Spatial and temporal variations in pH and total alkalinity at the beginning of the rainy season in the Changjiang Estuary, China

The results of field observation carried out in May 2003 were used to examine pH and total alkalinity behaviors in the Changjiang Estuary. It was showed that PH and total alkalinity took on clear spatial variations in values with the minima in the low salinity region. Like salinity, transect distributions of PH and total alkalinity (TA) in a downriver direction had a sharp gradient each. These gradients appeared in such a sequence that the TA gradient was earlier than salinity and PH gradients, and the salinity gradient was earlier than the PH gradient. These distribution characteristics seemed to be strongly influenced by the mixing process of freshwater and seawater, for both PH and total alkalinity had significant linear relationships with salinity and temperature. For PH, phytoplankton activities also had a significant impact upon its spatial distribution. During a period of 48 h, PH and total alkalinity changed within wide ranges for every layer of the two anchor stations, namely, Stas 13 and 20, which were located at the mixed water mass and seawater mass, respectively. For both Stas 13 and 20, PH and TA fluctuation of every layer could be very wide during a 4 h period. As a whole, the data of the two anchor stations showed that neither variations in salinity and temperature nor phytoplankton activities were the main factors strongly influencing the total alkalinity temporal variability on a small time scale. The data of Sta. 20 implied that both salinity variation and phytoplankton activities had a significant influence on PH temporal variability, but the same conclusion could not be drawn from the data of Sta. 13.

Microcystin-RR induces physiological stress and cell death in the cyanobacterium Aphanizomenon sp DC01 isolated from Lake Dianchi, China

The phytoplankton community in Lake Dianchi (Yunnan Province, Southwestern China) is dominated in April by a bloom of Aphanizomenon, that disappears Suddenly and is displaced by a Microcystis bloom in May. The reasons for the rapid bloom disappearance phenomenon and the temporal variability in the composition of phytoplankton assemblages are poorly understood. Cell growth, ultrastructure and physiological changes were examined in cultures of Aphanizomenon sp. DC01 isolated from Lake Dianchi exposed to different closes of rnicrocystin-RR (MC-RR) produced by the Microcystis bloom. MC-RR concentrations above 100 mu g L-1 markedly inhibited the pigment (chlorophyll-a, phycocyanin) synthesis and caused an increase of soluble carbohydrate and protein contents and nitrate reductase activity of toxin-treated blue-green algae. A drastic. reduction in photochemical efficiency of PSII (Fv/Fm) was also found. Morphological examinationn showed that the Aphanizomenon filaments disintegrated and file cells lysed gradually after 48 h Of toxin exposure. Transmission electron microscopy revealed that cellular inclusions of stressed cells almost leaked out completely and the cell membranes were grossly damaged. These findings demonstrate the allelopathic activity of Microcystis aeruginosa inducing physiological stress and cell death of Aphanizomenon sp. DC01 Although the active concentrations of microcystin were rather high, we propose that microcystin may function as allelopathic Substance due to inhomogeneous toxin concentrations close to Microcystis cells. Hence, it may play a role in species Succession of Aphanizomenon and Microcystis in Lake Dianchi.

辽河流域降雨侵蚀力的时空变化分析

降雨侵蚀力是反映流域降雨侵蚀能力的综合指标之一。根据辽河流域10个气象站的日降雨量资料,利用日降雨侵蚀力模型估算辽河流域的降雨侵蚀力。结果表明:辽河流域降雨侵蚀力的空间变异与降雨量的空间分布趋势基本一致,由东南向西北递减,变化于1 000~3 800 MJ.mm/(hm2.h.a)之间;降雨侵蚀力年内集中度高,6—8月3个月约占全年的80%;降雨侵蚀力年际变化大,年际变率Cv在0.367~0.649之间,采用时序系列的Mann-Kendall检验表明,降雨侵蚀力并无显著变化趋势;特别是在流域水土流失严重的西辽河地区,年降雨侵蚀力较小,但年内集中程度大,年际变化更突出。

Introduction to Molecular Analysis of Ectomycorrhizal Communities

A number of methods are available for those researchers considering the addition of molecular analyses of ectomycorrhizal (EcM) fungi to their research projects and weighing the various approaches they might take. Analyzing natural EcM fungal communities has traditionally been a highly skilled, time-consuming process relying heavily on exacting morphological characterization of EcM root tips. Increasingly powerful molecular methods for analyzing EcM communities make this area of research available to a much wider range of researchers. Ecologists can gain from the body of work characterizing EcM while avoiding the requirement for exceptional expertise by carefully combining elements of traditional methods with the more recent molecular approaches. A cursory morphological analysis can yield a traditional quantification of EcM fungi based on tip numbers, a unit with functional and historical significance. Ectomycorrhizal root DNA extracts may then be analyzed with molecular methods widely used for characterizing microbiota. These range from methods applicable only to the simple mixes resulting from careful morphotyping, to community-oriented methods that identify many types in mixed samples as well as provide an estimate of their relative abundances. Extramatrical hyphae in bulk soil can also be more effectively studied, extending characterization of EcM fungal communities beyond the rhizoplane. The trend toward techniques permitting larger sample sets without prohibitive labor and time requirements will also permit us to more frequently address the issues of spatial and temporal variability and better characterize the roles of EcM fungi at multiple scales.

Seeding nets with neutral spores of the red alga Porphyra umbilicalis (L.) Kutzing for use in integrated multi-trophic aquaculture (IMTA)

Nets in traditional Porphyra mariculture are seeded with conchospores derived from the conchocelis phase, and spend a nursery period in culture tanks or calm coastal waters until they reach several centimeters in length. Some species of Porphyra can regenerate the foliose phase directly through asexual reproduction, which suggests that the time, infrastructure, and costs associated with conchocelis culture might be avoided by seeding nets with asexual spores. Here, we present work from a short-term mariculture study using nets seeded with asexual spores (neutral spores) of a native Maine species of Porphyra. Porphyra umbilicalis (L.) Kutzing was selected for this proof of concept research because of its reproductive biology, abundance across seasons in Maine, and evidence of its promise as a mariculture crop. We studied the maturation, release, and germination of the neutral spores to develop an appropriate seeding protocol for nets, followed by development of a nursery raceway to provide an easily manipulated environment for the seeded nets. Neutral spores were produced throughout the year on the central Maine coast,however, there was a temporal variability in the number and survival of released neutral spores, depending upon thallus position in the intertidal zone. Small thalli were strictly vegetative, but most thalli reproduced by neutral spores- sexual reproduction was absent. Neutral spores germinated quickly at 10 and 15 'C, but germination was delayed at 5 degrees C. Unlike some algal zygotes and spores, neutral spores of R umbilicalis required light to germinate; however, irradiances of 25 and 100 mu mol photons M-2 S-1 were equally sufficient for germination. Rafts of seeded nets were deployed in Cobscook Bay, Maine, at two distances from salmon aquaculture pens and at a control site on a nearby, fallow aquaculture site (no salmon). There was no difference in nitrogen content of harvested thalli; however, both the density and the surface area of harvested thalli were different among the sites. The possible causes of these differences are discussed in the context of potential use of P umbilicalis in IMTA. (C) 2007 Elsevier B.V. All rights reserved.

Suspended particulate matter fluxes through the Straits of Dover, English Channel: observations and modelling

Suspended Particulate Matter (SPM) concentrations at various levels within the water column, together with salinity and temperature, were measured using water samples collected from six stations across the Straits of Dover. The sampling programme covered a 16-month period, undertaken during 23 cruises. On the basis of the spatial variability in the concentrations, the water bodies are divided by several boundaries, controlled by tidal and wind conditions. Within the water column, SPM concentrations were higher near the sea bed than in the surface waters. Throughout the cross-section, maximum concentrations occurred adjacent to the coastlines. Temporal variability in the SPM concentration exists on daily and seasonal scales within the coastal waters (4.2 to 74.5 mg L-1): resuspension processes, in response to semi-diurnal tidal cycles (with a period of around 12.4 h) and spring-neap cycles (with a period of 15 days) make significant contributions. Distinctive seasonal/annual concentration changes have also been observed. In the offshore waters, such variability is much less significant (0.9 to 6.0 mg L-1). In the summer the English Coastal Zone is associated with relatively high SPM concentrations: the Central Zone has a low and stable SPM concentration between these zones, there is a Transitional Zone, where there is a rapid response of SPM concentration to wind forcing. Finally, the French Coastal Zone is characterized by variable (sometimes high) SPM concentrations. Because of the zonation, SPM fluxes within the Dover Strait are controlled by different transport mechanisms. Within the Central Zone, the flux can be represented by the product of mean water discharges and SPM concentrations. However, within the coastal zones fluctuations in SPM concentrations on various time-scales must be considered. In order to calculate the maximum and minimum SPM fluxes, 10 cells were divided in the strait. A simple modelling calculation has been proposed for this complex area. The effect of spring-neap tidal cycles and seasonal changes can contribute significantly to the overall flux, which is of the order of 20 x 10(6) t.yr(-1) (through the Dover Strait, towards the North Sea). Such an estimate is higher than most obtained previously. (C) 2000 Ifremer/CNRS/IRD/Editions scientifiques et medicales Elsevier SAS.

胶州湾和东太平洋海隆(~13°N)沉积物微生物多样性研究

海洋是一个巨大的生态系统，多样的微生物是构成海洋生态系统的基本元素。海洋微生物的群落结构及演变深刻的反映着海洋生态系统的变迁。本文采用分子生物学技术，研究了近海沉积物生态系统——胶州湾沉积物中细菌的多样性、群落结构的时空演替规律以及远洋深海沉积物生态系统——东太平洋海隆北纬13o附近深海沉积物中细菌和古细菌群落结构沿沉积物断层的分布情况，结果表明在两处沉积物中，微生物群落的结构都与环境因子有显著的相关性，是反映海洋沉积物环境特征的重要（分子）标志物，并且可能在这些环境中参与生物地球化学循环等重要过程。 1.从胶州湾不同区域的8个代表性站点采集4个季度的沉积物样品。提取总基因组DNA，利用16S rDNA作为分子标记，采用克隆文库对胶州湾沉积物中细菌群落的组成、空间分布和季节演替规律进行了研究。结果显示沉积物中的细菌具有高度多样性，来自于13个细菌门，同时还有28%的未鉴定克隆，表明胶州湾沉积物中蕴藏着巨大的微生物资源。其中已鉴定的优势种群是α-、β-、γ-、δ-变形细菌、绿弯菌、厚壁菌、蓝细菌和放线菌。同时还包括酸杆菌、拟杆菌、浮霉菌、疣微菌、芽单胞菌、绿菌、梭杆菌、异常球菌-栖热菌等类群的存在。将各克隆库的组成与温度、总碳、总氮等环境因子结合分析，结果显示细菌群落结构更替的主要驱动力是季节变化所带来的温度等环境因子的演变。对数据库中与本研究所获得序列具有最近亲缘关系序列的来源环境进行分析表明，胶州湾中细菌群落受航运活动、水产养殖、重金属污染等人类活动的明显影响，同时这些活动表现出显著的空间特异性，比如C4和D6等站点明显受到航运活动的影响，而A3和Y1等站点则容易受到沿岸径流所带来的淡水和油污染的影响。 2.分别利用PCR-DGGE和克隆文库技术对东太平洋海隆北纬13o附近深海柱状沉积物样品中细菌和古菌群体进行研究，结果显示这些微生物群落沿四个分别代表不同沉积年代断层明显的成层分布，与环境因子结合分析表明这种成层分布与氧化还原性质等地球化学特征的成层分布相吻合，提示我们该生态系统中的微生物受到环境因子的巨大作用，同时也表明这些微生物可能参与该生态系统中硫、金属元素代谢等过程。通过系统发育分析，四个断层中的微生物群落中呈现出很多与热液活动相关的个体（其中34.7%的细菌序列和31%的古菌序列与来源于各种热液环境的序列具有最近的亲缘关系）。但总体群落结构分析表明该区域可能属于热液活动影响区域的边缘，处于从热液活动环境到普通的低温沉积物环境的过渡区域。 3.将在胶州湾和东太平洋海隆北纬13o附近海洋沉积物生态系统中都存在的优势细菌类群（α-、β-、γ-、δ-变形细菌和放线菌、绿弯菌、厚壁菌、酸杆菌、浮霉菌）进行系统发育分析和背景比较分析，结果显示两处沉积物中的细菌优势种群虽然在大类群上很多是相同的，但是可能由于两处沉积物中不同物理化学等环境因子的选择作用（如胶州湾的近海特征和人为活动，东太平洋深海特点和热液活动），而导致优势种群在系统发育关系上距离比较远。这表明独特的微生物群落结构，特别是优势种群的群落结构信息是描述特定环境生态系统的重要方面。本研究表明在全球环境变迁中,自然环境因子和人类活动都在深刻改变着微生物群落的结构和功能。本文阐述了在环境变迁特定时期两处沉积物生态系统中的微生物群落结构及时空差异，为研究大范围生态系统的演变提供了依据，同时也为在两处沉积物环境中进行微生物参与的生物地球化学研究奠定了基础。

岩溶洞穴系统溶解有机碳的时空演化及其环境意义

洞穴次生沉积物(尤其是石笋)所包含的古环境、古气候信息是当今研究的热点，但它所包含的环境气候信息对外界的响应灵敏度如何，这是最为关注的问题。石笋的微层厚度变化及荧光强度变化是来自洞穴上覆土壤中的有机碳沉积产生的，这些有机碳是由雨季早期冲刷进入洞穴形成的微层，微层厚度变化及荧光强度变化包含了环境(植被)、气候(温度和降水量)信息，它们可作为环境、气候替代指标使用，但需要进行现代环境、气候的校正，以往研究仅从某个侧面进行研究，系统研究有机碳在岩溶洞穴系统的演化过程较少。本论文通过对四个洞穴系统(凉风洞、七星洞、将军洞和犀牛洞)的溶解有机碳及其荧光系统的研究，探讨了溶解有机碳及其荧光的演化及其对环境气候的响应，根据分析论述，得出如下几点认识： 1． 通过对四个岩溶洞穴系统中DOC浓度月际、季节、年际变化研究，洞穴滴水在春季及夏初具有较大的DOC浓度，而在秋季变化最小、浓度也是最低的。滴水点出现DOC峰值的时间不一致，有的在春季、有的则在夏初，一方面反映降水时间的提前或推迟，另一方面也反映了水在洞穴顶板内的运移途径的长短等过程。个别滴水点能在不同时间出现不同的DOC浓度峰值，可能反映了滴水点对降水的响应灵敏，或不同的径流途径在时间上的提前或推迟，水动力条件的不同造成滴水补给源运移路径的差异应该是产生滴水点DOC浓度具有多个峰值的原因。由于洞穴次生沉积物在DOC的参与下形成，季节性的DOC高浓度产生较厚微层，但对降水敏感的滴水点可能产生了不同厚度的微层，不仅具有季节性微层，可能还能产生降水模式的微层。 2． 洞穴系统中溶解有机碳和荧光的空间变化分析上，得出溶解有机碳浓度在各个洞穴系统中纵向和横向上是有变化的。在滴水中滴水点间DOC浓度也有空间变化，而洞穴之间变化差异不明显，可能与土壤有机碳进入洞穴的运移途径有关；在土壤水中溶解有机碳浓度空间变化能反映了土壤有机碳的来源，即表层50cm以上的土壤层是输入土壤的有机碳主要来源。 3． 根据三维荧光光谱，四个岩溶洞穴系统的DOC的荧光类型可分为三个范围，即类富里酸、类蛋白和紫外类富里酸、类腐殖酸、类蛋白的混合荧光类型。在其它洞穴滴水的研究中未发现类腐殖酸类型的荧光峰，四个洞穴系统滴水中也不具有该类型荧光峰。在与植被类型的联系上反映出森林植被下的荧光波长变化较小，而土壤覆盖较连续的荧光强度较稳定。 4． 荧光波长的变化，反映了输入滴水中有机碳物质类型的差异，即有机碳在空间分布上的不均匀性和植被差异导致荧光波长的变化。从土壤水到洞穴滴水，溶解有机碳与荧光强度具有很好的线性相关性，表明洞穴滴水溶解有机碳是土壤有机碳运移至滴水中；土壤有机碳运移过程沿运移途径产生一系列变化，滴水DOC浓度低于土壤溶解有机碳一个数量级。土壤水DOC在将军洞的荧光强度除受外界因素影响，还受到内滤效应导致DOC浓度与荧光的强度线性关系不明显。在溶解有机碳和荧光的空间变化关系上，应联系表层环境对它们的影响，对它们充分认识才能得出合理的空间变化推论。 5． 荧光强度在洞穴滴水的变化趋势，一方面反映表层环境的变化，另一方面可能因水动力条件的不同，产生荧光性物质滤除效应，在DOC浓度变化较小的将军洞表现得最突出。在季节性水流输入的凉风洞和犀牛洞、和有滴水长期输入的七星洞和将军洞塘水，前三个洞穴塘水溶解有机碳及其荧光强度都明显高于滴水的，而后一洞穴塘水的低于滴水的，可能洞内蒸发作用对后者影响小，这样洞穴次生沉积除以表层环境的影响，其洞内环境的变化也可能是影响它的一个因素，但相对于表层环境变化，洞内的变化是微小的。 6． 从四个洞穴系统DOC变化来看，DOC浓度变化对植被类型变化不是很灵敏。从原生性喀斯特森林→灌丛草坡→灌草丛→刺丛草坡的岩溶洞穴系统，虽然土壤水DOC浓度变化较大，反映了输入土壤的及土壤中有机碳的分解难易程度，但在洞穴滴水中DOC浓度变化不是很明显，都显示相近的浓度水平。由于输入土壤的有机碳更新周期长，在水运移过程中受不同时间段降解的有机碳溶解，且来源不同的有机碳混合程度不同，导致不能很好地反映当年输入的有机碳的含量变化，应该是造成洞穴滴水DOC浓度不能很好区分植被类型的原因。 7． DOC浓度变化响应于降水量，也响应于气温。春夏季，当降水量达到一定雨量值(如有效降水量)时，入渗的雨水使表层有机物质溶入土壤水中，土壤水下渗到洞穴滴水中后，滴水DOC浓度较大，荧光强度也较大。降水对DOC浓度有稀释作用，是造成部分月份DOC浓度下降的原因。在7月份以前洞穴滴水DOC就已达到最大浓度，在8～10月份因气温高、降水量偏少，可能对微生物有抑制作用，造成其分解有机碳活动减弱，导致DOC浓度变化差异小。这反映了洞穴滴水DOC浓度与气候关系比较密切，进一步证实利用洞穴次生沉积物微层的厚度变化来反映气候变化是可行的，至少可以作为一个辅助指标来运用。 8． DOC及其荧光受多种因素影响，我们分析了pH、HCO3-、SIC、PPCO2、洞穴盖层厚度和岩石的溶解对它们的影响。分析表明洞穴盖层厚度和Ca2+、Mg2+离子浓度变化对它们的影响较大，pH变化范围小，认为它对DOC及其荧光的影响较小；HCO3-、SIC和PPCO2与DOC和荧光强度分别具有一些较好的线性关系(置信度=90%)，但总的趋势是线性关系不显著，这表明了HCO3-、SIC和PPCO2与DOC和荧光强度联系不明显，指出它们只是影响DOC及其荧光强度的一个次要因素，并不是主要因素。洞穴盖层厚度影响洞穴滴水DOC及其荧光，表明在应用洞穴次生沉积物记录指标反演洞穴环境变化的研究过程中，对于次生沉积物形成点的发生在洞穴顶板内的水文地化学过程应该有一个清晰的了解，才有可能获取完整、正确的信息。

Temporal and spatial variability in nitrogen uptake kinetics during harmful dinoflagellate blooms in the East China Sea

Temporal and spatial variability in the kinetic parameters of uptake of nitrate (NO3-), ammonium (NH4+), urea, and glycine was measured during dinoflagellate blooms in Changjiang River estuary and East China Sea coast, 2005. Karenia mikimotoi was the dominant species in the early stage of the blooms and was succeeded by Prorocentrum donghaiense. The uptake of nitrogen (N) was determined using N-15 tracer techniques. The results of comparison kinetic parameters with ambient nutrients confirmed that different N forms were preferentially taken up during different stages of the bloom. NO3- (V-max 0.044 h(-1); K-s 60.8 mu M-N) was an important N source before it was depleted. NH4+ (V-max 0.049 h(-1); K-s 2.15 mu M-N) was generally the preferred N. Between the 2 organic N sources, urea was more preferred when K. mikimotoi dominated the bloom (V-max 0.020 h(-1); K-s 1.35 mu M-N) and glycine, considered as a dominant amino acid, was more preferred when P. donghaiense dominated the bloom (V-max 0.025 h(-1); K-s 1.76 mu M-N). The change of N uptake preference by the bloom-forming algae was also related to the variation in ambient N concentrations. Published by Elsevier B.V.

Temporal and spatial variations in kinetics of alkaline phosphatase in sediments of a shallow Chinese eutrophic lake (Lake Donghu)

Monthly sediment and interstitial water samples were collected in a shallow Chinese freshwater lake (Lake Donghu) from three areas to determine if alkaline phosphatase activity (APA) plays an important role in phosphorus cycling in sediment. The seasonal variability in the kinetics of APA and other relevant parameters were investigated from 1995-1996. The phosphatase hydrolyzable phosphorus (PHP) fluctuated seasonally in interstitial water, peaking in the spring. A synchronous pattern was observed in chlorophyll a contents in surface water in general. The orthophosphate (o-P) concentrations in the interstitial water increased during the spring. An expected negative relationship between PHP and V-max of APA is not evident in interstitial water. The most striking feature of the two variables is their co-occurring, which can be explained in terms of an induction mechanism. It is argued that phosphatase activity mainly contributes to the driving force of o-P regeneration from PHP in interstitial water, supporting the development of phytoplankton biomass in spring. The V-max values in sediment increased during the summer, in Conjunction with lower K-m values in interstitial water that suggest a higher affinity for the substrate. The accumulation of organic matter in the sediment could be traced back to the breakdown of the algal spring bloom, which may stimulate APA with higher kinetic efficiency, by a combination of the higher V-max in sediments plus lower K-m values in interstitial water, in Summer. In summary, a focus On phosphatase and its substrate in annual scale may provide a useful framework for the development of novel P cycling, possible explanations for the absence of a clear relationship between PHP and APA were PHP released from the sediment which induced APA, and the presence of kinetically higher APA both in sediment and interstitial water which permitted summer mineralization of organic matter derived from the spring bloom to occur. The study highlighted the need for distinguishing functionally distinct extracellular enzymes between the sediment and interstitial water of lakes. (C) 2002 Elsevier Science Ltd. All rights reserved.

IMPACTS OF THE TROPICAL PACIFIC COUPLED PROCESS ON THE INTERANNUAL VARIABILITY IN THE INDIAN OCEAN

The basic features of climatology and interannual variations of tropical Pacific and Indian Oceans were analyzed using a coupled general circulation model (CGCM), which was constituted with an intermediate 2.5-layer ocean model and atmosphere model ECHAM4. The CGCM well captures the spatial and temporal structure of the Pacific El Nino-Southern Oscillation (ENSO) and the variability features in the tropical Indian Ocean. The influence of Pacific air-sea coupled process on the Indian Ocean variability was investigated carefully by conducting numerical experiments. Results show that the occurrence frequency of positive/negative Indian Ocean Dipole (IOD) event will decrease/increase with the presence/absence of the coupled process in the Pacific Ocean. Further analysis demonstrated that the air-sea coupled process in the Pacific Ocean affects the IOD variability mainly by influencing the zonal gradient of thermocline via modulating the background sea surface wind.

Variability of surface circulation in the South China Sea from satellite altimeter data

11-year satellite altimeter sea surface height (SSH) anomaly data from January 1993 to December 2003 are used to present the dominant spatial patterns and temporal variations of the South China Sea (SCS) surface circulation through Empirical Orthogonal Function (EOF) analysis. The first three EOF modes show the obvious seasonal variations of SSH in the SCS. EOF mode one is generally characterized by a basin-wide circulation. Mode two describes the double-cell basin scale circulation structure. The two cells were located off west of the Luzon Island and southeast of Vietnam, respectively. EOF mode three presents the mesoscale eddy structure in the western SCS, which develops into a strong cyclonic eddy rapidly from July to September. EOF mode one and mode three are also embedded with interannual signals, indicating that the SCS surface circulation variation is influenced by El Nino events prominently. The strong El Nino of 1997/98 obviously changed the SCS circulation structure. This study also shows that there existed a series of mesoscale eddies in the western SCS, and their temporal variation indicates intra-seasonal and interannual signals.