Organic matter mineralization in the pore water of a eutrophic lake (Aydat Lake,Puy de Dôme,France)

The chemical composition of the pore water from the sediment of a eutrophic lake is dominated by high concentrations of total dissolved CO₂ (up to 12 mM), reduced soluble iron (up to 2 mM) and dissolved silica (up to 1 mM). The pH lies within the range of 6.70 ± 0.02; this reflects that the pore water is efficiently buffered by the CO₂ acid/base system. This composition is directly related to the main diagenetic reactions which drive the organic matter mineralization i.e. methanogenesis and ferric oxides reduction. Other geochemical processes are of minor importance. A stoichiometric model based on these main reactions allow us: (i) to define a general formula for the organic matter which is close to Redfield's one for the C:N ratio, while the C:P ratio is much higher owing to a probable adsorption of phosphorus onto reactive surfaces of the solid and due to heterotrophic bacterial uptake; (ii) to calculate a global first order kinetic constant which drives the organo-polymers breakdown. Due to the strong influence on the trophic status of the lake caused by an excess of phosphate, special attention is devoted to this species. We show that the sediment-water interface is a source of dissolved phosphate when the hypolimnion is anoxic between May and November. This contribution represents about 17% of the river input and should be taken into account in any attempt toward lake restoration.     

The influence of fertilizers,soil organic matter and soil compaction on maize yields on the Surinam ‘Zanderij’ soils

Summary In connection with the growing interest in Surinam to exploit the soils in the hinterland, some trials were carried out on Zanderij soils to study productivity, fertilizer need and influence of some special soil factors on yield. The test crop was maize. The yields were generally low which might partly be attributed to the relative dry weather conditions during the trials. On all soils investigated, yield responses to phosphate application were high. On loamy soils there was sometimes a response to nitrogen and on sandy soils to potassium. Yields on sands were lower than on loamy sands and sandy loams. The most important yield determining soil factor proved to be organic matter. On compacted soils yields were considerably lower which was due to increased mechanical impedance for root growth and in some cases to inadequate aeration. Also published as Bulletin of the Agricultural Experiment Station, Paramaribo, Surinam. Also published as Bulletin of the Agricultural Experiment Station, Paramaribo, Surinam.     

Can tree species richness attenuate the effect of drought on organic matter decomposition and stabilization in young plantation forests?

Changes in precipitation due to climate change are likely to influence soil organic matter (SOM) decomposition and stabilization. In forests, increased tree species diversity could modulate the effects of drought on SOM decomposition and stabilization. We addressed this issue by a decomposition study under simulated drought (through precipitation reduction at Zedelgem, Belgium) and natural drought (ORPHEE, southern France) in young experimental plantations (tree species richness 1 to 5). In Zedelgem, the study focused on tree species richness around oak and beech trees. Two tea bag indices (TBI) – decomposition rate (k) and stabilization factor (S) – were calculated by measuring the decay of green and rooibos tea in soils. Overall, TBI's were higher in Zedelgem than at ORPHEE. In Zedelgem, k increased with tree species richness under drought around oak, indicating that tree species richness modulated the effects of drought on decomposition. Under beech, k decreased with drought while no effect of tree species richness was detected. S increased with drought under both oak and beech, without any effect of tree species richness. In ORPHEE, we did not detect any tree species richness effect on both TBIs. S decreased significantly, while k was marginally reduced under drought. The higher S under drought in Zedelgem and under control in OPRHEE suggests that the carbon sequestration potential under climate change would be dependent on the environmental context. Further, in young plantations, high species richness may modulate the drought effect on SOM decomposition, but not on stabilization.     

Morphology and ecology of Oblea rotunda (Diplopsalidaceae,Dinophyceae) from a new habitat: a brackish and hypertrophic ecosystem,the Étang de Bolmon (South of France).

A small thecate dinoflagellate was encountered during winter and spring in the phytoplankton community of a shallow, brackish and hypertrophic pond in the South of France. The abundance of material permitted its identification, using scanning electron microscopy, as Oblea rotunda Balech ex Sournia. However, morphological features showed some discrepancies with the typical characteristics of O. rotunda. Environmental hydrographic parameters in the pond were very different from marine ecosystems where O. rotunda is usually reported. In this polluted and alkaline pond, salinity was low, ranging from 1.1 to 6.2 p.s.u.; the maximum densities of O. rotunda (greater than 1?×?10⁵ cells l^???1) were observed at temperatures around 13°C, after a Cylindrotheca closterium?–?Heterocapsa rotundata bloom in early spring. These two species and other abundant taxa of the phytoplankton had seasonal patterns that could explain the presence of O. rotunda, since they could have been a food for this heterotrophic species. As this population showed most of the morphological criteria of O. rotunda, but with some variability and a different ecology, it is better considered as a variant of the marine species, rather than as a new species. This study provides additional data on the ecological and morphological features of this poorly known small peridinioid species, previously only reported from open seas and oceans.     

‘A genealogist's paradise’: France,Québec and the genealogics of race

Genealogy, or the study of one's ancestral patri-lineage, has a long and esteemed pedigree in French Canadian and Québécois history. From Cyprien Tanguay's late-nineteenth-century encyclopedias to René Jetté's updated versions more than a century later, genealogy has been an important component of French Canadian nationalisms. Tracing one's ancestry back to the early St. Lawrence settlement in the seventeenth century has provided Québécois subjects with opportune political and social capital with which to make territorial and national claims legitimate. Through a case study approach, I explain how genealogy provides the grounds upon which Québécois and French subjects remember a shared past. Specifically, I examine a variety of sites of memory in the French countryside, including a museum that relies on ‘genealogics’ to call the French Canadian Québécois back to its roots. As such, I demonstrate how the biological, read as a contemporary articulation of Balibar's notion of the racial supplément necessary to nation building, travels across the Atlantic.     

Chromatin and epigenetics in all their states: Meeting report of the first conference on Epigenetic and Chromatin Regulation of Plant Traits - January 14 – 15, 2016 - Strasbourg,France

In January 2016, the first Epigenetic and Chromatin Regulation of Plant Traits conference was held in Strasbourg, France. An all-star lineup of speakers, a packed audience of 130 participants from over 20 countries, and a friendly scientific atmosphere contributed to make this conference a meeting to remember. In this article we summarize some of the new insights into chromatin, epigenetics, and epigenomics research and highlight nascent ideas and emerging concepts in this exciting area of research.     

A food web analysis of the Río de la Plata estuary and adjacent shelf ecosystem: trophic structure,biomass flows,and the role of fisheries

This article performed a comprehensive assessment of the structure and functioning of the Río de la Plata estuary and adjacent shelf ecosystem, including the effect of fishing. A formerly implemented 37 trophic groups’ mass-balance model (Ecopath) was used to (1) evaluate the particular role of individual biotic components on the ecosystem; (2) characterize the ecosystem in terms of aquatic food web theory; and (3) assess the role of diverse fishing fleets on the ecosystem. Our results indicate a trophic structure and functioning common to other estuaries, where outstanding primary production exceeds consumption, and detritus accumulates in the system. Moreover, our analysis revealed an elevated total system throughput, herbivory outweighing detritivory, and an intermediate state in terms of ecosystem growth and development. Fisheries analyses showed widespread impacts produced by industrial bottom trawl fleets, and specific impacts produced by artisanal fisheries over several groups. Unexpectedly, the evaluation of the effects of fishing showed minor ecosystem consequences by the loss of secondary production and suggests exploitation rates at sustainable levels. This study sets up the basis for temporal ecosystem-level monitoring of the state of the Río de la Plata estuary and adjacent shelf ecosystem.     

Redescription of the geologically youngest albanerpetontid (?Lissamphibia): Albanerpeton inexpectatum Estes and Hoffstetter, 1976, from the Miocene of France

Albanerpeton inexpectatum Estes and Hoffstetter, 1976, the type species of Albanerpeton and the geologically youngest albanerpetontid, is rediagnosed and redescribed based on a large collection of jaws and frontals from Miocene fissure fills near La Grive-Saint-Alban, southeastern France. Intraspecific variation is documented in these elements, and is attributed to growth and individual differences. Synapomorphies of the upper jaws indicate that A. inexpectatum a) belongs in a clade whose members are otherwise known from the Upper Cretaceous-Paleocene of North America and b) is the sister species of an undescribed North American Paleocene species. The presence of A. inexpectatum in the Miocene of France is postulated to be the result of an Early or Middle Tertiary dispersal of an unknown ancestral species from North America into Europe. Cranial apomorphies of A. inexpectatum are interpreted as having strengthened the skull for burrowing in rocky soil and feeding.     

Regressive dynamic and denudation processes of vegetation on volcanoes in the ‘Chaîne des Puys’ (French Massif Central): assay of interpretation

Some large bald areas, taking up the southern volcanoes hill-sides of the Chaîne des Puys (French Massif Central) are studied on an ecological point of view, by means of Multiple Correspondence Analysis applied to a contingency array environmental variables X plots, the plots being preliminarily studied in a syntaxonomic way. Four denudation processes are determined: natural screes (related to high declivity), rubbles resulting of intense passage, excess of grazing and a spontaneous regression of senescent heaths (degenerate phase) would happen, especially when particular local conditions are realized (impoverishment of soils, inhibiting action of Calluna vulgaris (L.) Hull, remoteness of trees, exposure, lavas characteristics...).     

Lower limb bone structure of Middle Pleistocene hominins from the Caune de l’Arago (Tautavel,France): Evolutionary and functional comparison with the penecontemporaneous hominins of Sima de los Huesos (Atapuerca,Spain)

The Caune de l’Arago (Arago) and Sima de los Huesos (Sima) human bones from the European Middle Pleistocene are penecontemporaneous, although the Sima hominins are closely related to Neandertal, and Arago hominins present more archaic features. In previous and in press studies, the cross-sectional geometric properties (CSG) of lower limb bones of Arago and Sima have been studied separately without comparative analyses. Here, in order to bridge this gap, we use the same criteria for both samples to highlight evolutionary affinities and to compare their level and pattern of mobility. This study focuses on the femur, fibula and tibia from Arago and Sima with references to fossils from the sites of Trinil, Zhoukoudian and Lazaret, and ancient and recent Homo sapiens (including athletes and non-athletes). We analyze the cross-sectional areas, biomechanical bone “shape” indices (Ix/Iy, Imax/Imin) and pattern of cortical bone distribution. All lower limb bones from Arago have noticeably high to very high relative cortical areas and low to very low medullary areas. The overall femoral pattern in Arago, like Sima, is similar to that of Middle Pleistocene hominins (e.g., low femoral shape indices, Ix/Iy) and Neandertals (e.g., large cross-sectional size). However, the femoral midshaft in Sima presents prominent posteromedial cortical thickening, as a result of a spiral cortical reinforcement along the medial side of the diaphysis. This characteristic is specific to Neandertal and some Middle Pleistocene hominins. In contrast, the midshaft femoral pattern in Arago is close to that of some Homo erectus. We also note that the femoral cross-sectional size and relative cortical area in Arago differ drastically to the small size and low relative cortical area of Lazaret and Trinil hominins. The very high shape index at midshaft (i.e., high Imax/Imin) of the Arago tibia is observed in ancient H. sapiens and runners; the tibial posterior “pilaster” is found in Neandertals and ancient H. sapiens; and the flat or convex tibial faces are similar to Neandertals. Furthermore, the Arago fibulas show marked fibular posterolateral cortical reinforcement with low anteroposterior strengthening. These leg features (tibia, fibula) are also found in some Sima hominins (but not in all individuals). Consequently, this study confirms the presence of archaic features in Arago and the close evolutionary relationship between Sima and Neandertal. This proposition is mainly based on the femoral midshaft pattern influenced by the pelvofemoral complex, considered to be substantially genetically controlled. The leg functional analysis highlights a high level of mobility and travelling in uneven terrains or in mountainous areas in Arago, consistent with known environments and hunting practices. Previously, an analogous hypothesis was proposed put forward for Sima hominins.     

Relation between phosphate and organic matter in fish-pond sediments of the Deroua fish farm (Béni-Mellal, Morocco): implications for pond management

An experimental approach of the phosphate exchange across the water–sediment interface in fish ponds of the Deroua farm (Béni-Mellal, Morocco) is needed to understand the phosphate dynamics in these ponds in relation to their water quality. During this study, we conducted experiments to determine the P-fractions of the different pond sediments and to estimate the release from these sediments of phosphate available for algal uptake. We also determined the amount of phosphate needed to saturate the sediments of two different fish ponds under anoxic and oxic conditions. Phosphate release from sediments comes mainly from Fe(OOH)P and is more important in ponds lined with sheets. The accumulation of organic matter in sediments favours the installation of anoxic conditions and enhances the phosphate release from CaCO₃P, labile in these pond sediments. Under experimental conditions, org-P plays a minor role in the P-release. Oxic conditions, to the contrary, have an inhibitory effect on the P-release from sediments. About 80–98% of the P-adsorbed onto different pond sediments was recovered in the inorg-P-fractions. Aeration induces the oxidation of FeS to Fe(OOH) which can adsorb phosphate from solution. Besides, the presence of bacteria in pond sediments was essential to promote phosphate release under anoxic conditions by controlling the oxidation state of iron and the mineralization of the organic matter. Sheet-lined ponds, when insufficiently dried, accumulate a large quantity of organic matter in their sediments. After a decrease in pH, P is released from CaCO₃P and enhances the phytoplankton productivity responsible for renewed accumulation of organic matter. Org-C concentrations in sediments over 20 mg g^–1 d.w. favour the formation of toxic factors (Fe²⁺, Mn²⁺, NO₂ ^– and H₂S) harmful for carp growth. An extended period of drying efficiently enhances the mineralization of organic matter.     

Observations on the distribution and relative abundance of the scyphomedusan Chrysaora hysoscella (Linné, 1766) and the hydrozoan Aequorea aequorea (Forskål, 1775) in the northern Benguela ecosystem

Observations on the abundance of medusae at the surface were conducted in the northern Benguela ecosystem, over the period August 1997–June 1998. The results suggest that Chrysaora hysoscella is found inshore, whereas Aequorea aequorea tends to be found offshore. Although these relative observations are subject to bias caused by seasonal changes in the survey area, they are generally supported by the results of correlation analyses, and by the results of a more quantitative, cross-shelf trawl survey. Both species of medusae display marked patchiness, and can be very abundant. They appear to have mostly non-overlapping patterns of distribution in the upper layers of the water column, and so are able exert a consistent predation pressure across the width of the continental shelf. The estimates of biomass obtained are used as input variables to existing models of energy flow within the ecosystem.