Influence of allochthonous dissolved organic matter on pelagic basal production in a northerly estuary

Phytoplankton and heterotrophic bacteria are key groups at the base of aquatic food webs. In estuaries receiving riverine water with a high content of coloured allochthonous dissolved organic matter (ADOM), phytoplankton primary production may be reduced, while bacterial production is favoured. We tested this hypothesis by performing a field study in a northerly estuary receiving nutrient-poor, ADOM-rich riverine water, and analyzing results using multivariate statistics. Throughout the productive season, and especially during the spring river flush, the production and growth rate of heterotrophic bacteria were stimulated by the riverine inflow of dissolved organic carbon (DOC). In contrast, primary production and photosynthetic efficiency (i.e. phytoplankton growth rate) were negatively affected by DOC. Primary production related positively to phosphorus, which is the limiting nutrient in the area. In the upper estuary where DOC concentrations were the highest, the heterotrophic bacterial production constituted almost 100% of the basal production (sum of primary and bacterial production) during spring, while during summer the primary and bacterial production were approximately equal. Our study shows that riverine DOC had a strong negative influence on coastal phytoplankton production, likely due to light attenuation. On the other hand DOC showed a positive influence on bacterial production since it represents a supplementary food source. Thus, in boreal regions where climate change will cause increased river inflow to coastal waters, the balance between phytoplankton and bacterial production is likely to be changed, favouring bacteria. The pelagic food web structure and overall productivity will in turn be altered. (C) 2018 The Authors. Published by Elsevier Ltd.Peer reviewe

Recent developments in modeling of the stress derivative of magnetization in ferromagnetic materials

The effect of changing stress on the magnetization of ferromagnetic materials leads to behavior in which the magnetization may increase, or decrease, when exposed to the same stress under the same external conditions. A simple empirical law seems to govern the behavior when the magnetization begins from a major hysteresis loop. The application of the law of approach, in which the derivative of the magnetization with respect to the elastic energy supplied dM/dW is proportional to the magnetization displacement M an−M, is discussed

Contributions au colloque La conciliation dans le ressort de la cour d'appel de Toulouse, Acte 2

Ce document contient une partie des contributions au colloque "La conciliation dans le ressort de la cour d'appel de Toulouse, Acte 2" organisé par la cour d'appel de Toulouse et l'Institut de Droit Privé de l'Université Toulouse 1 Capitole : - Plaquette de présentation du colloque - Propos introductifs de M. Defix - Table ronde "la tentative de conciliation obligatoire préalable à la saisine du juge", interventions de Mme Leclercq et Mr Brugel - Table ronde "la tentative de conciliation obligatoire devant le juge", interventions de Mme Bruggeman et Me Capéla - Table ronde "la conciliation devant le conseil de prud'hommes", interventions de Mme Dupouey-Dehan et Mr Made

Contributions au colloque La conciliation dans le ressort de la cour d'appel de Toulouse, Acte 2

Ce document contient une partie des contributions au colloque "La conciliation dans le ressort de la cour d'appel de Toulouse, Acte 2" organisé par la cour d'appel de Toulouse et l'Institut de Droit Privé de l'Université Toulouse 1 Capitole : - Plaquette de présentation du colloque - Propos introductifs de M. Defix - Table ronde "la tentative de conciliation obligatoire préalable à la saisine du juge", interventions de Mme Leclercq et Mr Brugel - Table ronde "la tentative de conciliation obligatoire devant le juge", interventions de Mme Bruggeman et Me Capéla - Table ronde "la conciliation devant le conseil de prud'hommes", interventions de Mme Dupouey-Dehan et Mr Made

New young planetary nebulae in IPHAS

Original article can be found at: http://www.aanda.org/ Copyright The European Southern Observatory. DOI: 10.1051/0004-6361/200811575Aims. We search for very small-diameter galactic planetary nebulae (PNe) representing the earliest phases of PN evolution. The IPHAS catalogue of H-emitting stars provides a useful basis for this study since all sources present in this catalogue must be of small angular diameter. Methods. The PN candidates are selected based on their location in two colour-colour diagrams: IPHAS (r' - H) vs. (r' - i'), and 2MASS (J - H) vs. (H - ). Spectroscopic follow-up was carried out on a sample of candidates to confirm their nature. Results. We present a total of 83 PN candidates. We were able to obtain spectra or find the classification from the literature for 35 candidates. Five of these objects are likely to be new PNe, including one large bipolar PN discovered serendipitously close to an emission-line star. PN distances deduced from extinction-distance relations based on IPHAS field-star photometry are presented for the first time. These yield distance estimates for our objects in the range 2 kpc and 6 kpc. From the data in hand, we conclude that four of the discovered objects are probably young PNe.Peer reviewe

Net primary productivity estimates and environmental variables in the Arctic Ocean: An assessment of coupled physical-biogeochemical models

The relative skill of 21 regional and global biogeochemical models was assessed in terms of how well the models reproduced observed net primary productivity (NPP) and environmental variables such as nitrate concentration (NO3), mixed layer depth (MLD), euphotic layer depth (Zeu), and sea ice concentration, by comparing results against a newly updated, quality-controlled in situ NPP database for the Arctic Ocean (1959-2011). The models broadly captured the spatial features of integrated NPP (iNPP) on a pan-Arctic scale. Most models underestimated iNPP by varying degrees in spite of overestimating surface NO3, MLD, and Zeu throughout the regions. Among the models, iNPP exhibited little difference over sea ice condition (ice-free vs. ice-influenced) and bottom depth (shelf vs. deep ocean). The models performed relatively well for the most recent decade and towards the end of Arctic summer. In the Barents and Greenland Seas, regional model skill of surface NO3 was best associated with how well MLD was reproduced. . Regionally, iNPP was relatively well simulated in the Beaufort Sea and the central Arctic Basin, where in situ NPP is low and nutrients are mostly depleted. Models performed less well at simulating iNPP in the Greenland and Chukchi Seas, despite the higher model skill in MLD and sea ice concentration, respectively. iNPP model skill was constrained by different factors in different Arctic Ocean regions. Our study suggests that better parameterization of biological and ecological microbial rates (phytoplankton growth and zooplankton grazing) are needed for improved Arctic Ocean biogeochemical modeling

New low-resolution spectrometer spectra for IRAS sources

We present low-resolution spectra of 486 IRAS point sources with Fv(12 μm) in the range 20-40 Jy. This is part of an effort to extract and classify spectra that were not included in the Atlas of Low-Resolution Spectra and represents an extension of the earlier work by Volk & Cohen which covers sources with Fv(12 μm) > 40 Jy. The spectra have been examined by eye and classified into nine groups based on the spectral morphology. This new classification scheme is compared with the mechanical classification of the Atlas, and the differences are noted. Oxygen-rich stars on the asymptotic giant branch make up 33% of the sample. Solid state features dominate the spectra of most sources. We find that the nature of the sources as implied by the present spectral classification is consistent with the classifications based on broad-band colors of the sources.link_to_subscribed_fulltex