Relation between algal available phosphate in the sediments of the River Garonne and chemically-determined phosphate fractions

Concentrations of total and inorganic phosphate were measured in forty-seven sediments of the River Garonne (France) using an anion resin, NaOH 0.1 M, Ca-NTA and Na-EDTA. Algal available P was measured using Scenedesmus crassus. The sediments presented a wide range of Tot-P concentrations (226 to 923 μg g⁻¹). Resin P varied between 1.1 to 55.5 μg g⁻¹ and NaOH-P between 3.5 to 262 μg g⁻¹. NTA-P and EDTA-P varied between 13.9 and 178 μg g⁻¹ and between 14.4 to 261 μg g⁻¹ respectively. Algal available P varied between 8.8 to 262 μg g⁻¹/ All forms of P are highly correlated and specially with algal available P (r = 0.70, 0.77, 0.88 and 0.77 for resin-P, NaOH-P, NTA-P and EDTA-P respectively). Nevertheless the partial correlation between EDTA-P and algal available P dropped to 0.05 when the concentration of NTA-P was considered as constant, indicating a spurious correlation with apatitic phosphate (extracted by Na-EDTA). Because of the strongest R ² and the lowest standard error of estimate, phosphate extracted by Ca-NTA can be considered as the best predictor of algal available phosphate.     

Use of a multiple addition bioassay to determine limiting nutrients in eagle lake,California

This investigation uses anin vitro enrichment bioassay (in which all essential nutrients except one are added to each culture) to determine which nutrients are important to algal growth in Eagle Lake. The technique was developed when it was discovered that addition of individual nutrients produced little if any growth response. Laboratory bioassays correlated well with comparative studies in the lake. A great deal of variation was found throughout the year but P, N, Fe, and S were found to be limiting at one time or another. The north and south basins of the lake, which differ in morphometry, were also found to differ in the intensity spectrum of limitation. While P was the most important nutrient in both basins, the other nutrients were more limiting in the north basin than the south, and Fe, which was least limiting in the south, was very important in the north. The multiple enrichment bioassay has several advantages over other bioassays. Supported in part by Research Corporation     

Manifestation of a prolonged lag in the photosynthesis of heated spinach chloroplasts

When the time course for CO₂ fixation and O₂ evolution in isolated intact spinach chloroplasts was examined, we found a prolonged lag time in the early phase of photosynthesis after heat-treatment in the dark as well as an expected time-dependent decrease in the rate during the subsequent linear phase. Because the lengthening of the lag period was generally attributed to the depletion of sugar phosphates in the chloroplasts, we tested for the possible involvement of Calvin cycle intermediates in the change of the lag phase by heat-treatment When triose phosphate was added to the heated chloroplasts, the lag time was re-shortened without the rate in the linear phase being elevated to that measured in the control. Mg-ATP or triose phosphate plus oxaloacetate (previously known as protective chemicals) prevented the lengthening of the lag time when added prior to heat-treatment. Quantification of some metabolites in the chloroplasts confirmed that heavy losses had occurred for triose phosphate, fructose-1,6-bis-phosphate, glucose-6-phosphate, and fructose-6-phosphate. However, the level of 3-phosphoglyceric acid was increased. The presence of Mg-ATP during heat-treatment alleviated the losses of those sugar phosphates. Therefore, we conclude that the decrease in sugar phosphates in the chloroplasts, as part of the negative effect from heat-treatment, is the primary cause of the lengthened lag time during the initial phase of photosynthesis.     

Effect of sediment elutriate on the growth of Gymnodinium sp. (Dinophyceae). I.

Abstract

Sediments from the Emilia Romagna coast, an area periodically subjected to eutrophication, were investigated to determine the organic carbon and nitrogen content from the solid phase and organic and inorganic phosphorus, nitrogen and N/P ratio from a liquid elutriate from these sediments. The elutriates were tested for growth using a bioassay with a Gymnodinium sp. which previously caused extensive blooms in the Adriatic. Cultures were grown in the elutriates either enriched or unenriched with F/2 medium. Comparisons with controls were made on the basis of the maximum standing stock. The results obtained with the unenriched elutriates demonstrated the primary role of phosphate, while enriched elutriates produced slighter enhancement than the control. In most cases, the chemical composition of the elutriate was characterized by a negligible phosphate concentration, with respect to ammonium: the nutrient balance did not agree with the nutritional algal requirement. However, all the elutriates showed large quantities of inorganic and organic nitrogen. This finding could indicate that sediment-bound nitrogen may be a ready source of nitrogen for algal growth.     

Culturing Selenastrum capricornutum (Chlorophyta) in a synthetic algal nutrient medium with defined mineral particulates

Algal nutrient studies in chemically-defined media typically employ a synthetic chelator to prevent iron hydroxide precipitation. Micronutrient-particulate interactions may, however, significantly affect chemical speciation and hence biovailability of these nutrients in natural waters. A technique is described by which Selenastrum capricornutum Printz (Chlorophyta) may be cultured in a medium where trace metal speciation (except iron) is controlled, not by organic chelation, but by sorption onto titanium dioxide. Application of this culturing protocol in conjunction with results from sorption studies of nutrient ions on mineral particles provides a means of studying biological impacts of sorptive processes in aquatic environments.     

Experimental Evidence for the Isotope Effect in Photorespiration

Recent data on carbon isotope fractionation in photosynthesis are reviewed. Analysis of the carbon isotope composition in photosynthates and derivative products supports the hypothesis of the isotope effect in photorespiration. This hypothesis envisages the existence in a photosynthesizing cell of two carbon flows differing in isotope composition. One of these flows is enriched in ¹²C and associated with the assimilation pathway of photosynthesis. The other flow enriched in ¹³C circulates in the photorespiratory pathway. The relation between stimulated photorespiration and the carbon isotope composition of biomass supports this view. Our hypothesis of two interrelated isotope effects in photosynthesis leads to the conclusion that photosynthesis and photorespiration are coupled processes subject to periodical oscillations, where Rubisco acts as a main switch regulating these two pathways.     

A chemical characterization of an algal inhibitor obtained from chlamydomonas

This investigation was conducted to characterize the algal inhibitory material originally isolated by Proctor (1957b) from Chlamydomonas. Analysis of purified extracts demonstrated that the inhibitor was a mixture of fatty acids. The identity and relative percentages of most of the components of the mixture were determined by GLC analysis. There is evidence that unsaturated fatty acids were responsible for the majority of the toxicity.     

基于混沌理论的河流藻类生长特性分析——以德国易北河为例

针对藻类生长具有高度非线性特征和实际采样样本间隔稀疏的问题,采用了混沌理论对采样序列的混沌特征量进行估计。采用C-C方法估计时间序列的嵌入维和延迟时间,采用G-P算法对关联维进行估计,并采用小数据量法估计最大Lyapunov指数,最终可实现对最长可预测时长的估计。以易北河为例,对易北河水体叶绿素a 1997年至2001年间各年的观测序列进行了混沌分析,分析结果表明,各年的叶绿素a观测序列均具有低维混沌特性,关联维D=2.75—4.02,各年的叶绿素a序列的最长预测时间变化范围为8.01—18.94d,平均为13.98d(约2周)。采用同样方法对5a易北河连续日径流量时间序列分析表明,该径流量也具有低维混沌特性(最大Lyapunov指数λ1=0.0125),径流量的最长预测时间估计约为80d。气候因素的混沌特性对藻类生长表现出的混沌特征的影响可能要大于径流量等水文因素的影响。     

Phosphate uptake by blue green algae in vitro and in a lake during an algal bloom: Useful application of a force-flow relationship

A bioenergetic model, developed by M. Thellier, was applied to the ³²P-phosphate uptake data obtained with blue green algae and allowed the determination of a threshold concentration for the absorption of phosphate. Data obtained during an algal bloom of Oscillatoria rubescens showed that algal growth ceased when the phosphate concentration in the lake dropped below this threshold value. The resulting starvation led to an increase in the permeability of the membrane for phosphate.     

Vertical stratification in sediments from a young oligotrophic South African impoundment: implications in phosphorus cycling

Changes at the mud surface in Midmar Dam, following impoundment, were studied by examining vertical profiles of selected parameters in sediment cores. Distinct stratification in organic carbon, pH and exchangeable Al³⁺ was evident. Phosphate adsorption characteristics in the stratified sediments was quantified using Langmuir adsorption isotherms. The adsorption maxima and bonding energy constants in the surface sediments (0–3 cm) were markedly lower than those below 3 cm, indicating that the surface layers are less efficient at binding phosphate than the deeper layers. Radiotracer experiments indicate that the layers comprising the top 3 cm of sediment predominate in PO₄-P exchange with the overlying water.     

Interactions between riparian leaves and algal/microbial activity in streams

The effects of leaf leachates derived from six forest trees on algal biomass development was examined in a 3-week experiment in a New Zealand spring. The trees all occur in riparian zones and were Fagus sylvatica and Alnus glutinosa from Europe, Eucalyptus globulus from Australia, Pinus radiata from western North America, and two New Zealand species, Fuchsia excorticata and Nothofagus solandri. Leachates from five species inhibited algal growth relative to controls, whereas leachate from a sixth species (F. excorticata) was stimulatory. In contrast, cellulose breakdown was unaffected by five leachates and inhibited by the other (F. sylvatica). In a second experiment, colonization of leaves and inert substrata (polythene strips) by algae was examined with SEM after 16 days. Algal abundance was greatest on polythene strips and leaves of F. sylvatica, and substantially lower on the other species. Our results indicate that both leaf texture and chemical composition can affect algal colonization and growth, and that chemicals derived from leaves have the potential to both inhibit and stimulate ecosystem processes in streams.     

水动力条件下藻类动态模拟

藻类动态变化是其内部生理特征和外部驱动因素综合作用的结果。除了藻类自身生理因素及光、温度、营养盐等因素,水动力作用使底泥发生再悬浮所造成的营养盐的内源释放对藻类的影响也非常重要。1999年5月8日~6月24日在太湖湖泊生态系统研究站大型生态实验槽中进行了模拟水动力条件下的太湖藻类动态实验,并应用国外先进的PHREEQC软件从生物化学和生态动力学角度建立了藻类生态动力学模型。模型不仅考虑了氮循环及磷循环,还考虑了水动力条件引起的内源释放问题,根据2003年4月26~4月30日在河海大学环形水槽所做的底泥释放实验结果建立了水流和各形态氮磷营养盐释放的定量化关系。由于目前太湖的野外监测资料存在较明显的时空不一致性,模型参数率定的精度受到了较大影响。从室内模拟实验出发,通过对生态槽实验结果的模拟,确定和验证了模型的各参数值,计算结果显示模拟值能较好地拟合实验测量值,表明所建藻类生态动力学模型能较好地描述藻类及各种营养盐的动态变化,这对揭示藻类“水华”暴发机理有一定的意义。     

污染环境中的Smith系统生存分析

研究了环境污染对Smith系统中种群生存的长期影响,考虑到种群数量的变化对种群个体体内毒素浓度和环境中毒素浓度的影响,对传统的Smith系统进行了修正,并且给出了一些种群弱平均持续生存和绝灭的充分条件．在一定条件下得到了弱平均持续生存与绝灭的阈值．     

The effects of nutrient,pH and herbicide levels on algal growth

Growth inhibition of algae increased as herbicide concentrations increased, particularly with prometryn and fluometuron. However, picloram had no effect on algal growth while dinoseb inhibited only Lyngbya. There were no differences in growth rate of algae treated with different levels of potassium or phosphorus. High levels of calcium or magnesium increased growth rate of the algae tested. High levels of nitrogen or pH increased growth rates except when combined with prometryn or fluometuron.     

A Novel Ca2+ Signaling Pathway Coordinates Environmental Phosphorus Sensing and Nitrogen Metabolism in Marine Diatoms

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