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Juan J. Muñoz-Perez Jorge Roman-Sierra Marina Navarro-Pons Maria da Graça Neves Jose M. del Campo 《Geo-Marine Letters》2014,34(1):75-78
This Discussion provides comments on the application of grain-size trend analysis to Camposoto beach (SW Spain) reported by Poizot et al. (2013) in Geo-Marine Letters 33(4):263–272. Some of their results are updated or complemented by existing data from other studies carried out on Camposoto and other nearby beaches. For example, a detailed breakdown of beach nourishment volumes and costs is presented, and the influence of a horizontal reef flat on the tilting of the beach profile around the mean or the low water level is highlighted. Moreover, data from the displacement of dyed samples are used to evaluate the relationship between sediment transport speed (va) and current speed (V), the corresponding ratio being consistent with the range of values reported by several other authors. Finally, some minor, although still significant, differences are detected in some granulometric parameters as well as in the profile shape. Determining the reason for these discrepancies could enhance our current knowledge about the factors controlling short-term beach profile responses. 相似文献
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《Marine Policy》2014
This paper comments and discusses the article ‘Evaluating the influence of candidate terrestrial protected areas on coral reef condition in Fiji׳ by Klein et al. in Marine Policy 44 2014. Klein et al. integrate land-sea planning by optimising the design of Fiji׳s expanded protected area network to benefit coral reefs, while maintaining a terrestrial network that is representative of Fiji׳s various terrestrial ecosystems. They discuss the benefits of various spatial conservation models compared to a candidate protected area network proposed by Fiji׳s Protected Area Committee (FPAC), which is based on expert knowledge and a scoring system. This paper argues that their analyses are best interpreted as the FPAC network outperforming the models proposed by Klein et al. in protecting terrestrial biodiversity. The FPAC network performs better because it includes data that was not available for spatial modelling, especially the percentage of endemic species per ecosystem and the practicalities of protecting an area earmarked for conservation. This suggests that expert knowledge can be an important resource for conservation planning, especially in developing countries, and that spatial conservation planning should harness this knowledge. 相似文献
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Ocean Science Journal - St. Martin’s Island is a small sedimentary island situated at the southernmost part of Bangladesh (20°37.6′ N and 92°19.3′ E). The island is... 相似文献
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Confirmation of beach accretion by grain-size trend analysis: Camposoto beach, Cádiz, SW Spain 总被引：4，自引：4，他引：0
An application of the grain size trend analysis (GSTA) is used in an exploratory approach to characterize sediment transport on Camposoto beach (Cádiz, SW Spain). In May 2009 the mesotidal beach showed a well-developed swash bar on the upper foreshore, which was associated with fair-weather conditions prevailing just before and during the field survey. The results were tested by means of an autocorrelation statistical test (index I of Moran). Two sedimentological trends were recognized, i.e. development towards finer, better sorted and more negatively skewed sediment (FB–), and towards finer, better sorted and less negatively or more positively skewed sediment (FB+). Both vector fields were compared with results obtained from more classical approaches (sand tracers, microtopography and current measurements). This revealed that both trends can be considered as realistic, the FB+ trend being identified for the first time in a beach environment. The data demonstrate that, on the well-developed swash bar, sediment transported onshore becomes both finer and better sorted towards the coast. On the lower foreshore, which exhibits a steeper slope produced by breaking waves, the higher-energy processes winnow out finer particles and thereby produce negatively skewed grain-size distributions. The upper foreshore, which has a flatter and smoother slope, is controlled by lower-energy swash-backwash and overwash processes. As a result, the skewness of the grain-size distributions evolves towards less negative or more positive values. The skewness parameter appears to be distributed as a function of the beach slope and, thus, reflects variations in hydrodynamic energy. This has novel implications for coastal management. Figure
GSTA model for Camposoto Beach, Cádiz, with FB– (finer, better sorted, more negatively skewed) and FB+ (finer, better sorted, less negatively/more positively skewed) textural trends dominating the lower and upper foreshore respectively 相似文献
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中国真丝藻属Eudesme J.AG. (Chordariales, Phaeophyta)的研究 总被引：1，自引：0，他引：1
真丝藻属Eudesme是J.Agandh于1880年(J.Agardh 1880，p.29)建立的。其主要特征为：次生基部由直立初生中央轴及假根状丝体组成；初生中央轴由几个丝体束构成；假根状丝体则由中央丝体的基部产生；中央轴多管状，合轴分枝，由纵向排列的丝体组成，排列比较疏松；内皮层细胞从中央轴横向长出，稍网状排列；同化丝由内皮层末端细胞产生，不分枝，有密集的载色体；毛透明，从生长点或皮层丝体的基部产生；单室孢子囊无柄或在皮层丝体上有柄。
中国真丝藻，仅Lu Baoren和C.K. Tseng(1983)在“Common Seaweeds of China”中对Eudesme virescens(Cam.)J.Ag.作过描述外，未见其他更详细的报道。经过最近几年本文作者的研究发现中国真丝藻共有4种，除了Eudesme virescens(Cam.)J.Ag.外，另外还有黄海真丝藻Eudesme huanghaiensis Ding et Lu、青岛真丝藻 Eudesme qingdaoensis Ding et Lu和山东真丝藻Eudesme shandongensis Ding et Lu3种。 相似文献
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The northern Bay of Bengal velocity-depth profiles do not follow the velocity-depth curve for the North Atlantic volcanic margins, and only partially the Kerguelen plume velocity-depth curves. Compared with the South China Sea northern margin proxy, we still suggest that the Bay of Bengal crust is thinned continental crust intruded by post-rifting volcanics, as also shown by the interpretation of the numerous high-quality deep multichannel seismic profiles we collected there. What was supposed to be underplating might be sills intruded through the lower thinned continental crust. 相似文献
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There is increasing evidence that quartz cementation can be viewed as a process controlled by temperature and insensitive to effective stress. This view of quartz cementation in sandstones is often referred to as the illite-mica induced dissolution model (IMID), which assumes quartz dissolution to occur along stylolites and clay laminae rather than at quartz-quartz grain contacts. In the present comment it is argued that the exceptional reservoir quality in the Skagerrak Formation of the Heron Cluster, North Sea, is due to grain coatings and rapid Cenozoic burial limiting the exposure to quartz cementation. This line of reasoning implies overpressure has had neglectable porosity preserving effect in the Heron Cluster. 相似文献
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The increasing usage of sandy beaches as recreational resources has forced regional authorities of many tourist countries to remove all litter of fabricated origin and natural wrack from the beach. Consequently, a variety of heavy equipment has been developed during the last decades and is now used almost daily at many beaches. A field experiment, following a 'before-after-control-impact' (BACI) design, was conducted at the strandline of De Panne (Belgium) to investigate the impacts of mechanical beach cleaning on the strandline-associated meiofaunal assemblages, focussing on the free-living nematodes. Natural strandline assemblages were exposed to a one-off 5 cm deep mechanical beach cleaning and observed for 24 h. Differences between cleaned plots and those from control plots in terms of decreased percentage of organic matter, decreased total abundance and changed community structure were noticed from immediately after the experimental cleaning onwards and recovered to initial values after the following high water. Any impacts due to cleaning on species richness, Pielou's evenness and taxonomic diversity were shown to be minor in relation to the daily changes. Recolonization in the cleaned sediments is assumed to occur from the underlying sediments initiated by the elevated water table during the rising tide. 相似文献
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The 4.5 km-long gravel beach fronting the exclusive resort of the city of Nice, on the French Riviera, in southeastern France, was artificially nourished from 1976 to 2005 to the tune of 558,000 m3, making this long-term operation one of the most significant for gravel beaches in the world. Nourishment has ranged from nil in certain years (1979, 1980, 1983–85, and 2001–2002) to a peak of over 97,000 m3 in 2000. Analyses of 50 transects covering the beach highlight no significant change in net beach width over this 30-year period of massive gravel nourishment. A Principal Components Analysis and a Cluster Analysis used to detect patterns in the 87 beach-width measurement dataset show no clear spatial trends in transect groups that can be interpreted in terms of the morphology of the beach and the steep inner shoreface. Significant wave height off Nice shows no change over the period 1979–2005. Since there is no possibility for alongshore gravel leakage on the strongly embayed Nice beach, the relative stability in beach width clearly implies loss of recharged gravel offshore. Gravel loss following nourishment is favoured by: (1) the steep inner shoreface inherited from the geological context of Nice beach at the flanks of the southern Alps, and (2) the practise of artificial beach widening through flattening, in summer, of a narrow (5–15 m-wide) mobile zone of the profile in order to enhance the ‘carrying’ capacity of this highly touristic beach. Beach widening and flattening following nourishment bring close to the very steep inner shoreface zone several cubic metres of gravel for each metre of beach that may be permanently lost downslope during autumn and winter storms. Recharged gravel is redistributed alongshore and offshore leakage is probably enhanced where small narrow submarine canyon heads impinge on the beach, resulting in a very narrow shoreface. Mean beach width shows an oscillating alongshore pattern that may be due to the influence of these canyons as pathways of gravel loss offshore. However, there is no correlation between mean beach width and distance to the 10-m isobath, used as a surrogate for inner shoreface width. Storms are associated with plunging waves that are particularly effective and concentrated, on this almost tideless shore, over the narrow mobile zone of the beach profile where a series of steep reflective berms are built during storms. The high dynamic pressures associated with this narrow zone of concentrated wave breaking, and energy reflection from the steepened profile, are deemed to contribute to the permanent downslope loss of gravel. This situation of long-term gravel loss is probably accepted by the beach management authority because of the low cost of obtaining nourishment material and the advantages derived from a temporarily wider beach in terms of recreational space. 相似文献
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The macroalga Caulerpa prolifera colonized the Mar Menor coastal lagoon after the enlargement of the main inlet in 1972, coexisting now with the previous Cymodocea nodosa meadows. The physiological response and the photoacclimation capacity of both species were studied. For this purpose in vivo chlorophyll a fluorescence, photoprotective mechanisms and oxidative stress were measured in both species in summer 2010 and exposure-recovery experiments were conducted to determine the acclimation capacity of both species. The results suggest that C. prolifera behaves as a shade-adapted species with a low photoprotective capacity, light being one of the main factors governing its distribution in the lagoon. The high photosynthetic capacity and lack of photoinhibition found in C. nodosa suggest that this species is highly photoprotected. It also possesses a high concentration of lutein and a high de-epoxidation degree, related to a much higher NPQmax value. 相似文献
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The identification of potential coastal inundation caused by future sea level rise requires not only time series records from tide gauges, but also high-quality digital elevation models (DEMs). This study assesses the importance of DEM vertical accuracy in predicting inundation by sea level rise along the Valdelagrana beach and marshes of the Bay of Cádiz (SW Spain). A present-day (2000) and a projected (2100) high tide have been spatialized over a traditional (aerial photogrammetry) regional DEM of Andalusia with a horizontal spatial resolution of 10 m and a vertical accuracy of 0.68 m RMSE (root mean square error), and a LIDAR-derived DEM of the Valdelagrana study site with the same spatial resolution but a vertical accuracy of 0.205 m RMSE. The simulations are based on a bathtub model, which accounts for the effect of vertical barriers. The results reveal that the presence of infrastructures such as roads and salterns is the key to delimit the extent of water penetration during high tides in an otherwise homogeneously flat area comprising the beach and marshes of Valdelagrana. Moreover, in comparison with the highly accurate LIDAR DEM, the inundation areas derived from the lower-resolution DEM are overestimated by 72 % and 26 % for the present-day and future scenarios respectively. These findings demonstrate that DEM vertical accuracy is a critical variable in meaningfully gauging the impacts of sea level rise. 相似文献
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