Genetic variation of flesh colour in canthaxanthin fed rainbow trout

Genetic experiments were conducted using either random independent full-sib families (9 and 11 respectively) or sire-half-sib families (18) of rainbow trout who were fed an experimental diet supplemented with canthaxanthin. The resulting orange-red colour of the flesh from each fish was analyzed through spectrophotometry and expressed in standard terms of luminosity (Y), dominant wavelength (λd) and excitation purity (Pe). The following results were obtained : - There is a substantial genetic variability among families in each colorimetric parameter. Estimated values of heritability from full-sib and from half-sib families do not differ significantly. - Positive correlation between λd . and Pe, and negative correlations between Y and λd and between Y and Pe, are consistent with the pattern of canthaxanthin deposition in the flesh. Genetic correlations do not differ significantly from phenotypic ones. - Pigmentation intensity is correlated to fish weight. This relationship, however, accounts for but a minor part of colour variation among market-size fishes.Des expériences génétiques ont été réalisées chez la Truite arc-en-ciel sur des familles aléatoires et indépendantes de pleins-frères (au nombre de 9 et 11) ou demi-frères de pères (18), alimentées par un régime expérimental supplémenté en canthaxanthine. La couleur de chair orange-rouge obtenue chez chaque poisson a été analysée par spectrophotométrie et exprimée en termes standards de luminosité (Y), longueur d’onde dominante (λd) et pureté d’excitation (Pe). Les résultats obtenus sont les suivants : - Il y a une variabilité génétique notable entre familles pour chaque paramètre colorimétrique. Les valeurs d’héritabilité estimées à partir des familles de plein-frères et de demi-frères ne diffèrent pas significativement. - Les corrélations, positives entre λd et Pe et négatives entre Y et λd et entre Y et Pe, sont conformes au mode d’action de la canthaxanthine se déposant dans la chair. Les corrélations génétiques ne diffèrent pas significativement de leurs homologues phénotypiques. - L’intensité de la pigmentation est corrélée avec le poids des poissons. Cette relation toutefois n’explique qu’une part minime de la variation de couleur chez des animaux de taille marchande

A simulation-based optimisation approach to control nitrogen discharge by activated sludge under winter seasonal peak load

Wastewater treatment systems located in cold areas are under increasing pressure to remove nitrogen from their wastewater. As constraining operating conditions like dramatic influent load increases exacerbated by cold temperatures can occur (e.g. winter tourist resorts, ski resorts), specific technical treatment solutions have to be adapted. The objective of this research is to determine the maximal magnitude of load variation which can be applied in winter to an activated sludge treatment system. It aims at analyzing the effects of high influent load variations on the nitrogen removal capacity. Two operating strategies are investigated by dynamic simulations performed with ASM1: • A fixed aeration tank volume with a fixed MLTSS concentration • A variable aeration volume tank with a variable MLTSS concentration It is demonstrated that the variable aeration tank volume strategy is more efficient than the fixed volume strategy to face long-term peak load. To meet an effluent ammonia nitrate concentration of below 10 mgN·ℓ-1, a maximum input load increase by a factor 2 should be applied with the first strategy; whereas with the second strategy a load increase by a factor 4 should be applied (with constant oxygen presence time). If the oxygen presence time can be increased by 50% the maximum input load increase could reach a factor 6. Water SA Vol.32 (4) 2006: pp.561-56

Solid respirometry to characterize the nitrification kinetics: a better insight for modelling nitrogen conversion in vertical flow constructed wetlands

We developed an original method to measure nitrification rates at different depths of a vertical flow constructed wetland (VFCW) with variable contents of organic matter (sludge, colonized gravel). The method was adapted for organic matter sampled in constructed wetland (sludge, colonized gravel) operated under partially saturated conditions and is based on respirometric principles. Measurements were performed on a reactor, containing a mixture of organic matter (sludge, colonized gravel) mixed with a bulking agent (wood), on which an ammonium-containing liquid was applied. The oxygen demand was determined from analysing oxygen concentration of the gas passing through the reactor with an on-line analyzer equipped with a paramagnetic detector. Within this paper we present the overall methodology, the factors influencing the measurement (sample volume, nature and concentration of the applied liquid, number of successive applications), and the robustness of the method. The combination of this new method with a mass balance approach also allowed determining the concentration and maximum growth rate of the autotrophic biomass in different layers of a VFCW. These latter parameters are essential inputs for the VFCW plant modelling

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