Search publications of the members of the Royal Belgian institute of natural Sciences
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Assessing connectivity in young flatfish and its implementation in fisheries management.
- Recently, it has been shown that commercial fisheries target specific size/age classes, causing a loss of genetic diversity as well as altering life cycles (fisheries-induced evolution). This represents a serious threat for the future of commercial stocks. Such features have also been observed in the North Sea stocks of sole (Solea solea), which have been overfished in the past 20 years. For example, heavy fishing pressure has led to smaller individuals. Given its commercial importance in the North Sea fishery, a larger effort has to be made to preserve this valuable resource. To improve sole stock management, managers would benefit from an upgraded biological assessment of population structure and connectivity patterns. We will address the following questions: 1. Does larval dispersal vary in time and space? 2. What biotic and abiotic factors are driving larval connectivity? And once known, 3. Can we predict the impact of changes in physical and biological drivers? 4. Can we define sub-populations based on connectivity patterns? My research project aims at filling those gaps, by focusing on population connectivity at the larval and postlarval stages. A suite of 200 highly variable SNPs (Single Nucleotide Polymorphisms) and state-of-the-art genotyping (Illumina-Veracode) will be employed to investigate the population structure of sole at a regional scale (<150km) within the North Sea and eastern English Channel. Additional insights will be gained by otolith microchemistry, used to trace the movement of single individuals between spawning and nursery grounds. Temporal variability will be studied through the combination of two years of intensive sampling and historical datasets spanning the last two decades. Finally, results of hydrodynamic modelling of larval dispersal will be compared to collected data in order to investigate the role of selected biotic and abiotic factors in driving connectivity. Overall, this study will help the sustainable management of the fishery by defining significant ecological units, while the molecular markers will allow tracing any fish present on the market to its origin, hence fighting illegal fishing.
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How sensitive is sole larval dispersal in the North Sea to the parametrization of larval duration? A modelling study.
- Connectivity throughout the life cycle of flatfish remains an open question, especially at the early life stages. The case of sole (Solea solea) is of particular interest because it is one of the most valuable commercial species in the North Sea. It is crucial to understand how the spawning grounds and nurseries are connected and what are the processes influencing larval retention and dispersal in order to propose appropriate management measures. Especially, dispersal during the larval stage is still poorly known. The transport of sole larvae from the spawning grounds to the nurseries is driven by hydrodynamic processes but the final dispersal pattern and larval abundance at nurseries might be affected by biological processes and environmental factors. Larval Transport Models (LTMs) coupled to Individual-Based Models (IBMs) are more and more commonly used to assess the relative contribution of these processes on the larval dispersal. IBMs allow to take into account growth to estimate the duration of dispersal based on environmental conditions met by the larvae. These models may be sensitive to process parametrization and may give different results for parametrizations derived from the same data set. The Larvae&Co model (Lacroix et al., 2013) used in the frame of B-FishConnect project couples the 3D hydrodynamic model Coherens with an IBM of sole larvae. It is used here to investigate the impact of parametrization of the stage duration on the dispersal of sole larvae in the North Sea. In this study, we compare two parametrizations (Rochette et ai, 2012 and Lacroix et ai, 2013) of the stage duration (temperature dependent) derived from the same data set (mainly Fonds, 1979). We show that only small differences of the stage duration parametrization may induce significant differences of the dispersal pattern, connectivity and larval recruitment at nursery. This highlights the importance to parametrize biological processes with accuracy and the need to collect sufficient data (samples, genotypes and otoliths) and conduct experimental studies to derive biological processes parametrizations in order to improve model’s reliability.
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Ecosystem Models as Support to Eutrophication Management in the North Atlantic Ocean (EMoSEM).
- A major challenge in EU marine governance is to reach the good environmental status (GES) in the north-eastern Atlantic (NEA). Existing approaches do not integrate the eutrophication process in space (continuum river-ocean) and in time (past, present and future status). A strong need remains for (i) knowledge/identification of all the processes that control eutrophication and its consequences, (ii) consistent and harmonized reference levels assigned to each eutrophication-related indicator, (iii) identification of the main rivers directly or indirectly responsible for eutrophication nuisances in specific areas, (iv) an integrated transboundary approach and (v) realistic and scientific-based nutrient reduction scenarios. The SEAS-ERA project EMoSEM (http://www2.mumm.ac.be/emosem/) aims to develop and combine the state-of-the-art modelling tools describing the river-ocean continuum in the NEA continental seas with the objective to: (i) suggest innovative ecological indicators to account for HABs in the GES definition, (ii) estimate the needs to reach GES in all marine areas (distance-to-target requirement, DTTR), (iii) identify “realistic” scenarios of nutrient reduction in the river watersheds of NEA and (iv) assess the impact of the “realistic” scenarios in the sea, and compare to DTTR. Marine ecological models will be used to track the nutrients in the sea, and trace back their riverine or oceanic sources with the transboundary nutrient transport method (TBNT). TBNT application is a prerequisite for DTTR estimates. A generic watershed model applied to NEA rivers will calculate terrestrial nutrient exports to the sea under different scenarios: (i) A past “pristine-like” scenario, where natural nutrient exports are estimated in the absence of human influence and (ii) a series of future “realistic” scenarios, where different wastewater treatments and agricultural practices are combined. EMoSEM will deliver coupled river-coastal-sea mathematical models and will provide guidance to end-users (policy- and decision makers) for assessing and combating eutrophication problems in the NEA continental waters.
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Connectivity and genetic structure of flatfish for fisheries management and traceability in Belgium.
- Early life stages are critical in determining connectivity. Effective fishery management requires understanding of how spawning grounds and nurseries are connected and what processes influence larval retention and dispersal. These mechanisms maintain a high genetic diversity which is essential to grantee population resilience to environmental changes. Marine populations are often believed to be panmictic because there are few obvious barriers to gene flow in the ocean. However, recent work based on Next Generation Sequencing has shown that even highly mobile species have a population structure at reduced spatial scale. Once determined, population structure is the best level to monitor fish stocks. Each population has its own genetic signature therefore traceability system in the industry would highly benefit from a precise mapping and monitoring of stocks, especially for sole in the North Sea. Given its commercial importance in the North Sea fishery, a larger effort has to be made to preserve the flatfish valuable resource. In this project we will address the following questions: 1- Does larval dispersal vary in time and space? 2- What biotic and abiotic factors are driving larval connectivity? 3- Can we define sub-populations based on connectivity patterns? A suite of 1536 SNPs (Single Nucleotide Polymorphisms) and state-of-the-art genotyping (Illumina Golden Gate genotyping) have been employed to investigate the genetic population structure of sole larvae and post-larvae at the European scale. We have obtained four groups: (1) a mixed group with populations within the North Sea and eastern English Channel; and the three most geographically extreme populations were clearly separated: (2) the German Bight on one side and (3) the Celtic Sea and (4) the Irish Sea on the other side. Finally, results of hydrodynamic individual based model of larval dispersal developed by Lacroix and collaborators will be compared to collected da¬ta in order to investigate the role of selected biotic and abiotic factors in driving connectivity. Temporal variability will be studied combing three years of intensive sampling and historical data spanning the last two decades. Overall, this study will help the sustainable management of fishery by defining significant ecological units, while the molecular markers will allow tracing any fish present on the market to its origin, hence fighting illegal fishing and enabling efficient traceability.
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Minéralisation et genèse du gîte stratiforme de Ravandje (Iran central)
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Contribution à l'étude des Rutelinae du Sénégal II (Coleoptera, Scarabaeoidea, Melolonthidae, Rutelinae)
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La grotte sépulcrale de Humain (Marche-en-Famenne, B). Les restes humains et le gobelet campaniforme du Néolithique récent/final.
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Contribution to the knowledge of the bionomics of some steppe Westpalaearctic species belonging to tribe Prionini Latreille, 1802, with the description for the first time of the females of Polylobarthron margelanicum (Théry, 1896) and Mesoprionus petrovitzi (Holzschuh, 1981 (Coleoptera, Cerambycidae, Prioninae)
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Van bloem naar bloem, van bloemen tot zaadjes, er waren eens bijen
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Verslag van de KBVE-excursie in het Madegemveld op 4 juni 2011
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Origin of the high frequency variability of bio-optical properties in complex coastal environments (OO121246).
- This study describes physical processes (mainly the turbulence and re-suspension of particles due to turbulence) which control the micro scale variability of the bio-optical properties in highly turbid coastal waters. Time series analyses of different bio-optical and physical properties (temperature, salinity) have been performed from a boat in coastal waters. The data base gathers high frequency (1 Hz) simultaneous measurements performed during about 12 hours at four different days and locations in the highly turbid coastal environments of North Sea. We mainly focus on the concentrations of Chlorophyll and coloured detrital matter, back-scattering, and attenuation. For each parameter we consider the statistics (mean values, coefficients of variance and probability density functions) and the dynamics (Fourier power spectra). We found that these optical parameters (bbp, bpslope g, Refractive index-n and cp) are influenced by turbulence and inherit some of turbulence characteristics; high frequency noise, scales of variability at lower frequencies.
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Seasonal and inter-annual variability of air-sea CO2 fluxes and seawater carbonate chemistry in the Southern North Sea.
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Seasonal and inter-annual variability of air-sea CO2 fluxes and seawater carbonate chemistry in the Southern Bight of the North Sea.
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Operational oceanographic products for the Belgian scientific community.
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Reconstruction of complete space-time surface chlorophyll a (chl), total suspended matter (TSM) and sea temperature (SST) over the North Sea with monovariate and multivariate exploitations of the data interpolating empirical orthogonal functions method.
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Reconstruction of missing satellite total suspended matter data over the Southern North Sea and English Channel using Empirical Orthogonal Function decomposition of satellite imagery and hydrodynamical modelling.
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Uses of DINEOF algorithm (Data interpolation with Empirical Orthogonal Functions) for reconstruction and analysis of incomplete satellite databases over the North Sea and the Mediterranean, synthesis from the RECOLOUR project.
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REconstruction of COLOUR scenes: project summary, North Sea preliminary results, perspectives.
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Physical controls on biogeochemical dynamics along the land-ocean continuum: implications for coastal ocean modelling.
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Spectral relationships for atmospheric correction. II. Improving NASA's standard and MUMM near infra-red modeling schemes.
- Spectral relationships, reflecting the spectral dependence of water-leaving reflectance, rho(w)(lambda), can be easily implemented in current AC algorithms with the aim to improve rho(w)(lambda) retrievals where the algorithms fail. The present study evaluates the potential of spectral relationships to improve the MUMM (Ruddick et al., 2006, Limnol. Oceanogr. 51, 1167-1179) and standard NASA (Bailey et al., 2010, Opt. Express 18, 7521-7527) near infra-red (NIR) modeling schemes included in the AC algorithm to account for non-zero rho(w)(lambda(NIR)), based on in situ coastal rho(w)(lambda) and simulated Rayleigh corrected reflectance data. Two modified NIR-modeling schemes are investigated: (1) the standard NASA NIR-modeling scheme is forced with bounding relationships in the red spectral domain and with a NIR polynomial relationship and, (2) the constant NIR rho(w)(lambda) ratio used in the MUMM NIR-modeling scheme is replaced by a NIR polynomial spectral relationship. Results suggest that the standard NASA NIR-modeling scheme performs better for all turbidity ranges and in particular in the blue spectral domain (percentage bias decreased by approximately 50\%) when it is forced with the red and NIR spectral relationships. However, with these new constrains, more reflectance spectra are flagged due to non-physical Chlorophyll-a concentration estimations. The new polynomial-based MUMM NIR-modeling scheme yielded lower rho(w)(lambda) retrieval errors and particularly in extremely turbid waters. However, including the polynomial NIR relationship significantly increased the sensitivity of the algorithm to errors on the selected aerosol model from nearby clear water pixels. (C) 2013 Optical Society of America
