崇明东滩湿地干湿交替过程脲酶活性变化初探

以典型滨海湿地——崇明东滩为原型区域,采集湿地沉积物及海水样品,通过土柱模拟方法(30、35、40℃),研究了半月潮(15d左右为周期的"大潮")与日潮(一个太阴日内出现的涨潮和落潮)水分生态过程沉积物脲酶(Urease)活性及溶解性有机氮(DON)与铵态氮(NH+4-N)含量等的变化,计算了Urease活性的表观温度敏感性系数(Q’10),旨为揭示典型滨海湿地潮汐驱动下周期性干湿交替过程沉积物Urease活性的变化规律.半月潮过程,干燥沉积物(1%~3%)淹水后,Urease活性迅速增加.随着沉积物变干,酶活性逐渐下降.Urease活性对沉积物水分变化的敏感性随干湿交替频次的增加而下降.日潮过程对Urease活性的影响较小.30、35、40℃下,酶活性分别为(0.067±0.018)、(0.143±0.027)、(0.028±0.011)g·(10 g·h)-1.相比较而言,半月潮过程Urease活性明显低于日潮过程.这表明,干湿交替显著降低了沉积物Urease活性(30、35℃).半月潮过程中,沉积物Urease活性Q’10的最高值出现在35~40℃,而日潮过程中出现在30~35℃.因此,干湿交替可能增高了Urease活性Q’10的温度响应范围.此外,半月潮过程中,Urease活性主导着沉积物NH+4-N含量的变化(30、35℃),但其与DON含量之间并无显著相关性.日潮过程Urease活性与NH+4-N和DON含量之间均不显著相关.     

Competition of bloom-forming marine phytoplankton at low nutrient concentrations

Competition of three bloom-forming marine phytoplankton (diatom Skeletonema costatum, and dinoflagellates Prorocentrum minimum and Alexandrium tamarense) was studied through a series of multispecies cultures with di erent nitrate (NaNO3) and phosphate (NaH2PO4) levels and excess silicate to interpret red tide algae succession. S. costatum outgrew the other two dinoflagellates in nitrate and phosphate replete cultures with 10 mol/L Na2SiO3. Under nitrate limited (8.82 mol/L NaNO3) conditions, the growth of S. costatum was also dominant when phosphate concentrations were from 3.6 to 108 mol/L. Cell density of the two dinoflagellates only increased slightly, to less than 400 and 600 cells/mL, respectively. Cell density of S. costatum decreased with time before day 12, and then increased to 4000 cells/mL (1.5 mg/L dry biomass) at NaNO3 concentrations between 88.2 and 882 mol/L with limited phosphate (0.36 mol/L NaH2PO4) levels. In addition, P. minimum grew well with a maximal cell density of 1690–2100 cells/mL (0.5–0.6 mg/L dry biomass). Although S. costatum initially grew fast, its cell density decreased quickly with time later in the growth phase and the two dinoflagellates were dominant under the nitrate-limited and high nitrate conditions with limited phosphate. These results indicated that the diatom was a poor competitor compared to the two dinoflagellates under limited phosphate; however, it grew well under limited nitrate when growth of the dinoflagellates was near detection limits.     

Dissipation of Tidal Energy and Associated Mixing in a Wide Fjord

This paper sets out to test the hypothesis that vertical mixing due to the dissipation of the internal tide accounts for a significant proportion of the total vertical mixing in a fjordic basin during a period of deep water isolation. During July and August 1999 two locations in the Clyde Sea were instrumented with moored RD Instruments Acoustic Doppler Current Profilers (ADCPs) and conductivity-temperature-pressure chains: Station C2, near the shallow entrance sill (55 m water depth), and station C1 in the deep basin (155 m water depth). A bottom pressure recorder was also deployed at station C3 by the seaward entrance to the Clyde Sea in the North Channel of the Irish Sea. A Free-falling Light Yo-yo shear microstructure profiler (FLY) was used to measure the dissipation rate of turbulent kinetic energy (TKE) throughout the water column over 25 h at both C1 and C2. These were interspersed with two-hourly conductivity-temperature-depth casts at both sites. The observations show agreement between the dissipation rate of TKE estimated by using a microstructure profiler and that estimated from the decay of the internal tide as measured by the two ADCPs. However, to account for all the implied mixing it is necessary to invoke an additional source of buoyancy flux, the most probable candidate mechanism is enhanced internal wave breaking near the sill and at the sloping boundaries of the deep basin. In addition, the vertical eddy diffusivity estimated from the micro-structure profiler (O(0.5 cm² s^–1) indicates that internal tide induced mixing away from any boundaries contributed significantly to the overall level of mixing which is required to account for the observed evolution of the deep basin water properties.     

A model of oscillatory transport in granular soils, with application to barometric pumping and earth tides

A simple algebraic model is proposed to estimate the transport of a volatile or soluble chemical caused by oscillatory flow of fluid in a porous medium. The model is applied to the barometric pumping of vapors in the vadose zone, and to the transport of dissolved species by earth tides in an aquifer. In the model, the fluid moves sinusoidally with time in the porosity of the soil. The chemical concentration in the mobile fluid is considered to equilibrate with the concentration in the surrounding matrix according to a characteristic time governed by diffusion, sorption, or other rate processes. The model provides a closed form solution, to which barometric pressure data are applied in an example of pore gas motion in the vadose zone. The model predicts that the additional diffusivity due barometric pumping in an unfractured vadose zone would be comparable to the diffusivity in stagnant pore gas if the equilibration time is 1 day or longer. Water motion due to the M2 lunar tide is examined as an example of oscillatory transport in an aquifer. It is shown that the tidal motion of the water in an aquifer might significantly increase the vertical diffusivity of dissolved species when compared to diffusion in an absolutely stagnant aquifer, but the hydrodynamic dispersivity due to tidal motion or gravitational flow would probably exceed the diffusivity due to oscillatory advection.     

基于FBM法追踪秦皇岛海域赤潮迁移扩散

在Delft3D-FLOW模型模拟水动力的基础上,基于FBM粒子追踪法建立和验证赤潮迁移扩散模型.模拟了秦皇岛海域潮流和风生流,分析了风生流对赤潮迁移扩散的作用,对比分析了FBM法、拉格朗日法和常规布朗运动法在赤潮迁移扩散模拟中的特性,测试了模型Hurst指数的敏感性并得出其在赤潮模拟中的合理取值范围.主要结论为：①秦皇岛海域的赤潮主要随潮流的涨落而往复移动,一个涨落潮周期内赤潮的净迁移距离较小;②秦皇岛海域夏季潮流较弱,但风对赤潮迁移具有一定影响,易产生东北向风生流,导致赤潮更易往东北方向迁移;③Hurst指数较明显地影响粒子云的扩散范围,Hurst指数取0.80±0.03能比较真实地模拟秦皇岛海域赤潮的迁移扩散;④FBM法可模拟赤潮的non-Fickian扩散现象,使其模拟的粒子云扩散范围和分布形状明显优于拉格朗日法和常规布朗运动法.     

二十年来渤海生态环境参数的演化和相互关系

通过系统分析近２０ａ来渤海中部海域３ａ（１９８２－１９８３，１９９２－１９９３，１９９８－１９９９年）１０航次的生态环境特征参数的变化，描述了变化趋势，初步讨论了各种特征参数之间的相互关系。研究发现，近２０ａ来，渤海中部营养盐的浓度和结构（Ｎ／Ｐ和Ｓｉ／Ｎ）均发生显著变化，表现为：硝酸盐、亚硝酸盐、总无机氮持续增加，活性磷和硅显著降低，Ｎ／Ｐ值升高，Ｓｉ／Ｎ值下降。Ｎ／Ｐ值３ａ的五月和十月平均值分     

秦皇岛海域生态环境特征与赤潮监测

在简述秦皇岛海域自然环境特征与营养盐分布及赤潮生物特征的基础上，采用营养状态指数和浮游植物生态特征指标对该海域富营养化状态给予评价。调查表明，该海域自７０ 年代末以来共发现３２种赤潮生物。     

Behavior of a Small Pulsed River Plume in a Strong Tidal Cross-Flow in the Akashi Strait

We carried out a field study of a small river plume emptying into Osaka Bay near the Akashi Strait in western Japan, to understand the fate of its urban-runoff-laden waters. As the river is weak compared to tidal currents, we find that the behavior of the plume is strongly influenced by phasing between tidal stage and currents (a westward-traveling progressive tidal wave). When the tidal stage rises, sea water floods up the river, and concentrated river effluent cannot be seen in Osaka Bay. During most of the river’s ebb, a topographic eddy transports river effluent towards the energetic Akashi Strait, while strong vertical shear in the tidal flow mixes the effluent with seawater. However, there is a short interval of time during which the direction of tidal flow in the Strait changes direction and the magnitude of the current is weak. At this time, shear is weak enough to allow a stratified plume of concentrated river water to form, and this plume is driven offshore, and into Osaka Bay, by baroclinic circulation. A sewage outfall, which is located very close to the river mouth, is subjected to these same conditions and therefore exhibits similar behavior. Understanding the relation between tidal phase and plume behavior will be useful to Kobe City, as well as other cities in a similar environment, for minimizing the environmental effects of their wastewater and non-point-source runoff.     

自组织神经网络在有害赤潮预警研究中的应用

根据非线性理论及有害赤潮的特点，探讨应用人工神经网络原理进行赤潮预警预报的方法，提出网络可塑性较强，无监督的ART－KOHONEN网络模型，阐述了其基本原理和算法。将该模型应用于辽宁省营口市鲅鱼圈海域，结果表明：该方法能较理想地解决无训练样本的分类识别问题，具有较高的精度，可用于有害赤潮的预警预报工作。     

密闭培养对纤细角毛藻稳定同位素组成的影响

为研究碳源对赤潮藻生长的影响,以赤潮藻纤细角毛藻（Chaetoceros gracilis）为研究对象,在密闭条件下进行培养,模拟赤潮发生时碳源缺乏的生长环境;分析碳源不足对纤细角毛藻不同生长阶段的差异影响,采用密闭培养的方法,分别在正常组和缺氮组的营养条件下培养纤细角毛藻,测定生物量、营养盐浓度和碳氮稳定同位素组成等重要监测指标.结果表明:不同营养条件对纤细角毛藻的生物量存在显著影响.在正常组,c（NO₃--N）（NO₃--N为硝酸盐）随着培养时间呈下降趋势,ρ（NO₂--N）（NO₂--N为亚硝酸盐）和ρ（NH₄+-N）（NH₄+-N为铵盐）与藻类生物量呈显著正相关,ρ（PO₄3--P）（PO₄3--P为磷酸盐）和c（SiO₄2--Si）（SiO₄2--Si为硅酸盐）与藻类生物量呈显著负相关;在缺氮组,c（NO₃--N）、ρ（NO₂--N）、ρ（NH₄+-N）、ρ（PO₄3--P）和c（SiO₄2--Si）均与藻类生物量呈显著负相关.整个试验周期中,正常组和缺氮组δ13C和δ15N值越来越正.其中,正常组的δ13C值比缺氮组的更正,平均高2.286‰;缺氮组的δ15N值比正常组的更正,平均高3.307‰.正常组和缺氮组的δ13C、δ15N值与生物量均呈显著正相关.研究显示,碳源和氮源的不足分别会导致更正的δ13C和δ15N值,推测赤潮发生会导致δ13C和δ15N值偏正,赤潮藻的碳氮稳定同位素组成可以作为赤潮监测的指标和方法.