Zoogeography of marine Bryozoa around South Africa     

MK Boonzaaier-Davids  WK Florence  MJ Gibbons 《African Journal of Marine Science》2020,42(2):185-198

The zoogeography of marine Bryozoa around South Africa was investigated using published distribution records, museum catalogues, and an examination of previously unworked bryozoan material in (mostly) museum collections. Although a total of 276 valid species are recognised, it was not possible to unambiguously assess geographic patterns of diversity. At all depth zones examined (shore and inner-shelf, 0–30 m; mid- and outer-shelf, 31–350 m; bathyal, >500 m), there was a clear geographic structure to communities that mirrored established regional patterns of biogeography. Too few samples were collected from the shelf edge (351–500 m) and they were consequently excluded from zoogeographic analysis. Communities on the shore and inner-shelf and on the mid- and outer-shelf were more similar to each other than they were to bathyal communities, and the pronounced structure in bathyal communities suggests heterogeneity in the deep sea around South Africa.  相似文献   

Evolution of a Holsteinian (MIS 11c) palaeolake based on a 12‐ka‐long diatom record from Dethlingen (northern Germany)     

Andreas Koutsodendris  André F. Lotter  Emiliya Kirilova  Florence T. M. Verhagen  Achim Brauer  Jörg Pross 《Boreas: An International Journal of Quaternary Research》2013,42(3):714-728

To provide insights into the long‐term evolution of aquatic ecosystems without human interference, we here evaluate a decadal‐ to centennial‐scale‐resolution diatom record spanning about 12 ka of the Holsteinian interglacial (Marine Isotope Stage 11c). Using a partially varved sediment core from the Dethlingen palaeolake (northern Germany), which has previously been studied for palynological and microfacies signals, we document the co‐evolution of the aquatic and surrounding terrestrial environment. The diatom record is dominated by the genera Stephanodiscus, Aulacoseira, Ulnaria and Fragilaria. Based on the diatom assemblages and physical sediment properties, the evolution of the Dethlingen palaeolake can be subdivided into three major phases. During the oldest phase (lasting ～1900 varve years), the lake was ～10–15 m deep and characterized by anoxic bottom‐water conditions and a high nutrient content. The following ～5600 years exhibited water depths >20 m, maximum diatom and Pediastrum productivity, and a peak in allochtonous nutrient input. During this phase, water‐column mixing became more vigorous, resulting in a breakdown of anoxia. The youngest lake phase (～4000–5000 years) was characterized by decreasing water depth, turbulent water conditions and decreased nutrient loading. Based on our palaeolimnological data, we conclude that the evolution of the Dethlingen palaeolake during the Holsteinian interglacial responded closely to (i) changes within the catchment area (as documented by vegetation and sedimentation) related to the transition from closed forests growing on nutrient‐rich soils (mesocratic forest phase) to open forests developing on poor soils (oligocratic forest phase), and (ii) short‐term climate variability as reflected in centennial‐scale climate perturbations.  相似文献   

River flux uncertainties predicted by hydrological variability and riverine material behaviour     

Florentina Moatar  Michel Meybeck  Sébastien Raymond  François Birgand  Florence Curie 《水文研究》2013,27(25):3535-3546

Data on riverine fluxes are essential for calculating element cycles (carbon, nutrients, pollutants) and erosion rates from regional to global scales. At most water‐quality stations throughout the world, riverine fluxes are calculated from continuous flow data (q) and discrete concentration data (C), the latter being the main cause of sometimes large uncertainties. This article offers a comprehensive approach for predicting the magnitude of these uncertainties for water‐quality stations in medium to large basins (drainage basin area > 1000 km²) based on the commonly used discharge‐weighted method. Uncertainty levels – biases and imprecisions – for sampling intervals of 3 to 60 days are correlated first through a nomograph with a flux variability indicator, the quantity of riverine material discharged in 2% of time (M_2%). In turn, M_2% is estimated from the combination of a hydrological reactivity index, W_2% (the cumulative flow volume discharged during the upper 2% of highest daily flow) and the truncated b_50sup exponent, quantifying the concentration versus discharge relationship for the upper half of flow values (C = a q ^b50sup, for q > q₅₀, where q₅₀ is the median flow): M_2% = W_2% + 27.6b_50sup. W_2% can be calculated from continuous flow measurements, and the b_50sup indicator can be calculated from infrequent sampling, which makes it possible to predict a priori the level of uncertainty at any station, for any type of riverine material either concentrated (b_50sup > 0) or diluted (b_50sup > 0) with flow. A large data base of daily surveys, 125 station variables of suspended particulate matter (SPM), total dissolved solids (TDS) and dissolved and particulate nutrients, was used to determine uncertainties from simulated discrete surveys and to establish relationships between indicators. Results show, for example, that for the same relatively reactive basin (W_2% > 25%), calculated fluxes from monthly sampling would yield uncertainties approaching ±100% for SPM (b_50sup > 1.4) fluxes and ±10% for TDS (b_50sup = ?0.2). The application to the nitrate survey of the river Seine shows significant trends for the 1972–2009 records. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Direct and semi-direct aerosol radiative effect on the Mediterranean climate variability using a coupled regional climate system model     

Pierre Nabat  Samuel Somot  Marc Mallet  Florence Sevault  Marc Chiacchio  Martin Wild 《Climate Dynamics》2015,44(3-4):1127-1155

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First palaeomagnetic dating of ferricrete in New Caledonia: new insight on the morphogenesis and palaeoweathering of ‘Grande Terre’     

Brice Sevin  Caroline Ricordel‐Prognon  Florence Quesnel  Dominique Cluzel  Stéphane Lesimple  Pierre Maurizot 《地学学报》2012,24(1):77-85

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Modes of thickening of analogue weak lithospheres   总被引：4，自引：2，他引：4  

Florence Cagnard  Jean-Pierre Brun  Denis Gapais 《Tectonophysics》2006,421(1-2):145-160

Several compressional contexts, such as those involving juvenile or thickened crust, are expected to be associated with rather hot lithospheres whose mechanical behaviour remains poorly documented. In this paper, we present a series of analogue models dedicated to compression of lithospheres characterized by a thin upper brittle crust overlying a weak ductile crust and a ductile sub-Moho mantle. The models show that (1) deformation is controlled by the ductile layers that undergo distributed thickening, (2) thrust systems are limited to the upper brittle crust, (3) thrusting induces burial and stacking of upper crust pop-downs. The overall deformation patterns can be basically interpreted in terms of pop-down thrusting of the brittle crust and pure-shear type ductile flow of crust and mantle. Moreover, the models show that the sinking of supracrustal units does not require inverse density profiles but can be simply driven by compression. Model deformation patterns are consistent with those shared by many ancient belts, including not only Archaean granite–greenstone belts, but also more generally Paleoproterozoic ones. They provide also insights on deformation modes that may characterize modern thickened and abnormally hot domains like High Plateaus.  相似文献   

Mercury-binding proteins in the slipper limpet,Crepidula fornicata,exposed to increased soluble mercury     

Florence L. Harrison  Kathleen Watness  David A. Nelson  James E. Miller  Anthony Calabrese 《Estuaries and Coasts》1987,10(1):78-83

Crepidula fornicata were held in a flow-through bioassay system and exposed to sand-filtered seawater to which no soluble mercury (control) was added or to which either 5, 25, or 50 μg 1^?1 soluble Hg was added. At specific intervals during the 16-week experiment, a group of limpets was removed from each tank; one subgroup was exposed for 48 h to high concentrations of Hg, and another was analyzed for Hg-binding proteins by gelpermeation chromatography and spectrometry. Mortality from exposure to Hg in the 48-h acute toxicity tests was related to concentrations of Hg experienced both during the long-term exposure period and the 48-h exposure period. Chronic exposure to low levels of Hg resulted in increased amounts of total Hg in the whole body and in the low-molecular-weight Hg-binding proteins. No evidence was found for increased tolerance to Hg with preexposure.  相似文献   

Simulation des changements climatiques au cours du XXI^e siècle incluant l'ozone stratosphériqueSimulation of climate changes during the 21st century including stratospheric ozone     

Jean-François Royer  Daniel Cariolle  Fabrice Chauvin  Michel Déqué  Hervé Douville  Rong-Ming Hu  Serge Planton  Annie Rascol  Jean-Louis Ricard  David Salas Y Melia  Florence Sevault  Pascal Simon  Samuel Somot  Sophie Tyteca  Laurent Terray  Sophie Valcke 《Comptes Rendus Geoscience》2002,334(3):147-154

Two climate simulations of 150 years, performed with a coupled ocean/sea-ice/atmosphere model including stratospheric ozone, respectively with and without heterogeneous chemistry, simulate the tropospheric warming associated with an increase of the greenhouse effect of carbon dioxide and other trace gases since 1950 and their impact on sea–ice extent, as well as the stratospheric cooling and its impact on ozone concentration. The scenario with heterogeneous chemistry reproduces the formation of the ozone hole over the South Pole from the 1970s and its deepening until the present time, and shows that the ozone hole should progressively fill during the coming decades. To cite this article: J.-F. Royer et al., C. R. Geoscience 334 (2002) 147–154.  相似文献   

Paleolimnological evidence for increased landslide activity due to forest clearing and land-use since 3600 cal BP in the western Swiss Alps     

Florence Dapples  André F. Lotter  Jacqueline F.N. van Leeuwen  Willem O. van der Knaap  Sophia Dimitriadis  Daniel Oswald 《Journal of Paleolimnology》2002,27(2):239-248

Schwarzsee is located in the western Swiss Alps, in a region that has been affected by numerous landslides during the Holocene, as evidenced by geological surveys. Lacustrine sediments were cored to a depth of 13 m. The vegetation history of the lake's catchment was reconstructed and investigated to identify possible impacts on slope stability. The pollen analyses record development of forest cover during the middle and late Holocene, and provide strong evidence for regional anthropogenic influence such as forest clearing and agricultural activity. Vegetation change is characterized by continuous landscape denudation that begins at ca. 4300 cal. yrs BP, with five distinct pulses of increased deforestation, at 3650, 2700, 1500, 900, and 450 cal. yrs BP. Each pulse can be attributed to increased human impact, recorded by the appearance or increase of specific anthropogenic indicator plant taxa. These periods of intensified deforestation also appear to be correlated with increased landslide activity in the lake's catchment and increased turbidite frequency in the sediment record. Therefore, this study gives new evidence for a strong influence of vegetation changes on slope stability during the middle and late Holocene in the western Swiss Alps, and may be used as a case study for anthropogenically induced landslide activity.  相似文献   

Influence of combined changes in salinity and copper modulation on growth and copper uptake in the tropical green macroalga Ulva reticulata     

Florence Mamboya  Thomas J. Lyimo  Tommy Landberg  Mats Bjrk 《Estuarine, Coastal and Shelf Science》2009,84(3):326-330

The influence of salinity on growth and Cu uptake in the green macroalga Ulva reticulata collected from the intertidal area in the Western Indian Ocean was studied under controlled laboratory conditions. Exposure concentrations ranged from 5 to 500 μg Cu l⁻¹ at five salinities (ranging 20–40). The accumulation of Cu increased with decreasing salinity, so that the uptake at 500 μg Cu l⁻¹ was approximately 2.7, 2.4 and 2.0 times higher at salinities of 20, 25, and 30 respectively, than uptake at salinity of 35, and with uptake being lowest at salinity of 40. Ulva maintained a positive growth rate over the whole salinity range (20–40), with highest rates at salinity of 35. When exposing to Cu at low salinities (20 and 25), the growth rate of Ulva was strongly inhibited suggesting an increase in toxicity of Cu with decreasing salinity. EC50 and NOEC increased with increase in salinity, implying a reduced Cu toxicity at high salinities. It was concluded that salinity needs to be considered when using macroalgae, such as U. reticulata, as a bioindicator of heavy metals in areas with heavy rainfall, underground fresh water intrusion or in estuaries, as they might accumulate more metals and be more negatively affected.  相似文献