Effects of reef morphology variations on wave processes over fringing reefs     

《Applied Ocean Research》2019

Many low-lying tropical and sub-tropical atolls fringed by coral reefs are susceptible to coastal inundation during extreme wave events. Previous studies have shown that the infragravity (IG) wave is the dominant component of shoreline run-up compared to the sea and swell (SS) wave and the wave-induced setup. To better understand both the SS and IG wave dynamics over a fringing reef with various morphologies, a series of laboratory experiments were conducted in a wave flume based on an idealized fringing reef profile. The shoreline responses of waves to different reef morphologies with/without the reef crest, the lagoon and the reef surface roughness were examined. IG wave resonance on the reef flat was identified by a spectral analysis of the shoreline wave records. Subsequently, a numerical model based on the Boussinesq equations was validated by the experimental data. The model was then applied to investigate the impacts of varying reef morphologic features (fore-reef slope, reef-crest width, lagoon width, and reef roughness coefficient) on the shoreline wave motions.  相似文献   

老爷海潟湖内底层缺氧规模对南海季风气候节律的响应     

李英  张经  邓鸿  王道儒  朱卓毅 《海洋与湖沼》2014,45(4):719-733

在海南岛形成春旱时,老爷海潟湖内常常发生网箱养殖鱼类因缺氧(DO2mg/L或者30%)而迅速(1—2天内)大规模死亡的事件;然而,其中的缺氧成因至今仍未见相关研究报道。本文在2008—2011年对老爷海执行了7个航次的生物地球化学调查。在形成充沛春雨的2009年春季季风转换期所执行航次(气象条件表现为风速高和多雨)中,很难观察到底层缺氧现象;与此相对应,潟湖水体的垂直稳定度差,浮游植物群落以微微型(2μm)和微型(2—10μm)藻类占优势。在形成显著春旱的2010年春季季风转换期所执行航次(气象条件表现为微风和少雨)中有大规模底层缺氧形成,缺氧水体从内湾深坑水柱(水深约6m)底层一直蔓延到外湾浅水养殖区;与此相对应,内湾深坑水柱明显层化并形成高盐度生境,浮游植物群落以海洋角管藻(硅藻)占优势,而病毒丰度则达到所有7个航次调查中的最高值。在2008、2009和2011年西南季风盛行期所执行航次(气象条件表现为高温、微风和多雨)中都有小规模底层缺氧形成,且仅局限在内湾深坑底层水中;与此相对应,深坑水柱强烈层化并形成低盐度生境,浮游植物群落以微微型和微型藻类占优势。以上调查结果说明,老爷海潟湖内的底层缺氧规模对上界面的南海季风气候节律有着明显响应;其中,春旱气象条件在潟湖内湾所营造的水柱层化(阻碍复氧)和高盐度生境(有利于硅藻成为浮游植物群落优势种)相耦合,则可促成从潟湖内湾深坑底层一直蔓延到外湾网箱养殖区的大规模底层缺氧现象。  相似文献   

Anthropogenic organic contaminants in water, sediments and benthic organisms of the mangrove-fringed Segara Anakan Lagoon, Java, Indonesia   总被引：1，自引：0，他引：1  

Dsikowitzky L  Nordhaus I  Jennerjahn TC  Khrycheva P  Sivatharshan Y  Yuwono E  Schwarzbauer J 《Marine pollution bulletin》2011,62(4):851-80

Segara Anakan, a mangrove-fringed coastal lagoon in Indonesia, has a high diversity of macrobenthic invertebrates and is increasingly affected by human activities. We found >50 organic contaminants in water, sediment and macrobenthic invertebrates from the lagoon most of which were polycyclic aromatic compounds (PACs). Composition of PACs pointed to petrogenic contamination in the eastern lagoon. PACs mainly consisted of alkylated PAHs, which are more abundant in crude oil than parent PAHs. Highest total PAC concentration in sediment was above reported toxicity thresholds for aquatic invertebrates. Other identified compounds derived from municipal sewage and also included novel contaminants like triphenylphosphine oxide. Numbers of stored contaminants varied between species which is probably related to differences in microhabitat and feeding mode. Most contaminants were detected in Telescopium telescopium and Polymesoda erosa. Our findings suggest that more attention should be paid to the risk potential of alkylated PAHs, which has hardly been addressed previously.  相似文献   

Study of the macrophyte assemblages and application of phytobenthic indices to assess the Ecological Status of the Marano‐Grado Lagoon (Italy)     

Annalisa Falace  Daniele Curiel  Adriano Sfriso 《Marine Ecology》2009,30(4):480-494

Benthic macrophytes from 19 sites within the Marano‐Grado Lagoon were sampled in July 2007 in order to update the available information on the flora and vegetation and to assess the Ecological Status (ES) within the European Water Framework Directive (WFD). Data on macrophytes were analysed using two phytobenthic indices (EEI and R‐MaQI) recently set up to evaluate the ecological status of transitional environments in the Mediterranean eco‐region. Notwithstanding the extension (c. 160 km²) that places this lagoon as the second largest Italian transitional environment, ecological studies are relatively few. The present research revealed a relatively poor flora, mainly characterized by the dominance of low‐diversity settlements of Ulvaceae. Moreover, the absence of intensive aquaculture activities and commercial big harbours, which account for the new species introductions recorded in other lagoons, limits the presence of non‐autochthonous species. The comparison with previous data ( Curiel et al. 1998 ) highlighted the reduction of macrophyte coverage and biomass, especially Ulvaceae stands, and an increase in species richness. In particular, there was evidence of a worsening of the area north of the Grado bridge. This area, which in the past was colonized by widespread angiosperm coverage, at present is almost lacking in vegetation. According to these observations, by applying both the phytobenthic indices available in the literature for the transitional environments, the Marano‐Grado Lagoon showed a ‘Good–High’ quality in the central part of the basin and near the lagoon inlets and a ‘Poor–Bad’ quality in the northern and southern areas. The evaluation of some physico‐chemical parameters, coupled with the distribution of the angiosperms, also allowed a first delineation of the main lagoon water bodies.  相似文献   

华南沿海全新世沙坝及其改造利用   总被引：2，自引：0，他引：2  

李平日 《地理学报》1990,45(4):467-474

华南沿海沙坝为中、晚全新世形成，分为六个形成期。分析了沙坝的粒度和沉积 寺征及其分布规律。提出华南全新世沙坝的形成与砂源丰富、波浪较强、海平面已与现今相近、 勾造运动相对稳定、季风气候等条件有密切关系。认为沙坝对环境的主要不良影响是：1．产 上风沙灾害；2．烂湾坝阻塞或淤浅航遭。为此提出营造针阔叶混交防风林及配种草本、灌木 向意见。这些沙坝的主要有利因素是：且．含丰富的砂矿：2．形成漏湖式港湾；3．提烘发展农 木牧渔业的广阔空间；咯．可作为建设经济特区。沿海开发区和发展海滨旅游的土地资源。  相似文献   

基于RS和GIS的日照万平口潟湖湿地景观格局演变研究     

董晶  谢小平 《湿地科学与管理》2015,(1):43-48

以日照万平口潟湖湿地为研究对象,利用遥感影像及GIS技术,选取景观格局指数,对1990-2014年万平口潟湖湿地的景观格局变化进行研究。结果表明:自1990年到2014年,潟湖浅滩、绿地、建设用地的面积显著增加,养殖池和耕地在潟湖湿地范围内已全部转化为潟湖浅滩、绿地和建设用地。潟湖湿地的景观格局指数表明,湿地景观类型多样性呈下降趋势,均匀度指数增加,聚集度和连通性显著上升。从景观格局分析的结果来看,奥林匹克水上公园的建设在一定程度上优化了万平口潟湖湿地的景观格局,湿地景观破碎化程度有所下降,为了更好地开发和利用潟湖湿地资源,提出了一些保护对策和建议。  相似文献   

Factors driving the seasonal distribution of planktonic and epiphytic ciliates in a eutrophicated Mediterranean Lagoon     

Amel Dhib  Mounir Ben Brahim  Boutheina Ziadi  Fourat Akrout  Souad Turki  Lotfi Aleya 《Marine pollution bulletin》2013

We studied the distribution of planktonic and epiphytic ciliates coupled with environmental factors and microalgae abundance at five stations in Ghar El Melh Lagoon (Tunisia). Planktonic ciliates were monitored for a year and epiphytic ciliates were sampled during summer 2011 in concordance with the proliferation of the seagrass Ruppia cirrhosa. Ciliate assemblage was largely dominated by Spirotrichea followed respectively by Tintinnida of and Strombidiida. No significant difference was found in the distribution of ciliate species among the stations. Redundancy analysis indicates that abiotic factors (temperature and nutriments) have a significant effect on the dynamics of certain ciliates. For epiphytic ciliates, 4 species were identified: Tintinnopsis campanula, Aspidisca sp., Strombidium acutum and Amphorides amphora. Based on PERMANOVA analyses, ciliates exhibit significant correlations among months and stations. According to ACP, epiphyte distribution follows roughly those of R. cirrhosa and pH. Significant correlations were found between harmful dinoflagellates and both planktonic and epiphytic ciliates.  相似文献   

Hydrology of Okarito Lagoon and the inferred effects of selective logging in Okarito Forest     

J. M. Macpherson 《新西兰海洋与淡水研究杂志》2013,47(1):25-39

Okarito Lagoon (43° 11′S, 170° 14′E) is a small (20 km²) shore‐parallel, predominantly subtidal estuary, deepest near the landward end, and linked to the sea by two subtidal channels incised through shallow subtidal and intertidal flats which occupy the southern third of the lagoon. Tides at sea vary from 2.1m (spring) to 1.2 m (neap), but in the lagoon the tidal range is constant through the lunar cycle and varies from 0.80 m at the entrance to 0.17 m in the upper lagoon. Tidal water level and flow asymmetries in the subtidal channels are separated by a 1.7 h phase difference. Variations in the net discharge through the inlet result from changing flow cross‐sections rather than from variations in current velocities. Both the tidal‐averaged volume and the tidal compartment of the lagoon vary through the lunar cycle, from maxima at spring tides to minima at neap tides.

Freshwater inflows vary from less than 11 m³.s^‐1 to more than 750 m³.s^‐1. During storms, water level in the lagoon rises rapidly by 2–3 m, then declines to normal over several days. Three water masses, two with salinity and turbidity largely controlled by antecedent rainfall, normally occur in the lagoon. Suspended sediment concentrations in both freshwater inflows and lagoon waters are normally low but increase during floods. Most sediment is supplied by the Waitangi‐taona River or by erosion of tidal channel margins. The lagoon is floored with organic‐rich mud and sandy mud, deposited predominantly from suspension. Surface sediment is consistently muddier than subsurface sediment, probably reflecting an increase in the mud supply since diversion of the Waitangi‐taona River in 1967.

Comparisons of the estimated sediment yield and water inflow effects of the 1967 river diversion with short‐term observations during selective logging suggest that the effects of logging on sediment yield, water balance of the lagoon, and dissolved solids inputs will be small compared with changes caused by diversion of the Waitangi‐taona River.  相似文献   

Dynamics of water exchange and salt flux in the Macuse Estuary,central Mozambique,southern Africa     

《African Journal of Marine Science》2013,35(2):203-208

The Siberian subspecies of the red knot Calidris canutus canutus spends the non-breeding season largely in West Africa (Mauritania and Guinea Bissau), where approximately half a million occurred in the 1980s. It was a rarely seen in southern Africa in the early part of the 20th century, but there were about 12 500 in the 1970s and 1980s. The main sites were Langebaan Lagoon, Berg River Estuary, Olifants River Estuary (South Africa) and Walvis Bay Lagoon (Namibia). There was a decline in the number of red knots at Langebaan Lagoon in the 1990s, to around 20% of the number that occurred there in the 1980s. Numbers remained low in the 2000s. In addition, the percentage that remained during the austral winter (the breeding season in the Arctic) declined, and there was none during the period 2001–2009. This suggested that first-year birds, which largely comprise the austral winter population, were no longer travelling to southern Africa. The decline in numbers coincided with the decline in West Africa, but it was disproportionately larger in southern Africa. The observed pattern of change is consistent with a buffer effect, whereby southern Africa represents an extension to the range to less suitable habitat (requiring a 6 000 km extension to the migration) when the population size and competition is high in the main localities in West Africa. We are probably now witnessing the gradual decline in the number of adult birds who are fixed in their use of southern Africa as their non-breeding quarters.  相似文献   

Effect of coastal waves on sea level in Óbidos Lagoon,Portugal     

Madalena S. Malhadas  Paulo C. Leitão  Adélio Silva  Ramiro Neves 《Continental Shelf Research》2009

This study reports the role of waves, tide, wind and freshwater discharges over the sea level in Óbidos Lagoon, a coastal system connected to the sea through a narrow and shallow mobile inlet. To address the hydrodynamic features of this coastal system, the relative importance of different physical forcings were evaluated. For this purpose, observations together with realistic and idealized numerical modeling were used. Both model and measurements show that the lagoon sea level remains above offshore sea level during storm wave periods. Hence, a simplified inlet-lagoon idealized model was described through mathematical expressions, to understand and highlight the physical processes responsible for sea-level elevation.  相似文献