Search publications of the members of the Royal Belgian institute of natural Sciences
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Backscatter stability and influence of water column conditions: estimation by multibeam echosounder and repeated oceanographic measurements, Belgian part of the North Sea
- The European Union Marine Strategy Framework Directive requires Member States to monitor and assess the health status of their marine habitats. Belgium put forward that the spatial extent and distribution of the major habitats (sandy mud to mud, muddy sands to sands and coarse-grained sediments), as well as that of gravel beds may only fluctuate within a margin that is limited to the accuracy of the current sediment distribution maps. Due to their ability to provide simultaneous bathymetry and backscatter strength (BS), reflecting seabed nature, multibeam echosounder systems (MBES) provide a time- and costefficient solution to anticipate on this legal obligation. However, as there is no formal quality level scale for the BS and consequently no level of reliability of the final decibel values, evaluating the BS quantitative capabilities to monitor habitat changes remains challenging. In a monitoring context, it is absolutely necessary to investigate to what extent the mean MBES-measured BS variation -from one cruise to another- actually represents a significant change in seabed properties and not only a change in the conditions of the water column (e.g., variation in near-bed suspensions, biological effects, increased occurrence of micro bubbles in the sea surface due to wind) at the time of the measurement. In order to evaluate the relative accuracy and the repeatability of MBES BS and to examine the external sources of variance in acoustic signatures, repeated measurements combining MBES with an Acoustic Doppler current Profiler (ADP) have been performed during tidal cycles on reference areas in the Belgian part of the North Sea. Currents and BS in the water column and vertical profiling of oceanographic parameters have been investigated allowing studying the influence of water column conditions on the BS. Measurements were conducted using two MBES systems to evaluate repeatability between echosounders. Ultimate goal is to arrive at seabed mapping and analyses protocols to obtain harmonized data products from a collaborative seabed mapping community.
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Influence of shells and shell debris on backscatter strength: investigation using modeling, sonar measurements and sampling on the Belgian Continental Shelf
- Acoustic interaction theory and observation highlight the strong relation between the acoustic signal responses and the physical and biological processes acting on the seafloor and in the water column. Several descriptors such as sediment texture, porosity and surface roughness are identified as the main factors affecting the acoustic reverberation and backscatter signals. Shells can influence if not dominate the scattering on the seafloor(Jackson et al., 1986; Stanic et al., 1989 and Zhang, 1996). Scattering from both inclusions and partially buried shells on the sea-floor is described by Stanton (2000), and scattering from shells as a potential mechanism explaining the scattering above 200 kHz is highlighted by Ivakin (2009). In order to improve the knowledge on this matter, several institutions with different expertise are cooperating to integrate mathematical modeling and experimental results to better quantify the influence of shells and shell debris on the acoustic signal and scattering of sonar images. Mathematical 3D models of shell objects in a sediment matrix will be used to simulate the influence of the shells on acoustic signal and scattering. The physical arrangements of shells and their spatio-temporal population trends are also considered in the modeling. The models will be supported by direct sonar measurements of seafloor areas on the Belgian Continental Shelf, combined with sampling, visual observations, classification and shape analysis of the shells and shell debris.
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Irrigation and human niche construction. An example of socio-spatial organisation in the Zerqa Triangle, Jordan
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Living in the Burdur Plain. A diachronic reconstrunction of human subsistence (6500 - 200 BC)
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A narrow place can contain a thousand friends. Irrigation as a response to climate in the Zerqa triangle, Jordan
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A proposal for a Devonian- Carboniferous boundary based on the Hangenberg extinction event, as suggested by the transition in the Namur-Dinant Basin (Southern Belgium).
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The orbitally forced sequences of the Lower Tournaisian (Hastarian Substage) of Belgium: Climate reconstruction and time calibration.
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No deep diving: evidence of predation on epipelagic fish for a stem beaked whale from the late Miocene of Peru
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Physeteroids from the Miocene of Peru: new data on Acrophyseter and Livyatan support macroraptorial feeding in several extinct sperm whales
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IGCP 596– SDS Symposium, Brussels (September 20-22, 2015), Abstracts.
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IGCP 596– SDS Symposium, Brussels (September 20-22, 2015), Abstracts.
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IGCP 596-SDS Symposium, Field Guides: The Devonian and Lower Carboniferous successions in southern Belgium.
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The Famennian succession: marine, continental and reefal facies in the Dinant Synclinorium and Vesdre area.
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Reappraisal of the fossil seal Phoca vitulinoides from the Neogene of the North Sea Basin, with bearing on the geological age, phylogenetic affinities, and locomotion of a new diminutive Miocene phocine species
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The Middle Devonian succession in the Dinant Synclinorium.
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The Devonian– Carboniferous boundary and the Lower Carboniferous succession in the type area.
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Mineralogical, geochemical and isotopic (C and O) characterization of a complex (REE and HFSE) mineralized system related to the Matongo carbonatite (Burundi)
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Syntectonic emplacement of an Alkaline Massif in Burundi: consequences on fluid-rock interaction and element (REE, HFSE) mobility
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A syntectonic Alkaline Massif in Burundi: geometry, fluid-rock interaction and element (REE, HFSE) mobility.
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Grey monazite paleoplacers in Lower Cretaceous continental formations in the Mons Basin, Belgium.
