Search publications of the members of the Royal Belgian institute of natural Sciences
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Haline stratification in the Rhine-Meuse freshwater plume - a 3-dimensional model sensitivity analysis
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Optical remote sensing of chlorophyll a in case 2 waters by use of an adaptive two-band algorithm with optimal error properties
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Optical remote sensing in support of eutrophication monitoring in Belgian waters
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A coastal ocean model intercomparison study for a three-dimensional idealised test case
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The spectral reflectance and transparency of river plume waters
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On the signatures of river outflow fronts in radar imagery
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Development and application of an algorithm for detecting Phaeocystis globosa blooms in the Case 2 Southern North Sea waters
- While mapping algal blooms from space is now well-established, mapping undesirable algal blooms in eutrophicated coastal waters raises further challenge in detecting individual phytoplankton species. In this paper, an algorithm is developed and tested for detecting Phaeocystis globosa blooms in the Southern North Sea. For this purpose, we first measured the light absorption properties of two phytoplankton groups, P. globosa and diatoms, in laboratory-controlled experiments. The main spectral difference between both groups was observed at 467 nm due to the absorption of the pigment chlorophyll c3 only present in P. globosa, suggesting that the absorption at 467 nm can be used to detect this alga in the field. A Phaeocystis-detection algorithm is proposed to retrieve chlorophyll c3 using either total absorption or water-leaving reflectance field data. Application of this algorithm to absorption and reflectance data from Phaeocystis-dominated natural communities shows positive results. Comparison with pigment concentrations and cell counts suggests that the algorithm can flag the presence of P. globosa and provide quantitative information above a chlorophyll c3 threshold of 0.3 mg m(-3) equivalent to a P. globosa cell density of 3 x 10(6) cells L(-1). Finally, the possibility of extrapolating this information to remote sensing reflectance data in these turbid waters is evaluated.
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The COASTCOLOUR dataset
- The objective of the ESA DUE CoastColour project is to fully exploit the potential of the MERIS instrument for remote sensing of the coastal zone. The product requirements have been derived from a user consultation process. Users have provided in-situ data from many locations, which were used for algorithm development and validation. The MERIS data archive from 2005 onwards has been processed with the finally selected algorithms for 27 globally distributed coastal sites. The CoastColour dataset comprises an improved Level 1b product (L1P), a product that contains directional and normalised water leaving reflectances (L2R) and a product for water properties (L2W). The total data volume is 100TB. All data are online and available from the CoastColour Website. A near real time service was operated from October 2011 until end of the ENVISAT mission. Plans exist to continue the service with Sentinel data.
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Use of ocean color satellite data to study the dynamics of suspended particles in the Yangtze River plume (East China Sea)
- A multi-sensor algorithm is applied to MODIS and MERIS satellite data in order to quantify suspended particulate matter (SPM) in the Yangtze River plume (East China Sea). Several atmospheric correction methods are tested; a simple but operational method is finally selected as appropriate for MODIS, MERIS and GOCI satellite data. As most of the methods for atmospheric corrections of satellite data fail over such highly turbid waters, an adaptation of the black pixel assumption is used to correct for the aerosol contribution. The retrieved seawater reflectance at red wavebands appears as the most sensitive to SPM concentrations but tends to saturate at concentrations beyond 100 mg.l(-1). By opposition the near-infrared seawater reflectance does not saturate even at extremely high concentrations of 1000 mg.l(-1). Overall, the most robust relationship between the SPM concentration and seawater reflectance is obtained considering a spectral ratio between the near-infrared (e. g., 850 nm) and visible (e. g. 550 nm). This relationship is applied to atmospherically corrected ocean color satellite data to retrieve SPM concentrations in the Yangtze River plume. Results show that ocean color satellite data can be used to study the seasonal dynamics of SPM and better understand the role played by the main physical processes involved (river discharge, tidal cycles, wind and regional circulation).
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Spectral variations of light scattering by marine particles in coastal waters, from visible to near infrared
- Field measurements and Mie calculations of the particulate light-scattering coefficient (b(p), in m(-1)) in the near-infrared and visible spectral domains are combined to quantify and model the effect of particulate absorption on the b(p) spectral variations. The case of particles of coastal origin and assumed to follow a Junge-type size distribution is considered. A simple power-law function closely reproduces the near-infrared b(p) spectral variations, with a spectral slope varying in the range 0.1-1.4. In the visible (e.g., 440 nm), particulate absorption effects systematically lead to b(p) values 5-30\% lower than values predicted using a power-law function fitted in the near infrared and extrapolated to 440 nm. The respective influences of the particle size distribution and composition are investigated for both mineral and organic particle populations. Finally, an empirical model derived from theoretical calculations closely reproduces the actual b(p) spectral variations from near-infrared to short visible wavelengths, taking into account particulate absorption effects.
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Ostéologie et relations phylogénétiques des Gebrayelichtyidae (Halecostomi, Pycnodontomorpha), une extraordinaire famille de poissons du Crétacé supérieur marin du Liban, avec la description dun nouveau genre
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À propos de Paramesturus (Pycnodontomorpha) de l'Aptien inférieur marin d'Allemagne et de ses relations systématiques
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Les poissons crétacés de Nardò. 36°. Compléments à l'étude de Nardoechelys robinsi Taverne, 2002 (Teleostei, Anguilliformes)
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Les poissons crétacés de Nardò. 37°. Compléments à l'étude de Bannikovperca apula Taverne, 2010 (Teleostei, Beryciformes)
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Les poissons du Santonien (Crétacé supérieur) d'Apricena (Italie du Sud). 7°. Garganoclupea svetovidovi gen. et sp. nov. et Apricenaclupea ridewoodi gen. et sp. nov. (Teleostei, Clupeiformes)
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Tirer parti de tous les vestiges: os, coquilles, charbons, graines, pollen et spores
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Where is my jelly?
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OSERIT: A downstream service dedicated to the Belgian Coastguard Agencies
- The research project OSERIT aims at developing a “Oil Spill Evaluation and Response Integrated Tool” for the Belgian Coast Guard Agencies. This web-based tool will gather relevant, scientific based information needed to support the decision-making process in case of oil spilled at sea. OSERIT targets two categories of users. The first category includes operational users who need to access marine and oil spill drift forecast. The second category of users includes environmental representatives who need to compare several scenarios in order to assess the potential environmental consequences of various combating strategies. To meet this ambitious goal, a new web-based interface and a new 3D oil drift and fate mathematical model are being developed. This article first explains how OSERIT development is dictated by end-users requirements on its quickness, reliability, user-friendliness, accessibility and inherent quality. The main model features are then pr esented. Finally, the model performances are illustrated using a real case: the oil leak that happened in the Gannet field in August 2011. OSERIT should be ready for operational use in September 2012.
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Linking human activities to eutrophication in the Southern North Sea.
- The Southern North Sea faces eutrophication problems. They result from growing anthropogenic pressure in the river watersheds, and subsequent increase in nutrients (nitrogen and phosphorus) loading to the sea. Establishing the link between human activities and eutrophication problems requires the identification of the major nutrient sources and the ecological response of the coastal ecosystem to these nutrient alterations. This information is crucial to mitigate eutrophication in coastal zones by applying appropriate dual-nutrient reduction strategies, therefore achieving the Good Environmental Status of EU marine waters by 2020. Very recently, MIRO&CO has been upgraded to MIRO&CO V2 and coupled to a generic watershed model based on Riverstrahler/Seneque (Billen et al. 1994). A nutrient tracking approach (Ménesguen et al. 2006) has been adapted and implemented in MIRO&CO V2. The transboundary nutrient transport method has been used to track the nutrients in the sea, and trace back their sources (river, ocean, and atmosphere). This new model tool is used to assess the current eutrophication status in the Southern North Sea based on existing metrics (OSPAR, MSFD and WFD). This is a first and necessary step before assessing the impacts of realistic nutrient reduction scenarios on eutrophication problems. This work is done in the framework of the EMoSEM EU project (www2.mumm.ac.be/emosem/) that aims at providing support to eutrophication management in the North Atlantic Ocean, using state-of-the-art modelling tools.
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A modelling approach to trace the origin of jellyfish swarms in the Southern North Sea.
- The life cycle, the phenology and the interannual variability of jellyfish (i.e. cnidaria medusozoa scyphozoa) are under study across the world as there is debate on their increasing occurrence under human pressure (overfishing, eutrophication, climate change) (Condon et al. 2012). Beside interference in human activities, jellyfish swarms affect the marine food web as these organisms feed on fish eggs and larvae, and compete for food with adult fish (Lynam et al. 2005, Pauly et al. 2009). Whether jellyfish nuisance can be mitigated remains unclear and depends on our understanding of the causes of outbreaks. Most North Sea jellyfish species have a sessile polyp stage as part of their life cycle, and therefore need solid substrate to fix. While A. aurita polyps are visible along the Belgian and Dutch coasts, the location of other species polyps (e.g. Cyanea, Chrysaora) remains largely unknown. Tracing back the origin of an observed jellyfish swarm in the North Sea could help identifying the potential location of polyps and the timing and temperature of strobilation. A Lagrangian particle tracking model parameterized for jellyfish in the English Channel and the southern North Sea is used in backtracking (15 days) and forecast (3 days; forced by UKMO forecast) modes to study the potential origin and fate of jellyfish swarms. A backtracking simulation was applied on a jellyfish swarm observed in 2013 in the Belgian coastal zone . It allowed identifying potential areas of origin for the outbreak, raising new scientific questions. A first sensitivity study illustrates the wind influence on the backtracking simulation.
