Variation of colour patterns in larval Hydropsyche (Trichoptera): Implications for species identifications and the phylogeny of the genus     

Bernhard Statzner  Nathalie Mondy 《Limnologica》2009,39(2):177-183

Larvae of the lotic caddisfly genus Hydropsyche may occur in densities of thousands to several tens of thousands of individuals/m² across continents and running water types. Therefore, stream ecologists frequently face the task of identifying larvae of this genus. Early keys to larval Hydropsyche of Asia, Europe and North America often used the relatively complicated frontoclypeal colour pattern for species discrimination, whereas equivocal views about the variation of this pattern limited its use in recent keys. Has each species of a given species group a different (although intraspecifically variable) basic pattern of lighter spots on the darker frontoclypeus, or have all species of a group the same basic colour pattern that varies more or less intraspecifically? An answer to this question has obvious implications for the identification of the species as well as for the phylogeny of the genus, so we examined the variation of this colour pattern across ∼11,000 specimens of 10 Hydropsyche species from the Loire River (France).All 10 species had the same basic colour pattern on the frontoclypeus (six contrasting light patches on a dark background) that varied intraspecifically across a certain range of colour contrasts. Comparing other sources illustrating the frontoclypeus of Hydropsyche larvae provided more support for the idea that six contrasting light patches on the frontoclypeus is the typical basic colour pattern that varies within almost all European species; males of these species have a simple phallus form. Two European and many North American species of the genus (from the Ceratopsyche group) have a different basic colour pattern of seven light patches on the frontoclypeus that varies also intraspecifically; males of these species have a complicated phallus form.If the variation of such colour patterns in co-existing populations of several species is known, the relative contrast differences among the individual patches on the frontoclypeus and the form of the individual patches can provide valuable information for rapid species identification. Analysis of this variation may also contribute to phylogenetic studies of the genus Hydropsyche and other hydropsychids.  相似文献   

Cooling of Accretion-Heated Neutron Stars     

Rudy Wijnands  Nathalie Degenaar  Dany Page 《Journal of Astrophysics and Astronomy》2017,38(3):49

We present a brief, observational review about the study of the cooling behaviour of accretion-heated neutron stars and the inferences about the neutron-star crust and core that have been obtained from these studies. Accretion of matter during outbursts can heat the crust out of thermal equilibrium with the core and after the accretion episodes are over, the crust will cool down until crust-core equilibrium is restored. We discuss the observed properties of the crust cooling sources and what has been learned about the physics of neutron-star crusts. We also briefly discuss those systems that have been observed long after their outbursts were over, i.e, during times when the crust and core are expected to be in thermal equilibrium. The surface temperature is then a direct probe for the core temperature. By comparing the expected temperatures based on estimates of the accretion history of the targets with the observed ones, the physics of neutron-star cores can be investigated. Finally, we discuss similar studies performed for strongly magnetized neutron stars in which the magnetic field might play an important role in the heating and cooling of the neutron stars.  相似文献   

Estimates of Horizontal Groundwater Flow Velocities in Boreholes     

Martí Bayer-Raich  Anthony Credoz  Jordi Guimerà  Salvador Jordana  Diego Sampietro  Jordi Font-Capó  Nathalie Nief  Matthieu Grossemy 《Ground water》2019,57(4):525-533

Currently, monitoring tools can be deployed in observation boreholes to better assess groundwater flow, flux of dissolved contaminants and their mass discharge in an aquifer. The relationship between horizontal water velocity in observation boreholes and Darcy fluxes in the surrounding aquifer has been studied for natural flow conditions (i.e., no pumping). Interpretation of measurements taken with dilution tests, the colloidal borescope, the Heat Pulse Flowmeter, and other techniques require the conversion of observed borehole velocity u to aquifer Darcy flux q_∞ . This conversion is typically done through a proportionality factor α = u/q_∞ . In experimental studies as well as in theoretical developments, reported values of α vary almost three orders of magnitude (from 0.5 to 10). This large variability in reported values of α could be explained by: (1) unclear distinction between Darcy flux and water seepage velocity, (2) unclear definition of water velocity in the borehole, (3) effects of well screen and the presence of the measurement device itself on the observable velocities, and (4) hydraulic conditions in the borehole annulus. We address (1), (2) from a conceptual/theoretical perspective, and (3) by means of numerical simulations. We show that issue (1) in low porosity aquifers can yield to order-of-magnitude discrepancies in estimates of q_∞ ; (2) may result in discrepancies of up to 50%, and (3) can cause differences up to 20% of water velocity in the borehole void space compared to the theoretical case of an open borehole.  相似文献   

Performance of the LandSoil expert-based model to map erosion and sedimentation: application to a cultivated catchment in central Belgium     

Vincent Cantreul  Nathalie Pineux  Gilles Swerts  Charles Bielders  Aurore Degré 《地球表面变化过程与地形》2020,45(6):1376-1391

Intensive agricultural practices on sensitive soils induce high erosion rates in central Belgium. Expert-rules models quantify runoff and erosion at catchment scale, avoiding over-parameterization, and can include some direct or indirect connectivity features. The aim of this article is to test the ability of an expert-based model, LandSoil, to quantify runoff and to locate erosion and sedimentation areas in a small cultivated loamy catchment in Belgium during the years 2014, 2015 and 2016. Spatialized data are important for assessing model outputs and the erosive response. Measurements of runoff and observation of spatial erosion/deposition patterns, especially around major connectivity points, permitted an assessment of the reliability of the model results. Runoff modelling gave contrasting results (good linear adjustment at the outlet of the 83 ha sub-catchment (point 1): r² of 0.96, Nash–Sutcliffe criterion of 0.95; less good at the outlet of the 3.9 ha sub-catchment (point 2): r² of 0.28, Nash–Sutcliffe criterion of –0.47). For point 2 the poor results are explained by the very few runoff events observed, a scaling effect and the small area with a single land use. Graduated rulers demonstrate that the model is able to provide a coherent pattern of erosion/deposition. The study highlights great sensitivity to the effect of land use, land allocation, landscape design and slope gradients. Grass strips induce deposition of eroded particles when slopes are gentle (< 2%). Woodland strips decrease connectivity by being in the stream but deposit thinner sediment layers. Field boundaries have a role in the transport, but not really the quantity, of sediments. This model validation in the Belgian loess context allows us to use LandSoil in other similar environments in order to estimate the effects of landscape management scenarios. © 2020 John Wiley & Sons, Ltd.  相似文献   

Simulation of the 2004 tsunami of Les Saintes in Guadeloupe (Lesser Antilles) using new source constraints     

Cordrie  Louise  Gailler  Audrey  Escartin  Javier  Feuillet  Nathalie  Heinrich  Philippe 《Natural Hazards》2020,103(2):2103-2129

Natural Hazards - The arc of the Lesser Antilles is associated with a significant tectonic activity due to the subduction of the Atlantic oceanic plate under the Caribbean plate. Earthquakes in...  相似文献   

δ15N and δ13C in the Mondego estuary food web: Seasonal variation in producers and consumers     

Alexandra Baeta  Rute Pinto  Ivan Valiela  Pierre Richard  Nathalie Niquil  João C. Marques 《Marine environmental research》2009,67(3):109-116

Assessments of temporal variation in stable carbon and nitrogen ratios were used to examine seasonal trends of the water column and benthic food webs in the Mondego estuary (Portugal). There was a marked seasonality in weather and water column conditions, including nutrient supply and chlorophyll concentrations. In spite of the pronounced environmental changes, we found little evidence of seasonal variation in δ¹³C and δ¹⁵N of producers and consumers in the Mondego estuary, with a few notable exceptions. Nitrogen isotope ratios in macrophytes (Zostera noltii, Ulva sp., Enteromorpha sp., and Gracilaria sp.), and in two grazers (Idotea chelipes and Lekanesphaera levii) increased during late summer, with the highest δ¹⁵N values being measured in July, during a period of elevated temperatures and drought, which may have favored high rates of denitrification and heavier δ¹⁵N values. The results suggest that stable-isotope values from macrophytes and selected grazers are useful as tracers of seasonal changes in nitrogen inputs into estuaries, and that those of consumers reflect other factors beyond seasonal variations in N and C sources.  相似文献   

The planktonic food web of the Bizerte lagoon (south-western Mediterranean) during summer: I. Spatial distribution under different anthropogenic pressures     

Asma Sakka Hlaili  Boutheina Grami  Nathalie Niquil  Michel Gosselin  Dominique Hamel  Marc Troussellier  Hassine Hadj Mabrouk 《Estuarine, Coastal and Shelf Science》2008

The structure and the trophic interactions of the planktonic food web were investigated during summer 2004 in a coastal lagoon of south-western Mediterranean Sea. Biomasses of planktonic components as well as bacterial and phytoplankton production and grazing by microzooplankton were quantified at four stations (MA, MB, MJ and R) inside the lagoon. Station MA was impacted by urban discharge, station MB was influenced by industrial activity, station MJ was located in a shellfish farming sector, while station R represented the lagoon central area. Biomasses and production rates of bacteria (7–33 mg C m⁻³; 17.5–35 mg C m⁻³ d⁻¹) and phytoplankton (80–299 mg C m⁻³; 34–210 mg C m⁻³ d⁻¹) showed high values at station MJ, where substantial concentrations of nutrients (NO₃⁻ and Si(OH)₄) were found. Microphytoplankton, which dominated the total algal biomass and production (>82%), were characterized by the proliferation of several chain-forming diatoms. Microzooplankton was mainly composed of dinoflagellates (Torodinium, Protoperidinium and Dinophysis) and aloricate (Lohmaniellea and Strombidium) and tintinnid (Tintinnopsis, Tintinnus, Favella and Eutintinnus) ciliates. Higher biomass of these protozoa (359 mg C m⁻³) was observed at station MB, where large tintinnids were encountered. Mesozooplankton mainly represented by Calanoida (Acartia, Temora, Calanus, Eucalanus, Paracalanus and Centropages) and Cyclopoida (Oithona) copepods, exhibited higher and lower biomasses at stations MA/MJ and MB, respectively. Bacterivory represented only 35% of bacterial production at stations MB and R, but higher fractions (65–70%) were observed at stations MA and MJ. Small heterotrophic flagellates and aloricate ciliates seemed to be the main controllers of bacteria. Pico- and nanophytoplankton represented a significant alternative carbon pool for micrograzers, which grazing represented 67–90% of pico- and nano-algal production in all stations. Microzooplankton has, however, a relatively low impact on microphytoplankton, as ≤45% of microalgal production was consumed in all stations. This implies that an important fraction of diatom production would be channelled by herbivorous meso-grazers to higher consumers at stations MA and MJ where copepods were numerous. Most of the microalgal production would, however, sink particularly at station MB where copepods were scare. These different trophic interactions suggest different food web structures between stations. A multivorous food web seemed to prevail in stations MJ and MA, whereas microbial web was dominant in the other stations.  相似文献   

Visible and near-infrared spectrophotometry of the Deep Impact ejecta of Comet 9P/Tempel 1     

Klaus W. Hodapp  Greg Aldering  Anita L. Cochran  Emmanuel Pécontal  Nathalie Blanc  David K. Lynch  S. Mazuk  Richard C. Puetter 《Icarus》2007,187(1):185-198

We have obtained optical spectrophotometry of the evolution of Comet 9P/Tempel 1 after the impact of the Deep Impact probe, using the Supernova Integral Field Spectrograph (SNIFS) at the UH 2.2-m telescope, as well as simultaneous optical and infrared spectra using the Lick Visible-to-Near-Infrared Imaging Spectrograph (VNIRIS). The spatial distribution and temporal evolution of the “violet band” CN (0-0) emission and of the 630 nm [OI] emission was studied. We found that CN emission centered on the nucleus increased in the 2 h after impact, but that this CN emission was delayed compared to the light curve of dust-scattered sunlight. The CN emission also expanded faster than the cloud of scattering dust. The emission of [OI] at 630 nm rose similarly to the scattered light, but then remained nearly constant for several hours after impact. On the day following the impact, both CN and [OI] emission concentrated on the comet nucleus had returned nearly to pre-impact levels. We have also searched for differences in the scattering properties of the dust ejected by the impact compared to the dust released under normal conditions. Compared to the pre-impact state of the comet, we find evidence that the color of the comet was slightly bluer during the post-impact rise in brightness. Long after the impact, in the following nights, the comet colors returned to their pre-impact values. This can be explained by postulating a change to a smaller particle size distribution in the ejecta cloud, in agreement with the findings from mid-infrared observations, or by postulating a large fraction of clean ice particles, or by a combination of these two.  相似文献   

Sensitivity of simulated Asian and African summer monsoons to orbitally induced variations in insolation 126, 115 and 6 kBP   总被引：1，自引：1，他引：0  

Nathalie de Noblet  Pascale Braconnot  Sylvie Joussaume  Valérie Masson 《Climate Dynamics》1996,12(9):589-603

We have conducted four numerical experiments with an atmospheric general circulation model (AGCM) to investigate the sensitivity of Asian and African monsoons to small changes (–5 to +12%), with respect to present-day, in incoming solar radiation at the top of the atmosphere. We show that, during the mid-Holocene (6 kBP where kBP means thousands of years before present-day) and the last interglacial (126 kBP), the Northern Hemisphere seasonal contrast was increased, with warmer summers and colder winters. At the time of glacial inception (115 kBP) however, summers were cooler and winters milder. As a consequence, Asia and tropical North Africa experienced stronger (weaker) summer monsoons 6 and 126 kBP (115 kBP), in agreement with previous numerical studies. This present study shows that summer warming/cooling of Eurasia and North Africa induced a shift of the main low-level convergence cell along a northwest/southeast transect. When land was warmer (during the summer months 6 and 126 kBP), the monsoon winds converged further inland bringing more moisture into northern India, western China and the southern Sahara. The southern tips of India, Indochina and southeastern China, as well as equatorial North Africa became drier. When land was cooler (during the summer 115 kBP), the main convergence zone was located over the west Pacific and the wet (dry) areas were those that were dry (wet) 6 and 126 kBP. The location and intensity of the simulated precipitation maxima were therefore very sensitive to changes in insolation. However the total amount of monsoon rain in Asia as well as in Africa remained remarkably stable through the time periods studied. These simulated migrations of convective activities were accompanied by changes in the nature of precipitation events: increased monsoon rains in these experiments were always associated with more high precipitation events (> 5 mm day ^–1), and fewer light showers (1 mm day^–). Rainy days with rates between 1 and 5 mm day^–1 were almost unchanged.  相似文献   

Effects of mid‐twenty‐first century climate and land cover change on the hydrology of the Puget Sound basin,Washington     

Lan Cuo  Tazebe K. Beyene  Nathalie Voisin  Fengge Su  Dennis P. Lettenmaier  Marina Alberti  Jeffrey E. Richey 《水文研究》2011,25(11):1729-1753

The distributed hydrology–soil–vegetation model (DHSVM) was used to study the potential impacts of projected future land cover and climate change on the hydrology of the Puget Sound basin, Washington, in the mid‐twenty‐first century. A 60‐year climate model output, archived for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), was statistically downscaled and used as input to DHSVM. From the DHSVM output, we extracted multi‐decadal averages of seasonal streamflow, annual maximum flow, snow water equivalent (SWE), and evapotranspiration centred around 2030 and 2050. Future land cover was represented by a 2027 projection, which was extended to 2050, and DHSVM was run (with current climate) for these future land cover projections. In general, the climate change signal alone on sub‐basin streamflow was evidenced primarily through changes in the timing of winter and spring runoff, and slight increases in the annual runoff. Runoff changes in the uplands were attributable both to climate (increased winter precipitation, less snow) and land cover change (mostly reduced vegetation maturity). The most climatically sensitive parts of the uplands were in areas where the current winter precipitation is in the rain–snow transition zone. Changes in land cover were generally more important than climate change in the lowlands, where a substantial change to more urbanized land use and increased runoff was predicted. Both the annual total and seasonal distribution of freshwater flux to Puget Sound are more sensitive to climate change impacts than to land cover change, primarily because most of the runoff originates in the uplands. Both climate and land cover change slightly increase the annual freshwater flux to Puget Sound. Changes in the seasonal distribution of freshwater flux are mostly related to climate change, and consist of double‐digit increases in winter flows and decreases in summer and fall flows. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献