海洋酸化与磷限制对颗石藻（Emiliania huxleyi）生理特征的耦合效应

颗石藻既通过光合作用合成颗粒有机碳（POC）,又通过钙化作用产生颗粒无机碳（PIC）,对海洋碳循环有重要贡献。虽然已有一些研究报道海洋酸化通常可增加颗石藻细胞POC含量,减少细胞PIC含量,但是这些实验结果大部分是在营养盐浓度充足条件下获得,且较少研究关注营养盐浓度限制和海洋酸化对颗石藻的耦合作用。本文研究了在无机磷浓度限制条件下,赫氏颗石藻（Emiliania huxleyi）的主要生理指标对海洋酸化的响应特征。结果显示,海洋酸化和无机磷浓度限制协同降低了颗石藻的生长速率、相对电子传递速率和光能利用效率。无机磷浓度限制主导增加颗石藻的光合固碳量,并抵消了海洋酸化对细胞PIC含量及PIC/POC比率的负面效应。研究结果表明,无机磷浓度限制改变了颗石藻的两种固碳作用对海洋酸化的响应趋势,暗示在无机磷浓度不同的海域,颗石藻对海洋碳循环的贡献不同。     

不同铁浓度对一种颗石藻Emiliania huxleyi的生长及光合作用的影响

为探讨铁对颗石藻生长及光合作用的影响, 以分离于秘鲁上升流区域的两株不同基因型的赫胥黎艾氏藻Emiliania huxleyi RCC6660与RCC6666为研究对象, 在调整5种铁浓度(0、50、100、500、1 000 nmol/L)的Aquil培养基中培养, 比较其生长率、色素含量、营养盐消耗、颗粒有机物含量及叶绿素荧光特性参数的差异。实验结果表明: 铁浓度未对两株藻的生长产生显著影响, 但0 nmol/L时RCC6660的比生长率显著高于RCC6666(P < 0.05)。随着铁浓度的减少, 细胞粒径和体积减小, 最大电子传递速率(rETR_max)和表观光能利用效率降低。我们推测RCC6660为了保护细胞在低铁时免受光损伤, 通过叶黄素循环以及高度钙化的外壳实现光保护, 而RCC6666通过更多其他形式的非光化学荧光淬灭的手段。由于钙化是个耗能过程, 低钙化的RCC6666的光能利用效率在低铁浓度下也更高。但RCC6660的rETR_max更大, 拥有较高的光合潜力, 这可能与其拥有的更高含量的色素有关。本研究揭示了不同基因型、不同钙化程度的两株Emiliania huxleyi对不同铁浓度的差异响应, 及铁限制条件下光保护机制和光能利用的不同, 为进一步研究光合和钙化作用的偶联机制提供了参考。     

早渐新世钙质超微化石演变与营养盐及二氧化碳关系

南海北部早渐新世发生明显的营养供给和二氧化碳浓度的变化，相关地质记录为研究颗石藻的生理机制提供了理想的自然实验室。在本研究中，我们建立了一个新的颗石藻群落演化的指标，定义为E*比值。该比值由富营养属种和中等-贫营养属种的相对丰度计算而得（E^*=e/(e+c)×100，e代表富营养属种，c代表中等-贫营养属种）。其中富营养属种包括小Reticulofenestra， Reticulofenestra lockeri组，Reticulofenestra bisecta组和Coccolithus pelagicus组，而中等-贫营养属种包括Cyclicargolithus spp.。E^*指标与早渐新世营养盐指标具有较强的相关性，但在不同二氧化碳浓度的条件下表现不同的公变趋势。将群落组合与已发表的二氧化碳浓度数据对比，我们提出颗石藻可能在二氧化碳持续降低的环境下改变其对碳源和营养盐的利用方式，指示颗石藻的碳浓缩机制可能开始于早渐新世。     

天津近岸浮游植物群落对海洋酸化和硝酸盐加富的响应

为了评估海洋酸化和富营养化耦合作用对近海浮游生态环境的影响,本研究以天津市近岸海域浮游植物群落的生物地球化学指标为研究对象,分别采用一次性及连续培养的方式模拟自然水华及稳态条件,探究其对二氧化碳(CO₂)和硝酸盐浓度变化及二者耦合作用的响应。实验条件设置如下:1)对照:二氧化碳分压p(CO₂)40.53 Pa、无硝酸盐添加;2)酸化:p(CO₂)101.3 Pa、无硝酸盐添加;3)加N:p(CO₂)40.53 Pa、添加硝酸盐50 μmol·L^–1;4)酸化加N:p(CO₂)101.3 Pa、添加硝酸盐50 μmol·L^–1。实验结果表明,硝酸盐加富比酸化更加显著地促进浮游植物群落总叶绿素(Chl a)生物量及颗粒有机碳(POC)和颗粒有机氮(PON)积累,酸化和加N使浮游植物群落粒径大小升高。连续培养实验表明,酸化和N加富对Chl a、生物硅(BSi)、PON浓度、PON与颗粒有机磷(POP)比值(N/P)、POC与BSi比值(C/BSi)及沉降速率有协同交互作用,对POP和POC浓度及POC与PON比值(C/N)有拮抗性交互作用。在一次性培养后,酸化显著降低了浮游植物群落的沉降速率;而在连续培养后,酸化和N加富使浮游植物群落沉降速率显著升高。这些结果表明酸化和N加富对与近岸浮游植物相关的生物地球化学循环及在不同生长阶段的种群碳沉降存在不同的潜在影响及交互效应。     

南海IODP U1501站早中新世海洋沉积物长链烯酮来源与含量变化

海洋沉积物中的长链烯酮由海洋单细胞钙化藻类颗石藻生产,是一种被广泛应用于古气候研究领域中的分子标记物。长链烯酮碳同位素是重建地质历史时期海水、大气CO₂浓度的可靠方法之一。在此方法中,需要利用颗石大小对颗石藻生理参数b值进行修正,因此需要厘清哪类颗石藻对烯酮的贡献是一个重要的科学问题。目前认为新生代海洋沉积物中主要的长链烯酮生产者为Noelaerhabdaceae科的颗石藻,包含Emiliania huxleyi,Gephyrocapsa spp.,Reticulofenestra spp.,Cyclicargolithus spp.,但对它们具体的贡献程度仍然未知。因此,本文以南海国际大洋发现计划IODP U1501站早中新世海洋沉积物为研究材料,对比了沉积物中颗石与烯酮的绝对含量,发现Cyclicargolithus属的颗石丰度与烯酮含量具有显著的相关性(r=0.44,p<0.01),而Reticulofenestra spp.的相关性较弱(r=0.09,p=0.5)。研究认为早中新世长链烯酮的主要生产者为Cyclicargolithus属,Reticu...     

离体培养的虫黄藻(Symbiodinium voratum)对温度和光照的生理响应

虫黄藻是珊瑚礁生态系统中最主要的初级生产者，并在珊瑚礁的建造过程中起着关键作用。为探究虫黄藻对温度和光照的生理响应，本研究以E型虫黄藻（Symbiodinium voratum）为实验对象，通过室内培养，并结合谢尔福德耐受性定律建立了基于温度的虫黄藻生长速率的耐受性模型。结果显示：E型虫黄藻在光强90μE培养下，最适生长温度为22.56℃，适温范围为16.72—28.40℃；温度培养实验中，23℃时，虫黄藻中有机碳（C）、氮（N）积累最多； 27℃时，虫黄藻PSⅡ的原初光能转化效率（F_v/F_m）显著高于其余两个温度组；光照培养实验中，E型虫黄藻在温度23℃培养下，光强的适宜范围为100—200μE；并通过提高细胞内叶绿素a含量和F_v/F_m两种方式应对外界光照不足。     

南海北部晚第四纪颗石藻生产力变化及其影响因素

通过对南海北部MD05-2904岩心进行有机地球化学分析,以长链不饱和烯酮作为颗石藻生产力的替代性指标,讨论颗石藻生产力的变化及其影响因素。结果显示,260ka以来,颗石藻生产力有着明显的冰期/间冰期变化:冰期高,间冰期低;冰阶高,间冰阶低;在轨道尺度上岁差周期明显,反映出太阳辐射、东亚季风对颗石藻生产力在长期尺度上起调控作用;而由于特殊的地理位置,河流输送的营养盐对本区海洋初级生产力的影响可能也较大;与前人研究结果一致,同时认为,在地质历史上沉积速率变化大的区域,对生物标记物的含量和堆积速率的对比讨论,更有利于反映生产力的变化。     

夏季南黄海浮游甲壳动物死体比例的初步研究

浮游动物死体是海洋沉降碳通量的重要组成部分,研究浮游动物死体对于准确评估特定海区生物泵碳通量具有十分重要的意义。为了解夏季南黄海浮游甲壳动物在自然海区的死亡情况,采用2019年7~8月在南黄海获取的浮游动物样品,使用中性红染色法分析了浮游甲壳动物死体的平面分布及其受控环境因素。结果表明,夏季南黄海浮游甲壳动物平均丰度为(1 378.3±929.84) ind./m³,其死体比例在5.0%~68.8%之间,平均为33.3%±16.6%。桡足类是浮游甲壳动物的主要类群,平均丰度为(1 202.9±937.4) ind./m³,死体比例在3.6%~69.7%之间,平均为38.6%±17.0%,与全球海域浮游桡足类的平均死体比例相当。不同浮游甲壳动物优势种的死体比例存在差异。其中,拟长腹剑水蚤(Oithona similis)死体比例最高(62.0%),鸟喙尖头溞(Penilia avirostris)最低(17.9%)。与环境因子的相关性分析结果表明,海水温度和盐度是影响夏季南黄海浮游甲壳动物死体比例的主要影响因子。小拟哲水蚤(Paracalanus parvus)死体比例和表层温度显著正相关,拟长腹剑水蚤和近缘大眼剑水蚤(Corycaeus affinis)的死体比例与表底温差具有显著的正相关;而表层盐度与克氏纺锤水蚤(Acartia clausi)的死体比例存在正相关关系。该研究结果可为深入认识南黄海海洋生态动力学过程和海洋碳通量等相关研究提供重要的参考资料。     

颗石藻Pleurochrysis carterae形成休眠体的环境诱因分析

利用实验生理生态学方法对Pleurochrysis carterae种群增殖过程中出现丝状体的环境诱因进行了研究,从营养胁迫、钙化抑制胁迫、低温胁迫以及外源α-酮戊二酸的影响等几个方面,探讨了环境因子对P.carterae细胞休眠的诱导作用。结果表明,氮营养盐水平在P.carterae形成丝状体过程中有重要的作用,氮缺乏和氮限制会明显诱导丝状体的早期大量形成,即细胞快速进入休眠期。磷缺乏和磷限制对颗石藻丝状体形成的短期诱导作用不显著。正常钙化的颗石藻在缺钙环境中钙壳逐渐脱落、细胞裸露、没有种群增殖、不形成丝状体。低温胁迫下,颗石藻细胞不分裂,但细胞维持游泳的钙化单细胞状态,不形成丝状体。外源α-酮戊二酸对颗石藻形成丝状体具有浓度相关的效应,小于1.2mmol/L的浓度抑制丝状体的早期发生;1.2mmol/L及以上浓度的α-酮戊二酸能诱导丝状体早期发生。     

海洋酸化对浮游植物生理生态影响的研究进展

当前全球气候变化下的上层海洋变暖与酸化对以浮游植物为主的海洋生态系产生了重大影响，理解此背景下的海洋浮游植物生理生态响应，对我们理解和抑制全球气候变化具有重要意义。在全球大气二氧化碳分压（pCO₂）升高情景下，浮游植物通过光合作用、微生物循环等过程，通过不同功能群对海洋生源要素循环模式的改变，进而影响区域及全球海洋的生物地球化学循环。研究全球浮游植物对海洋酸化生理生态的响应使得我们对生物地球化学系统的认识更加全面、系统。     

Assessing the Validity of Seismo-Acoustic Predictor Equations for Obtaining Seabed and Sub-Surface Sediment Physical Properties

The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.     

Flow Cytometric Analysis of Coastal Lagoon Bacterioplankton and Picophytoplankton: Fixation and Storage Effects

The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics.     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,     

Estimation of Sediment Properties during Benthic Impact Experiments

Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges.