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1.
Coastal wetlands provide important ecological services to the coastal zone, one of which is sediment retention. In this study we investigated sediment retention across a range of geomorphological settings and across vegetation zones comprising coastal wetlands. We selected six coastal wetlands dominated by mangroves over a gradient from riverine to tidal settings in Southeast Queensland, Australia. Each site was comprised of three distinct vegetation communities distributed as parallel zones to the coast line: seaward fringe mangroves, landward scrub mangroves and saltmarsh/ cyanobacteria mat of the high intertidal zone. We measured suspended sediment retention and sedimentation rates. Additionally, in order to assess the origin of sediment transported and deposited in the mangroves, glomalin, a novel terrestrial soil carbon tracer, was used. Our results show a mean average sedimentation of 0.64 ± 0.01 mg cm−2 spring tide−1, which was variable within sites, regardless of geomorphological setting. However, geomorphological setting influenced spatial patterns of sediment deposition. Riverine mangroves had a more homogeneous distribution of sediments across the intertidal zone than tidal mangroves, where most sedimentation occurred in the fringe zone. Overall, the fringe zone retained the majority of sediment entering the coastal wetland during a tidal cycle with 0.90 ± 0.22 mg cm−2 spring tide−1, accounting for 52.5 ± 12.5% of the total sedimentation. The presence of glomalin in suspended sediments, and thus the relative importance of terrigenous sediment, was strongly influenced by geomorphological setting, with riverine mangroves receiving more glomalin in suspended solids than tidal mangroves. Glomalin was also differentially deposited within the vegetation zones at different geomorphological settings: primarily at the fringe zone of tidal mangroves and within the scrub zone of riverine mangroves. The differences we observed in the spatial distribution of sedimentation and the difference in the origin of the sediment deposited in riverine and tidal mangroves are likely to have an impact on ecological processes.  相似文献   

2.
Measurements of methane (CH4) so far have always shown supersaturation in the entire North Sea relative to the atmospheric partial pressure and the distribution of surface CH4 reveals a distinct increase towards the shore. Since North Sea sediments presumably are an insignificant source for CH4 the coastal contribution via rivers and tidal flats gains in importance.In this work, CH4 data from the River Weser, the back barrier tidal flats of Spiekeroog Island (NW Germany), and the German Bight are presented. Results from the River Weser are compared to other rivers draining into the German Bight. Measurements in the tidal flat area of Spiekeroog Island highlight this ecosystem as an additional contributor to the overall CH4 budget of the southern North Sea. A tidally driven CH4 pattern is observed for the water column with maximum values during low tide. Tidal flat sediments turn out to be the dominating source because pore waters discharged during low tide are highly enriched in CH4. In contrast, the freshwater contribution to the tidal flats by small coastal tributaries has almost no impact on water column CH4 concentrations. The CH4 level seems to be disturbed irregularly by wind forcing due to elevated degassing and prevention of advective flow when tidal flats remain covered by water.Based on our data, two model calculations were used to estimate the impact of tidal flats on the CH4 budget in the German Bight. Our results demonstrate that the back barrier tidal flats of the east Frisian Wadden Sea contribute CH4 in an order of magnitude between the Wash estuary and River Elbe and thus have to be considered in budget calculations.  相似文献   

3.
内潮耗散与自吸-负荷潮对南海潮波影响的数值研究   总被引：1，自引：0，他引：1  
利用非结构三角形网格的FVCOM海洋数值模式,在其传统二维潮波方程中加入参数化的内潮耗散项和自吸-负荷潮项,计算了南海及其周边海域的M_2、S_2、K_1和O_1分潮的分布。与实测值的比较表明,引入这两项对模拟准确度的提高有明显效果。根据模式结果本文计算分析了研究海域的潮能输入和耗散。能量输入计算表明,能通量是潮能输入的最主要构成部分,通过吕宋海峡断面进入南海的M_2和K_1分潮能通量分别为38和29GW;半日周期的自吸-负荷潮能量输入以负值居多,而全日周期的自吸-负荷潮能量输入以正值居多,因而自吸-负荷潮减弱了南海的半日潮,并加强了南海的全日潮。引潮力的作用也减弱了半日潮而加强了全日潮,但其作用要小于自吸-负荷潮。潮能耗散的分析显示底摩擦耗散在沿岸浅水区域起主导作用,内潮耗散则主要发生在深水区域。内潮耗散的最大值出现在吕宋海峡,且位于南海之外的海峡东部的耗散量大于位于南海之内的海峡西部的耗散量。对M_2和K_1分潮吕宋海峡的内潮耗散总值分别达到16和23GW。  相似文献   

4.
Nutrient (C, N and P) fluxes were monitored in a microtidal semi-arid mangrove system, which links a semi-enclosed shallow coastal lagoon with the Gulf of California. We assessed the role of the mangrove ecosystem as a nutrient sink/source and determined how mangrove litterfall rates, tidal regime and climate factors influence these fluxes. Despite high seasonal differences in DOC, POC, N-NO3− and TP levels, nutrient concentrations were only marginally influenced by either hydrological variables or the concentration of these fractions in the adjacent lagoon. The carbon budget appeared to be balanced throughout the study. Retention rates in the mangrove system were related to litterfall rates. Export of DIN was observed mainly in the wet season due to the low nitrogen assimilation efficiency of the system. Import of organic nitrogen was related to the high retention efficiency of particulate organic nitrogen. Phosphorus fractions were imported and retained in the mangrove supporting previous findings that mangroves are phosphorus sinks. Finally, through a simple meta-analysis we tested the quantitative importance of main variables (tidal flow, tidal elevation, tidal range, rainfall, mangrove catchment area, litterfall) controlling mangrove nutrient dynamics. Although results suggest that generalizations can be made about factors regulating nutrient export from mangroves, the lack of statistical significance highlights the relative importance of the local environment for the magnitude of nutrient exchange in mangroves. Future research should focus on finding mechanistic models to explain these general patterns, taking into account the main biogeochemical processes and their roles in coastal ecosystem ecology.  相似文献   

5.
A change in the elevation of bare tidal flats outside a mangrove area is an indispensable factor for the sustainable development of mangroves. Waterline extraction, as an effective and economical tool used in reconstructing the terrain of an intertidal zone, has been widely applied to open-coast tidal flats by constructing a digital elevation model (DEM). However, mangrove wetlands are usually located in wave-sheltered sites, such as estuaries and bays that have narrow tidal channels flanked by tidal flats. Changes in water level are affected by the dry-wet processes of complex landforms caused by tides. This article takes as a study case the area of Yingluo Bay, which covers the core region of the Zhanjiang and Shankou National Mangrove National Nature Reserve in southwestern China. Waterline extraction based on seventeen multisource and multispectral satellite images obtained from December 2014 to April 2015, combining the finite-volume coastal ocean model (FVCOM) hydrodynamic model in an iterative process, was used to generate a topographical map of the bare tidal flat outside the mangrove area in Yingluo Bay. The quality of the iterative DEMs was evaluated via six transects of a ground-based survey using Real - time kinematic (RKT) GPS in May 2015. The mean absolute error (MAE) and root mean square error (RMSE) of the DEM decreased with an increase in the number of iterations. In this study, the DEM in the third iteration was used as the final output because the difference from the previous iterative DEM satisfied an inversion-stopping criterion. The MAE and RMSE of the final DEM with the measured data were 0.072 and 0.09?m, respectively, without considering small tidal creeks. The method used in this study can be an effective and highly precise approach for detecting and reconstructing the historical terrain of a bare tidal flat outside a mangrove area. This work also has great importance regarding intertidal resource management and the sustainable development of mangroves facing the vulnerable coastal ecological environment.  相似文献   

6.
The Arcachon lagoon is a 156 km2 temperate mesotidal lagoon dominated by tidal flats (66% of the surface area). The methane (CH4) sources, sinks and fluxes were estimated from water and pore water concentrations, from chamber flux measurements at the sediment–air (low tide), sediment–water and water–air (high tide) interfaces, and from potential oxidation and production rate measurements in sediments. CH4 concentrations in waters were maximal (500–1000 nmol l−1) in river waters and in tidal creeks at low tide, and minimal in the lagoon at high tide (<50 nmol l−1). The major CH4 sources are continental waters and the tidal pumping of sediment pore waters at low tide. Methanogenesis occurred in the tidal flat sediments, in which pore water concentrations were relatively high (2.5–8.0 μmol l−1). Nevertheless, the sediment was a minor CH4 source for the water column and the atmosphere because of a high degree of anaerobic and aerobic CH4 oxidation in sediments. Atmospheric CH4 fluxes at high and low tide were low compared to freshwater wetlands. Temperate tidal lagoons appear to be very minor contributor of CH4 to global atmosphere and to open ocean.  相似文献   

7.
象山港潮滩坡度对潮动力影响的数值研究   总被引：2，自引：0，他引：2  
象山港属于狭长型半封闭港湾,湾内分布有大面积潮滩。多年以来象山港内实施了大量海岸工程及养殖工程,湾内潮滩坡度发生了显著变化。基于非结构网格和有限体积数值模式（FVCOM）建立象山港三维潮动力模型,研究湾内不同区域潮滩坡度变化对象山港潮动力过程的影响机理。结果表明：潮滩坡度下降将增大湾内纳潮量,进而增大M2分潮振幅和迟角,反之则反。铁港潮滩坡度的减小（增大）,将改变底部耗散项,进而增大（减小）M4分潮振幅。由于M2和M4分潮的振幅在湾顶较大,所以湾顶（铁港）潮滩坡度对象山港潮动力过程的影响明显大于侧岸（西沪港）。西沪港潮滩坡度对象山港潮动力过程的影响是局部的。铁港、西沪港潮滩坡度对湾内潮汐不对称、余流及潮能影响显著。铁港潮滩坡度的改变均会减弱湾内落潮占优程度。西沪港区域潮滩坡度的减小将减弱湾内落潮占优趋势,反之则反。铁港和西沪港潮滩坡度的减小,将增大余流大小及潮能密度,进而潮能耗散增大,反之则反。研究结果对河口海岸潮滩区域的工程建设及生态修复有重要参考价值。  相似文献   

8.
Lagoa de Araruama in the state of Rio de Janeiro, Brazil, is a hypersaline coastal lagoon as a result of semi-arid climate conditions, a small drainage basin and a choked entrance channel. The lagoon has been continuously hypersaline for at least 4·5 centuries, but the mean salinity has varied substantially. It has recently decreased from 57 to 52 as indicated by density (salinity) measurements between 1965 and 1990.Analysis of more than 20 years of salinity time series data, in addition to monthly lagoon cruises to measure the spatial salinity distribution, indicate that the lagoon salinity largely fluctuates in response to the difference between evaporation and precipitation. The major factor explaining the long-term trend of decreasing salinity in the lagoon is the constant pumping of 1 m3s−1of freshwater to the communities surrounding the lagoon from an adjacent watershed, and subsequent discharge of this water into Lagoa de Araruama. The net salt budget is primarily a balance between the advective import of salt from the coastal ocean and eddy diffusive export of salt to the ocean, although the extensive mining of salt from the lagoon during past decades is also a small but significant contribution to the salt budget. The flushing half-life is proposed as a useful time scale of water exchange, is calculated based on a combination of hydrological and tidal processes, and is excellent for comparison of lagoons and assessing water quality changes. The flushing half-life measures 83·5 days for Lagoa de Araruama, considerably longer than for most other coastal lagoons. The proposed dredging of a second ocean channel to Lagoa de Araruama is probably not a good idea. It is likely to accelerate the decrease of lagoon salinity and somewhat improve the lagoon water exchange. At the same time, this will eliminate the apparent buffering capacity provided by the hypersaline environment, and thus may potentially cause water quality problems.  相似文献   

9.
互花米草及其对海岸的防护作用   总被引：28，自引：0，他引：28  
本文论述了互花米草在滩涂中种植的时间、种植的方法及其生长的适应性。文中着重讨论互花米草在海岸工程中防浪和消浪能力。与工程护岸比较，互花米草护岸是最经济、合理和有效的。通过本文的讨论为今后利用互花米草进行海岸防护提供依据  相似文献   

10.
根据广西海岸滩涂开发利用现状以及开发与保护需求,将滩涂资源分为已开发利用滩涂、规划开发利用滩涂、严格保护滩涂和潜在可开发利用滩涂4类,通过2016年遥感影像分析识别,广西海岸滩涂资源总面积为98 013hm2,其中已开发利用滩涂(渔业、旅游及所有建设用地)面积为25 211hm2,占滩涂总面积的25.72%;规划开发利用滩涂(港口、工业、城市规划)面积9 412hm2,占滩涂总面积的9.6%;严格保护滩涂(滩涂海洋生态红线区)面积23 538hm2,占滩涂总面积的24.02%。基于此,分析出潜在可开发利用滩涂共39 852hm2,占滩涂总面积的41%,并提出滩涂可持续开发利用建议。  相似文献   

11.
On the basis of the satellite maps of sea level anomaly(MSLA) data and in situ tidal gauge sea level data,correlation analysis and empirical mode decomposition(EMD) are employed to investigate the applicability of MSLA data,sea level correlation,long-term sea level variability(SLV) trend,sea level rise(SLR) rate and its geographic distribution in the South China Sea(SCS).The findings show that for Dongfang Station,Haikou Station,Shanwei Station and Zhapo Station,the minimum correlation coefficient between the closest MSLA grid point and tidal station is 0.61.This suggests that the satellite altimeter MSLA data are effective to observe the coastal SLV in the SCS.On the monthly scale,coastal SLV in the western and northern part of SCS are highly associated with coastal currents.On the seasonal scale,SLV of the coastal area in the western part of the SCS is still strongly influenced by the coastal current system in summer and winter.The Pacific change can affect the SCS mainly in winter rather than summer and the affected area mostly concentrated in the northeastern and eastern parts of the SCS.Overall,the average SLR in the SCS is 90.8 mm with a rising rate of(5.0±0.4) mm/a during1993–2010.The SLR rate from the southern Luzon Strait through the Huangyan Seamount area to the Xisha Islands area is higher than that of other areas of the SCS.  相似文献   

12.
Many shorebirds on their non-breeding grounds feed on macrobenthic fauna which become available at low tide in coastal intertidal flats. The Eastern Curlew Numenius madagascariensis in Moreton Bay Australia, varies greatly in density among different tidal flats. This study asks: how important is the abundance of intertidal prey as a predictor of this variation? We quantified feeding curlews’ diet across 12 sites (different tidal flats, each re-visited at least eight times), through 970 focal observations. We also estimated the abundance of total macrobenthic fauna, potential prey taxa and crustacean prey on each tidal flat; measured as the number of individuals and a relative biomass index per unit substrate surface area obtained from substrate core samples. We estimated curlew density at each site using low-tide surveys from every site visit.  相似文献   

13.
Silva et al. propose a new method for quantifying benthic net community production (NCP) of tidal flats under submerged condition, based on the monitoring of water pCO2 in a transparent benthic chamber around high tide. I demonstrate here with theoretical considerations that this method is inappropriate for coastal environments, because it allows only the quantification of the change in the dissolved CO2 which, at classical seawater pH, is only ∼10% of the change of the dissolved inorganic carbon (DIC). Total Alkalinity and/or DIC must be measured at the beginning and end of incubations in order to compute NCP in coastal environments. However, I also demonstrate that when pH is below 7, more than 95% of the DIC change occurs in the CO2 pool. The method proposed by Silva et al. is thus valuable for freshwater environments with acidic, low alkalinity waters, where monitoring the water pCO2 in a vial or chamber provides alone a very close approximation of the planktonic or benthic net community production.  相似文献   

14.
The mangrove Avicennia marina var. australasica occurs on the temperate coastlines of New Zealand's north island and New South Wales, Victoria and South Australia in South East Australia. Mangroves are increasing in area with seaward expansion in New Zealand and landward expansion in temperate Australia. Their expansion has been viewed as unnatural. With pressure from residential and coastal development, planning and management authorities in both countries are being exerted to allow for the removal and destruction of mangroves, partly for protecting and re-instating other impacted habitats such as saltmarsh and mudflats and partly to maintain recreational and amenity values of coastal communities. Estuary management planning is a useful tool that can integrate and balance policy directions for mangroves and other estuarine habitats in a strategic manner. Mangroves should not be considered as ‘bad’ in isolation but viewed as part of the mosaic of tidal habitats important for estuary function and health.  相似文献   

15.
随着卫星高度计资料的不断丰富,通过对卫星高度计所得潮汐调和常数进行插值或拟合得到潮汐同潮图成为可能。本文拟对T/P(TOPEX/POSEIDON)、Jason-1和Jason-2卫星高度计数据进行分析,得到南海区域星下观测点处四个主要分潮(M2、S2、K1和O1分潮)的调和常数,进而利用双调和样条插值方法对其进行插值,获取南海同潮图。首先,以1992～2016年T/P和Jason卫星高度计所得海面高度数据为基础,利用调和分析方法计算了南海星下观测点处M2、S2、K1和O1四个主要分潮的调和常数,并与40个验潮站数据进行了对比,最大矢量均差为4.99cm,说明分析所得调和常数与利用验潮站资料提取的调和常数的误差较小。进而采用双调和样条插值方法对星下点调和常数进行插值,得到了南海四个主要分潮的同潮图,所得结果与全球潮汐模型TPXO7.2模式结果的矢量均差分别为4.69、2.46、3.13和2.42 cm,与141个验潮站处观测结果的矢量均差分别为22.59、10.26、10.24和8.51 cm。此外,插值所得四个主要分潮的无潮点位置与前人研究结果相近。上述实验结果表明:利用双调和样条插值方法对卫星高度计所得调和常数进行插值能够获取较为准确的同潮图。  相似文献   

16.
We adopt a parameterized internal tide dissipation term to the two-dimensional (2-D) shallow water equations, and develop the corresponding adjoint model to investigate tidal dynamics in the South China Sea (SCS). The harmonic constants derived from 63 tidal gauge stations and 24 TOPEX/Poseidon (T/P) satellite altimeter crossover points are assimilated into the adjoint model to minimize the deviations of the simulated results and observations by optimizing the bottom friction coefficient and the internal tide dissipation coefficient. Tidal constituents M2, S2, K1 and O1 are simulated simultaneously. The numerical results (assimilating only tidal gauge data) agree well with T/P data showing that the model results are reliable. The co-tidal charts of M2, S2, K1 and O1 are obtained, which reflect the characteristics of tides in the SCS. The tidal energy flux is analyzed based on numerical results. The strongest tidal energy flux appears in the Luzon Strait (LS) for both semi-diurnal and diurnal tidal constituents. The analysis of tidal energy dissipation indicates that the bottom friction dissipation occurs mainly in shallow water area, meanwhile the internal tide dissipation is mainly concentrated in the LS and the deep basin of the SCS. The tidal energetics in the LS is examined showing that the tidal energy input closely balances the tidal energy dissipation.  相似文献   

17.
As coastal lagoons serve as nursery areas for some marine and estuarine fish, selective pressures of these brackish or hypersaline lagoons may influence the genetic structure of species and populations. We examined spatial and temporal genetic patterns at eight microsatellite loci in white seabream [Diplodus sargus (Linnaeus 1758)] recruits from the Mar Menor (Southeast Spain) and compared these loci with those in coastal populations from the open sea, observing a high degree of genetic diversity and spatio‐temporal genetic stability. However, the results suggest the presence of subpopulations or genetic substructures in the Mar Menor D. sargus population that could be interpreted as a homogeneous mixture of individuals from three differentiated subpopulations in the Mediterranean and evidence of the Wahlund effect. It also suggests that D. sargus adults return to their original spawning habitat, thus conserving the genetic differences among the respective populations over time. Overall, this study demonstrates the importance of the Mar Menor coastal lagoon as a nursery area for the conservation of genetic diversity of D. sargus populations.  相似文献   

18.
潮汐变化研究对于沿海地区海洋工程、洪涝灾害预防和海洋资源开发利用等各方面都有着非常重要的意义。之前的潮汐变化研究主要基于多年逐时验潮站观测,而验潮站数据无论是站点的个数还是站点的位置,都存在很大的局限性,这对我们研究海盆尺度的潮汐变化规律形成了一定程度的阻碍。前人基于25年的T/P-Jason卫星高度计数据发现南海中央深海海盆主要分潮振幅存在异常大的趋势,这是由于中尺度海洋运动对潮汐调和分析干扰导致的虚假结果。本文首次使用了X-TRACK软件处理过的长达27年的T/P-Jason卫星高度计观测来研究整个南海的主要分潮振幅的长期趋势。经过X-TRACK处理后的卫星观测数据在整个南海的准确性和完整性都有了显著的提升。同时,我们使用了权重最小二乘法来消除长周期采样导致的潮汐混淆的影响。我们发现在南海大部分海域,4大主要分潮的振幅都存在显著的变化趋势。振幅和迟角变化的极值主要分布在吕宋海峡西部、马六甲海峡和台湾海峡等水深和岸线变化剧烈的近海海域,振幅最大的上升趋势可达2.75 mm/a,振幅最大的下降趋势可达–2.16 mm/a。南海主要分潮振幅的长期趋势与河流径流以及人类活动密切相关。  相似文献   

19.
The study aims to compare the differences of macrofauna communities of wetlands at 3-year-forest- age, 5-year-forest-age Sonneratia apetala artificial mangroves, 5-year-forest-age Kandelia candel ar- tificial mangroves with the same restoration background, and the naked tidal flat in the Qi’ao Island Mangrove Nature Reserve of Zhuhai, Guangdong Province. The results show that there were signif- icant structural differences in macrofauna communities among four kinds of habitats. The increase of biomass and species diversity of macrofauna at 3-year-forest-age S. apetala artificial mangroves was obviously faster than that at 5-year-forest-age K. candel artificial mangroves whose average tree height was close to that of 3-year-forest-age S. apetala artificial mangroves. The BIOENV analysis shows that it was related to the rapid growth of S. apetala, which rapidly changed the light level and shading conditions in the forests. The 5-year-forest-age S. apetala artificial mangroves had lower macrofauna species diversity but higher density and biomass than K. candel artificial mangroves with the same forest age. This was due to the rapid changes of physical and chemical properties of habitat soil by the ecological restoration of S. apetala artificial mangroves as well as the changed food sources possibly caused by the leaf-litter of such non-indigenous mangrove species S. apetala. However, further survey should be conducted on whether there are any negative ecological impacts of large-scale cultivation of S. apetala on macrofauna communities, so as to evaluate correctly S. apetala’s role in the restoration of coastal mangrove ecosystems.  相似文献   

20.
汕头3种人工红树林湿地大型底栖动物群落的比较   总被引：1，自引：1，他引：0  
对广东省汕头市莲阳河口区恢复背景相同的拉关木(Laguncularia racemosa)、无瓣海桑(Sonneratia apetala)、海桑(Sonneratia caseolaris)3种人工林和光滩湿地中大型底栖动物群落进行比较研究。结果显示,4种生境中大型底栖动物优势种(Y0.02)存在差异;相似性分析检验(One-Way ANOSIM)表明4种生境间大型底栖动物群落结构差异显著。等级聚类和非参数多变量标序也显示4种生境间的大型底栖动物群落结构差异显著。3种人工林中,无瓣海桑、海桑人工林中大型底栖动物群落结构较为相似;3种人工林中大型底栖动物物种多样性和生物量从大到小的排列次序为:拉关木海桑无瓣海桑。BIOENV分析表明大型底栖动物分布与林地土壤p H、有机质、砂粒和粉粒含量、红树植物平均株高、平均胸径、平均基径和冠幅(南北×东西)这些理化因子显著相关,这进一步证实了红树植物种类对林地大型底栖动物多样性和分布的影响。  相似文献   

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