A study of coral reef resilience and implications of adaptive management and rehabilitation in Khanh Hoa Province, Vietnam

The Province of Khanh Hoa, Vietnam, is located in the western South China Sea and boasts a shoreline of 385 km and many islands. Previous studies have indicated the extreme diversity and abundance of coral reefs in its waters as compared with other coastal provinces of Vietnam. A study on the resilience of coral reefs against increased surface water temperature and anthropogenic impact is conducted at 19 reef sites in 2015. At each site, a series of parameters (e.g., coral covers, genus diversity, and coral recruitment, substratum heterogeneity, depth, water exchange level, and sediment deposit and water temperature) are measured quantitatively or semi-quantitatively. The measured data are rated based on the relationship between the parameter values and coral susceptibility; the consideration that reef health reflects the biological capability to adapt to environmental changes and the recruitment potential if bleached; and positive or negative influences of physical factors in the mitigation of thermal stress and protecting corals from bleaching. A cumulative analysis enables researchers to divide the studied reefs into four categories based on varying levels of reef health to support resilience, recovery, and vulnerability in the case of increased water temperature. Relevant management interventions for each category and other supporting activities are suggested to enhance management effectiveness and to plan the rehabilitation of coral reefs for biodiversity conservation and touristic development, taking into account the involvement of related stakeholders.     

基于新型高频声学多普勒流速剖面仪的河口近底部边界层观测初探

河口物质输运、能量交换与底边界层内的水动力过程密切相关,底边界层参数(如切应力、拖曳系数)的确定至关重要。挪威Nortek公司生产的新型声学多普勒流速剖面仪AD2CP相比传统ADCP具有高频、低噪的优点,可用于高频(16Hz)流速剖面观测,而被广泛应用于底边界层观测的ADV只能测量单点高频流速。本文采用AD2CP在长江口南槽最大浑浊带区域进行座底式观测,并与同步近底部三脚架上ADV的观测结果进行对比。结果表明,使用AD2CP测得的近底部平均流速与ADV的测量结果吻合良好;使用惯性耗散法计算了底切应力,基于ADV的单点高频流速数据计算结果为2.16×10~(-2)～5.69×10~(-1)N/m~2,基于AD2CP的结果为2.09×10~(-2)～4.26×10~(-1)N/m~2,二者范围大致相当。在此基础上,基于AD2CP数据计算出摩阻流速为4.55×10~(-3)～2.06×10~(-2)m/s、底拖曳系数范围为1.84×10~(-4)～2.49×10~(-3),与ADV的计算结果基本一致。此外,由于AD2CP可以获得高频的流速剖面数据,优于单点ADV,具备观测近底部边界层参数和边界层内湍流剖面的潜力。     

庙西南凸起馆陶组油气差异成藏规律

针对庙西南凸起馆陶组主要成藏砂体类型与油气富集程度的差异,分析油气运聚条件及其对油气成藏的影响,总结差异成藏规律。研究表明,油田区为多断阶“脊—断”接力式油气运聚模式,油气先沿馆陶组底部区域砂岩输导脊向高部位断阶区横向运移,再由“通脊”断裂将油气分配至浅层聚集成藏。增压应力的分布与强度是影响油气运移与保存的关键,控制主要成藏砂体类型与油气富集程度。增压区利于油气保存而不利于油气运移,以厚砂体成藏为主;弱增压区、亚增压区利于油气运移但不利于油气保存,主要为薄砂体成藏。构造低部位弱增压与高部位增压型断块运移与保存条件最优,油气最为富集。同一断块内部,“脊—断”条件控制不同井区的油气丰度,“通脊”断裂切至输导脊的构造位置越高、在输导脊上累计错动面积越大,该区域的油气丰度也越高。这种油气差异成藏规律有效指导了庙西南凸起馆陶组的高效评价,同时为类似地区的油气勘探提供了重要参考价值。     

梨树断陷断陷期小宽断裂带构造应力场数值模拟

在小宽断裂带构造解析基础之上,根据地质资料以及前人提供的岩石物理学参数建立了梨树断陷区的二维地质和数值模型。进行了构造应力场数值模拟,分析了梨树断陷小宽断裂带断陷期小宽断裂带断陷期在沙河子期(K1sh)、营城期(K1yc)、登楼库期(K1d)的构造应力场特征。模拟结果显示：(1)沙河子期在左旋走滑应力状态下,小宽断裂带处于近NE—SW方向的拉张应力状态,剪应力在沿着断裂带SW—NE走向逐渐减小; (2)营城期在右旋走滑的应力状态下,小宽断裂带处于近NW—SE向的拉张力状态,剪应力最大值位于断裂带的最中间部位;(3)登楼库期在左旋走滑的应力状态下,断裂带处于SWW—NEE向的张拉应力状态,剪应力最大值位于断裂带西南段。     

波致应力的近似求解及其太平洋特征分析

基于波致应力计算中对海浪谱和波浪增长率公式的敏感性分析,选择适当的波致应力近似求解方法,计算和探讨了太平洋波致应力的时空分布特征。敏感性分析中,选择了4种常用的波浪增长率公式和3种经验解析海浪谱。推导了计算波致应力的单波公式,并将其与JONSWAP谱积分公式和Elfouhaily谱积分公式进行比较,同时使用了由风速和有效波高资料构造的Elfouhaily谱积分公式计算太平洋波致应力。结果表明:Belcher等(1993)的波浪增长率计算公式估算的波致应力与实验数据吻合度较好,同时适用ERA-interim数据;当波龄小于1.2时运用Elfouhaily谱积分公式更合适,当波龄大于1.2时运用单波公式更快速有效;太平洋的波致应力分布与风场之间存在明显的相关性;2009年1月、4月、7月和10月太平洋波致应力的季节性特征分析表明四个季节的西风带波致应力较其他地区都更强盛,而在时间变化上1月和10月为波致应力整体较为强盛的时期。     

三疣梭子蟹几丁质酶基因(PtCht6)的克隆及其在免疫中的功能分析

几丁质酶(chitinase)在甲壳动物的蜕皮、消化和免疫等很多生物学过程中发挥重要功能,为深入探讨几丁质酶的免疫防御机制,本实验利用RACE技术克隆了三疣梭子蟹(Portunus trituberculatus)PtCht6基因。该基因cDNA全长2736bp,开放阅读框(ORF)2103bp,编码700个氨基酸,具有几丁质酶GH18家族典型特征。利用实时荧光定量技术分析PtCht6在三疣梭子蟹不同组织、不同蜕皮阶段、不同病原感染以及低盐胁迫(11)下的表达特征,结果显示:PtCht6在各组织中均有表达且在肝胰腺中的表达量最高;在不同蜕皮时期的肝胰腺中,其表达量由蜕皮后期(A/B)、蜕皮间期(C)、蜕皮前期(D)依次递减(P0.05);人工感染WSSV和副溶血弧菌后.PtCht6的表达量在肝胰腺中分别于12h、72h达到最大值,在血细胞中均于12h达到最大值,且相较于对照组,整体显著上调表达(P0.05);低盐胁迫能够显著抑制该基因的表达,最高抑制73倍(P0.05)。同时发现,低盐环境下感染WSSV后,该基因达到峰值的时间明显延迟(至少延迟12h.P0.05)。该研究结果预示PtCht6作为免疫因子参与三疣梭子蟹的病原防御,且低盐胁迫在一定程度上抑制了该基因的免疫功能。     

急性高温胁迫对虹鳟二倍体和三倍体幼鱼hsps基因表达的影响

本文以二倍体和三倍体虹鳟(Oncorhynchus mykiss)幼鱼为实验对象,探究急性高温胁迫下,不同倍性虹鳟热休克蛋白家族(hsps)基因表达水平。选取二倍体和三倍体虹鳟幼鱼,分别进行常温处理(14℃)和高温胁迫(22℃),并在高温胁迫48h后,将虹鳟置于常温(14℃)恢复48h。分别在实验开始的0,12,24,48,72和96h进行取样,测定实验虹鳟肝脏和肌肉组织中的hsp70s(hsp70a,hsp70b),hsp90s (hsp90a1a,hsp90a2a,hsp90a1b,hsp90a2a,hsp90b1,hsp90b2)mRNA水平。结果表明:hsp70s和hsp90s的各个亚型均能对热胁迫做出反应,并具有应答幅度的组织特异性和时间特异性。在胁迫6和24h后,上述基因mRNA水平达到最高,随后降低。三倍体幼鱼肝脏和肌肉hsps mRNA表达水平的峰值显著高于二倍体幼鱼。研究结果显示,三倍体虹鳟对高温环境更为敏感,需要消耗更多的能量用于适应高温环境。     

不同开口比人工鱼礁体水动力特性及礁体稳定性研究

为研究方型人工鱼礁体开口比的变化对其水动力特性的影响,利用Fluent软件模拟了边长为3m、开口比为0～0.6之间7种不同方型鱼礁体周围水流场,通过分析水流场变化规律得到了礁体流场效应、阻力系数随开口比的变化情况;基于Morison方程计算了礁体在波流作用下的受力及其抗滑移、抗倾覆安全系数。研究结果表明:当礁体开口比小于0.2时,背涡区范围较大,流场效应明显;随着开口比的增大,礁体产生的上升流范围及竖直向最大速度分量逐渐减小;对于方形开口礁体,阻力系数与开口比的关系式为Cd=0.875φ+1.088(R2=0.963,P<0.01);随着开口比的增大,礁体所受最大波流作用力、抗滑移及抗倾覆安全系数逐渐减小,但礁体不会发生滑移和倾覆,可为实际礁体结构的设计提供参考。     

Comparison of Strain-rate Dependent Stress-Strain Behavior from Ko-consolidated Compression and Extension Tests on Natural Hong Kong Marine Deposits

This article presents results from a series of K_o-consolidated compression and extension triaxial tests on specimens from undisturbed samples of Hong Kong Marine Deposits (HKMD). To investigate the strain-rate effects, a total of seven K_o-consolidated triaxial tests were conducted including four compression tests and three extension tests. After K_o-consolidation, the triaxial test specimens were sheared at step-changed axial strain rates under three different confining pressures of 50 kPa, 150 kPa, and 400 kPa, respectively. The step-changed strain rates were applied in the following order: +2%/h, +0.2%/h, +20%/h, -2%/h (unloading) and +2%/h (reloading) for the four compression tests and -2%/h, -0.2%/h, -20%/h, +2%/h (unloading) and -2%/h (reloading) for the three extension tests. The results are reported and analyzed in the paper. The results show that the strain rate effects, the stress-strain characteristics, and the effective stress paths of the specimens for tests in a compression state are different from those for tests in an extension stage. One order of magnitude increase in axial strain rate causes an average 8.6% increase in undrained shear strength for compression tests and a 12.1% increase for extension tests. It is also found that the failure mode of the specimens in compression is different from that in extension. The stress-strain behavior of specimens shows strain-softening and a clear shear band in compression tests, but strain-hardening without any clear shear band in extension tests for the same absolute value of axial strain.