Pierre Gernez

Pierre Gernez
University of Nantes | UNIV Nantes · Département des Sciences de la Vie

PhD

About

40
Publications
13,182
Reads
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793
Citations
Citations since 2016
29 Research Items
696 Citations
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2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150
Introduction
Research topics: Marine optics; Ocean color remote sensing; Coastal ecosystems; Oyster aquaculture; intertidal zone
Additional affiliations
August 2009 - July 2011
University of California, San Diego
Position
  • PostDoc Position
Description
  • https://scripps.ucsd.edu/labs/oceanoptics/
December 2005 - July 2009
Sorbonne Université
Position
  • PhD Student
Description
  • http://omtab.obs-vlfr.fr/people.htm

Publications

Publications (40)
Article
Full-text available
AimThe spread of non-indigenous species in marine ecosystems world-wide is one of today's most serious environmental concerns. Using mechanistic modelling, we investigated how global change relates to the invasion of European coasts by a non-native marine invertebrate, the Pacific oyster Crassostrea gigas. LocationBourgneuf Bay on the French Atlant...
Article
Full-text available
Beyond key ecological services, marine resources are crucial for human food security and socio-economical sustainability. Among them, shellfish aquaculture and fishing are of primary importance but become more vulnerable under anthropogenic pressure, as evidenced by reported mass mortality events linked to global changes such as ocean warming and a...
Article
Full-text available
Aquaculture increasingly contributes to global seafood production, requiring new farm sites for continued growth. In France, oyster cultivation has conventionally taken place in the intertidal zone, where there is little or no further room for expansion. Despite interest in moving production further offshore, more information is needed regarding th...
Article
Full-text available
Accurate habitat mapping methods are urgently required for the monitoring, conservation, and management of blue carbon ecosystems and their associated services. This study focuses on exposed intertidal seagrass meadows, which play a major role in the functioning of nearshore ecosystems. Using Sentinel-2 (S2) data, we demonstrate that satellite remo...
Article
Full-text available
Seagrass meadows are monitored in the frame of several environmental programs worldwide, including the Water Framework Directive (WFD), to evaluate the ecological status of European coastal and transitional water bodies. The large size, spatial complexity, and interannual variability of seagrass ecosystems significantly challenge field monitoring....
Article
Full-text available
Rugulopteryx okamurae is a species of brown macroalgae belonging to the Dictyotaceae family and native to the north-western Pacific. As an Invasive Alien Species (IAS), it was first detected in the Strait of Gibraltar in 2015. Since then, R. okamurae has been spreading rapidly through the submerged euphotic zone, colonizing from 0 to 50 m depth and...
Article
Full-text available
The combined use of satellite-derived environmental data and a dynamic energy budget (DEB) model to determine Pacific oyster growth potential was adapted for the South African marine environment. Study areas consisted of the West Coast (high-chlorophyll, low temperature) and the South Coast (variable chlorophyll, higher temperature) ecoregions. Chl...
Article
Blooms of the marine dinoflagellate Lepidodinium chlorophorum cause green seawater discolorations affecting the recreational use and the tourism economy along southern Brittany (NE-Atlantic, France). Hypoxic conditions associated with phytoplankton biomass recycling are suspected to cause fauna mortalities. An in situ monitoring was performed in 20...
Article
Full-text available
Habitat engineers make strong and far-reaching imprints on ecosystem processes. In intertidal mudflats, the dominant primary producer, microphytobenthos (MPB), often forms high biomass patches around oyster reefs. We evaluate multiple hypotheses linking MPB with oyster reefs, including oyster biodeposition, meiofaunal grazing, and abiotic factors,...
Article
Full-text available
The presence of hydrosols, taken as suspension of micro- or macroscopic material in water, strongly alters light propagation and thus the radiance distribution within a natural or artificial water volume. Understanding of hydrosols impacts on the light propagation is limited by our ability to accurately handle the angular scattering phase function...
Article
Full-text available
A R T I C L E I N F O Keywords: Bivalve Pacific oyster Dynamic energy budget (DEB) Marine spatial planning (MSP) Offshore aquaculture Site selection, climate change A B S T R A C T Aquaculture development in Europe, while critical to the European Union (EU) Blue Growth strategy, has stagnated over the past decades due largely to high competition fo...
Article
Full-text available
Oyster production has historically taken place in intertidal zones, and shellfish farms already occupy large extents of the French intertidal space. The expansion of French shellfish aquaculture within intertidal areas is therefore spatially limited, and moving production to the subtidal offshore environment is considered to be a possible solution...
Article
Full-text available
Plain Language Summary Intertidal mudflats support a high biological productivity sustained mainly by microalgae living in the sediment. Microalgae form a dense biofilm at the surface of the mud during daytime low tides and fix a high quantity of inorganic carbon into organic carbon through photosynthesis. Microalgae can be resuspended along with t...
Technical Report
Full-text available
Executive summary and recommendations The EU Water Framework Directive 1 (WFD) is an ambitious legislation framework to achieve good ecological and chemical status for all surface waters and good quantitative and chemical status for groundwater by 2027. A total of 111,062 surface waterbodies are presently reported on under the Directive, 46% of whi...
Presentation
Full-text available
For most people, the reflection of the Sun (or Moon) light on the sea surface is an open place for romanticism and reveries. From beaches to space, the sparkling patch of sunlight reflected on the wavy ocean can be readily observed by any kind of optical imager; from the naked eye to modern sensors embarked on satellites. For most oceanographers, t...
Presentation
Full-text available
The potential for and productivity of shellfish aquaculture is strongly influenced by sea surface temperature (SST), and the concentration and nature of suspended particulate matter (SPM), which can both be monitored from space to determine shellfish growth conditions. Phytoplankton is a main food source for suspension-feeding bivalves. In too high...
Presentation
Full-text available
In Europe, oyster production has historically taken place in intertidal zones. Shellfish farms already occupy large extents of intertidal space, and sometimes have for more than a century. The possibility of expanding shellfish aquaculture in intertidal areas is therefore spatially limited, and is also constrained by carrying capacity, water qualit...
Article
Full-text available
Marine diseases have major impacts on ecosystems and economic consequences for aquaculture and fisheries. Understanding origin, spread and risk factors of disease is crucial for management, but data in the ocean are limited compared to the terrestrial environment. Here we investigated how the marine environment drives the spread of viral disease ou...
Article
Full-text available
Satellite remote sensing (RS) is routinely used for the large-scale monitoring of microphytobenthos (MPB) biomass in intertidal mudflats and has greatly improved our knowledge of MPB spatio-temporal variability and its potential drivers. Processes operating on smaller scales however, such as the impact of benthic macrofauna on MPB development, to d...
Article
Full-text available
The implementation of accurate atmospheric correction is a prerequisite for satellite observation and water quality monitoring in coastal areas. The potential of the fast-line-of-sight atmospheric analysis of spectral hypercubes (FLAASH) was investigated here for the medium resolution imaging spectrometer (MERIS). As the comparison between discrete...
Preprint
Full-text available
Satellite remote sensing (RS) is routinely used for the large-scale monitoring of microphytobenthos (MPB) biomass in intertidal mudflats, and has greatly improved our knowledge of MPB spatio-temporal variability and its potential drivers. Processes operating at smaller scales however, such as the impact of benthic macrofauna on MPB development, to...
Article
Full-text available
The algorithms of Novoa et al. (2017) and Gons et al. (2005) were recalibrated and applied to Sentinel2 data to retrieve suspended particulate matter (SPM) and chlorophyll a (chl a) concentration in the environmentally and economically important intertidal zones. Sentinel2-derived chl a and SPM concentration distributions were analyzed at the scale...
Article
Full-text available
The accurate measurement of suspended particulate matter (SPM) concentrations in coastal waters is of crucial importance for ecosystem studies, sediment transport monitoring, and assessment of anthropogenic impacts in the coastal ocean. Ocean color remote sensing is an efficient tool to monitor SPM spatio-temporal variability in coastal waters. How...
Article
Full-text available
Monte Carlo simulations are used to compute the uncertainty associated to light backscattering measurements in turbid waters using the ECO-BB (WET Labs) and Hydroscat (HOBI Labs) scattering sensors. ECO-BB measurements provide an accurate estimate of the particulate volume scattering coefficient after correction for absorption along the short instr...
Article
The invasion of the wild oyster Crassostrea gigas along the western European Atlantic coast hasgenerated changes in the structure and functioning of intertidal ecosystems. Considered as an invasivespecies and a trophic competitor of the cultivated conspecific oyster, it is now seen as a resource byoyster farmers following recurrent mass summer mort...
Article
Full-text available
At the end of the SPOT4 mission, a four-month experiment was conducted in 2013 to acquire high spatial (20 m) and high temporal (5 days) resolution satellite data. In addition to the SPOT4 (Take5) dataset, we used several Landsat5, 7, 8 images to document the variations in suspended particulate matter (SPM) concentration in the turbid Gironde and L...
Article
Full-text available
High resolution satellite data of the Medium Resolution Imaging Spectrometer in full resolution mode (MERIS FR, pixel size is 300 m) were used to study the impact of suspended particulate matter (SPM) on oyster-farming sites in a macrotidal bay of the French Atlantic coast where SPM concentration can exceed 100 g m-3. Because MERIS standard SPM con...
Article
Full-text available
We examined the within-day variability in seawater optical properties and biogeochemical constituents for a high-latitude location in the Ross Sea, Antarctica, during development of the annual spring phytoplankton bloom. Measurements of particulate organic carbon concentration POC, chlorophyll-a concentration Chl, and particle size distribution wer...
Conference Paper
Full-text available
Benthic microalgae can make a substantial contribution to the food web in coastal ecosystems, in particular diatoms, which dominate photo‐autotrophic assemblages in intertidal mudflats. They form dense biofilms in the most superficial sediment layers and contribute to their stabilization. Many studies investigated the spatio‐temporal dynamics of th...
Article
Full-text available
Optical variability occurs in the near-surface and upper ocean on very short time and space scales (e.g., milliseconds and millimeters and less) as well as greater scales. This variability is caused by solar, meteorological, and other physical forcing as well as biological and chemical processes that affect optical properties and their distribution...
Article
Full-text available
Time series measurements of fluctuations in underwater downward irradiance, Ed, within the green spectral band (532 nm) show that the probability distribution of instantaneous irradiance varies greatly as a function of depth within the near-surface ocean under sunny conditions. Because of intense light flashes caused by surface wave focusing, the n...
Article
The changes in shape, amplitude, and timing in the diel variability of the particulate beam attenuation coefficient (cp) were investigated at 4 and 9 m during two seasonal cycles at an oceanic site in the northwestern Mediterranean Sea under contrasting physical and trophic situations. We observed a diel cycle in cp during the winter mixing of the...
Article
Full-text available
1] A field characterization of the amplitude and periods of the underwater light field fluctuations is presented on the basis of field measurements of the downward and upward irradiances at a deep-sea mooring in the Mediterranean Sea (BOUSSOLE site). The optical time series at this site includes multispectral irradiance measurements at two depths a...

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Cited By

Projects

Projects (6)
Project
CoastObs will develop a service platform for coastal water monitoring with validated products derived from EO. In dialogue with users from various sectors, CoastObs will establish innovative EO-based products: monitoring of seagrass and macroalgae, phytoplankton size classes, primary production, and harmful algae as well as higher level products such as indicators and integration with predictive models. For these products, CoastObs will establish sustainable supply chains that can be directly integrated into the users’ systems.
Project
The role of microbial biodiversity in the functioning of marine tidal flat sediments (BIO-Tide) is an Horizon 2020 ERA-NET COFUND project financed by the Biodiversa program. The aim of the project is to bring together scientists and stakeholders in studying the relationships between microbial diversity and ecosystem functioning/services in intertidal environments
Archived project
L’observation des communautés petits poissons pélagiques (Anchois et Sardines) dans le golfe de Gascogne est réalisée selon une approche écosystémique et intégrée. Une telle approche est basée sur l’observation simultanée des compartiments environnementaux, biologiques et humains qui influencent la dynamique des poissons. Ce projet propose une analyse spatialisé multi-niveaux trophiques (phytoplancton – zooplancton – poissons) dans le golfe de Gascogne pour renforcer les éléments scientifiques nécessaires à la mise en œuvre d’une gestion écosystémique des pêches de petits poissons pélagiques. L’interaction entre le zooplancton et les poissons sera au centre de l’analyse. Le couplage d’outils modernes (télédétection spatiale, imagerie et acoustique halieutique) permettra d’explorer les relations entre les distributions spatiales de plancton et de petits poissons pélagiques à haute résolution, dans la couche superficielle des eaux du Golfe, à travers des méthodes cartographiques. Ecosystemic fish communities observation approaches are based on the simultaneous observation of all the ecosystem compartments that have an influence on fish dynamics (i.e. environmental, biotic and anthropic components of the ecosystem). This project aims at developping a spatially explicit, cross trophic levels (phytoplankyton – zooplankton – fish) analysis of the bay of Biscay to strenghen the scientific basis of the ecosystemic approach of small pelagic fish (Anchovy and Sardine) fisheries. This project will focus on the Zooplankton – Fish interactions. The integration of modern observing tools and methods such as remote sensing, imaging and acoustics will enable the exploration of the relations between the spatial distributions of plankton and small pelagic fish at high resolution, in the surface waters of the Bay of Biscay.