Diatom Thalassiosira weissflogii in oligotrophic versus eutrophic culture: models and ultrastructure

Populations of marine diatom Thalassiosira weissflogii were grown in continuous cultures enriched with f/2 medium. One of the two contrasting cultures (‘eutrophic’) received 5.6 times more nutrients than the other (‘oligotrophic’). Two mathematical models are analyzed to estimate eutrophication differences. The second model based on the Michaelis–Menten uptake and Droop growth shows that cells in the eutrophic culture should have about 56% higher content of silica which is the limiting nutrient. Diatom samples were prepared for the transmission electron microscopy after cells have been kept in chemostats for 37 days. The structure of diatom cells was investigated and a comparison is made between cells grown in oligotrophic and eutrophic conditions. In eutrophic culture, dividing cells were encountered more frequently while cell concentration was approximately equal in both chemostats. The central vacuole of cells in eutrophic culture accumulated dispersed and compact material from amorphous to spherical shape. In some cells the large central vacuole had fibrilar and peppered dense materials in addition to translucent granules, vesicules and multivesicular bodies. In the cytoplasm we found increased number of multivesicular bodies, dense and lucent granules some of which enclose membrane particles and lucent vesicules. Dense material depositions observed in the vacuole are also seen in the cytoplasm associated with organelles, mitochondria and plasmalemma. Cells have well-developed, active and slightly increased number of dictyosomes (5–6). Some dictyosomes with dense secretory material in the cistern are apparently engaged in a granule formation process. Functional significance of dense material in the central vacuole, which has not been observed in cells grown in oligotrophic condition, is discussed.     

Seasonal dynamics of macro-algae in the South Lake of Tunis

The macro-algae communities observed in the south lake of Tunis are characterized by the predominance of nitrophilous algae which are in the order of biomass importance:Ulva, Cladophora andEnteromorpha. We have noted seasonal changes of alga distribution. The wind appears to be one of the most important factors influencing this distribution. The total biomass reaches a maximum in the spring. Rapid decomposition of the biomass leads to a severe ecological imbalance, resulting in crises of anoxia and fish death. A restoration project has already started. It aims at removal of contaminated muds and the introduction of a new circulation system. The main objectives of this work were to collect information on the distribution and biomass of the phytobenthic communities as a first step in the constitution of a database for further comparison.     

POLLUTION THREATS IN THE MEDITERRANEAN SEA: AN OVERVIEW

This overview summarises the present knowledge on major sources of pollution, which are of concern for the Mediterranean Sea. Eutrophication, red tides, organic loads, hydrocarbon spills, heavy metal contamination and their biological effects are described on the light of the ecological characteristics of the Mediterranean. In particular special attention is paid to the "new pollution" processes; i.e. , the introduction of novel substances with biological activity that might have synergetic effects with "classical pollutants". Different compartments and marine ecosystems are considered and compared. The degree of anthropogenic impact and its apparent trends are discussed. Possible monitoring plans and remedial actions for a sustainable management of coastal zones subjected to increasing pollution are also suggested.     

滇池水华综合控制对策探讨

水华污染已成为滇池目前面临的主要环境问题，滇池水华治理被国家列为重中之重的项目而予以高度重视，据多年的监测资料，滇池水华的各类主要是蓝藻门的微囊藻，其次为束丝藻和鱼腥藻。该文从多方面分析了滇池水华泛滥的原因，在此基础上提出了滇池水华控制和富营养化治理的综合对策，特别强调了滇池水华必须坚持控制污染源与生态修复相结合的原则。     

太湖水质指标相关性与富营养化特征分析

为研究太湖第一阶段治理水质富营养化的特征，根据1999年10月采样数据，对总磷、总氮等与富营养化相关的水质指标进行了统计分析。发现透明度与叶绿素a之间并未表现出显著的相关性，而在聚类图中，悬浮物与总磷、总氮显示出密切关系。指出农村面源仍是太湖中营养物质的重要来源。     

嘉陵江河口段枯水期水质分析

对嘉陵江河口段2010年2,3,4月枯水期选取总磷（TP）、叶绿素a（Cha）含量、pH值、溶氧量等作为指标进行水质检测分析。结果表明：随着降雨量的持续减少、气温的回升、蒸发的加快、水位的下降等使得干旱期嘉陵江富营养化有加重的趋势。4月份嘉陵江降雨增加、旱情有所缓解,各项指标出现一个相对稳定的下降,同时在温度上升、营养盐输入等大环境的影响下各富营养指标会有一个相对稳定的上升。三峡大坝建成后富营养化成为水环境突出问题之一,特别是对干旱期内嘉陵江富营养化应引起足够重视,加强监督保护嘉陵江生态相对稳定。     

应用生态动力学模型评价上海淀山湖富营养化控制方案

近年来,由于淀山湖入湖河流和环湖污水排放,淀山湖水质严重富营养化,夏季高温季节蓝藻水华时有发生。基于最近开展的比较系统的大规模水文、水质、生物同步监测和底质氮磷营养盐释放通量实验,进行入湖氮磷营养盐通量计算分析。通过建立淀山湖水动力一生态动力学耦合模型,利用同步实测和历史资料进行水动力模型和生态动力学模型的率定验证,模拟典型风场作用下的淀山湖三维流场特征;利用生态动力学模型系统研究淀山湖氮磷营养盐和藻类的时空变化和演替规律,初步掌握淀山湖的富营养化过程;综合评价了污染负荷削减、水力调度（水体停留时间）等措施对控制淀山湖富营养化的作用,明确磷是淀山湖藻类生长的关键营养盐限制因子。模型预测结果表明,磷负荷削减50％以上才能使淀山湖夏季蓝藻生物量开始下降;削减90％以上的营养盐负荷才能有效抑制蓝藻水华;水体停留时间的长短是藻类是否过度繁殖的重要条件,加大引水流量,减少淀山湖水体停留时间是有效控制蓝藻水华的重要途径;目前阶段,与控制营养盐负荷（50％）相比,增大引水流量可以更有效地降低蓝藻暴发时的生物量。     

富营养化水体中微囊藻毒素（MCs）去除技术研究进展

当前,随着工业的发展水体富营养化程度日益严重。引起富营养化的主要藻类一蓝藻,能够释放对人体及鱼类具有多器官毒性、遗传性和致癌性的毒素——微囊藻毒素（MCs）。MCs治理技术种类繁多,传统的物理法如：混凝沉淀、膜过滤、活性炭吸附、气浮以及直接过滤只能对简单的处理细胞内的MCs;化学氧化法、光催化氧化法以及高级氧化法虽然能有效处理水体中的MCs．但有成本高、易二次污染和操作复杂等缺点,难以满足日益严格的环保要求;生物酶法除了具有生物降解法所具有的廉价、无二次污染、降解彻底和易操作等特点外,还被刺用来监控水体中MCs,它将成为今后重点研究的技术领域．     

洪湖、梁子湖水体富营养化研究

2015年3月对洪湖、梁子湖进行了水质监测。依据实测数据,结合洪湖湿地自然保护区和梁子湖林业局监测数据和文献数据,采用综合营养状态指数法对洪湖、梁子湖的富营养化状态进行评价;并根据各因子在综合营养状态指数中所占比重和地表水水质标准,对各因子做了比较。结果表明:洪湖、梁子湖综合营养状态指数分别为57.2、42.5。即洪湖为轻度富营养、梁子湖为中营养;各因子对洪湖、梁子湖富营养化的贡献大致相同,即Chla为首,TP、COD_(Mn)和SD次之、TN最后。     

四丰山水库富营养化状况

通过对四丰山水库2006至2010年监测数据的统计,分析水库水质富营养化状况,指出水质富营养化的危害,并提出避免水质恶化的建议.