黄河口滨岸潮滩湿地系统氮生物循环特征与循环模式研究

潮滩湿地处于海陆相互作用地带，是响应全球变化和人类活动较为敏感的生态系统 之一。潮滩湿地是海岸带一个非常重要的生态类型，作为陆地和海洋过渡区的重要组成 部分，承接来自陆地人类活动带来的大量含氮物质。潮滩湿地氮的生物循环特征不但影 响湿地系统自身的调节机制，而且其在环境介质中的特殊动力学过程也与一系列全球环 境问题息息相关。为了更深入的理解潮滩湿地氮的生物循环特征及其关键机制，论文以 黄河口滨岸潮滩翅碱蓬湿地为研究对象，通过野外样品采集、原位实验、微区试验，研 究了湿地土壤氮的时空分布与化学转化特征，探讨了湿地植物生物量与氮累积季节变化 特征以及湿地植物残体分解及分解过程氮动态特征，建立了湿地植物-土壤系统氮循环 分室模式，主要结论如下：（1）潮滩湿地土壤氮含量具有明显的水平变异和空间结构， TN、NO3 --N 和C/N 具有明显空间分布格局，其空间变异性均以向低潮滩延伸且受潮汐 涨落影响较大的方向最大；微地貌特征和潮汐微域物理扰动是导致空间异质性的两个重 要随机因素，水盐条件、土壤类型和潮汐物理扰动是三个重要结构因素；（2）潮滩湿地 土壤氮含量在不同时期的垂直分布均存在较高变异性，主要与有机质分布、潮汐影响、 水分条件以及陆源影响程度有关；潮滩湿地土壤的氮含量具有明显季节变化特征，主要 与水分状况及受潮汐影响的程度有关；（3）潮滩湿地土壤氮的净矿化/硝化速率均呈波动 变化，并受生物固持、反硝化、温度、水分、C/N 和pH 等因素影响；潮滩湿地0~15cm 土壤的净矿化量和净硝化量分别介于0.33~27.81kg·hm-2 和1.19~15.99kg·hm-2，高潮滩湿 地维持无机氮的能力明显强于中潮滩和低潮滩湿地；（4）两种表现型翅碱蓬的生物量 均具有明显季节变化和空间结构分形特征，二者的地上生物量具有自相似性，分别遵从 D=2.012 和2.366 的分形生长过程；（5）沉积强度显著影响翅碱蓬种子的出苗和幼苗存 活，适度沉积可刺激幼苗生长，重度沉积对幼苗生长则具有抑制作用；沉积可促使幼苗 被埋部分发育为根系，反映了其对潮滩较强沉积环境的特殊适应对策；（6）两种表现 型翅碱蓬根、茎和枯落物的TN 含量均呈递减变化，符合指数衰减模型，叶是二者重要 氮储库，分配比高达46.91±16.97%和55.21±9.79%；中潮滩植被的N/P 为9.87±3.47＜14， 其生长受N 限制，低潮滩植被的N/P 为15.73±5.00＜16，其生长同时受N、P 限制，但 更受P 限制；（7）潮滩湿地植物残体在水盐含量较高或沉积较强条件下的失重率和分解 速率一般较高，反之则较低；温度、水分、盐分和pH 是影响残体相对分解速率的重要 摘 要 II 因素；（8）当分解环境的养分状况不发生较大改变时，残体相对分解速率在很大程度上 取决于基质质量，当养分状况因潮汐养分交换、潮汐物理扰动、沉积物矿化等发生较大 改变时，残体相对分解速率在很大程度上取决于分解环境养分供给状况；（9）潮滩湿地 植物残体在不同水盐梯度和沉积强度下的氮含量、C/N 的变化模式整体较为一致，水盐 条件和沉积强度对残体氮绝对量的变化具有重要影响，C/N 对分解过程中氮养分的调控 作用更为重要；（

微生物——铊相互作用的生物地球化学研究——以真菌（Fungus）为例

铊是一种有毒有害的重金属元素，已经引起了广泛的关注。本论文通过对黔西南铊矿区土壤和沉积物样品的菌株分离、铊高耐受性菌株的筛选、胞外吸附、富集、亚细胞水平区系分布、絮凝实验及ITS序列等实验研究分析，并结合铊的地球化学相关研究，较系统地阐述了真菌--铊的生物地球化学过程机理，得出以下结论： 1、与环境背景区相比，黔西南滥木厂铊矿区内的河流、土壤中铊的已有不同程度的积累，直接导致了当地微生物生物量在很大程度上的降低，微生物生物量与铊含量间有显著的负相关关系。研究区内的沉积物、土壤中的微生物区系结构和数量发生了明显变化，细菌、真菌及放线菌数量均出现显著降低，而且三大微生物对重金属污染的敏感性大小也不一样，即放线菌>细菌>真菌。从土壤样品中分离到的主要菌群仍为常见种属，如青霉属（Penicillium）、木霉属（Trichoderma）、拟青霉（Paecilomyces）等。 2、经过初筛菌株的铊耐受性实验，在1000 mg/L水平筛选得到九株高耐受性菌株。吸附实验表明：微生物菌株对铊的吸附效率在4.63～16.89%，且随着环境中铊浓度的上升而降低，这可能是因为铊浓度的升高加大了对微生物生长的抑制作用，所形成的菌丝体（或菌丝球）减少，表面积也相应减少，从而导致了吸附效率的下降。各种常量元素和铊的关系呈显著相关性，钙、钾和钠等常量元素也是微生物赖以维持生存的因子，可能由于微生物细胞对钙、钾的吸附方式与对铊的吸附方式类似。因此，随着铊处理浓度的上升，钙和钾的吸附量也随之减少，而钠则呈现相反的趋势。 3、富集实验表明，九株菌株对铊的富集量随着铊处理浓度上升而降低，其影响趋势与对生物量的影响趋势基本一致，最高可达到7189 mg/kg，最大富集系数为7.2。九株菌株对常量元素的富集与对铊的富集并无明显的相关性，但在考察铊处理浓度对常量元素的富集影响时发现，铊处理浓度的上升与对钙的富集量表现出较强的正相关；而对钾、钠、镁的富集影响并不明显。 4、亚细胞水平上的铊分布研究表明，铊的富集优先顺序为：细胞质>细胞壁>细胞器。亚细胞水平的区隔化作用是微生物对铊的主要耐受机制，细胞质是赋存铊的主要场所（53.83～79.45 %）。结合各亚细胞组分中常量元素与铊之间的相关性，并联系前人的研究，Tl+主要是通过细胞壁的Na+ -K+ ATPase和K+ -电位门通道进入细胞内的从而影响细胞的正常代谢的，而Ca2+的活化更有助于这一过程。 5、絮凝实验表明，培养三天后的发酵液对矿区废水中铊的去除率最高可达到70.49 %，最佳影响因子组合为：pH=8，温度为16℃，搅拌时间为4分钟。菌株的絮凝活性最高可达到57.32%，最佳影响因子组合为：pH=8，温度为14℃，搅拌时间为4分钟。 6、通过对九株铊高耐受性菌株的ITS序列分析及其在Gene Bank中的BLAST比对结果表明，五株菌株同属于木霉属（Trichoderma），两株菌株同属于青霉属（Penicillium）。这表明这两类真菌对铊的适应性较强，为以后寻找铊高耐受性菌株及其资源化利用提供了理论基础。

Stability shear stress and equilibrium cross-sectional geometry of sheltered tidal channels

This study relates tidal channel cross-sectional area (A) to peak spring discharge (Q) via a physical mechanism, namely the stability shear stress ( tau sub(S)) just necessary to maintain a zero gradient in net along-channel sediment transport. It is assumed that if bed shear stress ( tau ) is greater than tau sub(S), net erosion will occur, increasing A, and reducing tau similar to (Q/A) super(2) back toward tau sub(S). If tau < tau sub(S) there will be net deposition, reducing A and increasing tau toward tau sub(S). A survey of the literature allows estimates of Q and A at 242 sections in 26 separate sheltered tidal systems. Assuming a single value of tau sub(S) characterizes the entire length of a given tidal channel, it is predicted that along-channel geometry will follow the relation Ah sub(R) super(1) super(/) super(6) similar to Q. Along-channel regressions of the form Ah sub(R) super(1) super(/) super(6) similar to Q super( beta ) give a mean observed value for beta of 1.00 plus or minus 0.06, which is consistent with this concept. Results indicate that a lower bound on tau sub(S) (and an upper bound on A) for stable channels is provided by the critical shear stress ( tau sub(C)) just capable of initiating sediment motion. Observed tau sub(S) is found to vary among all systems as a function of spring tidal range (R sub(sp)) according to the relation tau sub(S) approximately 2.3 R sub(sp) super(0.79) tau sub(C). Observed deviations from uniform tau sub(S) along individual channels are associated with along-channel variation in the direction of maximum discharge (i.e., flood-versus ebb-dominance).

the ebb-tidal delta of the venice lagoon,Italy

Very high-resolution seismic lines were collected offshore the Venice Lagoon in the framework of the Co.Ri.La'New very high resolution seismic methods to study the Venice Lagoon subsoil' project. The 140 km boomer profiles led to the identification of a convex-upward,lens-shaped body just outside the Lido inlet,one of the three lagoon inlets,which has been interpreted as an ebb-tidal delta.The comparison between the scismostratigraphic setting og this deposit, as revealed by the seismic lines,and the analyses of historicalbathymetric maps highlighted the key role of human interventions in the formation and evolution of the Lido inlet cbb-tidal delta.To preserve the lagoon environment but also to ensure a navigable way, human interventions at the Lidoinlet,performed since the fourteenth centtury, caused profound variations in the inlet dynamics,ldading to a progressive increase in the sediment dispersion from the lagoon interior towards the sea. The ebb-tidal delta of the Lido nilet is thus a very recent feature compared with the formation of the Venice lagoon and formed mainly as a consequence of the construction of the two jetties that have bound the inlet form AD 1886 to the present day.

TIDAL DEPENDENCE OF PHOTOINHIBITION OF PHOTOSYNTHESIS IN MARINE MACROPHYTES OF THE SOUTH CHINA SEA

PHOTOSYSTEM-II; CHLOROPHYLL FLUORESCENCE; ULVA-ROTUNDATA; ELECTRON-TRANSPORT; FIELD EXPERIMENTS; O-2 EVOLUTION; QUANTUM YIELD; TEMPERATURE; MACROALGAE; RESPONSES

Numerical simulation of principal tidal constituents in the South China Sea, Gulf of Tonkin and Gulf of Thailand

The principal tidal constituents M-2, S-2, K-1 and O-1 in the South China Sea, Gulf of Tonkin and Gulf of Thailand are simulated simultaneously using the numerical scheme of Kwok et al. (1995 Proceedings of the 1st Asian Computational Fluid Dynamics Conference, pp. 16-19). The average differences between the computed and observed harmonic constants are mostly within 5 cm and 10 degrees for amplitudes and phase-lags, respectively. The simulated tidal regimes in the present model are believed to be more accurate than the previous numerical results. Our studies confirm that a clockwise rotating M-2 amphidromic system lies in the southeast of the Gulf of Thailand and an S-2 amphidromic system at the near-shore area of the northeast South China Sea. The linear tidal energy equation developed by Garrett (1975 Deep-Sea Research 22, 23-35) is generalized to the nonlinear case. Based on the numerical results, the energy budgets in the South China Sea and its subareas, namely the Taiwan Strait, the Gulf of Tonkin, the Gulf of Thailand and the remaining area are investigated. The tidal motion in the Taiwan Strait is maintained mainly by the energy fluxes from the East China Sea for both semidiurnal and diurnal species and partially from the Luzon Strait for semidiurnal species. For the other parts of the South China Sea, the tidal motion is mainly maintained by the energy fluxes through the Luzon Strait. The energy inputs from the tide-generating force are negative for semidiurnal species and positive for diurnal species. (C) 1999 Elsevier Science Ltd. All rights reserved.

Annual cycle of stratification and tidal fronts in the Bohai Sea: A model study

In general, competition between buoyancy mechanisms and mixing dynamics largely determines the water column structure in a shelf sea. A three dimensional baroclinic ocean model forced by surface heat fluxes and the 2.5 order Mellor-Yamada turbulence scheme is used to simulate the annual cycle of the temperature in the Bohai Sea. The difference between the sea surface temperature (SST) and sea bottom temperature (SBT) is used to examine the evolution of its vertical stratification. It is found that the water column is well-mixed from October to March and that the seasonal thermocline appears in April, peaks in July and then weakens afterwards, closely following the heat budget. In addition, the Loder parameter based on the topography and tidal current amplitude is also computed in order to examine tidal fronts in the BS, which are evident in summer months when the wind stirring mechanism is weak.

Tidal current observation in the southern Yellow Sea in the summers of 2001 and 2003

Direct current observations in the Yellow Sea interior are very scarce due to intense fishing and trawling activities. Most previous studies on tides in the area were based on coastal measurements or satellite altimeter sea levels and have not been rigorously compared with direct measurements. In this paper, tidal currents are studied with current profiles from three bottom-moored Sontek Acoustic Doppler Profilers (ADPs) deployed in the southern Yellow Sea in summer of 2001 and 2003. The measured current series were dominated by tidal currents. Maximum velocities are between 40-80 cm/s at the mooring stations. M-2 current is the most dominant primary tidal constituent, while MS4 and M-4 are the most significant shallow water tides with much smaller amplitudes than the primary tides.