The effects of riprap in enhancing the abundance and coexistence of Gobiidae along the southern Caspian Sea coast

Many natural coastal habitats around the world are being replaced by hard coastal defense structures as a result of rising sea levels and increasing intensity of storms. To examine the potential effects of riprap on gobies in the nearshore zone of the southern Caspian Sea, we used angling to compare their abundance and diversity in 13 riprap and natural habitats (sandy and gravel shores) from April 2012 through April 2013. In total, 819 gobies of three species, Caspian sand goby Neogobius pallasi (N?=?433), round goby Neogobius melanostomus (N?=?206), and Caspian goby Neogobius caspius (N?=?180) were collected. No round gobies were caught from sandy shores and only two Caspian gobies were caught from gravel habitats, while all three species were abundant in riprap shores. A significant difference was observed in CPUE of all three goby species among shore types, with riprap sites having the highest abundance. PERMANOVA and nMDS demonstrated differences in goby assemblages among all three habitats. There were significant differences in round goby and Caspian goby sizes among riprap and natural habitats, while there were no significant differences in Caspian sand goby size among habitat types. In general deployment of riprap, especially in an area characterized as having natural shores with low structural complexity, could enhance the abundance and coexistence of nearshore gobies and act as a dispersal vector.     

Monitoring shoreline shift under rapid sea-level change on the Caspian Sea observed over 60 years of satellite and aerial photo records

The Caspian Sea is the world’s largest inland water body and endures rapid fluctuations in sea level and shoreline changes. The present study investigates and analyzes shoreline changes in the two areas of Tajan and Sefidrud on the southern coasts of the Caspian Sea using aerial photos, affixed with TM, ETM, and OLI images from Landsat satellites, as well as images rendered by Google Earth, all within the time period from 1955 to 2018. Shoreline changes were analyzed using the waterline algorithm on high resolution aerial photos and images from the Google Earth engine. Shoreline extraction on Landsat images was conducted after comparing six different indices, of which the wetness index exhibited the least mean error (1.3 m). Calculations on shoreline changes were undertaken in 4 time periods using the DSAS extension in Arc GIS 10.3 including 1955–1977, 1977–1995, 1995–2002 and 2002–2018. Coastal accretion on the Tajan shoreline after decreases in sea level were evident in the first, third, and fourth time periods, while coastal erosion was discernible in the second time period during significant increases in sea level. The situation, however, was different for the coasts of Sefidrud. The shoreline was divided into 14 distinct parts where the shoreline change rate was inconsistent with the actual changes in sea level. The dismatch between sea level and shoreline changes in the Sefidrud region points to the existence of a different set of factors, in addition to the sea level, which significantly affect the status of the coastlines.     

Spatiotemporal relationships between life stages of the invasive ctenophore,Mnemiopsis leidyi,and environmental parameters in the southern Caspian Sea

Spatiotemporal relationships between developmental stages (cydippid, transition and adult) of the comb jelly Mnemiopsis leidyi and environmental parameters were seasonally evaluated using the random forest (RF) model along the Iranian coasts of the Caspian Sea. The mean density of M. leidyi in spring, summer, autumn and winter were 8, 54, 130, and 15 ind m⁻³, respectively. The density of various stages, particularly cydippid, showed a decreasing trend with increase in depth. Cydippids had the highest abundance with a lower percentage in the deeper layers and colder seasons. Temperature was found to be the most influential parameter on the distribution of M. leidyi’s life stages, particularly cydippids, with a stronger effect in spring and summer. The highest densities for all life stages were observed above 20 °C with an explosive growth at above 25 °C for the cydippids. Moreover, cydippids were strongly influenced by all the three stages of the copepod Acartia tonsa (nauplius, copepodite and adult), especially its later developmental stages. Due to the presence of M. leidyi, the maximum zooplankton abundance has shifted to cold seasons. There was also a relationship between M. leidyi with barnacle larvae and rotifers in the cold seasons. The interrelationships among the life stages of M. leidyi, particularly between the transition and cydippid, was a major factor in its population dynamics. The relationship curves between these environmental parameters and the life stages of M. leidyi were nonlinear and mostly sigmoidal (not absolutely linear). The magnitude of parameter importance and relationships curves varied with season and life stage.     

Endemic Caspian Sea mollusks in hotspot and non-hotspot areas differentially affected by anthropogenic pressures

The Caspian Sea is renowned for its endemic mollusk biodiversity. However, over the past decades, increasing anthropogenic pressures have caused decreases in abundances and even extinction of species. Both key pressures and endemic taxa are distributed spatially unevenly across the Caspian Sea, suggesting that ecologically different taxa such as gastropods and bivalves are also affected differentially. In addition, hotspot and non-hotspot areas for these taxa might differ quantitatively in pressure scores and qualitatively in key individual anthropogenic pressures. To test this working hypothesis, hotspot areas for endemic bivalve and gastropod species were identified using stacked species ranges. Cumulative and individual pressure scores were estimated for hotspot and non-hotspot areas of bivalves and gastropods. Differences in cumulative and individual pressure scores were tested for significance using non-parametric MANOVA and Wilcoxon rank sum tests, respectively. We identified various mollusk biodiversity hotspots across locations and depths, which are differentially affected both in terms of cumulative pressure scores and in the composition of the contributing individual pressures. Similarly, hotspot and non-hotspot areas for both bivalves and gastropods are differentially affected by anthropogenic pressures. By defining endemic hotspot areas and the respective anthropogenic pressures, this study provides an important baseline for mollusk-specific conservation strategies.     

Risk assessment of trace elements bioaccumulated in golden gray mullet (Liza aurata) harvested from the southern Caspian Sea

Determination of trace element levels (arsenic, As; cadmium, Cd; cobalt, Co; chromium, Cr; copper, Cu; iron, Fe; lead, Pb; manganese, Mn; nickel, Ni; selenium, Se; and zinc, Zn) in the edible part (muscle) of golden gray mullet (Liza aurata: Mugilidae) and the potential health risk from consuming this fish were assessed. Sixty fish were caught by beach seine along the south-central shoreline of the Caspian Sea (Mazandaran province). Concentrations of trace elements were determined by ICP-AES. The mean concentration of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn in the muscle of golden gray mullet were 1.39, 0.036, 0.260, 0.514, 1.87, 5.66, 1.29, 0.181, 0.971, 2.01 and 7.41 mg kg^?1 wet weight, respectively. Although the higher concentrations of Cr and Cu were recorded in this study in comparison to previous studies, maximum levels of trace elements, except for As and Ni, were lower than the international standards proposed by the World Health Organization (WHO), the Ministry of Agriculture, Fisheries, and Food of the United Kingdom (MAFF), and the United States Environmental Protection Agency (USEPA). Daily intakes of these trace elements through fish consumption were compared with the established values. The hazard quotients calculated for all trace elements showed that the examined fish are considered safe for human consumption.     

Seasonal variability of circulation and air-sea interaction in the Caspian Sea based on a high resolution circulation model

The Caspian Sea is the largest closed basin on Earth, with unique physical characteristics and complex bathymetry. Sparse measurements and coarse resolution models have not yet provided a full picture of its dynamics. In this study, a high resolution (～3.3 km) Regional Ocean Modeling System (ROMS) was used to study its annual and seasonal circulation patterns, and distributions of salinity and temperature. Temperature and salinity nudging were implemented which forced the model to follow in situ observations. This approach effectively limited the model error in predicting the temperature and salinity. The model successfully reproduced sea surface temperature and salinity over the entire basin. The simulated sea surface salinity showed three salinity fronts over the Caspian Sea. The salinity profile was vertically uniform in deep waters of the Caspian Sea. In contrast, the vertical thermal structure formed the seasonal thermocline at a depth of 15–40 m which was intensified in summer. In general, the seasonal variability of water temperature or salinity was confined to the upper 100 m of the water column. Simulations revealed an impermanent weak northward current along the eastern coasts of the Middle Caspian Sea, a persistent strong southward current along its western coasts and a permanent deep anticyclonic gyre over the Southern Caspian Sea. Using a high resolution model, this study also reports several mesoscale and small scale structures in the Caspian Sea which have not been reported before.     

水位上升条件下陡坡破坏离心模型试验研究

基于变形与破坏过程耦合分析的研究思路,针对水位上升条件下黏性土陡坡变形破坏开展了离心模型试验,测定了试验过程中边坡的位移时程及其分布,并进行点对分析确定了边坡破坏过程,揭示了边坡的破坏机理。研究结果表明：水位上升引起的陡坡剪切破坏从坡脚开始,逐渐向上发展与坡顶张拉裂缝共同形成整体滑裂面;水位上升过程导致陡坡产生显著变形并在一定区域内集中,出现了明显的变形局部化,导致该处出现局部破坏,局部破坏逐渐发展并贯通形成滑裂面;滑裂面形成后边坡变形主要出现在滑动体内部,滑动体上不同点的位移特征受到所在位置的影响。     

Sea level variability in East China Sea and its response to ENSO

Sea level variability in the East China Sea (ECS) was examined based primarily on the analysis of TOPEX/Poseidon altimetry data and tide gauge data as well as numerical simulation with the Princeton ocean model (POM). It is concluded that the inter-annual sea level variation in the ECS is negatively correlated with the ENSO index, and that the impact is more apparent in the southern area than in the northern area. Both data analysis and numerical model results also show that the sea level was lower during the typical El Nio period of 1997 to 1998. El Nio also causes the decrease of the annual sea level variation range in the ECS. This phenomenon is especially evident in the southern ECS. The impacts of wind stress and ocean circulation on the sea level variation in the ECS are also discussed in this paper. It is found that the wind stress most strongly affecting the sea level was in the directions of 70o and 20o south of east, respectively, over the northern and southern areas of the ECS. The northwest wind is particularly strong when El Nio occurs, and sea water is transported southeastward, which lowers the sea level in the southern ECS. The sea level variation in the southern ECS is also significantly affected by the strengthening of the Kuroshio. During the strengthening period of the Kuroshio, the sea level in the ECS usually drops, while the sea level rises when the Kuroshio weakens.     

浅谈水位涨率法对单站洪水的预报

为了解决跨国界河流洪水预报问题,以广西平而水文站和水口水文站为例,采用以水位涨率为参数的相应水位法进行洪水预报。结果：洪水预见期,平而水文站为26h,水口水文站为13h,且预报精度均符合《水文情报预报规范》的要求。     

Coastal trapped waves in the southern Caspian Sea

Previous studies reported coastal trapped waves (CTWs) in the Caspian Sea (CS). This study deals with the generation mechanisms, the temporal and spatial variability of CTWs in this area, and their transformations during propagation from the origin to the destination using recent measurements and high-resolution numerical simulations. CTWs are observed at all stations with periods of 2–6 days after northerly storms. The Absheron Peninsula, old Sefidrud delta, and Nur coasts were identified as the CTWs prone regions. The generation of CTWs in these locations was confirmed using numerical experiments. The propagation away from the generating location of CTWs was analyzed using a representative real wind storm. In the west part of the CS, the generation mechanism of CTWs is mainly similar to the barotropic Kelvin waves; in contrast, it is similar to the continental shelf waves in the southern shelves. The results can be used to study the contribution of generated CTWs to the transport of sediment and biological materials in all large lakes.     

巴音河冲洪积扇前缘地下水位上升灾害特征及影响因素

针对柴达木盆地巴音河冲洪积扇前缘地下水位上升,严重影响到该地区百姓日常生活及生命安全的问题,开展了水资源利用现状调查、水文地质补充钻探、水文物探及水土样测试等勘察工作,阐明了研究区地下水位上升的灾害特征,并从水文气象、地形地貌特征、水文地质条件和人类活动等方面,采用层次分析法计算导致地下水上升灾害的各影响因素权重。结果表明,研究区径流量、降水量、引水灌溉和地下水动力条件是地下水位上升的主要因素,4者权重之和为0.7642。     

长江口洪季水动力对海平面上升的响应特征

考虑到海平面上升对长江口水动力构成的严重威胁,该文基于MIKE21软件建立了长江口二维水动力数学模型,采用实测潮位、流速以及流向资料对模型进行了验证。对相关文献和IPCC报告进行总结归纳,得到2100年海平面保守上升值约为0.5 m。运用验证好的数学模型对海平面上升0.5 m后长江口洪季水动力进行了数值模拟。计算结果表明:海平面上升后,涨潮时间增长,落潮时间缩短;海平面上升0.5 m后,长江口南北支、南北港以及南北槽高潮位增加了0.43 m–0.46 m,高潮位增幅沿程向上减小,北支上段涨潮动力受阻较明显(潮位增幅较大);海平面上升0.5 m后,北支流速增幅比南支大,北支上段落潮流量增幅达82.8%,对北支水道的发展有利。总体而言,海平面上升对目前长江口沿岸的标准构成了一定威胁,但对已经衰退的北支水道有利。     

鄂尔多斯乌海地下水水位上升原因分析

鄂尔多斯盆地西北部最干旱的乌海地区地下水水位近几年来持续上升,地下水溢出地表形成了一些水泡子,部分居民房屋地基遭受到渗水的浸泡。分析乌海地区渗水、地下水、地表水、降水中的同位素与水化学成分,结合水量平衡分析与地质构造特点,对乌海地下水水位上升的原因进行深入研究。结果表明:乌海地区降水与地下水的δ18O-δD关系点分布没有落在同一条蒸发线上,当地降水对乌海地区的地下水没有补给;乌海地区南北向断裂带上地下水的δ18O与δD值比东西向断裂带上的富集,溶解总固体(TDS)小于1 g/L,与乌海地区的涌水一致,由此推测乌海地下水水位上升主要是因为南北向断裂带涌水所致;鄂尔多斯地区地下水的3He/4He与3H分析结果表明,岩石圈中的高导低速层可能是深循环地下水的导水构造。     

Contributors to tidal duration asymmetry with varied coastline configurations on western shelf of Yellow Sea

Coastal management in China is confronted with an urgent choice between natural restoration and maintenance of existing seawalls and reclaimed land for economic development. A key criterion for making this decision is the resilience to coastal flooding, which depends on the ability to predict tidal level. Tidal duration asymmetry (TDA) is a key parameter in determination of the arrival and duration of flood tides. This study selected the western inner shelf of the Yellow Sea (WYS) as the study area and investigated the responses of TDA to different shoreline configurations and relative sea level rise. The responses of TDA to shoreline reconstruction yielded spatial variability locally and remotely. In the nearshore area, the responses of TDA to the complex ocean environment mainly originated from the combined functions of reflection, bottom friction, and advection, which controlled the energy transfer from M₂ or S₂ constituents to their overtides or compound tides. The sensitivity of TDA to coastline typologies was not limited to coastal waters but could stretch over the entire inner shelf. The vulnerability of tidal responses was due to the displacement of the M₂ amphidrome of the Kelvin wave on the WYS, which in turn changed tidal energy fluxes over the regime. The relative sea level rise could intensify the feedback of TDA to seawalls and land reclamation.

     

黄海和东海的环流数值模拟研究

本文从海洋三维原始动力学方程出发,考虑真实地形及(1/4)°×(1/4)°的水平网格,同时考虑黑潮和潮流,数值模拟黄海和东海的环流系统,主要结论是:1)模拟调和常数与分布于该区的81个台站的实测调和常数相比,日分潮振幅和位相的平均绝对误差分别为1.7cm和5.2°,半日分潮M_2振幅和位相的平均绝对误差分别为4.1cm和3.7°;2)模拟的黑潮路径与长期观测结果相吻合;3)黑潮进入研究区域后,一分支从台湾东北部分离出来后进入东海,影响可达29°N,这与海洋普查的调查结果以及文献中的结果一致;4)黑潮的一个分支北上形成对马暖流的一部分,且对马暖流是多源的,对马暖流通过对马海峡进入日本海,同时模拟结果显示一支由日本海进入研究区域的海流,后者需进一步调查和研究;5)黄海表层流主要沿南下方向,在近底层。中国和朝鲜的沿岸流为南下,黄海底层海盆由一顺时针方向的环流控制着,在中国成山头以外的北黄海底层,存在一较弱的逆时针环流。     

海平面上升的研究现状及其影响对策研究

气候变化引起的海平面上升对沿海地区构成极大的威胁,造成不同程度的破坏和损失。海平面上升已经成为全球重要的环境问题,受到社会各界的高度重视。本研究对全球及中国海平面上升趋势的研究现状进行了总结,分析了海平面上升的影响,为了防止海平面上升带来的巨大危害,提出了防治海平面上升的具体对策。要将预防未来与现状治理结合起来,从整体上减轻海平面上升危害,以确保二十一世纪中国沿海地区资源、环境、经济和社会的可持续发展。     

冬、夏季北黄海悬浮物分布特征

利用国家908专项ST02区块(北黄海)水体专项调查2007年夏、冬资料,应用浊度观测资料对悬浮物质量浓度进行线性拟合,得到较好的反演结果。在北黄海海域选取了具有代表性的9个断面,利用反演的悬浮物质量浓度,综合温度、盐度等水文要素,辅以冬、夏季山东半岛沿岸流、北黄海冷水团和黄海暖流的季节变化特征,着重分析了冬、夏季北黄海悬浮物分布特征、形成原因以及季节变化。研究结果表明,冬、夏山东半岛北部沿岸、成山头海域和老铁山水道以及旅顺湾附近海域始终为高悬浮物浓度区,呈现出近岸高,离岸低,底层高,表层低的态势。夏季,水体垂向层结显著,受北黄海冷水团以及沿岸流的作用,老铁山水道附近及山东半岛北部沿岸的高悬浮物浓度值区基本不能进入北黄海,只能沿岸分布,并且由于海底底质为粘土质以及沿岸流的共同作用,成山头附近海域悬浮物浓度值很高,但基本为局地再悬浮,没有向外输送的趋势。冬季受强劲东北风的影响,水体垂向混合均匀,悬浮物浓度值比夏季高得多,悬浮物的分布受黄海暖流、沿岸流以及地形的影响,特别是成山头附近海域,存在一个显著的高悬浮物浓度值区,并具有向南输送的特征。     

库水位升降变化对关门山水库大坝应力和面板脱空的影响分析

面板脱空是造成混凝土面板堆石坝面板裂缝的重要原因,会对面板乃至大坝的安全稳定造成不利影响。文章以关门山水库大坝为例,利用数值模拟方法研究了库水位升降变化对面板脱空的影响。结果显示,库水位的循环升降作用,会加剧大坝混凝土面板的脱空现象,对面板乃至大坝的安全稳定运行造成不利影响,需要在设计和运行中采取有针对性的措施,保证大坝的安全稳定运行。     

Interannual and intra-annual cycles of satellite-derived chlorophyll-a concentrations in the Caspian Sea

Variability of phytoplankton in the Caspian Sea (CS) is related to the complex orography, the variety of physical and chemical processes, and climatic indices. Here, interannual and intra-annual variability of satellite-derived chlorophyll-a concentrations (Chl-a) were studied using wavelet analysis during 2002–2019 in different regions of the CS. Self-Organizing Maps (SOM) analysis performed to classify the CS into the areas of similar variability of satellite-derived Chl-a. Wavelet spectral analysis showed that the Chl-a variability regulated by four primary periodic cycles: 0.5-year, 1-year, 2 to 2.5-year, and 3 to 5-year. The 0.5 and 1-year wavelet cycles mostly depicted the intensity of seasonality patterns. The 2–2.5-year and 3–5-year cycles of Chl-a showed non-stationary coherence with corresponding low-frequency cycles of NAO and ENSO. The 3–5-year wavelet amplitudes of Chl-a strongly correlated with NAO and ENSO in the southern CS. Weak correlations of 2–2.5-year cycle wavelet amplitudes of Chl-a with NAO and ENSO suggested that variations do not always directly translate to a biological response. A negative anomaly in the Chl-a autumn peaks observed during 2011–2016 in the middle and southern CS, when NAO phases were persistently positive. The interannual variations of summer peaks in the northern CS, and autumn peaks in the middle and southern CS were broadly related to the precipitation. SST and wind stress. Moreover, it was shown that the Volga discharge has a significant influence on Chl-a variability in the northern CS.