The relationship between seagrass (Posidonia oceanica) decline and sulfide porewater concentration in carbonate sediments

In this study we test the hypothesized negative relationship between seagrass status and porewater hydrogen sulfide (H₂S) levels, through a comparative analysis within a range of seven Posidonia oceanica meadows growing over carbonate sediments in the NW Mediterranean Sea around Mallorca Island. The studied meadows range from meadows growing on sediments with very low sulfide porewater concentrations (4.6 μM) to those growing over higher sulfide conditions (33.5 μM). Organic matter content, sulfate reduction rates and sulfide porewater concentrations in the sediments were determined concurrently with the assessment of demographic plant dynamics (specific mortality and net population growth rates). Sulfide porewater concentration increased with increasing organic matter content in the sediment, while net population growth decreased significantly with low increases of sulfide concentrations. Our results confirm the previously suspected vulnerability of seagrass meadows growing on carbonate sediments to increased sulfide levels. An excess of 10 μmols H₂S L⁻¹ porewater is identified to already conduce P. oceanica meadows to decline, which this study identifies, particularly, as strongly sensitive to sulfides. The results reported here suggest that even moderate increases in organic carbon inputs may lead to enhancement of dissolved sulfides and may be an important factor for seagrass status in these iron-depleted carbonate sediments from the Mediterranean Sea.     

南海S08-57站柱样岩心地球化学特征及古海洋学意义

对南海S08-57站柱样岩心的CaCO3、SiO2、Al2O3、TFe2O3、MgO、CaO、Na2O、K2O、TiO2、P2O5、MnO、Cu、Pb、Zn、Co、Ni、Ba、Sr、Rb、V、Cr、La、Ce和Ta的含量变化进行了分析;根据CaCO3含量变化建立了碳酸钙地层时标,提出了南海碳酸钙地层学的SB4.0事件,进一步完善了南海标准碳酸钙地层学时标;讨论了沉积物地球化学特征及古海洋学意义。结果表明,S08-57柱样岩心的SB3.33m事件附近存在一次强碳酸盐沉积,Al2O3、TiO2、Nb、SiO2、K2O、Ta、La、Rb、Ce、MgO、Zn、TFe2O3、Na2O、V、Pb和Cr的沉积曲线与CaCO3近似呈镜像关系。     

An Advanced Probabilistic Neural Network for the Design of Breakwater Armor Blocks

In this study,an advanced probabilistic neural network(APNN)method is proposed to reflect the global probability density function(PDF)by summing up the heterogeneous local PDF which is automatically determined in the individual standard deviation of variables.The APNN is applied to predict the stability number of armor blocks of breakwaters using the experimental data of van der Meer,and the estimated results of the APNN are compared with those of an empirical formula and a previous artificial neural network(ANN)model.The APNN shows better results in predicting the stability number of armor blocks of breakwater and it provided the promising probabilistic viewpoints by using the individual standard deviation in a variable.     

Cerium anomaly and cerium thermodynamics in the sea water

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黄河三角州沿岸及相邻渤海海域碳酸盐研究(英文)

对黄河三角州陆地上河道,河口、潮间带及毗邻渤海海域沉积物中的碳酸盐含量作了分析,在此基础上划分出含量不同的沉积区和亚区。沉积区的划分和其物源有十分良好的对应关系,同一沉积区内的亚区则主要和粒度有关,从而间接反映了水动力环境与生物作用的控制性影响。黄河口沉积物中碳酸盐含量与粒度成反比,其他物源的沉积物则各不相同。黄河口及邻近渤海海域中粘土粒级和碳酸盐含量等值线反映出黄河细粒级沉积物扩散的方向、强度和范围。海洋生源沉积是影响渤海东部和中部沉积物中碳酸盐含量分布的主要因素。     

中太平洋北部海盆沉积物中钙质超微化石溶解相与地层年代

本文通过对中太平洋北部海盆表层和柱状沉积物中钙质超微化石的分析鉴定,讨论了该调查区处在溶跃面以下表层沉积物中钙质超微化石的种数与水深变化的关系,推测出本调查区中Ⅰ区的碳酸盐补偿深度约5300米。根据地层中出现的标准化石,对柱状岩芯M_(14)进行了地层年代划分。最上部地层年代约为27万年前,向下1米处年代约为44万年前,3.66米处年代约为122万年前。     

东海2万年来碳酸盐溶解作用变化:翼足类的记录

对东海84个表层沉积样品和5个重力柱状样中的翼足类和浮游有孔虫丰度、浮游有孔虫碎壳率和底栖有孔虫群中胶结质类的比例等进行了定量分析,确定了东海现代文石补偿深度（ACD）位于约600 m处,碳酸盐溶跃面在约1 400 m处.末次冰期时随着碳酸盐溶解作用的显著减弱,ACD大幅度下降至现代的1 000 m之下.     

埕岛海域浅水区人工构筑物周边海底地形演化与海洋灾害地质现象关系研究

高分辨率的回声测深、旁侧声纳及3．5kHz浅地层剖面的探测发现：埕岛海域浅水底坡人工构筑物周边沉积物块体运动极为发育。这种使局部浅水区浅层沉积物向深水洼地填充的沉积物再搬运营力，大大减缓了埕岛海域浅水区人工构筑物周围水力冲刷凹坑的水深增大幅度，而凹坑边缘区域在沉积物块体运动、海洋水动力侵蚀和底床固结沉降的共同作用下，水深平均增加幅度高达0．4m／a，“凹坑”面积逐年扩大，边坡坡度平均每年以5‰减缓。     

楚科奇海与白令海表层沉积中的钙质和硅质微体化石研究

通过对北冰洋楚科奇海和令海41个表层沉积样品中的有孔虫、介形类等钙质微体化石和硅藻、放射虫、海绵骨针等硅质微体化石的定量分析，发现表层沉积中浮游有孔虫几乎缺失，这可能与该区表层生产力相对低、碳酸盐溶解作用较强有关，而底栖有孔虫和硅质微体化石的丰度分布则明显受表层沉积物类型、表层初级生物生产力和碳酸盐溶解作用所控制。其中，北冰洋楚科奇海陆架区有孔虫丰度和分异度低，含少量浅水介形类，放射虫在陆架浅水区缺失，但含有较多硅藻和海绵骨针等其它硅质微体化石，反映该区由于海冰、表层海水温度较冷而导致表歧初级生产力相对低。白令海陆坡区底栖有孔虫丰度比较科奇海高一个数量级，底栖有孔虫分异度也相对高，硅藻、放射虫、海绵骨针等硅质微体化石的丰度与钙质化石一样，其丰度比楚科奇海明显高，反映表层初级生产力相对高。根据白令海陆坡区底栖有孔虫和硅质微体化石丰度、底栖有孔虫胶结质壳比值的水深变化，推测该区碳酸盐溶跃层和补偿深度（CCD）相对浅，分别位于水深2000m和3800m处。     

中太平洋海盆碳酸钙溶解带及其特征

本文通过对不同水深区沉积物中组分、生物面貌、矿物、ＣａＣＯ３含量和碳酸钙溶解率等特征的分析和对比，把本区碳酸钙溶解深度带划分为碳酸钙溶跃面（小于３７００ｍ）、弱溶带（３７００～４８００ｍ）、强溶带（４８００～５２００ｍ）和全溶带（大于５２００ｍ）。提出本海域碳酸钙补偿深度界面约在５２００ｍ。文中还阐述了不同碳酸钙溶解带及其沉积物特征，认为造成这种特征的主要原因是随着水深变化碳酸钙溶解程度不同以及与南极底层流等因素的影响有关。