle. The first derivative of a wide Gaussian filter serves to delineate the full-waveform range limits. Because of turbidity current heterogeneity and complexity of multiple layers radiative transfer model, a drastic simplification is applied by normalizing the cumulative full-waveform to 1, transforming each pixel of the water column into spectrum of intensity ranging from 0 to 1 from bottom to top. A transposition between range and bottom-top information facilitates the water index correction below the sea water level provided by 1064-nm discrete echoes. All echoes remain accessible with maximums of cumulative full-waveform third derivative.

Published
2019
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41. Full-Waveform LiDAR Pixel Analysis for Low-Growing Vegetation Mapping of Coastal Foredunes in Western France

Author

Launeau, Patrick, Giraud, Manuel, Ba, Antoine, Moussaoui, Saïd, Robin, Marc, Debaine, Françoise, Lague, Dimitri, Le Menn, Erwan, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Numérique de Nantes (LS2N), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-École Centrale de Nantes (ECN)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Littoral, Environnement, Télédétection, Géomatique (LETG - Nantes), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Géosciences Rennes (GR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Université de Nantes (UN)-Université de Nantes (UN)-École Centrale de Nantes (ECN)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique (IMT Atlantique), Normandie Université (NU)-Normandie Université (NU)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École Pratique des Hautes Études (EPHE), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), and Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS)

Subjects
hyperspectral, ray tracing, Science, coastal foredune, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, full-waveform LiDAR, low-vegetation cover, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, ComputingMilieux_MISCELLANEOUS
Abstract

The monitoring of coastal sand dunes requires regular high-resolution aerial photography along hundreds of kilometers of coastal strips. Light detection and ranging (LiDAR) is now the most widely used method for detailed topographic and vegetation studies. The aim of this work is to show how the full-waveform shapes returned from single or multiple targets can carry information relating to low-vegetation cover and ground roughness of dunes. This work focuses on marram grass, widely involved in the development of mobile dunes. Low-growing plants often exhibit identical pigmentary composition and can only be distinguished by the height of their foliage, which modifies the shape of the LiDAR waveform around the main returns at the top of the foliage. We show that ray tracing of full LiDAR waveforms on the regular grid of pixels of hyperspectral images, acquired synchronously, can resolve the confusion between low-vegetation gradients and bare sand by analyzing the waveform damping induced by cumulating microdiffusion on foliage height, but also with glint effects on the surface roughness of compact materials. Analysis of successive shorelines of wet to dry sand, sand to pioneer couch grass, and couch grass to consolidating marram grass can thereby be conducted routinely.

Published
2018

44. Photosynthetic epibionts and endobionts of Pacific oyster shells from oyster reefs in rocky versus mudflat shores

Author

Barillé, Laurent, Le Bris, Anthony, Méléder, Vona, Launeau, Patrick, Robin, Marc, Louvrou, Ioanna, Ribeiro, Lourenço, and Repositório da Universidade de Lisboa

Subjects
Pigments, Chlorophyll, Bivalves, Chloroplasts, Algae, Plant Cell Biology, Materials Science, lcsh:Medicine, Marine and Aquatic Sciences, Plant Science, Cyanobacteria, Research and Analysis Methods, Oysters, Plant Cells, Animals, Biomass, Crassostrea, Photosynthesis, lcsh:Science, Symbiosis, Materials by Attribute, Diatoms, Liquid Chromatography, Bacteria, Organic Pigments, Pigmentation, lcsh:R, Chromatographic Techniques, Organisms, Biology and Life Sciences, Eukaryota, Malacology, Biodiversity, Molluscs, Cell Biology, Plants, Plankton, Invertebrates, High Performance Liquid Chromatography, Phytoplankton, Physical Sciences, Earth Sciences, Reefs, lcsh:Q, Cellular Structures and Organelles, Cellular Types, Zoology, Research Article
Abstract

The Pacific oyster, Crassostrea gigas (Thunberg), is the main bivalve species cultivated in the world. With global warming enabling its reproduction and larval survival at higher latitudes, this species is now recognized as invasive and creates wild oyster reefs globally. In this study, the spatial distribution of photosynthetic assemblages colonizing the shells of wild C. gigas was investigated on both a large scale (two contrasting types of reefs found in mudflats and rocky areas) and a small scale (within individual shells) using a hyperspectral imager. The microspatial distribution of all phototrophs was obtained by mapping the Normalized Difference Vegetation Index (NDVI). Second derivative (δδ) analyses of hyperspectral images at 462, 524, 571 and 647 nm were subsequently applied to map diatoms, cyanobacteria, rhodophytes and chlorophytes, respectively. A concomitant pigment analysis was carried out by high performance liquid chromatography and completed by taxonomic observations. This study showed that there was high microalgal diversity associated with wild oyster shells and that there were differences in the structure of the phototropic assemblages depending on the type of reef. Namely, vertically-growing oysters in mudflat areas had a higher biomass of epizoic diatoms (hyperspectral proxy at δδ462 nm) and were mainly colonized by species of the genera Navicula, Nitzschia and Hippodonta, which are epipelic or motile epipsammic. The assemblages on the horizontal oysters contained more tychoplanktonic diatoms (e.g. Thalassiosira pseudonana, T. proschkinae and Plagiogrammopsis vanheurckii). Three species of boring cyanobacteria were observed for both types of reef: Mastigocoleus testarum, Leptolyngbya terrebrans, and Hyella caespistosa, but the second derivative analysis at 524 nm showed a significantly higher biomass for the horizontally-growing oysters. There was no biomass difference for the boring chlorophyte assemblages (δδ647 nm), with two species: Eugomontia testarum and Ostreobium quekettii observed for both types of reef. This study shows that oyster shells are an idiosyncratic but ubiquitous habitat for phototrophic assemblages. The contribution of these assemblages in terms of biomass and production to the functioning of coastal areas, and particularly to shellfish ecosystems, remains to be evaluated.

Published
2017

45. Total nitrate uptake by an invasive benthic foraminifer in marine sediments.

Author

Choquel, Constance, Geslin, Emmanuelle, Metzger, Edouard, Filipsson, Helena L., Risgaard-Petersen, Nils, Launeau, Patrick, Giraud, Manuel, Jauffrais, Thierry, Jesus, Bruno, and Mouret, Aurélia

Subjects
FORAMINIFERA, MARINE sediments, BIOGEOCHEMICAL cycles, BENTHIC ecology, INTRODUCED species, ECOLOGICAL models, NITROGEN cycle, BENTHOS
Abstract

Oxygen availability impacts the marine nitrogen cycle at a range of spatial and temporal scales. Invasive organisms have shown to sustainably affect sediment geochemistry and benthic ecology. Nonionella sp. T1 was recently described as an invasive benthic foraminifer in the North Sea region. Here, we demonstrate the impact of this denitrifying species on the foraminifera fauna and the nitrogen cycle of the Gullmar Fjord (Sweden). The foraminifera contribution to benthic denitrification was estimated by coupling living foraminifera micro-distribution, denitrification rate measurement and sedimentary nitrate 2D distribution. Nonionella sp. T1 dominated the foraminifera fauna and could denitrify up to 50-100% of nitrate porewater in oxygenated bottom waters of the fjord. Contrastingly, at the deepest hypoxic low-nitrate station, denitrifying foraminifera species were scarce and did not contribute to nitrogen removal (~ 5%). Our study showed that benthic foraminifera can be a major contributor of nitrogen mitigation in oxic coastal ecosystems and should be included in ecological and diagenetic models aiming at understanding biogeochemical cycles coupled to nitrogen. [ABSTRACT FROM AUTHOR]

Published
2020
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48. A geomorphologist’s dream come true: synoptic high resolution river bathymetry with the latest generation of airborne dual wavelength lidar

Author

Lague, Dimitri, Launeau, Patrick, Michon, Cyril, Gouraud, Emmanuel, Juge, Cyril, Gentile, William, Hubert-Moy, Laurence, Crave, Alain, Géosciences Rennes (GR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Littoral, Environnement, Télédétection, Géomatique (LETG - Rennes), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Caen Normandie (UNICAEN), Université de Nantes (UN)-Université de Nantes (UN), European Geosciences Union, Dubigeon, Isabelle, Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École Pratique des Hautes Études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN)

Subjects
[SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology
Abstract

International audience; Airborne, terrestrial lidar and Structure From Motion have dramatically changed our approach of geomorphology,from low density/precision data, to a wealth of data with a precision adequate to actually measure topographicchange across multiple scales, and its relation to vegetation. Yet, an important limitation in the context of fluvialgeomorphology has been the inability of these techniques to penetrate water due to the use of NIR laser wavelengthsor to the complexity of accounting for water refraction in SFM. Coastal bathymetric systems using a green lidar canpenetrate clear water up to 50mbut have a resolution too coarse and deployment costs that are prohibitive for fluvialresearch and management. After early prototypes of narrow aperture green lidar (e.g., EEARL NASA), major lidarmanufacturer are now releasing dual wavelength laser system that offer water penetration consistent with shallowfluvial bathymetry at very high resolution (> 10 pts/m2) and deployment costs that makes the technology, finallyaccessible. This offers unique opportunities to obtain synoptic high resolution, high precision data for academicresearch as well as for fluvial environment management (flood risk mapping, navigability,. . . ).In this presentation, we report on the deployment of the latest generation Teledyne-Optech Titan dual-wavelengthlidar (1064 nm + 532 nm) owned by the University of Nantes and Rennes. The instrument has been deployed overseveral fluvial and lacustrine environments in France. We present results and recommendation on how to optimizethe bathymetric cover as a function of aerial and aquatic vegetation cover and the hydrology regime of the river.In the surveyed rivers, the penetration depth varies from 0.5 to 4 m with discrete echoes (i.e. onboard detection),heavily impacted by water clarity and bottom reflectance. Simple post-processing of the full waveform recordallows to recover an additional 20 % depth.As for other lidar techniques, the main challenge lies in the post-processing of the massive amount of data generatedby the instrument (typically 10 billions points for 60 km of rivers). Yet the very high density of the raw point clouddata (40 pts/m2 on topography, 20 pts/m2 on bathymetry) and the full waveform nature of the signal offers newopportunities to develop classification and change detection algorithms. In this context, we present a new automatedworkflow to extract automatically the water surface (a critical aspect for refraction correction) and submerged datain highly complex fluvial environments based on a combined analysis of the 1064 nm and 532 nm channels.We conclude that topo-bathymetric lidar is getting close to being an operational technique for fluvial bathymetryoffering a vast range of applications in hydrology, ecohydrology, geomorphology and river management

Published
2016

49. Microspatial variability in community structure and photophysiology of calcified macroalgal microbiomes revealed by coupling of hyperspectral and high-resolution fluorescence imaging

Author

Perkins, R, Williamson, Christopher J, Brodie, J, Barillé, L, Launeau, Patrick, Lavaud, J, Yallop, Marian, Jesus, B, School of Earth and Ocean Sciences [Cardiff], Cardiff University, The Natural History Museum [London] (NHM), Mer, molécules et santé EA 2160 (MMS), Le Mans Université (UM)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Université de Nantes - UFR des Sciences Pharmaceutiques et Biologiques, Université de Nantes (UN)-Université de Nantes (UN), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), School of Biological Sciences [Bristol], and University of Bristol [Bristol]

Subjects
[SDV]Life Sciences [q-bio], [SDE]Environmental Sciences, QE
Abstract

International audience; Calcifying coralline macroalgae provide biogenic habitats colonised by epiphytic microalgae that contribute significantly to community productivity. Georeferenced hyperspectral and high-resolution fluorescence imaging were coupled to microspatially mapped community composition and relative biomass of macroalgal host and epiphyte microalgal groups, and their weighted contributions to productivity within host fronds of Corallina officinalis on upper and lower zones of a rocky shore were determined. Lower shore epiphytes were dominated by filamentous diatoms (Bacillariophyta), confined to the apex of the frond structure, which were low light acclimated but retained a high capacity for photoprotective down regulation and contributed up to 51% of total community productivity. Upper shore epiphytes were dominated by green algae (Chlorophyta) and single-celled diatoms (principally Cocconeis spp.), which were high light acclimated but present at far lower relative biomass and contributed negligibly to productivity. The host, C. officinalis was the main primary producer. Variation in light environment resulting from differences in shore height and shading within the host macroalga, likely play a large role in determining patterns in epiphyte community structure, biomass and productivity observed. Additionally, microspatial gradients in photophysiological parameters along the host macroalga likely resulted from age-dependent variation in pigments as well as the gradient in light environment.

Published
2016

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