Characterization of a new lectin involved in the protoplast regeneration of <Emphasis Type="Italic">Bryopsis hypnoides</Emphasis>     

牛建峰  王广策  吕芳  周百成  彭光 《中国海洋湖沼学报》2009,27(3):502-512

A group of coenocytic marine algae differs from higher plants,whose totipotency depends on an intact cell(or protoplast).Instead,this alga is able to aggregate its extruded protoplasm in sea water and generate new mature individuals.It is thought that lectins play a key role in the aggregation process.We purified a lectin associated with the aggregation of cell organelles in Bryopsis hypnoides.The lectin was ca.27 kDa with a pI between pH 5 and pH 6.The absence of carbohydrate suggested that the lectin was ...  相似文献   

A numerical method for the study of shear band propagation in soft rocks     

Marta Castelli  Andrea Allodi  Claudio Scavia 《国际地质力学数值与分析法杂志》2009,33(13):1561-1587

This paper investigates the possibility of interpreting progressive shear failure in hard soils and soft rocks as the result of shear propagation of a pre‐existing natural defect. This is done through the application of the principles of fracture mechanics, a slip‐weakening model (SWM) being used to simulate the non‐linear zone at the tips of the discontinuity. A numerical implementation of the SWM in a computation method based on the boundary element technique of the displacement discontinuity method (DDM) is presented. The crack and the non‐linear zone at the advancing tip are represented through a set of elements, where the displacement discontinuity (DD) in the tangential direction is determined on the basis of a friction law. A residual friction angle is assumed on the crack elements. Shear resistance decreases on elements in the non‐linear zone from a peak value at the tip, which is characteristic of intact material, to the residual value. The simulation of a uniaxial compressive test in plane strain conditions is carried out to exemplify the numerical methodology. The results emphasize the role played by the critical DD on the mechanical behaviour of the specimen. A validation of the model is shown through the back analysis of some experimental observations. The results of this back analysis show that a non‐linear fracture mechanics approach seems very promising to simulate experimental results, in particular with regards to the shear band evolution pattern. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Coupled surface water–groundwater model and its application in the arid Shiyang River basin,China     

Li‐Tang Hu  Zhong‐Jing Wang  Wei Tian  Jian‐Shi Zhao 《水文研究》2009,23(14):2033-2044

The planning and management of water resources in the Shiyang River basin, China require a tool for assessing the impact of groundwater and stream use on water supply reliabilities and improving many environment‐related problems such as soil desertification induced by recent water‐related human activities. A coupled model, integrating rule‐based lumped surface water model and distributed three‐dimensional groundwater flow model, has been established to investigate surface water and groundwater management scenarios that may be designed to restore the deteriorated ecological environment of the downstream portion of the Shiyang River basin. More than 66% of the water level among 24 observation wells have simulation error less than 1·0 m. The overall trend of the temporal changes of simulated and observed surface runoff at the Caiqi gauging station remains almost the same. The calibration was considered satisfactory. Initial frameworks for water allocation, including agricultural water‐saving projects, water diversion within the basin and inter‐basin water transfer, reducing agricultural irrigation area and surface water use instead of groundwater exploitation at the downstream were figured out that would provide a rational use of water resources throughout the whole basin. Sixteen scenarios were modelled to find out the most appropriate management strategies. The results showed that in the two selected management options, the groundwater budget at the Minqin basin was about 1·4 × 10⁸ m³/a and the ecological environment would be improved significantly, but the deficit existed at the Wuwei basin and the number was about 0·8 × 10⁸ m³/a. Water demand for domestic, industry and urban green area would be met in the next 30 years, but the water shortage for meeting the demand of agricultural water use in the Shiyang River basin was about 2·2 × 10⁸ m³/a. It is suggested that more inter‐basin water transfer should be required to obtain sustainable water resource use in the Shiyang River basin. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Implementation of the European Water Framework Directive: Natural variability associated with the CARLIT method on the rocky shores of the Ligurian Sea (Italy)     

Valentina Asnaghi  Mariachiara Chiantore  Rosa‐Maria Bertolotto  Valeriano Parravicini  Riccardo Cattaneo‐Vietti  Federico Gaino  Paolo Moretto  Davide Privitera  Luisa Mangialajo 《Marine Ecology》2009,30(4):505-513

The Water Framework Directive (WFD) 2000/60/EC, adopted by the European Community in 2000 with the goal of maintaining and improving the aquatic environments, requires that member states achieve and maintain a good ecological status of all water bodies by 2015. In the marine context, the ecological status has to be quantified applying indexes based on appropriate key biological elements, which allow the categorization of water bodies into five Ecological Status (ES) classes. The CARLIT index is a cartographic monitoring tool enabling the Ecological Quality Ratio (EQR) to be calculated using macroalgae in coastal hard bottoms as a key biological element; at present it is being applied in Spain, France and Italy. To detect actual changes of water quality and, consequently, rely on the application of indexes for the assessment of the ecological status in the marine environment, it is necessary to evaluate their sensitivity to natural variability at different temporal and spatial scales. In this study we present a first quantification of natural (spatial and temporal) variability of EQR‐CARLIT quality assessment in 2006 and 2007 along the Ligurian coast (North‐Western Mediterranean, Italy). The EQR‐CARLIT values recorded along the Ligurian coastline show that natural variability of EQR‐CARLIT is low and that it does not affect the attribution of a given stretch of coast to a particular ES class, in agreement with the major human pressures acting in the area (urbanization, river load, sea‐farming). A small‐scale variability was detected, strengthening the use of cartography of the whole rocky shore, whenever possible, or, alternatively, the assessment of the ecological status for long stretches of coast, to encompass the small‐scale variability due to local factors.  相似文献   

Difficulties in separating hurricane induced effects from natural benthic succession: Hurricane Isabel,a case study from Eastern Virginia,USA     

C. Hughes  C.A. Richardson  M. Luckenbach  R. Seed 《Estuarine, Coastal and Shelf Science》2009

Hurricane Isabel reached the Eastern seaboard of North America on 18 September 2003 causing estimated damage >3 billion US dollars and the death of ∼50 people. Isabel is considered to be one of the most significant tropical cyclones to affect Virginia, since the Chesapeake Potomac Hurricane of 1933 and Hurricane Hazel in 1954. A study of the temporal changes in the benthic fauna pre- and post-hurricane was conducted on an intertidal sandflat within the dynamic barrier island system near Wachapreague, Eastern Virginia. Replicate sediment cores were collected 3 weeks before Isabel made landfall and further samples were collected on 5 occasions over the following 20 months. An immediate effect of Isabel was a doubling in the number of species, a significant increase in invertebrate species diversity (H′) and a rise in opportunistic species and deposit feeders, but a non-significant increase in the total number of organisms. Changes in infauna occurred such that by the end of the study there were significantly increased numbers of species, faunal abundances and community diversity measures, as compared with pre-hurricane samples, suggesting a potentially positive medium-term effect of this hurricane perturbation. The most notable direct effects of the hurricane were on the relative abundances of feeding guilds with a reduction in interface feeders from 87% pre-hurricane to 64% post-hurricane, and an increase in surface deposit feeders from 7% pre-hurricane to 20% post-hurricane. The study highlights potential problems in interpreting post-perturbation data when insufficient pre-perturbation data exist.  相似文献   

Benthic nitrate biogeochemistry affected by tidal modulation of Submarine Groundwater Discharge (SGD) through a sandy beach face, Ria Formosa, Southwestern Iberia     

C. Rocha  J. Ibanhez  C. Leote   《Marine Chemistry》2009,115(1-2):43-58

To investigate both the role of tides on the timing and magnitude of Submarine Groundwater Discharge (SGD), and the effect on benthic nitrogen biogeochemistry of nitrate-enriched brackish water percolating upwards at the seepage face, we conducted a study of SGD rates measured simultaneously with seepage meters and mini-piezometers, combined with sets (n = 39) of high resolution in-situ porewater profiles describing NH₄⁺, NO₃⁻, Si(OH)₄ and salinity distribution with depth (0–20 cm). Sampling took place during two consecutive spring tidal cycles in four different months (November 2005, March, April and August 2006) at a backbarrier beach face in the Ria Formosa lagoon, southern Portugal. Our results show that the tide is one of the major agents controlling the timing and magnitude of SGD into the Ria Formosa. Intermittent pumping of brackish, nitrate-bearing water at the beach face through surface sediments changed both the magnitudes and depth distributions of porewater NH₄⁺ and NO₃⁻ concentrations. The most significant changes in nitrate and ammonium concentrations were observed in near-surface sediment horizons coinciding with increased fraction of N in benthic organic matter, as shown by the organic C:N ratio. On the basis of mass balance calculations executed on available benthic profiles, providing ratios of net Ammonium Production Rate (APR) to Nitrate Reduction Rate (NRR), coupled to stoichiometric calculations based on the composition of organic matter, potential pathways of nitrogen transformation were speculated upon. Although the seepage face occasionally contributes to reduce the groundwater-borne DIN loading of the lagoon, mass balance analysis suggests that a relatively high proportion of the SGD-borne nitrogen flowing into the lagoon may be enhanced by nitrification at the shallow (1–3 cm) subsurface and modulated by dissimilatory nitrate reduction to ammonium (DNRA).  相似文献   

Variations of Kuroshio geostrophic transport south of Japan estimated from long-term IES observations     

Koji Kakinoki  Shiro Imawaki  Hiroshi Uchida  Hirohiko Nakamura  Kaoru Ichikawa  Shin-Ichiro Umatani  Ayako Nishina  Hiroshi Ichikawa  Mark Wimbush 《Journal of Oceanography》2008,64(3):373-384

Two inverted echo sounders were maintained on coastal and offshore sides of the Kuroshio south of Japan from October 1993 to July 2004. Applying the gravest empirical mode method, we obtained a time series of geostrophic transport. Estimated transports generally agree well with geostrophic transports estimated from hydrography. Their agreement with the hydrographic transports is better than that of transports estimated from satellite altimetry data. The geostrophic transport is expressed as the surface transport per unit depth multiplied by the equivalent depth. The geostrophic transport varies mostly with the surface transport and fractionally with the equivalent depth. Seasonal variation of the geostrophic transport has a minimum in March and a maximum in September, with a range of about one fifth of the total transport.  相似文献   

Sulfide and iron control on mercury speciation in anoxic estuarine sediment slurries   总被引：2，自引：0，他引：2  

Seunghee Han  Anna Obraztsova  Patrizia Pretto  Dimitri D. Deheyn  Joris Gieskes  Bradley M. Tebo   《Marine Chemistry》2008,111(3-4):214-220

In order to understand the role of sulfate and Fe(III) reduction processes in the net production of monomethylmercury (MMHg), we amended anoxic sediment slurries collected from the Venice Lagoon, Italy, with inorganic Hg and either potential electron acceptors or metabolic byproducts of sulfate and Fe(III) reduction processes, gradually changing their concentrations. Addition of sulfide (final concentration: 0.2–6.3 mM) resulted in an exponential decrease in the sulfate reduction rate and MMHg concentration with increasing concentrations of sulfide. Based on this result, we argue that the concentration of dissolved sulfide is a critical factor controlling the sulfate reduction rate, and in turn, the net MMHg production at steady state. Addition of either Fe(II) (added concentration: 0–6.1 mM) or Fe(III) (added concentration: 0–3.5 mM) resulted in similar trends in the MMHg concentration, an increase with low levels of Fe additions and a subsequent decrease with high levels of Fe additions. The limited availability of dissolved Hg, associated with sulfide removal by precipitation of FeS, appears to inhibit the net MMHg production in high levels of Fe additions. There was a noticeable reduction in the net MMHg production in Fe(III)-amended slurries as compared to Fe(II)-amended ones, which could be caused by a decrease in the sulfate reduction rate. This agrees with the results of Hg methylation assays using the enrichment cultures of anaerobic bacteria: whereas the enrichment cultures of sulfate reducers showed significant production of MMHg (4.6% of amended Hg), those of Fe(III), Mn(IV), and nitrate reducers showed no production of MMHg. It appears that enhanced Fe(III)-reduction activities suppress the formation of MMHg in high sulfate estuarine sediments.  相似文献   

Analysis of threshold and incipient conditions for sediment movement     

A.A. Beheshti  B. Ataie-Ashtiani 《Coastal Engineering》2008

Prediction of threshold conditions and incipient motion is the essential issue for the study of sediment transport. This work compares existing empirical threshold curves proposed for Shields diagram, a method based on the concept of probability of sediment movement, and an empirical method based on movability number. These methods are used to predict the incipient motion conditions for experimental runs taken from various studies. Most of the experimental data, used in this work, have not been used before in derivation of alternative formulations for Shields diagram and other methods. The empirical threshold curves based on the Shields entrainment function was the least successful at predicting the measured incipient motion conditions, while the use of the movability number gives good predictions of critical shear velocity compared with experimental data.  相似文献   

Evaluation of ENVISAT ASAR data for sea surface wind retrieval in Hong Kong coastal waters of China   总被引：2，自引：1，他引：1  

XU Qing  LIN Hui  ZHENG Quanan  XIU Peng  CHENG Yongcun  LIU Yuguang 《海洋学报(英文版)》2008,27(4):57-62

The C-band wind speed retrieval models, CMOD4, CMOD - IFR2, and CMOD5 were applied to retrieval of sea surface wind speeds from ENVISAT （European environmental satellite） ASAR （advanced synthetic aperture radar） data in the coastal waters near Hong Kong during a period from October 2005 to July 2007. The retrieved wind speeds are evaluated by comparing with buoy measurements and the QuikSCAT （quick scatterometer） wind products. The results show that the CMOD4 model gives the best performance at wind speeds lower than 15 m/s. The correlation coefficients with buoy and QuikSCAT winds are 0.781 and 0.896, respectively. The root mean square errors are the same 1.74 m/s. Namely, the CMOD4 model is the best one for sea surface wind speed retrieval from ASAR data in the coastal waters near Hong Kong.  相似文献