The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Sylvain Ouillon - One of the best experts on this subject based on the ideXlab platform.
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Application of the support vector regression method for turbidity assessment with MODIS on a shallow Coral Reef Lagoon (Voh-Koné-Pouembout, New Caledonia)
Water, 2017Co-Authors: Guillaume Wattelez, Jean-michel Fernandez, Sylvain Ouillon, Cecile Dupouy, Jérôme Lefevre, Farid JuillotAbstract:Particle transport by erosion from ultramafic lands in pristine tropical Lagoons is a crucial problem, especially for the benthic and pelagic biodiversity associated with Coral Reefs. Satellite imagery is useful for assessing particle transport from land to sea. However, in the oligotrophic and shallow waters of tropical Lagoons, the bottom reflection of downwelling light usually hampers the use of classical optical algorithms. In order to address this issue, a Support Vector Regression (SVR) model was developed and tested. The proposed application concerns the Lagoon of New Caledonia—the second longest continuous Coral Reef in the world—which is frequently exposed to river plumes from ultramafic watersheds. The SVR model is based on a large training sample of in-situ turbidity values representative of the annual variability in the Voh-Koné-Pouembout Lagoon (Western Coast of New Caledonia) during the 2014–2015 period and on coincident satellite reflectance values from MODerate Resolution Imaging Spectroradiometer (MODIS). It was trained with reflectance and two other explanatory parameters—bathymetry and bottom colour. This approach significantly improved the model's capacity for retrieving the in-situ turbidity range from MODIS images, as compared with algorithms dedicated to deep oligotrophic or turbid waters, which were shown to be inadequate. This SVR model is applicable to the whole shallow Lagoon waters from the Western Coast of New Caledonia and it is now ready to be tested over other oligotrophic shallow Lagoon waters worldwide.
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application of the support vector regression method for turbidity assessment with modis on a shallow Coral Reef Lagoon voh kone pouembout new caledonia
Water, 2017Co-Authors: Guillaume Wattelez, Jean-michel Fernandez, Sylvain Ouillon, Cecile Dupouy, Jérôme Lefevre, Farid JuillotAbstract:Particle transport by erosion from ultramafic lands in pristine tropical Lagoons is a crucial problem, especially for the benthic and pelagic biodiversity associated with Coral Reefs. Satellite imagery is useful for assessing particle transport from land to sea. However, in the oligotrophic and shallow waters of tropical Lagoons, the bottom reflection of downwelling light usually hampers the use of classical optical algorithms. In order to address this issue, a Support Vector Regression (SVR) model was developed and tested. The proposed application concerns the Lagoon of New Caledonia—the second longest continuous Coral Reef in the world—which is frequently exposed to river plumes from ultramafic watersheds. The SVR model is based on a large training sample of in-situ turbidity values representative of the annual variability in the Voh-Kone-Pouembout Lagoon (Western Coast of New Caledonia) during the 2014–2015 period and on coincident satellite reflectance values from MODerate Resolution Imaging Spectroradiometer (MODIS). It was trained with reflectance and two other explanatory parameters—bathymetry and bottom colour. This approach significantly improved the model’s capacity for retrieving the in-situ turbidity range from MODIS images, as compared with algorithms dedicated to deep oligotrophic or turbid waters, which were shown to be inadequate. This SVR model is applicable to the whole shallow Lagoon waters from the Western Coast of New Caledonia and it is now ready to be tested over other oligotrophic shallow Lagoon waters worldwide.
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Biogeochemical typology and temporal variability of Lagoon waters in a Coral Reef ecosystem subject to terrigeneous and anthropogenic inputs (New Caledonia).
Marine Pollution Bulletin, 2010Co-Authors: Renaud Fichez, Sylvain Ouillon, Pascal Douillet, Aymeric Jouon, F. Gutierrez, Sandrine Chifflet, Philippe Gérard, Christian GrenzAbstract:Abstract Considering the growing concern about the impact of anthropogenic inputs on Coral Reefs and Coral Reef Lagoons, surprisingly little attention has been given to the relationship between those inputs and the trophic status of Lagoon waters. The present paper describes the distribution of biogeochemical parameters in the Coral Reef Lagoon of New Caledonia where environmental conditions allegedly range from pristine oligotrophic to anthropogenically influenced. The study objectives were to: (i) identify terrigeneous and anthropogenic inputs and propose a typology of Lagoon waters, (ii) determine temporal variability of water biogeochemical parameters at time-scales ranging from hours to seasons. Combined ACP-cluster analyses revealed that over the 2000 km 2 Lagoon area around the city of Noumea, “natural” terrigeneous versus oceanic influences affecting all stations only accounted for less than 20% of the spatial variability whereas 60% of that spatial variability could be attributed to significant eutrophication of a limited number of inshore stations. ACP analysis allowed to unambiguously discriminating between the natural trophic enrichment along the offshore–inshore gradient and anthropogenically induced eutrophication. High temporal variability in dissolved inorganic nutrients concentrations strongly hindered their use as indicators of environmental status. Due to longer turn over time, particulate organic material and more specifically chlorophyll a appeared as more reliable nonconservative tracer of trophic status. Results further provided evidence that ENSO occurrences might temporarily lower the trophic status of the New Caledonia Lagoon. It is concluded that, due to such high frequency temporal variability, the use of biogeochemical parameters in environmental surveys require adapted sampling strategies, data management and environmental alert methods.
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Biogeochemical typology and temporal variability of Lagoon waters in a Coral Reef ecosystem subject to terrigeneous and anthropogenic inputs (New Caledonia)
Marine Pollution Bulletin, 2010Co-Authors: Renaud Fichez, A. Jouon, Sylvain Ouillon, Pascal Douillet, S. Chifflet, P. Gérard, F. Gutierrez, Christian GrenzAbstract:Considering the growing concern about the impact of anthropogenic inputs on Coral Reefs and Coral Reef Lagoons, surprisingly little attention has been given to the relationship between those inputs and the trophic status of Lagoon waters. The present paper describes the distribution of biogeochemical parameters in the Coral Reef Lagoon of New Caledonia where environmental conditions allegedly range from pristine oligotrophic to anthropogenically influenced. The study objectives were to: (i) identify terrigeneous and anthropogenic inputs and propose a typology of Lagoon waters, (ii) determine temporal variability of water biogeochemical parameters at time-scales ranging from hours to seasons. Combined ACP-cluster analyses revealed that over the 2000 km2 Lagoon area around the city of Nouméa, "natural" terrigeneous versus oceanic influences affecting all stations only accounted for less than 20% of the spatial variability whereas 60% of that spatial variability could be attributed to significant eutrophication of a limited number of inshore stations. ACP analysis allowed to unambiguously discriminating between the natural trophic enrichment along the offshore-inshore gradient and anthropogenically induced eutrophication. High temporal variability in dissolved inorganic nutrients concentrations strongly hindered their use as indicators of environmental status. Due to longer turn over time, particulate organic material and more specifically chlorophyll a appeared as more reliable nonconservative tracer of trophic status. Results further provided evidence that ENSO occurrences might temporarily lower the trophic status of the New Caledonia Lagoon. It is concluded that, due to such high frequency temporal variability, the use of biogeochemical parameters in environmental surveys require adapted sampling strategies, data management and environmental alert methods.
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Spatio-temporal variability in suspended particulate matter concentration and the role of aggregation on size distribution in a Coral Reef Lagoon
Marine Geology, 2008Co-Authors: Aymeric Jouon, Jean-michel Fernandez, Sylvain Ouillon, Pascal Douillet, Jean-pierre Lefebvre, Xavier Mari, Jean-marie FroidefondAbstract:This paper presents the concentration and size distribution of suspended particles in the South-West Coral Reef Lagoon of the island of New Caledonia. Data are provided by filtration techniques, Optical BackScattering (OBS) measurements and in situ laser diffraction particle sizing. The concentration of suspended particles increased from Reef to land. A bottom nepheloïd layer occurred over the entire Lagoon, and was more distinct on the nearshore area. Small particles were more abundant in the bottom nepheloïd layer than in the overlying water column. The concentration of suspended particles showed more variability over space than over time. Conversely, the particle size distribution of suspended particles showed more variability at a given location over a month (time variability) than at a given moment over the Lagoon (space variability). Analysis showed that aggregates represented a large fraction of suspended particles. Microscope visualization and chemical analysis of a sample suggest the inclusion of a transparent exopolymeric matrix. The relative abundance of aggregates over suspended particle volume concentration was found to increase as the quantity of suspended particle decreased. The spatial distribution of the relative abundance of aggregates suggests more aggregates proximal to Coral Reefs. The high concentration of aggregates at low turbidity and the spatial distribution of the relative abundance, infer that aggregation is induced by the presence of organic ligands. Unlike optical backscattering and light attenuation measurements that are size sensitive measurements of suspended particle concentration, in situ laser diffraction particle sizing provides a relevant optical measurement of suspended particulate matter in such an aggregate-dominated system.
Jean-michel Fernandez - One of the best experts on this subject based on the ideXlab platform.
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Application of the support vector regression method for turbidity assessment with MODIS on a shallow Coral Reef Lagoon (Voh-Koné-Pouembout, New Caledonia)
Water, 2017Co-Authors: Guillaume Wattelez, Jean-michel Fernandez, Sylvain Ouillon, Cecile Dupouy, Jérôme Lefevre, Farid JuillotAbstract:Particle transport by erosion from ultramafic lands in pristine tropical Lagoons is a crucial problem, especially for the benthic and pelagic biodiversity associated with Coral Reefs. Satellite imagery is useful for assessing particle transport from land to sea. However, in the oligotrophic and shallow waters of tropical Lagoons, the bottom reflection of downwelling light usually hampers the use of classical optical algorithms. In order to address this issue, a Support Vector Regression (SVR) model was developed and tested. The proposed application concerns the Lagoon of New Caledonia—the second longest continuous Coral Reef in the world—which is frequently exposed to river plumes from ultramafic watersheds. The SVR model is based on a large training sample of in-situ turbidity values representative of the annual variability in the Voh-Koné-Pouembout Lagoon (Western Coast of New Caledonia) during the 2014–2015 period and on coincident satellite reflectance values from MODerate Resolution Imaging Spectroradiometer (MODIS). It was trained with reflectance and two other explanatory parameters—bathymetry and bottom colour. This approach significantly improved the model's capacity for retrieving the in-situ turbidity range from MODIS images, as compared with algorithms dedicated to deep oligotrophic or turbid waters, which were shown to be inadequate. This SVR model is applicable to the whole shallow Lagoon waters from the Western Coast of New Caledonia and it is now ready to be tested over other oligotrophic shallow Lagoon waters worldwide.
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application of the support vector regression method for turbidity assessment with modis on a shallow Coral Reef Lagoon voh kone pouembout new caledonia
Water, 2017Co-Authors: Guillaume Wattelez, Jean-michel Fernandez, Sylvain Ouillon, Cecile Dupouy, Jérôme Lefevre, Farid JuillotAbstract:Particle transport by erosion from ultramafic lands in pristine tropical Lagoons is a crucial problem, especially for the benthic and pelagic biodiversity associated with Coral Reefs. Satellite imagery is useful for assessing particle transport from land to sea. However, in the oligotrophic and shallow waters of tropical Lagoons, the bottom reflection of downwelling light usually hampers the use of classical optical algorithms. In order to address this issue, a Support Vector Regression (SVR) model was developed and tested. The proposed application concerns the Lagoon of New Caledonia—the second longest continuous Coral Reef in the world—which is frequently exposed to river plumes from ultramafic watersheds. The SVR model is based on a large training sample of in-situ turbidity values representative of the annual variability in the Voh-Kone-Pouembout Lagoon (Western Coast of New Caledonia) during the 2014–2015 period and on coincident satellite reflectance values from MODerate Resolution Imaging Spectroradiometer (MODIS). It was trained with reflectance and two other explanatory parameters—bathymetry and bottom colour. This approach significantly improved the model’s capacity for retrieving the in-situ turbidity range from MODIS images, as compared with algorithms dedicated to deep oligotrophic or turbid waters, which were shown to be inadequate. This SVR model is applicable to the whole shallow Lagoon waters from the Western Coast of New Caledonia and it is now ready to be tested over other oligotrophic shallow Lagoon waters worldwide.
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Spatio-temporal variability in suspended particulate matter concentration and the role of aggregation on size distribution in a Coral Reef Lagoon
Marine Geology, 2008Co-Authors: Aymeric Jouon, Jean-michel Fernandez, Sylvain Ouillon, Pascal Douillet, Jean-pierre Lefebvre, Xavier Mari, Jean-marie FroidefondAbstract:This paper presents the concentration and size distribution of suspended particles in the South-West Coral Reef Lagoon of the island of New Caledonia. Data are provided by filtration techniques, Optical BackScattering (OBS) measurements and in situ laser diffraction particle sizing. The concentration of suspended particles increased from Reef to land. A bottom nepheloïd layer occurred over the entire Lagoon, and was more distinct on the nearshore area. Small particles were more abundant in the bottom nepheloïd layer than in the overlying water column. The concentration of suspended particles showed more variability over space than over time. Conversely, the particle size distribution of suspended particles showed more variability at a given location over a month (time variability) than at a given moment over the Lagoon (space variability). Analysis showed that aggregates represented a large fraction of suspended particles. Microscope visualization and chemical analysis of a sample suggest the inclusion of a transparent exopolymeric matrix. The relative abundance of aggregates over suspended particle volume concentration was found to increase as the quantity of suspended particle decreased. The spatial distribution of the relative abundance of aggregates suggests more aggregates proximal to Coral Reefs. The high concentration of aggregates at low turbidity and the spatial distribution of the relative abundance, infer that aggregation is induced by the presence of organic ligands. Unlike optical backscattering and light attenuation measurements that are size sensitive measurements of suspended particle concentration, in situ laser diffraction particle sizing provides a relevant optical measurement of suspended particulate matter in such an aggregate-dominated system.
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A combined modelling and geochemical study of the fate of terrigenous inputs from mixed natural and mining sources in a Coral Reef Lagoon (New Caledonia)
Marine Pollution Bulletin, 2006Co-Authors: Jean-michel Fernandez, Sylvain Ouillon, Christophe Chevillon, Pascal Douillet, Renaud Fichez, Romain Le GendreAbstract:Open-cast mining for Ni, Cr and Co was conducted in the south-west part of New Caledonia during the 20th century. Abandoned mining and prospecting sites were severely affected by erosion, resulting in an increase in the load of terrigenous particles transported to the Coral Reef Lagoon. This article assesses the impact of a typical small catchment area (La Coulée River, 85 km2 watershed) on two bays (Boulari and Sainte Marie) located near Noumea, New Caledonia's main city. This multi-disciplinary study combines geochemical, sedimentological, and hydrodynamic approaches. Ni and Cr concentrations contained in the geochemical matrix phase of the pelitic fraction were determined. The study of the geochemical signatures together with sedimentological data and 3D numerical simulations of the transport of non-settling particles throughout the Lagoon demonstrated that terrigenous inputs from the Coulée River were mainly transported and deposited along the shoreline, reaching areas as distant as Sainte Marie Bay. Although quantitatively low (about 3% of the pelite mass of the bay sediments), the terrigenous inputs in Sainte Marie Bay originating from the Coulée River could be traced. The metal content in suspended matter was over 7000 mg kg−1 for Ni and 4200 mg kg−1 for Cr.
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A combined modelling and geochemical study of the fate of terrigenous inputs from mixed natural and mining sources in a Coral Reef Lagoon (New Caledonia)
Marine pollution bulletin, 2005Co-Authors: Jean-michel Fernandez, C. Chevillon, Sylvain Ouillon, Pascal Douillet, Renaud Fichez, Romain Le GendreAbstract:Open-cast mining for Ni, Cr and Co was conducted in the south-west part of New Caledonia during the 20th century. Abandoned mining and prospecting sites were severely affected by erosion, resulting in an increase in the load of terrigenous particles transported to the Coral Reef Lagoon. This article assesses the impact of a typical small catchment area (La Coulee River, 85 km2 watershed) on two bays (Boulari and Sainte Marie) located near Noumea, New Caledonia's main city. This multi-disciplinary study combines geochemical, sedimentological, and hydrodynamic approaches. Ni and Cr concentrations contained in the geochemical matrix phase of the pelitic fraction were determined. The study of the geochemical signatures together with sedimentological data and 3D numerical simulations of the transport of non-settling particles throughout the Lagoon demonstrated that terrigenous inputs from the Coulee River were mainly transported and deposited along the shoreline, reaching areas as distant as Sainte Marie Bay. Although quantitatively low (about 3% of the pelite mass of the bay sediments), the terrigenous inputs in Sainte Marie Bay originating from the Coulee River could be traced. The metal content in suspended matter was over 7000 mg kg(-1) for Ni and 4200 mg kg(-1) for Cr.
Pascal Douillet - One of the best experts on this subject based on the ideXlab platform.
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Biogeochemical typology and temporal variability of Lagoon waters in a Coral Reef ecosystem subject to terrigeneous and anthropogenic inputs (New Caledonia).
Marine Pollution Bulletin, 2010Co-Authors: Renaud Fichez, Sylvain Ouillon, Pascal Douillet, Aymeric Jouon, F. Gutierrez, Sandrine Chifflet, Philippe Gérard, Christian GrenzAbstract:Abstract Considering the growing concern about the impact of anthropogenic inputs on Coral Reefs and Coral Reef Lagoons, surprisingly little attention has been given to the relationship between those inputs and the trophic status of Lagoon waters. The present paper describes the distribution of biogeochemical parameters in the Coral Reef Lagoon of New Caledonia where environmental conditions allegedly range from pristine oligotrophic to anthropogenically influenced. The study objectives were to: (i) identify terrigeneous and anthropogenic inputs and propose a typology of Lagoon waters, (ii) determine temporal variability of water biogeochemical parameters at time-scales ranging from hours to seasons. Combined ACP-cluster analyses revealed that over the 2000 km 2 Lagoon area around the city of Noumea, “natural” terrigeneous versus oceanic influences affecting all stations only accounted for less than 20% of the spatial variability whereas 60% of that spatial variability could be attributed to significant eutrophication of a limited number of inshore stations. ACP analysis allowed to unambiguously discriminating between the natural trophic enrichment along the offshore–inshore gradient and anthropogenically induced eutrophication. High temporal variability in dissolved inorganic nutrients concentrations strongly hindered their use as indicators of environmental status. Due to longer turn over time, particulate organic material and more specifically chlorophyll a appeared as more reliable nonconservative tracer of trophic status. Results further provided evidence that ENSO occurrences might temporarily lower the trophic status of the New Caledonia Lagoon. It is concluded that, due to such high frequency temporal variability, the use of biogeochemical parameters in environmental surveys require adapted sampling strategies, data management and environmental alert methods.
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Biogeochemical typology and temporal variability of Lagoon waters in a Coral Reef ecosystem subject to terrigeneous and anthropogenic inputs (New Caledonia)
Marine Pollution Bulletin, 2010Co-Authors: Renaud Fichez, A. Jouon, Sylvain Ouillon, Pascal Douillet, S. Chifflet, P. Gérard, F. Gutierrez, Christian GrenzAbstract:Considering the growing concern about the impact of anthropogenic inputs on Coral Reefs and Coral Reef Lagoons, surprisingly little attention has been given to the relationship between those inputs and the trophic status of Lagoon waters. The present paper describes the distribution of biogeochemical parameters in the Coral Reef Lagoon of New Caledonia where environmental conditions allegedly range from pristine oligotrophic to anthropogenically influenced. The study objectives were to: (i) identify terrigeneous and anthropogenic inputs and propose a typology of Lagoon waters, (ii) determine temporal variability of water biogeochemical parameters at time-scales ranging from hours to seasons. Combined ACP-cluster analyses revealed that over the 2000 km2 Lagoon area around the city of Nouméa, "natural" terrigeneous versus oceanic influences affecting all stations only accounted for less than 20% of the spatial variability whereas 60% of that spatial variability could be attributed to significant eutrophication of a limited number of inshore stations. ACP analysis allowed to unambiguously discriminating between the natural trophic enrichment along the offshore-inshore gradient and anthropogenically induced eutrophication. High temporal variability in dissolved inorganic nutrients concentrations strongly hindered their use as indicators of environmental status. Due to longer turn over time, particulate organic material and more specifically chlorophyll a appeared as more reliable nonconservative tracer of trophic status. Results further provided evidence that ENSO occurrences might temporarily lower the trophic status of the New Caledonia Lagoon. It is concluded that, due to such high frequency temporal variability, the use of biogeochemical parameters in environmental surveys require adapted sampling strategies, data management and environmental alert methods.
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Spatio-temporal variability in suspended particulate matter concentration and the role of aggregation on size distribution in a Coral Reef Lagoon
Marine Geology, 2008Co-Authors: Aymeric Jouon, Jean-michel Fernandez, Sylvain Ouillon, Pascal Douillet, Jean-pierre Lefebvre, Xavier Mari, Jean-marie FroidefondAbstract:This paper presents the concentration and size distribution of suspended particles in the South-West Coral Reef Lagoon of the island of New Caledonia. Data are provided by filtration techniques, Optical BackScattering (OBS) measurements and in situ laser diffraction particle sizing. The concentration of suspended particles increased from Reef to land. A bottom nepheloïd layer occurred over the entire Lagoon, and was more distinct on the nearshore area. Small particles were more abundant in the bottom nepheloïd layer than in the overlying water column. The concentration of suspended particles showed more variability over space than over time. Conversely, the particle size distribution of suspended particles showed more variability at a given location over a month (time variability) than at a given moment over the Lagoon (space variability). Analysis showed that aggregates represented a large fraction of suspended particles. Microscope visualization and chemical analysis of a sample suggest the inclusion of a transparent exopolymeric matrix. The relative abundance of aggregates over suspended particle volume concentration was found to increase as the quantity of suspended particle decreased. The spatial distribution of the relative abundance of aggregates suggests more aggregates proximal to Coral Reefs. The high concentration of aggregates at low turbidity and the spatial distribution of the relative abundance, infer that aggregation is induced by the presence of organic ligands. Unlike optical backscattering and light attenuation measurements that are size sensitive measurements of suspended particle concentration, in situ laser diffraction particle sizing provides a relevant optical measurement of suspended particulate matter in such an aggregate-dominated system.
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correspondence between the distribution of hydrodynamic time parameters and the distribution of biological and chemical variables in a semi enclosed Coral Reef Lagoon
Estuarine Coastal and Shelf Science, 2007Co-Authors: Jean-pascal Torréton, Aymeric Jouon, Séverine Jacquet, Emma Rochellenewall, Vincent Faure, Pascal DouilletAbstract:Hydrodynamic modeling can be used to spatially characterize water renewal rates in coastal ecosystems. Using a hydrodynamic model implemented over the semi-enclosed Southwest Coral Lagoon of New Caledonia, a recent study computed the flushing lag as the minimum time required for a particle coming from outside the Lagoon (open ocean) to reach a specific station [Jouon, A., Douillet, P., Ouillon, S., Fraunie ´, P., 2006. Calculations of hydrodynamic time parameters in a semi-opened coastal zone using a 3D hydrodynamic model. Continental Shelf Research 26, 1395e1415]. Local e-flushing time was calculated as the time requested to reach a local grid mesh concentration of 1/e from the precedent step. Here we present an attempt to connect physical forcing to biogeochemical functioning of this coastal ecosystem. An array of stations, located in the Lagoonal channel as well as in several bays under anthropogenic influence, was sampled during three cruises. We then tested the statistical relationships between the distribution of flushing indices and those of biological and chemical variables. Among the variables tested, silicate, chlorophyll a and bacterial biomass production present the highest correlations with flushing indices. Correlations are higher with local e-flushing times than with flushing lags or the sum of these two indices. In the bays, these variables often deviate from the relationships determined in the main Lagoon channel. In the three bays receiving significant riverine inputs, silicate is well above the regression line, whereas data from the bay receiving almost insignificant freshwater inputs generally fit the Lagoon channel regressions. Moreover, in the three bays receiving important urban and industrial effluents, chlorophyll a and bacterial production of biomass generally display values exceeding the Lagoon channel regression trends whereas in the bay under moderate anthropogenic influence values follow the regressions obtained in the Lagoon channel. The South West Lagoon of New Caledonia can hence be viewed as a coastal mesotrophic ecosystem that is flushed by oligotrophic oceanic waters which subsequently replace the Lagoonal waters with water considerably impoverished in resources for microbial growth. This flushing was high enough during the periods of study to influence the distribution of phytoplankton biomass, bacterial production of biomass and silicate concentrations in the Lagoon channel as well as in some of the bay areas. 2007 Elsevier Ltd. All rights reserved.
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A combined modelling and geochemical study of the fate of terrigenous inputs from mixed natural and mining sources in a Coral Reef Lagoon (New Caledonia)
Marine Pollution Bulletin, 2006Co-Authors: Jean-michel Fernandez, Sylvain Ouillon, Christophe Chevillon, Pascal Douillet, Renaud Fichez, Romain Le GendreAbstract:Open-cast mining for Ni, Cr and Co was conducted in the south-west part of New Caledonia during the 20th century. Abandoned mining and prospecting sites were severely affected by erosion, resulting in an increase in the load of terrigenous particles transported to the Coral Reef Lagoon. This article assesses the impact of a typical small catchment area (La Coulée River, 85 km2 watershed) on two bays (Boulari and Sainte Marie) located near Noumea, New Caledonia's main city. This multi-disciplinary study combines geochemical, sedimentological, and hydrodynamic approaches. Ni and Cr concentrations contained in the geochemical matrix phase of the pelitic fraction were determined. The study of the geochemical signatures together with sedimentological data and 3D numerical simulations of the transport of non-settling particles throughout the Lagoon demonstrated that terrigenous inputs from the Coulée River were mainly transported and deposited along the shoreline, reaching areas as distant as Sainte Marie Bay. Although quantitatively low (about 3% of the pelite mass of the bay sediments), the terrigenous inputs in Sainte Marie Bay originating from the Coulée River could be traced. The metal content in suspended matter was over 7000 mg kg−1 for Ni and 4200 mg kg−1 for Cr.
Farid Juillot - One of the best experts on this subject based on the ideXlab platform.
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Application of the support vector regression method for turbidity assessment with MODIS on a shallow Coral Reef Lagoon (Voh-Koné-Pouembout, New Caledonia)
Water, 2017Co-Authors: Guillaume Wattelez, Jean-michel Fernandez, Sylvain Ouillon, Cecile Dupouy, Jérôme Lefevre, Farid JuillotAbstract:Particle transport by erosion from ultramafic lands in pristine tropical Lagoons is a crucial problem, especially for the benthic and pelagic biodiversity associated with Coral Reefs. Satellite imagery is useful for assessing particle transport from land to sea. However, in the oligotrophic and shallow waters of tropical Lagoons, the bottom reflection of downwelling light usually hampers the use of classical optical algorithms. In order to address this issue, a Support Vector Regression (SVR) model was developed and tested. The proposed application concerns the Lagoon of New Caledonia—the second longest continuous Coral Reef in the world—which is frequently exposed to river plumes from ultramafic watersheds. The SVR model is based on a large training sample of in-situ turbidity values representative of the annual variability in the Voh-Koné-Pouembout Lagoon (Western Coast of New Caledonia) during the 2014–2015 period and on coincident satellite reflectance values from MODerate Resolution Imaging Spectroradiometer (MODIS). It was trained with reflectance and two other explanatory parameters—bathymetry and bottom colour. This approach significantly improved the model's capacity for retrieving the in-situ turbidity range from MODIS images, as compared with algorithms dedicated to deep oligotrophic or turbid waters, which were shown to be inadequate. This SVR model is applicable to the whole shallow Lagoon waters from the Western Coast of New Caledonia and it is now ready to be tested over other oligotrophic shallow Lagoon waters worldwide.
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application of the support vector regression method for turbidity assessment with modis on a shallow Coral Reef Lagoon voh kone pouembout new caledonia
Water, 2017Co-Authors: Guillaume Wattelez, Jean-michel Fernandez, Sylvain Ouillon, Cecile Dupouy, Jérôme Lefevre, Farid JuillotAbstract:Particle transport by erosion from ultramafic lands in pristine tropical Lagoons is a crucial problem, especially for the benthic and pelagic biodiversity associated with Coral Reefs. Satellite imagery is useful for assessing particle transport from land to sea. However, in the oligotrophic and shallow waters of tropical Lagoons, the bottom reflection of downwelling light usually hampers the use of classical optical algorithms. In order to address this issue, a Support Vector Regression (SVR) model was developed and tested. The proposed application concerns the Lagoon of New Caledonia—the second longest continuous Coral Reef in the world—which is frequently exposed to river plumes from ultramafic watersheds. The SVR model is based on a large training sample of in-situ turbidity values representative of the annual variability in the Voh-Kone-Pouembout Lagoon (Western Coast of New Caledonia) during the 2014–2015 period and on coincident satellite reflectance values from MODerate Resolution Imaging Spectroradiometer (MODIS). It was trained with reflectance and two other explanatory parameters—bathymetry and bottom colour. This approach significantly improved the model’s capacity for retrieving the in-situ turbidity range from MODIS images, as compared with algorithms dedicated to deep oligotrophic or turbid waters, which were shown to be inadequate. This SVR model is applicable to the whole shallow Lagoon waters from the Western Coast of New Caledonia and it is now ready to be tested over other oligotrophic shallow Lagoon waters worldwide.
Renaud Fichez - One of the best experts on this subject based on the ideXlab platform.
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Biogeochemical typology and temporal variability of Lagoon waters in a Coral Reef ecosystem subject to terrigeneous and anthropogenic inputs (New Caledonia).
Marine Pollution Bulletin, 2010Co-Authors: Renaud Fichez, Sylvain Ouillon, Pascal Douillet, Aymeric Jouon, F. Gutierrez, Sandrine Chifflet, Philippe Gérard, Christian GrenzAbstract:Abstract Considering the growing concern about the impact of anthropogenic inputs on Coral Reefs and Coral Reef Lagoons, surprisingly little attention has been given to the relationship between those inputs and the trophic status of Lagoon waters. The present paper describes the distribution of biogeochemical parameters in the Coral Reef Lagoon of New Caledonia where environmental conditions allegedly range from pristine oligotrophic to anthropogenically influenced. The study objectives were to: (i) identify terrigeneous and anthropogenic inputs and propose a typology of Lagoon waters, (ii) determine temporal variability of water biogeochemical parameters at time-scales ranging from hours to seasons. Combined ACP-cluster analyses revealed that over the 2000 km 2 Lagoon area around the city of Noumea, “natural” terrigeneous versus oceanic influences affecting all stations only accounted for less than 20% of the spatial variability whereas 60% of that spatial variability could be attributed to significant eutrophication of a limited number of inshore stations. ACP analysis allowed to unambiguously discriminating between the natural trophic enrichment along the offshore–inshore gradient and anthropogenically induced eutrophication. High temporal variability in dissolved inorganic nutrients concentrations strongly hindered their use as indicators of environmental status. Due to longer turn over time, particulate organic material and more specifically chlorophyll a appeared as more reliable nonconservative tracer of trophic status. Results further provided evidence that ENSO occurrences might temporarily lower the trophic status of the New Caledonia Lagoon. It is concluded that, due to such high frequency temporal variability, the use of biogeochemical parameters in environmental surveys require adapted sampling strategies, data management and environmental alert methods.
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Biogeochemical typology and temporal variability of Lagoon waters in a Coral Reef ecosystem subject to terrigeneous and anthropogenic inputs (New Caledonia)
Marine Pollution Bulletin, 2010Co-Authors: Renaud Fichez, A. Jouon, Sylvain Ouillon, Pascal Douillet, S. Chifflet, P. Gérard, F. Gutierrez, Christian GrenzAbstract:Considering the growing concern about the impact of anthropogenic inputs on Coral Reefs and Coral Reef Lagoons, surprisingly little attention has been given to the relationship between those inputs and the trophic status of Lagoon waters. The present paper describes the distribution of biogeochemical parameters in the Coral Reef Lagoon of New Caledonia where environmental conditions allegedly range from pristine oligotrophic to anthropogenically influenced. The study objectives were to: (i) identify terrigeneous and anthropogenic inputs and propose a typology of Lagoon waters, (ii) determine temporal variability of water biogeochemical parameters at time-scales ranging from hours to seasons. Combined ACP-cluster analyses revealed that over the 2000 km2 Lagoon area around the city of Nouméa, "natural" terrigeneous versus oceanic influences affecting all stations only accounted for less than 20% of the spatial variability whereas 60% of that spatial variability could be attributed to significant eutrophication of a limited number of inshore stations. ACP analysis allowed to unambiguously discriminating between the natural trophic enrichment along the offshore-inshore gradient and anthropogenically induced eutrophication. High temporal variability in dissolved inorganic nutrients concentrations strongly hindered their use as indicators of environmental status. Due to longer turn over time, particulate organic material and more specifically chlorophyll a appeared as more reliable nonconservative tracer of trophic status. Results further provided evidence that ENSO occurrences might temporarily lower the trophic status of the New Caledonia Lagoon. It is concluded that, due to such high frequency temporal variability, the use of biogeochemical parameters in environmental surveys require adapted sampling strategies, data management and environmental alert methods.
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Origin, Transport, and Future of the Natural and Anthropogenic Inputs to the Southwest Lagoon of New Caledonia
2008Co-Authors: Renaud Fichez, P. Douillet, J.m. Fernandez, C. Chevillon, V. Faure, L. Breau, S. Chifflet, P. Gérard, L. Hédouin, A. LapetiteAbstract:For the past ten years, the ird (Institut de recherche pour le developpement) has developed a multidisciplinary programme dealing with the effects of natural and anthropogenic terrigenous inputs on the New Caledonia Coral Reef Lagoon which is currently subjected to environmental pressure due to population increase and development of the mining industry. The ongoing study focused on three main categories of inputs: (i) particles generated by erosion processes and responsible for excessive sediment inputs in the Lagoon, (ii) metals exhibiting a potentially lethal effect on the Lagoon biota, (iii) nutrients responsible for eutrophication. This article presents three examples of environmental issues that could be addressed through complementary research approaches: (i) the dispersion of terrigenous inputs as commended by currents, (ii) the fate of metals in the Lagoon and their accumulation in the biota, (iii) the effects of nutrient enrichment on pelagic communities. Results are presented while keeping in mind the necessary applied outcomes requested from a research programme devoted to development issues. Such outcomes are mainly related to the identification of suited environmental diagnostic tools and to the development of modelling approaches yielding synthetic and predictive information on the status and fate of Coral Reef Lagoons subject to anthropogenic stress.
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A combined modelling and geochemical study of the fate of terrigenous inputs from mixed natural and mining sources in a Coral Reef Lagoon (New Caledonia)
Marine Pollution Bulletin, 2006Co-Authors: Jean-michel Fernandez, Sylvain Ouillon, Christophe Chevillon, Pascal Douillet, Renaud Fichez, Romain Le GendreAbstract:Open-cast mining for Ni, Cr and Co was conducted in the south-west part of New Caledonia during the 20th century. Abandoned mining and prospecting sites were severely affected by erosion, resulting in an increase in the load of terrigenous particles transported to the Coral Reef Lagoon. This article assesses the impact of a typical small catchment area (La Coulée River, 85 km2 watershed) on two bays (Boulari and Sainte Marie) located near Noumea, New Caledonia's main city. This multi-disciplinary study combines geochemical, sedimentological, and hydrodynamic approaches. Ni and Cr concentrations contained in the geochemical matrix phase of the pelitic fraction were determined. The study of the geochemical signatures together with sedimentological data and 3D numerical simulations of the transport of non-settling particles throughout the Lagoon demonstrated that terrigenous inputs from the Coulée River were mainly transported and deposited along the shoreline, reaching areas as distant as Sainte Marie Bay. Although quantitatively low (about 3% of the pelite mass of the bay sediments), the terrigenous inputs in Sainte Marie Bay originating from the Coulée River could be traced. The metal content in suspended matter was over 7000 mg kg−1 for Ni and 4200 mg kg−1 for Cr.
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A combined modelling and geochemical study of the fate of terrigenous inputs from mixed natural and mining sources in a Coral Reef Lagoon (New Caledonia)
Marine pollution bulletin, 2005Co-Authors: Jean-michel Fernandez, C. Chevillon, Sylvain Ouillon, Pascal Douillet, Renaud Fichez, Romain Le GendreAbstract:Open-cast mining for Ni, Cr and Co was conducted in the south-west part of New Caledonia during the 20th century. Abandoned mining and prospecting sites were severely affected by erosion, resulting in an increase in the load of terrigenous particles transported to the Coral Reef Lagoon. This article assesses the impact of a typical small catchment area (La Coulee River, 85 km2 watershed) on two bays (Boulari and Sainte Marie) located near Noumea, New Caledonia's main city. This multi-disciplinary study combines geochemical, sedimentological, and hydrodynamic approaches. Ni and Cr concentrations contained in the geochemical matrix phase of the pelitic fraction were determined. The study of the geochemical signatures together with sedimentological data and 3D numerical simulations of the transport of non-settling particles throughout the Lagoon demonstrated that terrigenous inputs from the Coulee River were mainly transported and deposited along the shoreline, reaching areas as distant as Sainte Marie Bay. Although quantitatively low (about 3% of the pelite mass of the bay sediments), the terrigenous inputs in Sainte Marie Bay originating from the Coulee River could be traced. The metal content in suspended matter was over 7000 mg kg(-1) for Ni and 4200 mg kg(-1) for Cr.