Experimental investigations into the influence of biofilms and environmental factors on short-term microtopographic fluctuations of supratidal sandstone

In this study laboratory experiments were used to explore the role of biofilms, formed by lithobiontic microorganism communities, in causing hourly surface changes of supratidal sandstone and the potential linkage to long-term rock decay. To isolate the influence of individual environmental factors (temperature and humidity) on rock surface changes (expansion and contraction), a colonized (biofilm-covered) and a non-colonized sandstone block (biofilm-free) underwent the same univariate microclimatic simulations closely controlled by an environmental chamber. Simulations were run under three different light conditions, with a natural light lamp on, on and off at 20-min intervals and off, to investigate the impact of light on rock surface dynamics. Measured with a traversing micro-erosion meter (TMEM), two-hourly microtopographic fluctuations of these two sandstone blocks were compared in the same environment. Induced by microclimatic variations, surface movements of significantly higher magnitude (12–120% under varying tempeature and 121–154% under varying humidity) and different change patterns were observed on the colonized block, indicating the primary role of biofilm in driving microtopographic fluctuations of supratidal sandstone. However, thermally driven changes of similar magnitude and pattern were observed on both surfaces, suggesting other mechanisms also operating on the non-colonized rock surface in this process. Due to the sensitivity of biofilm microorganism communities to light, the magnitude and pattern of surface changes was impacted by light condition. Because biofilms increased the magnitude and number of cycles of expansion and contraction of the experimental rock surface, we propose that lithobiontic biofilms facilitate the detachment of grains and granular disintegration on the rock surface, consequently contributing to rock decay and accelerating the rate of breakdown of supratidal rock. This short-term episode therefore needs to be superimposed on longer term studies to fully understand the role of biofilms in rock surface change. © 2019 John Wiley & Sons, Ltd.     

Long-term coastal erosion assessment along the coast of Karnataka,west coast of India

Coastal areas are always under frequent threat from various natural processes and man-induced activities. Coastal erosion is recognized as the permanent loss of land along the shoreline resulting in the transformation of the coast. The current study focuses on long-term coastal erosion analysis of the entire Karnataka coast using Remote Sensing, Geographical Information System (GIS), Linear Regression Rate (LRR), and End Point Rate (EPR) techniques. Analysis of 26 (1990 to 2016) years of erosion using Landsat images by the use of the Digital Shoreline Analysis System (DSAS) tool has been done. The results show a high erosion rate at Ullal during this period (LRR -1.3m/yr) and accretion at Devbagh (LRR 3.2 m/yr). The southern Karnataka coast faces severe erosion especially at Ullal, where the settlement is high. At Thanirbhavi, Mukka, Kota, and Om Beaches erosion also is noticed. Both anthropogenic activities like ports, seawalls, breakwaters, etc. and natural processes like long shore drift, seasonal variation, etc. are factors affecting the shoreline change along the Karnataka coast.     

Evolution of Modern Yellow River Delta Coast

This paper deals with the development and evolution of modem Yellow River delta and the erosion or deposition rates of its different sections. In June, 1996.Yellow Rivers terminal course was artificially turned eastwards to empty into the sea and then the 1 lth lobe of the modem Yellow River delta began to form. This course change may mark the beginning of the 3rd subdelta formation. As a result of that. the Yellow River delta advances towards east by north with the 1st, 2nd and 3rd subdeltas arranged in succession. Coast zone in the deltaic area is divided into 7 different sections according to their different erosion or deposition rates: the relatively stable section from Dakou River to Shunjiang Stream, the weakly retreating section from Shunjiang Stream to the Tiaohe River mouth, the strongly retreating section from the Tiaohe River mouth to the station 106. the artificially stable section due to stone dam protection from the station 106 to Gudong Oilfield, the strong deposition section from Gudong Oilfield to Dawenliu Haipu, the weakly deposition section from Dawenliu Haipu to the Zimai Stream mouth, and the stable section from the Zimai Stream mouth to the Jiaolai River mouth. It is predicted that the erosion and deposition situations of the sections will nearly remain the same in 10 years, but the retreating and silting-up rates will tend to become slower gradually. Human activities have an evident influence on the changes of the coastline.     

黄海北部近岸鱼类资源数量分布与群体结构

通过 1998 年 6 月和 9 月共 24 个站位的底拖网调查,分析了黄海北部近岸渔获物的组成,其结果表明,该海域鱼类资源量指数较低,为 17.068 kg / 网·h,鱼类资源经济品质结构低值化,鱼类资源群体结构小型化、低龄化更加突出,一些个体小、价值不高的种类如青鳞鱼、鳀鱼、斑鰶等占据了春季渔获量的主要部分,秋季捕获的经济鱼类如兰点马鲛、鲐鱼等全部是当年生幼鱼。     

福建沿海风暴潮特征的分析

通过普查1960-2001年正面登陆我国东南沿海的台风,分析了福建沿海风暴潮的特征及其可能原因。台湾海峡特殊地形对福建沿海风暴潮的时空分布有明显影响,登陆岸段不同,台湾海峡对风暴潮的影响作用也不同,导致福建沿海风暴潮出现明显不同的分布和变化特征。当台风位于台湾海峡时,其大风区位置利范围不同,会影响福建沿海各地风暴增水的幅度。台风横穿台湾海峡时,易使福建沿海台风大风区中心岸段出现双增水峰现象,第一个增水峰出现在台风离开台湾岛进入台湾海峡后,第二个增水峰出现在台风登陆福建沿海前后。台风横穿台湾海峡有时会引起台湾海峡北部出现奇异增水现象,风暴潮与天文潮之间的相互作用可能是其重要原因。奇异增水峰往往出现在天文潮低潮附近,此时实际潮位并不高。     

Amplitude,frequency and drivers of Caspian Sea lake-level variations during the Early Pleistocene and their impact on a protected wave-dominated coastline

The Caspian Sea, the largest isolated lake in the world, witnessed drastic lake-level variations during the Quaternary. This restricted basin appears very sensitive to lake-level variations, due to important variations in regional evaporation, precipitation and runoff. The amplitude, frequency and drivers of these lake-level changes are still poorly documented and understood. Studying geological records of the Caspian Sea might be the key to better comprehend the complexity of these oscillations. The Hajigabul section documents sediment deposited on the northern margin of the Kura Basin, a former embayment of the Caspian Sea. The 2035 m thick, well-exposed section was previously dated by magneto-biostratigraphic techniques and provides an excellent record of Early Pleistocene environmental, lake-level and climate changes. Within this succession, the 1050 m thick Apsheronian regional stage, between ca 2·1 Ma and 0·85 Ma, represents a particular time interval with 20 regressive sequences documented by sedimentary and palaeontological changes. Sequences are regressing from offshore to coastal, lagoonal or terrestrial settings and are bounded by abrupt flooding events. Sediment reveals a low energy, wave-dominated, reflective beach system. Wave baselines delimiting each facies association appear to be located at shallower bathymetries compared to the open ocean. Water depth estimations of the wave baselines allow reconstruction of a lake-level curve, recording oscillations of ca 40 m amplitude. Cyclostratigraphic analyses display lake-level frequency close to 41 kyr, pointing to allogenic forcing, dominated by obliquity cycles and suggesting a direct or indirect link with high-latitude climates and environments. This study provides a detailed lake-level curve for the Early Pleistocene Caspian Sea and constitutes a first step towards a better comprehension of the magnitude, occurrence and forcing mechanisms of Caspian Sea lake-level changes. Facies models developed in this study regarding sedimentary architectures of palaeocoastlines affected by repeated lake-level fluctuations may form good analogues for other (semi-)isolated basins worldwide.     

Heterogeneous tide-surge interaction during co-occurrence of tropical and extratropical cyclones in the radial sand ridges of the southern Yellow Sea

The Radial Sand Ridges(RSRs)area in the southern Yellow Sea are subject to tropical and extratropical cyclone activities frequently,in which the special geometry feature and moving stationary tidal system result in complex storm-induced hydrodynamic processes,especially the tide-surge interactions.We studied a rare weather event influenced simultaneously by an extratropical cyclone EX1410 and Typhoon Vongfong as an example to investigate the characteristics of storm surges,wave-surge,and tide-surge interaction in the RSRs area,and applied a high-resolution integrally-coupled ADCIRC+SWAN model,in which the meteorological forcing inputs are simulated by the WRF-ARW model.The model is validated by records from 4 tide gauges and 2 wave buoys along the Yellow Sea coast.Results show that the tide-surge interactions are of considerable regional heterogeneousness.The surge curves at Lüsi(in south RSRs)and Jianggang(in middle RSRs)have abrupt falls near the time of low tide,where the peak occurrence time of interaction residuals tend to shift towards the mid-ebb period.Significant increase of bed shear stress in shallow waters was proved the dominant factor to affect the tide-surge interaction in broad tidal flats of the RSRs area.Differently,the interaction pattern in the Xiyang Trough(in north RSRs),showed a unique rising in mid-flood period due to the phase advances of real surge waves in relatively deep waters.Therefore,we suggested to the local flood risk management that the tide-surge interaction tends to alleviate the flooding risk in the RSRs area around the time of high tide,but aggravate the risk on the rising tide in the Xiyang Trough and on the falling tide in large-scale tidal flats of the southem RSRs area.     

中小河流对长江水下三角洲远端泥沉积的贡献:以椒江和瓯江为例

海洋沉积物的来源、输运过程及其归宿一直是海洋沉积学的重要研究课题。浙闽沿岸泥区的沉积物主要来自长江及浙闽沿岸的中小河流,对后者的贡献量进行定量化分析是相关研究比较薄弱的环节,这个问题的难点可能是缺乏同时指示"物源"和"供应量"两个指标的示踪物。本文以椒江和瓯江这两条河流对浙闽沿岸泥区的贡献为切入点,运用了粒度端元和黏土矿物两种示踪指标进行研究,目的有两个:一是综合评价两种示踪指标的效率,二是定量化地了解中小河流对浙闽沿岸泥区的贡献。借助端元粒度分析模型对浙闽沿岸泥区的表层样粒度数据进行分解,划分出4个不同的端元,结果显示,EM1端元表现出长江来源的属性,EM2端元表现出椒江和瓯江等沿岸中小河流来源的属性,EM3端元可能来源于研究区南部并有向北输送的趋势,EM4端元可能来源于陆架中部的残留砂沉积区。基于特征粒级的进一步分析表明,研究区6个站位的柱样沉积物中都出现了第一特征粒级,在3.91~9.29 μm之间,推测与长江口外悬浮颗粒物有关,并认为柱样所在的区域都会受到长江入海泥沙的影响。黏土矿物由于具有粒度依赖性,在定量探讨椒江与瓯江的泥沙贡献量时,只能指示小于2 μm的细颗粒物的贡献量,而粒度端元作为一种"全粒度"的指标,在相对封闭的系统内,可以同时解答"从哪里来"和"有多少"这两个示踪问题,是受限比较小的示踪物指标,未来在定量研究物源方面可能会有较大的作用。     

基于观测的南海越南沿岸次表层涡旋

In this study, subsurface eddies near the Vietnam coast of the South China Sea were observed with in situ observations, including Argo, CTD, XBT and some processed and quality controlled data. Based on temperature profiles from four Argo floats near the coast of Vietnam, a subsurface warm eddy was identified in spring and summer. The multi-year Argo and Global Temperature and Salinity Profile Programme(GTSPP) data were merged on a seasonal basis based on the data interpolating variational analysis(DIVA) method to reconstruct the three-dimensional temperature structure. There is a warm eddy in the central subsurface at 12.5°N, 111°E below300 m depth in spring, which does not exist in autumn and is weak in winter and summer. From CSIRO Atlas of Regional Seas(CARS) and Generalized Digital Environment Model(GDEM) reanalysis data, this subsurface warm eddy is also verified in spring.     

砂质海岸整治修复效果模糊综合评价研究——以营口月亮湾为例

本文采用模糊综合评价方法,从自然环境效果、景观生态效果、沙滩资源效果和社会经济效果4个方面研究构建了砂质海岸整治修复效果综合评价指标体系与评价方法,并以营口月亮湾为例进行了实证研究。结果表明:本文提出的砂质海岸整治修复效果综合评价方法涵盖内容全面,指标获取可行,评价结果明确,整体方法实用。营口月亮湾砂质海岸整治修复效果总体评价结果为优秀,综合评分为2.636 2,其中社会经济效果贡献率为30.52%,沙滩资源效果贡献率为30.17%,自然环境效果和景观生态效果贡献率分别为19.88%和19.44%。