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111.
Mélina C.Z. Laurent Olivier Gros Jean-Pierre Brulport Françoise Gaill Nadine Le Bris 《Marine environmental research》2009,67(2):83-88
Large organic falls to the benthic environment, such as dead wood or whale bones, harbour organisms relying on sulfide-oxidizing symbionts. Nothing is known however, concerning sulfide enrichment at the wood surface and its relation to wood colonization by sulfide-oxidizing symbiotic organisms.In this study we combined in situ hydrogen sulfide and pH measurements on sunken wood, with associated fauna microscopy analyses in a tropical mangrove swamp. This shallow environment is known to harbour thiotrophic symbioses and is also abundantly supplied with sunken wood. A significant sulfide enrichment at the wood surface was revealed. A 72 h sequence of measurements emphasized the wide fluctuation of sulfide levels (0.1–>100 μM) over time with both a tidal influence and rapid fluctuations. Protozoans observed on the wood surface were similar to Zoothamnium niveum and to vorticellids. Our SEM observations revealed their association with ectosymbiotic bacteria, which are likely to be sulfide-oxidizers. These results support the idea that sunken wood surfaces constitute an environment suitable for sulfide-oxidizing symbioses. 相似文献
112.
Jeremy Hills Margaret Carlisle Martin Le Tissier David Muir Caroline Robinson 《Marine Policy》2009,33(6):887
Management of the coastal zone often focuses on “islands” of high value ecosystems, in terms of economic value or conservation. However, integrated management requires landscape-level analysis of all ecosystem values. The biodiversity portfolio analysis (BPA) method is derived from the logic used in share (equity) portfolio management in terms of balancing within a portfolio the returns with the risks. Optimising the returns from a share portfolio, or a suite of ecosystems in a landscape, is dependent on the relationship between the units in terms of risk and return. Three case studies are then presented to test the applicability of the BPA method at the international (North West Europe), regional (Durham Heritage Coast, UK) and local (part of South Uist, Outer Hebrides, UK) spatial scale. The Biodiversity Portfolio Analysis for NW Europe showed that risk and return were highly correlated in the studied Member States. The ranking of risk and return, with the highest first, was Ireland > UK > France=Netherlands > Belgium. For these Member States the risks to ecosystem service provision were positively correlated with GNI (r=0.97, P<0.01); suggesting that the higher the economic importance of coastal and marine resources in a Member State the more at risk the resources are. The regional and local case studies were more focussed on providing information on which to base Integrated Coastal Zone Management (ICZM) decision making; both case studies used stakeholder participation to determine risks and returns. The conclusions from these two case studies show how the BPA method can be useful in terms of setting ICZM priorities and in addressing local coastal issues. The BPA involves making a number of assumptions, however, it does provide coastal managers with a potential tool to strategically plan due to increased awareness of the interaction between the ecosystems in the portfolio.There is a need for such techniques, which involve stakeholder participation and which create objective outcomes, to support the implementation of ICZM. 相似文献
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For any specific wind speed, waves grow in period, height and length as a function of the wind duration and fetch until maximum values are reached, at which point the waves are considered to be fully developed. Although equations and nomograms exist to predict the parameters of developing waves for shorter fetch or duration conditions at different wind speeds, these either do not incorporate important variables such as the air and water temperature, or do not consider the combined effect of fetch and duration. Here, the wind conditions required for a fully developed sea are calculated from maximum wave heights as determined from the wind speed, together with a published growth law based on the friction velocity. This allows the parameters of developing waves to be estimated for any combination of wind velocity, fetch and duration, while also taking account of atmospheric conditions and water properties. 相似文献
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The method of Wang [Wang, Y.-H., 2007. Formula for predicting bedload transport rate in oscillatory sheet flow. Coastal Engineering 54, 594–601] to predict the wave friction factor is discussed. At the threshold of sediment entrainment the proposed equation produces a wide scatter of data points when plotted against an equation based on the Shields parameter. It is shown that a better correlation coefficient can be obtained by calculating the critical wave friction factor directly from the wave period, as well as the sediment and water properties. 相似文献
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A three‐dimensional phenomenological model is developed to describe the long‐term creep of gypsum rock materials. The approach is based on the framework of continuum damage mechanics where coupling with viscoelasticity is adopted. Specifically, a local damage model based on the concept of yield surface is proposed and deeply investigated. Among the many possibilities, we choose in this work its coupling with a generalized Kelvin–Voigt rheological model to formulate the whole behavior. Long‐term as well as short‐term relaxation processes can be integrated in the model by means of as many as necessary viscoelastic processes. The numerical discretization is described for an easy integration within a finite element procedure. Finally, a set of numerical simulations is given to show the possibilities of the presented model. It shows good agreement with some experimental results found in the literature. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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To determine the genetic structure of the bay anchovy (Anchoa mitchilli) within Chesapeake Bay, 16 isozyme systems encoding 21 loci for 20 population were examined using horizontal starch gel electrophoresis. Contingency Chisquare analysis revealed significant allelic frequency differences at nine loci (AAT-1, AAT-2, ALD-1, CPK-2, GAP-1, GLY-1, LDH-1, MDH-1, and MDH-2). Two loci, ALD-1 and MDH-1, were responsible for nine of 14 tests not conforming to Hardy-Weinberg expectations, with some of these deviations attributed to possible scoring and/or sampling error. Estimates for mean average heterozygosity were relatively high, ranging from 0.40 to 0.096, with 33–57% of the loci polymorphic. A low Fst value (0.041) along with high genetic identity estimates (I=0.997) indicated little substructuring of bay anchovy populations within Chesapeake Bay. 相似文献