Éditeur(s) : INRA : Institut National de la Recherche Agronomique Université des Antilles. Service commun de la documentation
Extrait de : 52e congrès annuel de la Société caribéenne des plantes alimentaires / 52nd annual meeting of the Caribbean food crops society (CFCS), du 10 au 16 juillet 2016. INRA, CFCS
Description : In the new context of the agro-ecological transition, present agricultural systems will have to produce more and better in a more constraint world. Mixed crop livestock systems (MCLS) represent sound alternative ways to progressively achieve these goals through crop-livestock integration (CLI). CLI exploits the synergies between cropping and livestock systems through organic fertilization with manure or plant association, use of crop residues to feed livestock, .... It offers many opportunities to improve productivity, as well as to increase resource use efficiency and improve the resilience of the whole farming system. In the scientific literature, authors advocate the interest of MLCS and CLI, based on theoretical considerations, modelling and empirical evidence from local case studies. But these studies do not clearly identify the respective roles of diversity of activities and CLI management practices in improving performances at the level of the whole farming system. Our aim was thus to assess CLI at farm scale in a range of MCLS and to explain farm performances by analyzing the combination of activities and the level of integration. We conducted our analyses in Guadeloupe, (French West Indies), where MCLS and CLI are complex but important challenges for local agricultural. In order to analyze CLI in a holistic and systemic way, we applied a method traditionally used in ecology, ecological network analysis, to study the structure, functioning and performance of agrosystems. This method was implemented on a range of Guadeloupian MCLS where CLI practices where identified. Nitrogen was retained to conduct the analysis due to its central role for both animal and vegetal productions. The ENA method allows an estimation of productivity, resilience, efficiency, productivity and self- sufficiency of the flows network. Our results show that 1/ efficiency and resilience appear correlated to the complexity and intensity of the network of flows; 2/ efficiency and resiliency are positively correlated when we consider them in terms of N flows; 3/ in the Guadeloupian context, CLI concerns mainly specific practices, as feeding pigs with a wide range of crop residues and organic fertilization of small market gardens and plots used to grow tubers. But at whole system level, CLI remains rare and mainly depends on conventional management practices as mineral fertilization and animal complementation of some farming activities as sugar cane, cattle breeding and banana. Moreover, the combination of productions implemented determines the potential of CLI and related performances linked to relative N efficiency of each production. Consequently, performance and especially efficiency and self-sufficiency depend more on the nature of the activity than on CLI management practices. There is still a gap between theoretical studies and CLI in practice, even though CLI is more complicated than simple flows and provides other services and functions. Dans le nouveau contexte de la transition agro-écologique, les systèmes agricoles actuels devront produire plus et les améliorer dans plus de monde de contrainte. Les systèmes mélangés de bétail de culture (MCLS) représentent des manières alternatives saines d'atteindre progressivement ces buts par l'intégration de culture-bétail (CLI). Le CLI exploite les synergies entre l'emblavage et les systèmes de bétail par la fertilisation organique avec l'association d'engrais ou d'usine, utilisation des résidus de culture d'alimenter le bétail,?. Il donne beaucoup d'occasions d'améliorer la productivité, aussi bien que d'augmenter l'efficacité d'utilisation de ressource et d'améliorer la résilience du système d'exploitation agricole entier. Dans la littérature scientifique, les auteurs préconisent l'intérêt de MLCS et de CLI, basé sur des considérations théoriques, modeler et des preuves empiriques des études de cas locales. Mais ces études n'identifient pas clairement les rôles respectifs de la diversité des activités et des pratiques de gestion de CLI en améliorant des interprétations au niveau du système d'exploitation agricole entier. Notre but était ainsi d'évaluer le CLI à l'échelle de ferme dans une gamme de MCLS et d'expliquer des interprétations de ferme en analysant la combinaison des activités et du niveau de l'intégration. Nous avons réalisé nos analyses en Guadeloupe, (des Antilles françaises), où MCLS et le CLI sont des défis complexes mais importants pour agricole local. Afin d'analyser le CLI d'une manière holistique et systémique, nous avons appliqué une méthode traditionnellement employée en écologie, analyse réseau écologique, pour étudier la structure, le fonctionnement et l'interprétation des agrosystems. Cette méthode a été appliquée sur une chaîne de Guadeloupian MCLS où des pratiques en matière de CLI où identifiée. L'azote a été maintenu pour réaliser l'analyse due à son rôle central pour les productions animales et végétales. La méthode d'ENA permet une évaluation de la productivité, de la résilience, de l'efficacité, de la productivité et de l'autosuffisance du réseau d'écoulements. Nos résultats prouvent que 1 efficacités et résiliences semblent corrélées avec la complexité et l'intensité du réseau des écoulements ; 2 efficacité et élasticité sont franchement corrélés quand nous les considérons en termes d'écoulements de N ; 3 dans le contexte de Guadeloupian, CLI concerne principalement des pratiques spécifiques, en tant que les porcs de alimentation par un large éventail de résidus de culture et de fertilisation organique de petits jardins du marché et complots employés pour cultiver des tubercules. Mais à au niveau système entier, le CLI demeure rare et dépend principalement des pratiques de gestion conventionnelles en tant que complémentation minérale de fertilisation et d'animal de quelques activités agricoles comme canne à sucre, élevage et banane. D'ailleurs, la combinaison des productions mises en application détermine le potentiel du CLI et des interprétations relatives liés à l'efficacité relative de N de chaque production. En conséquence, l'interprétation et particulièrement l'efficacité et l'autosuffisance dépendent davantage de la nature de l'activité que sur des pratiques de gestion de CLI. Il y a toujours un espace entre les études et le CLI théoriques dans la pratique, quoique le CLI soit plus compliqué que des écoulements simples et fournisse d'autres services et fonctions.
Siècle(s) traité(s) : 21
Droits : CC-BY-NC-ND - Attribution - Pas d'utilisation commerciale - Pas de modification
Permalien : http://www.manioc.org/fichiers/V16247
V16247

Éditeur(s) : Université des Antilles. Service commun de la documentation University of West Indies, Trinidad &Tobago
Extrait de : 52e congrès annuel de la Société caribéenne des plantes alimentaires / 52nd annual meeting of the Caribbean food crops society (CFCS), du 10 au 16 juillet 2016. INRA, CFCS
Description : Crop nutrient management is a critical component of productivity and quality. Commercial horticulture has relied almost exclusively on inorganic nutrient sources to satisfy plant nutritional requirements. Compost tea represents a sustainable alternative technology but its use has not been extensively researched. A factorial experiment was conducted subjecting lettuce plants to four increasing concentrations of compost tea; 0, 5, 10 and 20 % (m/v) applied at either 100 or 200 cm3 plant-1 day-1, for 30 days. At the end of the trial, measurements were made of leaf area (LA), yield, shoot and root dry mass (DM), root to shoot ratio, and nitrogen (N) and phosphorus (P) contents of shoots and roots. Compost tea concentration significantly (P < 0.05) affected all growth indices showing a similar pattern. Increasing concentration up to 10 % (m/v), positively improved growth and yield above the control. Increasing further to 20 % (m/v) reduced LA, yield and dry mass. For these variables, applying compost tea at 200 cm3 plant-1 day-1 resulted in a better response. Increasing concentration of compost tea showed a directly proportional relationship to shoot and root N content. However, the effect was non-significant for P. Yield and shoot DM were affected by the combination of compost tea concentration and application rate. Similar patterns of increasing yield were seen for increasing concentration within both rates however, the differences were significant for all concentrations at the higher application rate. Application of 200 cm3, 5 % compost tea resulted in the greatest yield, shoot and root DM. In addition to root DM, root surface area was significantly correlated with yield and shoot DM. Compost tea used at appropriate concentrations improved root growth and lettuce productivity.
Siècle(s) traité(s) : 21
Droits : CC-BY-NC-ND - Attribution - Pas d'utilisation commerciale - Pas de modification
Permalien : http://www.manioc.org/fichiers/V16281
V16281

Résumé : Written on verso: "S.S. 'Lady Sybil' unloading nitrate of soda in Havana harbor"
CHC5017
Havana (Cuba)

Droits : http://merrick.library.miami.edu/digitalprojects/copyright.html
chc50170001030001001
1307

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : The natural 15N abundance method for estimating symbiotic biological N2-fixation was tested on legume trees from two rain forests on contrasting soils (oxisols and spodosols) in French Guiana. When possible, the significance of N2-fixing species in the plant community was evaluated in terms of density, biomass and contribution of N2-fixation to the building up of the total nitrogen mass in the leaves. Of the two sites, the rain forest on spodosols was the less favourable for application of the [delta]15N method: the available soil nitrogen was isotopically similar to fixed-N2. Hence, the results showed that a reliable estimate of N2-fixation could not be obtained. A substantial contribution of fixed-N2 to the nitrogen nutrition of legumes was found on oxisols, with an average value of 54 % Ndfa (Nitrogen derived from the atmosphere). The contribution of the N2-fixing legumes to the biomass of the stand was estimated to be 2 t ha[minus sign]1 for the leaf biomass and 136 t ha[minus sign]1 for the total above-ground plant biomass. With 7.5 % of trees in the stand able to fix N2 (462 out of 6156), N2-fixation was estimated to be 7 kg ha[minus sign]1 y[minus sign]1. These results are the first use of the [delta]15N method to estimate nitrogen input by N2-fixing legumes to a natural rain forest. The inter-site variability observed in the [delta]15N of the non-fixing plants suggested different nitrogen-cycling processes in the two soils. The [delta]15N of the non-N2-fixing plants could be related to the soil nitrogen availability and be used as an indicator of efficient or non-efficient nitrogen-cycling rain forests. The spatial variability of the [delta]15N in the plant-available soil nitrogen pool and the nitrogen balance in tropical rain forests are discussed.
ISSN: 0266-4674

hal-01032201
https://hal.archives-ouvertes.fr/hal-01032201
DOI : 10.1017/S0266467499000644

Éditeur(s) : Elsevier
Résumé : A coupled three-dimensional physical-biogeochemical model was developed in order to simulate the ecological functioning of the Rio de la Plata estuary and plume. The biogeochemical model reproduces the nitrogen cycle between five compartments: dissolved inorganic nitrogen, phytoplankton, zooplankton, detritus and dissolved organic nitrogen. The coupling is tested in seasonal climatological configurations and for the particular year 1999. The circulation is forced with Parana and Uruguay rivers discharges, NCEP wind and tide. The biogeochemical model includes loads of inorganic and organic nitrogen from both rivers. The model reproduces the correct tidal amplitudes in the estuary, as well as the most outstanding features of the observed horizontal and vertical structures of the salinity plume. Simulated surface chlorophyll a concentrations exhibit maximum values all year long seaward of the turbidity front, between the 0.5 and 15 isohalines, in agreement with SeaWiFS images of the area. The model simulates well the low primary production in the light-limited highly turbid tidal river (20 gC/m(2)/yr), the high production area in the frontal zone where it can reach 500 gC/m(2)/yr, and the nutrient-limited production in the outer estuary and inner shelf (300 gC/m(2)/yr), with realistic values in each case. According to the 1999 model simulation, the tidal river is the location of organic nitrogen remineralization with a consequent increase of the inorganic pool. At the entrance of the frontal zone, inorganic nitrogen represents about 75% of the whole nitrogen pool, it is reduced to 50% at its sea end-member. The outer estuary has the same sink role for inorganic nitrogen, suggesting that organic nitrogen is the major form exported to the shelf.
Continental Shelf Research (0278-4343) (Elsevier), 2005-03 , Vol. 25 , N. 5-6 , P. 629-653

Droits : 2004 Elsevier Ltd.
http://archimer.ifremer.fr/doc/2005/publication-334.pdf
DOI:10.1016/j.csr.2004.10.003
http://archimer.ifremer.fr/doc/00000/334/

Éditeur(s) : Gauthier-Villars
Résumé : The distribution and behaviour of nutrients (nitrate, nitrite, ammonia, silicate and phosphate) have been examined over the course of a year in two major Scottish estuaries, the Forth and Tay. Maximum concentrations of nitrate and silicate in both estuaries occur in winter, when mixing is conservative. By contrast maximum phosphate, ammonia and nitrite concentrations (notably in the Forth) are observed in summer, these are related to lower oxygen concentrations both within the water column and sediments. Phosphate, ammonia and nitrite concentrations are high in the Forth relative to the Tay. Phosphate behaviour in plots for both estuaries show some common features including removal at low salinity, mid estuary inputs and simple dilution at high salinity. The results are interpreted on the basis of removal onto particles at low salinity followed by desorption at higher salinity together with an input from sediment porewaters. In the Forth the phosphate flux from sediments during the summer is estimated to be 1.98 +/- 1.25 mmol m-2 day-1. At this time the river input of phosphorus is only 10- 14 % of the mid estuary input. Under low river flow conditions in summer a large turbidity maximum (400-500 mg l-1 suspended solids) develops in the Forth estuary and this results in removal of phosphate. Removal is less dramatic in the Tay estuary as the turbidity is wind generated and therefore rarely exceeds 100 mg 1-1. Water quality in the Forth (as defined by the occurrence of low dissolved oxygen concentrations and the presence of species such as ammonia and nitrite) is inferior to that of the Tay. Relative to contaminated estuaries however concentrations in both estuaries are low. By virtue of its high fresh water discharge the Tay is a more significant source of nitrate to the North Sea during the winter than is the Forth. In the Forth bacterial mineralisation and nitrification of organic nitrogen occurs in the upper estuary, this results in an input of nitrate and consumption of dissolved oxygen. Further downstream broad mid estuarine peaks of nitrite and ammonia are observed indicative of a benthic source. Estimates of this source for ammonia and nitrite are 19-44 and 3.9-8.1 mmol m-2 day-1 respectively. In winter the main source of nitrogen to the Forth is from the river but in summer mid estuarine sources dominate. In the outer Tay a peak in dissolved ammonia is estimated to represent an input of 0.5-1.1 tonnes N day-1, this is attributed to sewer inputs from Dundee.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1992 , Vol. 15 , N. 3 , P. 261-277

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00100/21160/18779.pdf
http://archimer.ifremer.fr/doc/00100/21160/

Éditeur(s) : HAL CCSD IWA Publishing
Résumé : International audience
UV spectrophotometry is largely used for water and wastewater quality monitoring. The measurement/estimation of specific and aggregate parameters such as nitrate and dissolved organic carbon (DOC) is possible with UV spectra exploitation, from 2 to multi wavelengths calibration. However, if nitrate determination from UV absorbance is known, major optical interferences linked to the presence of suspended solids, colloids or dissolved organic matter limit the relevance of UV measurement for DOC assessment. A new method based on UV spectrophotometric measurement of raw samples (without filtration) coupling a dual pathlength for spectra acquisition and the second derivative exploitation of the signal is proposed in this work. The determination of nitrate concentration is carried out from the second derivative of the absorbance at 226 nm corresponding at the inflexion point of nitrate signal decrease. A short optical pathlength can be used considering the strong absorption of nitrate ion around 210 nm. For DOC concentration determination the second derivative absorbance at 295 nm is proposed after nitrate correction. Organic matter absorbing slightly in the 270-330 nm window, a long optical pathlength must be selected in order to increase the sensitivity. The method was tested on several hundred of samples from small rivers of two agricultural watersheds located in Brittany, France, taken during dry and wet periods. The comparison between the proposed method and the standardised procedures for nitrate and DOC measurement gave a good adjustment for both parameters for ranges of 2-100 mg/L NO3 and 1 30 mg/L DOC. (C) 2016 Elsevier Ltd. All rights reserved.
ISSN: 0043-1354

hal-01460742
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01460742
DOI : 10.1016/j.watres.2016.11.010
PUBMED : 27838025

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A new method was proposed to determine the nitrogen content of nitrocelluloses (NCs). It is based on the finding of a linear relationship between the nitrogen content and the molar ratio of nitrite-to-nitrate ions released after alkaline hydrolysis. Capillary electrophoresis was used to monitor the concentration of nitrite and nitrate ions. The influences of hydrolysis time and molar mass of NC on the molar ratio of nitrite-to-nitrate ions were investigated, and new insights into the understanding of the alkaline denitration mechanism of NCs, underlying this analytical strategy is provided. The method was then tested successfully with various explosive and non-explosive NC-containing samples such as various daily products and smokeless gunpowders. Inherently to its principle exploiting a concentration ratio, this method shows very good repeatability in the determination of nitrogen content in real samples with relative standard deviation (n=3) inferior to 1.5%, and also provides very significant advantages with respect to sample extraction, analysis time (1h for alkaline hydrolysis, 3min for electrophoretic separation), which was about 5 times shorter than for the classical Devarda's method, currently used in industry, and safety conditions (no need for preliminary drying NC samples, mild hydrolysis conditions with 1M sodium hydroxide for 1h at 60°C).
Journal of Hazardous Materials

hal-01103120
https://hal.archives-ouvertes.fr/hal-01103120
PUBMED : 25562808

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A strong non linear relationship between nitrate and organic matter (assessed by dissolved organic carbon, DOC) has been recently demonstrated by Taylor and Townsend (2010), namely for freshwaters. In this context, our study explores this relation from the behavior of sets of normalized UV spectra (same area under each spectrum) of different water samples showing a hidden isosbestic point (HIP) around 225 nm. This HIP is linked to the existence of a simple relation between nitrate and DOC, the proportions of which vary according to the sampling location and environmental factors. In a second step, a simple linear model is proposed for nitrate-DOC relationship (α⋅NO3+β⋅DOC=1) and a validation is proposed for more than 150 samples of different Brittany rivers and lakes. For samples of the largest watershed, a complementary exploitation from data acquired during the different campaigns confirmed the seasonal evolution between spring (high nitrate/low DOC) and autumn (high DOC/low nitrate). Further investigation on other freshwater samples is needed in order to improve the limits of this linear model.
ISSN: 0045-6535

hal-01063932
https://hal.archives-ouvertes.fr/hal-01063932
DOI : 10.1016/j.chemosphere.2014.03.034
PUBMED : 24875878

Éditeur(s) : Adac-cryptogamie
Résumé : Very few attempts have been made in order to investigate the role of nutrients on cellular growth and toxin production in dinoflagellates associated with DSP (Diarrhetic Shellfish Poison). Some preliminary results are presented here, aiming at a better knowledge of inorganic nitrogen and organic phosphorus effects upon division rate and toxin content of Prorocentrum lima (PL2V spanish strain). Nitrogen have a positive effect on growth rate, up to a threshold value of 880muM.l-1. Above this threshold the rate decreases. There is no effect on toxin content since okadaic acid and DTX1 cell contents remain low (4.8 +/- 0.5 pg.cell.-1) and steady. Phosphorus effect upon division rate follows a non-linear relationship, whereas cellular toxic content is inversely proportional to growth rate.
Peu d'études ont été réalisées sur l'influence des nutriments sur la croissance et la toxicité de dinoflagellés producteurs de poisons diarrhéiques (Diarrhetic Shellfish Poison = DSP). Des résultats préliminaires sont présentés ici en ce qui concerne l'effef de concentrations croissantes d'azote inorganique et de phosphore organique sur le taux de division et la production toxinique de Prorocentrum lima (souche espagnole PL2V). L'azote a une influence positive sur la croissance de cette microalgue jusqu'à une valeur seuil de 880 μM.l#-1. Au-delà de ce seuil, le taux de division diminue. Par contre, l'effet sur la toxicité n'est pas significatif, les concentrations en acide okadaïque et DTXI restant relativement faibles (4.8 ± 0.5 pg.cell.· l ) et stables. Le phosphore agit intégralement sur le taux de division et il y a une relation inverse entre ce dernier et le contenu toxinique cellulaire.
Cryptogamie Algologie (0181-1568) (Adac-cryptogamie), 1992-08 , Vol. 13 , N. 3 , P. 187-195

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00133/24469/22483.pdf
http://archimer.ifremer.fr/doc/00133/24469/

Éditeur(s) : Edp Sciences S A
Résumé : A study on nitrogenous and phosphorous waste production in European seabass (Dicentrarchus labrax) was carried out in a flow-through land-based farm. The main objectives were (i) to calculate nitrogenous (N) and phosphorous (P) waste production (particulate and dissolved) from in situ measurements for different rearing ponds with specific fish biomasses, fish sizes and flow rates, (ii) to establish nitrogenous and phosphorous waste production budgets, ratios and equations, and (iii) to compare, for the whole farm, in situ measurements to estimate N and P waste production from waste equations. Waste production was manifest by an increase in concentrations of total ammonia nitrogen, total Kjeldhal nitrogen, particulate nitrogen, dissolved phosphorus and total phosphorus concentrations in the outlet water compared to the inlet water for both batches and whole farm. However, no production of nitrite or nitrate was observed. In our budgets, the N and P amounts from biomass gains and wastes were explained by the N and P derived from feed over the range 83.9-105.2 % and 66.5-104.6 % respectively, depending on the fish batch. Values were respectively 103.4 and 87.5 % for the same calculations in the farm. When the whole-farm waste production was calculated from previous equations derived from batches, and then compared with the measured data, the percentages of recovery (estimated by the ratio predicted data/measured data) were 88 and 94 % for total-N and total-P respectively.
L'étude de la production des déchets (azote et phosphore) d'une ferme de production de bars (Dicentrarchus labrax) est réalisée. Cette étude à pour objectif (i) de mesurer in situ la production des déchets azotés et phosphores sous forme particulaire et soluble, pour différents bassins d'élevage présentant des caractéristiques variables en terme de biomasse de poisson, de taille des poissons, de débit de l'eau de renouvellement, (ii) d'établir des équations de production de déchets à partir des données précédemment acquises, (iii) de comparer, pour l'ensemble des rejets au niveau de la ferme, les résultats obtenus par des mesures in situ, d'une part, et à l'aide des équations, d'autre part. La production de déchets se traduit par une augmentation des concentrations de l'azote particulaire, de l'azote ammoniacal, de l'azote organique dissous, ainsi que du phosphore particulaire et dissous. Aucune augmentation des nitrates et nitrites n'est observée. L'établissement des budgets d'azote et de phosphore permettent de rendre compte, selon les bassins, du devenir de 88,2 à 105,2 % de l'azote et de 66,2 à 104,6 % du phosphore introduits dans les bassins sous forme de nourriture en granulés. L'étude des budgets réalisée par les deux méthodes (mesures in situ et utilisation des équations) montre que les budgets établis à l'aide des équations rendent compte respectivement de 88 et 94 % de récupération de l'azote et du phosphore. Ces résultats sont respectivement de 103,4 et 87,5 % lorsqu'ils sont établis par des mesures in situ.
Aquatic Living Resources (0990-7440) (Edp Sciences S A), 1998-07 , Vol. 11 , N. 4 , P. 247-254

Droits : 1998 Published by Elsevier SAS
http://archimer.ifremer.fr/doc/1998/publication-872.pdf
DOI:10.1016/S0990-7440(98)89007-4
http://archimer.ifremer.fr/doc/00000/872/

Éditeur(s) : Blackwell science
Résumé : An experiment was conducted in six earthen ponds with 20 shrimps m(-2) Litopenaeus stylirostris (Stimpson) during the warm season in New Caledonia to study the dynamics of wastes in relation with water exchange rate (WER). The nitrogen budget was established, taking into account the different forms of nitrogen in the water, sediment, feed and shrimp. Data from a wide range of treatments applied in unreplicated ponds were treated using regression analysis to establish the relationship between WER and partial nitrogen budget, sediment characteristics and shrimp performance. To compare effluent quality between treatments during the season, data were analysed using the non-parametric sign test. The water outflow was characterized by a decrease in the concentrations of N-mineral forms (TAN, NO2--NO3-), an increase in the concentration of organic soluble and sestonic organic forms (expressed in terms of particulate nitrogen, particulate organic carbon, chlorophyll a) compared with the water inflow. Increasing WER increased the amount of exported wastes and mainly in the organic forms and TAN can be considered as negligible. The nitrogen budget showed that 19-46% of nitrogen input (feed+water) was exported into the coastal environment. The results showed that the quality of the sediment decreased as WER decreased. The potential negative impact of the developing industry in New Caledonia on the costal environment could be partially reduced in a first step by decreasing WER. However, if applied in the farms, this practice should be linked to a close survey of the evolution of sediment quality.
Aquaculture Research (1355-557X) (Blackwell science), 2006-06 , Vol. 37 , N. 9 , P. 938-948

Droits : 2006 Blackwell Publishing, Inc.
http://archimer.ifremer.fr/doc/2006/publication-1811.pdf
DOI:10.1111/j.1365-2109.2006.01515.x
http://archimer.ifremer.fr/doc/00000/1811/

Éditeur(s) : HAL CCSD Taylor & Francis
Résumé : International audience
In spite of several studies on factors affecting nitrogen (N) export in water, the spatiotemporal variability of N export is rarely addressed. This review aims at discussing the different factors involved in N export in water and the intra-annual variability of N occurrences in rivers at a watershed scale. From the analysis of the existing works some recommendations on future research work are proposed regarding (i) other N forms than nitrate being systematically considered for routine analysis or experimental studies (at least Kjheldal nitrogen), (ii) hydrologists and biogeochemists working together to better understanding of N dynamics according to water pathways, especially during “situations at risk,” (iii) water quality monitoring being reinforced both spatially and temporally, especially thanks to high frequency instrumentation, and (iv) accurate data on watersheds needed to give better explanations of N variations. We argue that a better understanding of spatiotemporal variability could greatly enhance the remediation of N export impacts, which is crucial to anticipate the impacts of global changes
ISSN: 1064-3389

hal-01195736
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01195736
DOI : 10.1080/10643389.2015.1010432

Éditeur(s) : HAL CCSD Elsevier
Résumé : Eperua falcata (Aublet), a late-successional species in tropical rainforest and one of the most abundant tree in French Guiana, has developed an original strategy concerning N-acquisition by largely preferring nitrate, rather than ammonium (H. Schimann, S. Ponton, S. Hattenschwiler, B. Ferry, R. Lensi, A.M. Domenach, J.C. Roggy, Differing nitrogen use strategies of two tropical rainforest tree species in French Guiana: evidence from N-15 natural abundance and microbial activities, Soil Biol, Biochem. 40 (2008) 487-494). Given the preference of this species for nitrate, we hypothesized that root exudates would promote nitrate availability by (a) enhancing nitrate production by stimulating ammonium oxidation or (b) minimizing nitrate losses by inhibiting denitrification. Root exudates were collected in situ in monospecific planted plots. The phytochemical analysis of these exudates and of several of their corresponding root extracts was achieved using UHPLC/DAD/ESI-QTOF and allowed the identification of diverse secondary metabolites belonging to the flavonoid family. Our results show that (i) the distinct exudation patterns observed are related to distinct root morphologies, and this was associated with a shift in the root flavonoid content, (ii) a root extract representative of the diverse compounds detected in roots showed a significant and selective metabolic inhibition of isolated denitrifiers in vitro, and (iii) in soil plots the abundance of nirK-type denitrifiers was negatively affected in rhizosphere soil compared to bulk. Altogether this led us to formulate hypothesis concerning the ecological role of the identified compounds in relation to N-acquisition strategy of this species. (C) 2013 Elsevier Masson SAS. All rights reserved.
ISSN: 0981-9428

hal-01032437
https://hal.archives-ouvertes.fr/hal-01032437
DOI : 10.1016/j.plaphy.2013.05.003

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Over the last two decades, climate change has become a major environmental and public health concern due to the increase of the mean temperature on the Earth and its consequences on extreme meteorological events such as floods and droughts. These events induce very low or very high river flows that may impair surface water quality, and therefore result in potential health impacts when used for drinking water production. The present study aims at assessing the impact of hydrologic regime on surface water quality with a particular emphasis on total organic carbon (TOC) and nitrate. Water quality data from three French rivers acquired over a 27 years period, from January 1983 to December 2009, show the influence of extreme flows. Variation in TOC and nitrate concentrations showed opposite patterns for the whole range of flow rate (from less than 10% up to more than 100% of the mean flow). Regarding fluxes, TOC increased continuously with flow rate while nitrate was stable for very high discharges. The C/N ratio expressed from TOC and nitrate concentrations showed high values for extreme flows and particularly for very low flow rates, generally in summer, where nitrate is assimilated by biomass. Considering TOC and nitrate fluxes, it is confirmed that the worst situations were encountered for very high flow rates, namely for TOC exportation during surface runoff which was related to heavy rains or floods. These findings are of great importance with regard to the adaptation for drinking water treatment in facing extreme hydrological conditions, of which the frequency is increasing with climate change.
ISSN: 0022-1694

hal-00878009
https://hal.archives-ouvertes.fr/hal-00878009
DOI : 10.1016/j.jhydrol.2012.11.006

Éditeur(s) : Gauthier-Villars
Résumé : The analysis of humic compounds by elemental analysis, PY-GC-MS and HPLC techniques permitted determination of the origin of organic inputs, essentially terrestrial, and the effects of environmental conditions in the deposits along a north-south transect through the Rhone delta, from the river mouth to the open sea. In the prodelta the sedimentation of fine particles enriches the sediments in organic matter. The humic compound contents were relatively low in sediments, perhaps due to a rapid burying of organic matter which leads to anoxic conditions. In sediments fulvic acids are more abundant than humic acids. Elemental analysis indicated that fulvic acids were enriched in hydrogen and nitrogen as compared to humic acids. Furthermore, H/C and N/C ratios increased in the fulvic and humic acids towards the open sea, related to a more marine character. Pyrolysis analysis showed some differences between the chemical composition of fulvic acids which correspond to low molecular weights enriched in carbohydrates, and that of humic acids, high molecular weight compounds which are enriched in phenols and aromatic hydrocarbons. The pyrolysis-derived phenols were abundant near the river mouth, decreasing towards the open sea as nitrogen-containing-compounds increased. Near the river mouth, the abundance of phenolic aldehydes demonstrated by HPLC emphasized the existence of fresh organic matter. On the other hand, off the mouth, an increase in phenolic acids could indicate a more degraded organic material. The fractionation of humic acids in various classes of molecular weight species using ultrafiltration (Amicon membranes) and their analysis showed that, close to the river mouth, the large proportion of the high molecular weight humic compounds observed was enriched in phenols and carbohydrates, probably inherited from the terrestrial ligno-cellulosic complex. This process seemed to be superimposed on the increase of molecular weights which is usually observed as the environment becomes purely marine. These humic compounds would derived either from organic matter from terrestrial soils swept along by the river flow, after deposition on its bed or, more probably, from high molecular weight compounds which, associated with the mineral phase, flocculated when reaching the fluvio-marine front. Generally, the low molecular weight fractions were enriched in hydrogen and nitrogen. Near the river mouth, nitrogen-containing compounds were concentrated in the low molecular weight classes which correspond to organic molecules regarded as humic precursors. Off the mouth, they were incorporated into the high molecular weight complexes, certainly of marine origin.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1992 , Vol. 15 , N. 1 , P. 61-74

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00101/21187/18804.pdf
http://archimer.ifremer.fr/doc/00101/21187/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Benzo[a]pyrene (B[a]P), the prototype molecule of polycyclic aromatic hydrocarbons, exhibits genotoxic and carcinogenic effects, which has led the International Agency for Research on Cancer to recognize it as a human carcinogen. Besides the well-known apoptotic signals triggered by B[a]P, survival signals have also been suggested to occur, both signals likely involved in cancer promotion. Our previous work showed that B[a]P induced an hyperpolarization of mitochondrial membrane potential (ΔΨm) in rat hepatic epithelial F258 cells. Elevated ΔΨm plays a role in tumor development and progression, and nitric oxide (NO) has been suggested to be responsible for increases in ΔΨm. The present study therefore aimed at evaluating the impact of B[a]P on NO level in F258 cells, and at testing the putative role for NO as a survival signal, notably in link with ΔΨm. Our data demonstrated that B[a]P exposure resulted in an NO production which was dependent upon the activation of the inducible NO synthase. This enzyme activation involved AhR and possibly p53 activation. Preventing NO production not only increased B[a]P-induced cell death but also blocked mitochondrial hyperpolarization. This therefore points to a role for NO as a survival signal upon B[a]P exposure, possibly targeting ΔΨm
ISSN: 0887-2333

hal-01163757
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01163757
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01163757/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01163757/file/Benzo%5Ba%5Dpyrene-induced%20nitric.pdf
DOI : 10.1016/j.tiv.2015.06.010

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Introduction Evidence has accumulated that exposure to ambient air pollution during pregnancy may influence preterm birth (PTB) in urban settings. Conversely, this relation has barely been investigated in rural areas where individual characteristics (demographic, socioeconomic, and psychosocial factors) and environmental co-exposures may differ. Objective We examined the association between prenatal exposure to traffic-related air pollution and PTB among pregnant women from the PELAGIE mother–child cohort (Brittany, France, 2002–2006) living in urban (n=1550) and rural (n=959) settings. Methods Women’s residences were classified as either urban or rural according to the French census bureau rural–urban definitions. Nitrogen dioxide (NO2) concentrations at home addresses were estimated from adjusted land-use regression models as a marker of traffic-related pollution. Associations between NO2 concentrations and PTB were assessed with logistic regression models. Results Prevalence of PTB was similar among women living in urban (3.2%) and in rural (3.5%) settings. More positive socioeconomic characteristics and health behaviors but more single-parent families were observed among urban women. NO2 exposure averaged 20.8±6.6 µg m−3 for women residing in urban areas and 18.8±5.6 µg m−3 for their rural counterparts. A statistically significant increased risk of PTB was observed among women exposed to NO2 concentrations ≥16.4 µg m−3 and residing in urban areas but not among their rural counterparts. Discussion The results of this study, conducted in a region with interspersed urban–rural areas, are in line with previous findings suggesting an increased risk of PTB associated with higher NO2 concentrations for women living in urban areas. The absence of association among their rural counterparts for whom exposure levels were similar suggests that environmental mixtures and psychosocial inequalities might play a role in this heterogeneity
ISSN: 0013-9351

hal-01165108
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01165108
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01165108/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01165108/file/Air%20pollution%20%26%20preterm%20birth%20PELAGIE_HAL-accepted.pdf
PUBMED : 26092808

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Introduction Considered in times gone by as a hostile environment and visited by only sailors and fishermen (Saffache, 2003). Later on as a place of healing, today, the marine environment serves as a receptacle for the most toxic effluents. In an effort to evaluate such a phenomenon, and above all, the impact it has on the environment, two forms of pollution will be highlighted, oil discharge and nitrogen and phosphorus-based products. 1. Oil Pollution: scope, consequences and anti-pollution ...

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.516
http://journals.openedition.org/etudescaribeennes/516

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
The shallow water bivalve Codakia orbicularis lives in symbiotic association with a sulfur-oxidizing bacterium in its gills. The endosymbiont fixes CO2 and thus generates organic carbon compounds, which support the host's growth. To investigate the uncultured symbiont's metabolism and symbiont-host interactions in detail we conducted a proteogenomic analysis of purified bacteria. Unexpectedly, our results reveal a hitherto completely unrecognized feature of the C. orbicularis symbiont's physiology: the symbiont's genome encodes all proteins necessary for biological nitrogen fixation (diazotrophy). Expression of the respective genes under standard ambient conditions was confirmed by proteomics. Nitrogenase activity in the symbiont was also verified by enzyme activity assays. Phylogenetic analysis of the bacterial nitrogenase reductase NifH revealed the symbiont's close relationship to free-living nitrogen-fixing Proteobacteria from the seagrass sediment. The C. orbicularis symbiont, here tentatively named `Candidatus Thiodiazotropha endolucinida', may thus not only sustain the bivalve's carbon demands. C. orbicularis may also benefit from a steady supply of fixed nitrogen from its symbiont-a scenario that is unprecedented in comparable chemoautotrophic symbioses.
ISSN: 2058-5276

hal-01545904
https://hal.archives-ouvertes.fr/hal-01545904
DOI : 10.1038/nmicrobiol.2016.193