Biomass-dependent effects of common carp on water quality in shallow ponds

We examined the biomass-dependent effects of common carp (Cyprinus carpio) on water quality in 10 ponds at the Eagle Mountain Fish Hatchery, Fort Worth, Texas, USA. Ponds contained 0–465 kg ha⁻¹ of common carp. We measured limnological variables at weekly intervals for four weeks in early summer, after which ponds were drained and the biomass of fish and macrophytes was determined. Common carp biomass was significantly positively correlated with chlorophyll a, total phosphorus, total nitrogen, and Keratella spp. density and negatively correlated to bushy pondweed (Najas guadalupensis) biomass. In addition, we combined our data with data from comparable studies to develop more robust regression models that predict the biomass-dependent effects of common carp on water quality variables across a wide range of systems.     

Biomanipulation and its feasibility for water quality management in shallow eutrophic water bodies in The Netherlands

Biomanipulation as a tool for lake restoration is discussed mainly using literature data. It is based on the exploitation of the interactions both within and between the trophic levels in an aquatic ecosystem. Important among the interactions are: competition for light and nutrients between aquatic macrophytes and phytoplankton and among different phytoplankton species; grazing by planktonic and benthic filter feeders; and size-selective predation by fish. In several case studies biomanipulation has proved to be successful in restorating mildly eutrophic small waterbodies. However, for long-term stability of the restored ecosystems supplementary measures like reducing the external nutrient loadings are needed. The feasibility of the different biomanipulation measures to improve the water quality in shallow Dutch lakes is discussed. Preliminary results on biomanipulation experiments in enclosures withOscillatoria agardhii and the benthic filter feederDreissena polymorpha are given.     

The effect of temperature and water quality on the in vitro development and survival of Asellus aquaticus (Crustacea: Isopoda) eggs

The rate of development and degree of survival of Asellus aquaticus eggs outside the marsupium of ovigerous females are affected by water quality and temperature. Eggs were maintained in polluted river water and relatively clean canal water. Developmental rates increase with increased temperature, but survival decreases. Eggs from polluted site ovigerous females survive better in clean water than in polluted water. Eggs from clean site ovigerous females maintained in polluted water have significantly lower survival rates than eggs from the polluted site at all temperatures tested. The developmental rate of clean site eggs is increased significantly in polluted water at 10–25 °C, possibly as a response to the stress imposed upon them.It is suggested that the method outlined might form the basis of a useful bioassay technique for measuring water quality.     

Interrelationships between water and cellular metabolism inArtemia cysts

Cysts of the crustaceanArtemia are a useful model for studies on intracellular water because they are capable of essentially complete and reversible desiccation. We have used a variety of techniques on this system, the present work being an attempt to estimate the density of intracellular water (ρ_w). The density of individual cysts was evaluated from sedimentation velocity. Heptane displacement methods were used to determine the volume of a known mass of cysts, from which the density was calculated. The two methods produce comparable results. It was shown that the densities and water contents of large masses of cysts accurately reflect those of individual cysts. Cyst densities (ρ_c) were determined over the entire range of water content from 0 to 0.63 weight fraction of water (W _f), and temperature dependence was measured for 0.61W _f over 2–41°C. The following refer to 25°C. No marked change was detected in ρ_c until the water content exceeded 0.15W _f, at which ρ_c decreased as a linear function of Wf to maximum water content. However, the cyst does not behave ideally in the sense that the densities of the nonaqueous components and added water are not additive as a function ofW _f. The partial specific volume of water in cysts at maximum hydration was estimated to be 3% larger than that of pure water. These observations are compared with density measurements on other systems, and with previous findings on the physical properties of water in this system.     

Application of an unsupervised artificial neural network technique to multivariant surface water quality data

Surface water contamination from agricultural and urban runoff and wastewater discharges from industrial and municipal activities is of major concern to people worldwide. Classical models can be insufficient to visualise the results because the water quality variables used to describe dynamic pollution sources are complex, multivariable, and nonlinearly related. Artificial intelligence techniques with the ability to analyse multivariant water quality data by means of a sophisticated visualisation capacity can offer an alternative to current models. In this study, the Kohonen self-organising feature maps (SOM) neural network was initially applied to analyse the complex nonlinear relationships among multivariable surface water quality variables using the component planes of the variables to determine the complex behaviour of water quality parameters. The dependencies between water quality variables were extracted and interpreted using the pattern analysis visualised in component planes. For further investigation, the k-means clustering algorithm was used to determine the optimal number of clusters by partitioning the maps and utilising the Davies–Bouldin clustering index, leading to seven groups or clusters corresponding to water quality variables. The results reveal that the concentrations of Na, K, Cl, NH₄-N, NO₂-N, o-PO₄, component planes of organic matter (pV), and dissolved oxygen (DO) were significantly affected by seasonal changes, and that the SOM technique is an efficient tool with which to analyse and determine the complex behaviour of multidimensional surface water quality data. These results suggest that this technique could also be applied to other environmentally sensitive areas such as air and groundwater pollution.     

The filtration rate of the zebra mussel Dreissena polymorpha used for water quality assessment in Dutch rivers

The effects of contaminated river water on the filtration rate of zebra mussels from a clean reference site were studied. After a 48-h exposure period to filtered water from the rivers Rhine, Meuse and Amstel (The Netherlands), the filtration rate was measured. It was demonstrated that water from contaminated locations inhibited the filtration rate. Inhibition was higher during low water levels in the rivers Rhine and Meuse than during high water levels, suggesting that contaminants are diluted during high water levels. It is concluded that the shortterm filtration assay with D. polymorpha can be used for assessing water quality.     

Evaluation of water corrosion,scaling extent and heterotrophic plate count bacteria in asbestos and polyethylene pipes in drinking water distribution system

Corrosion and scaling is one of the most important factors influencing drinking water quality that cause health disorders and economic problems. The aim of this study was to evaluate these phenomena in two sources of surface (Makou city) and ground water (Khoy city) in water networks. Corrosion and scaling potential was surveyed by Langelier, Ryzener, aggressiveness, Larson and Puckorius Indices and with measuring water physical, chemical, and microbial parameters. Statistical paired samples t-test displayed significant difference in means value of Langelier, Ryzener, Puckorius indices between cold and warm seasons of the year in Khoy samples and significant difference in means value of Ryzener, Puckorius and aggressiveness indices between cold and warm seasons of the year in Makou samples (p-value <0.001). Heterotrophic plate count water samples investigated in two cold and hot seasons in Khoy were respectively 14 ± 16 cfu ml^?1 and 41 ± 26 cfu ml^?1 and in the town of Makou were 11 ± 7 cfu ml^?1 and 61 ± 29 cfu ml^?1, respectively. In terms of health impacts, corrosion in different mains is important, then providing proper measures for balancing water quality before entering to the network and substituting of mains to prevent economic and health problems are necessary.     

Survival of Helicobacter pylori in well water

The mortality of a clinical Helicobacter pylori strain was assessed by inoculating it in untreated well water, filtered well water, and autoclaved well water. Two different temperatures (5 and 25 °C) were used during the experimental period. Because Escherichia coli is commonly used as indicator of faecal pollution of water, we compared the survival of H. pylori using E. coli as indicator of its persistence. H. pylori was not culturable 48 h after inoculation, whereas the population of E. coli, monitored at the same temperature, decreased slowly, especially in filtered water. In untreated water, both H. pylori and E. coli survived less well than in filtered and autoclaved water. In general the survival of H. pylori and E. coli was better in filtered water than in autoclaved water and the ability of H. pylori to survive several days in water at 5 °C is reported, supporting the observation that H. pylori survives better at 5 °C than at higher temperature. This suggests a possible faecal–oral transmission of H. pylori in the presence of a contaminated water.     

广东省水质现状及驱动因素

水质现状评估及其驱动因素分析是实现水生态保护、水资源利用和水污染治理的关键,对于水生态系统的可持续发展具有重要意义。以广东省七大流域为研究区,基于2019-2020年间的溶解氧（DO）、透明度（SDD）、悬浮物（SPM）、叶绿素a （Chla）、氨氮（NH₃N）、总氮（TN）、总磷（TP）7个指标的水质监测数据,综合运用单因子指数法（SI）和综合水质指数（WQI）评价方法,分丰水期（N=66）和枯水期（N=54）评估研究区的水质现状,并探讨水质参数与地形、气象、社会经济和土地覆被类型等驱动因素之间的相关关系。SI评估结果显示广东七大流域主要以工业污水、农业面源等造成的Chla和TN浓度超标、部分水体富营养化严重为主,同时伴有溶解氧浓度偏低的问题;WQI评估结果显示研究区有57%以上的采样点属于中等以下水质。Chla、SPM、NH₃N和TP浓度具有显著的季节和驱动因素差异：丰水期的Chla和TP浓度低于枯水期,但SPM和NH₃N浓度高于枯水期。枯水期DO、TN和WQI的显著性影响因子为丰水期的1/3左右;这种季节差异可能是流域内降雨、营养盐负荷和土地覆被类型导致的复杂地表径流及面源污染所致。珠江三角洲河网区、粤西诸河、韩江下游以及粤东诸河练江流域的水质问题突出。未来水生态系统的可持续发展研究可以借助长时间序列、多频次、高分辨率的遥感监测手段和多种数值模拟方法以及常规水质评估模型,探讨气候变化、河岸带产业结构和流域土地利用方式对面源污染的影响,以进一步厘清降雨强度、三产结构和土地利用方式转变对区域水质变化的影响。     

New generation water quality guidelines for ecosystem protection

1. Water quality guidelines are important for the management of water resources. Initially, guidelines focused on quality for domestic drinking water and for agricultural, recreational and industrial purposes. More recently, the emphasis has been on ecosystem protection, as well. 2. This paper discusses the key elements of new risk-based water quality guidelines being developed in Australia and New Zealand, that should lead to more effective management and protection of aquatic ecosystems. 3. There are three essential elements to this new approach: (i) it is ecosystem-based— ideally the guidelines should be, as far as possible, ecosystem-specific; (ii) it is issue-based— the guidelines should focus on the actual issues or problems caused by physical, chemical and biological stressors rather than on the individual indicators, as at present; and (iii) it is risk-based. There is generally great difficulty in deciding whether adverse biological effects will result from various stressors added to an ecosystem. The new approach develops guideline ‘packages’ for each issue and, where possible, for each ecosystem type. Each ‘package’ consists of specified key performance indicators, trigger levels for these indicators (that is, levels which indicate the degree of risk that adverse biological effects may occur), and for high risk situations (where trigger levels are exceeded) a protocol for considering the effect of ecosystem-specific factors in reducing (or enhancing) the biological effects. 4. This paper presents a case study related to a highly relevant aquatic ecosystem issue in Australia, namely the excessive growth of cyanobacteria (blue-green algal blooms), to illustrate how the new risk-based guidelines might be applied.     

黄菖蒲叶片对水分的生物学响应及其净化水质作用

为解决漓江流域水质下降和生态系统退化的关键问题,开展黄菖蒲抗逆性以及水质净化作用研究,为漓江水陆交错带生态修复的植物选择提供科学依据。采用盆栽试验,研究了黄菖蒲在不同基质内不同淹水胁迫下的叶片生长情况,共设5个处理,并在全土基质中开展净化水质实验。结果表明:随着水淹深度的增加,黄菖蒲叶片数明显下降;半淹处理对黄菖蒲生长最有利;水淹时间对黄菖蒲叶片数、叶长、叶宽与叶面积有极显著影响;黄菖蒲叶片长度、宽度和叶片数随淹水处理没有明显差异,基质对黄菖蒲的生长无显著差异;水分比基质对黄菖蒲生长影响大;种植黄菖蒲处理后pH减小为中性,在一定程度上可以净化水质,但对氮磷的净化效果不明显。     

白刺沙堆退化与土壤水分的关系

近几十年来,我国西北干旱区白刺沙堆退化严重,导致固定沙丘活化,流沙掩埋绿洲,造成了严重危害。如何尽可能长期保持白刺沙堆的稳定、防止白刺沙堆活化成为绿洲保护和沙漠化防治急需解决的问题。在多年野外观察的基础上,提出了"土壤水分收支不平衡所导致的土壤水分减少是白刺沙堆退化的主要原因"的研究假设。但是,由于缺少长期的野外观测试验,这个假设一直未被很好地证明。为了证明这个假设,在甘肃民勤的绿洲外围选择了雏形、发育、稳定和死亡四个退化阶段的白刺沙堆,于2008年1月至2012年6月利用中子水分仪和土壤烘干称重法对土壤水分进行了长期观测。结果表明:各样地的土壤含水量均呈现出2008年最大,2009年和2011年次之,2010年最小的趋势。年内变化是春季土壤含水量最低,夏季逐渐增加,随后逐渐减小。在不同发育阶段,雏形阶段的土壤含水量最大,且降水容易下渗。稳定和死亡阶段的白刺沙堆土壤含水量很低,降水难以下渗,只有大的降水事件发生时,水分才可以下渗。因此,稳定和死亡阶段白刺沙堆的土壤水分经常在植物的凋萎点之下,是造成白刺沙堆退化重要原因。证明了"土壤水分减少是白刺沙堆退化的原因"的研究假设。研究结果对今后的植物固沙实践活动会有积极的参考意义。     

Efficacy of bromochlorodimethylhydantoin againstLegionella pneumophila in industrial cooling water

Summary Free residual chlorine and bromine can be generated in water from bromochlorodimethylhydantoin (BCDMH). Efficacy of chlorine from inorganic sources has been studied extensively, but there is much less information on the efficacy of bromine againstL. pneumophila; only a few efficacy studies of organically-derived. halogen appear in the literature and the results from different studies conflict or are difficult to interpret. This paper describes the efficacy of halogen from BCDMH against planktonic, pure cultureL. pneumophila in an industrial cooling water. There was no difference in efficacy between halogen derived from organic or inorganic sources in controlled laboratory experiments. Effective doses in laboratory studies cannot be translated directly to field applications because of significant differences in the microbiology. However, the data suggest that disinfection (>99.9% reduction in viability within 10 min) of planktonic, pure cultureL. pneumophila can be achieved with about 1 ppm free residual halogen (expressed as chlorine) from BCDMH in a typical industrial cooling water.     

Salinity,water use and yield of maize: Testing of the mathematical model ecosys

There is a need to establish how root water uptake should be calculated under saline conditions, and to test calculated uptake against experimental data recorded under documented site conditions. In this study, the ecosystem simulation model ecosys was expanded to include an ion transfer-equilibrium-exchange model used to calculated electrical conductivity and osmotic potential. This expanded model was tested against experimental data for maize growth and water use reported under different irrigation and salinity levels at four different sites in the western U.S. to determine if salinity effects on crop growth and water use could be modelled from the effects of salinity on soil osmotic potential. The model was able to reproduce reductions in water use and phytomass yields on salinized (10 g total salts kg^–1 water) soils that ranged from 10 to 50% of those on non-salinized controls. In general, these reductions increased with increasing irrigation deficits. These reductions arose in the model from reduced canopy water potentials and conductances caused by reduced osmotic potentials in the saline soils. The hypothesis that salinity effects on crop growth and water use are caused by salinity effects on soil osmotic potential appear to be supported under the range of conditions included in this study. Models such as ecosys that are based on general hypotheses for the effects of salinity upon biological activity may be well adapted for general use in assessing the effects of salinity on crop growth and water use with different soils, managements and climates.     

3HOH-osmotic water fluxes and ultrastructure of an epithelial syncytium

Summary Ultrastructural changes associated with osmotically-induced water transport and water permeability were examined in two flatworm species,Schistosoma mansoni andHymenolepis diminuta. The structure of the surface layer of these parasites is unusual in that it is a syncytial epithelial layer that lacks tight junctions and lateral extracellular spaces. The permeability coefficients observed in this study are therefore necessarily associated only with the transcellular route of transepithelial transport. The ultrastructural changes associated with volume transport across the epithelial syncytium were also unusual in that the basally located channels extending distally from the inward-facing membrane into the syncytial layer remained open regardless of the direction of water flow.Despite the structural differences, most of the features of diffusive (P _d ) and osmotic (P _osm ) water fluxes across the syncytium resembled those observed in other epithelia: (i) Low water permeability with maximum values of 4.1×10^–5 forP _d and 9.6×10^–5 forP _osm.(ii)P _osm>P _d by 2.0- to 3.2-fold. (iii) Outward water permeability less than inward water permeability. This asymmetry could not be attributed to collapsing channels when net volume transport was directed outward since channels in the syncytium remained open regardless of the direction of water flow. The asymmetry could be explained by tissue contraction or swelling when bathed in anisotonic fluids. (iv)P _osm values were not significantly altered by tissue unstirred layers but bothP _osm andP _d values were underestimated when the bulk fluid was not vigorously stirred.The lower permeability inS. mansoni relative toH. diminuta may be attributed to the membranous surface coat of the former species.     

Biological and water quality effects of artificial mixing of Arbuckle Lake,Oklahoma, during 1977

This paper describes the effects of total lake mixing with 16 axial flow (Garton) pumps on the water quality, algal biomass and community metabolism of Arbuckle Lake, Oklahoma.Pumping began on July 1, 1977, and subsequently lowered the thermocline throughout the lake. The concentration of dissolved oxygen rose in formerly anoxic strata. Water quality in the former hypolimnion improved. Concentration of ammonia and BOD₅ decreased, and concentrations of manganese remained unchanged in 1977 compared to the control year (1976). But, concentrations of sulfide in the hypolimnion were higher in 1977 than in 1976. Algal biomass as chlorophyll a was about the same in 1977 as in 1978. The depth of the Secchi disc was also the same. An algal bloom did not occur. Pumping decreased the ratio gross production: community respiration as measured by a free water method, suggesting that lakes which are artificially mixed will have lower net primary productivities than lakes which are not artificially mixed.     

Separating the effects of water quality and urbanization on temperate insectivorous bats at the landscape scale

Many local scale studies have shown that bats respond to water quality degradation or urbanization in a species‐specific manner. However, few have separated the effects of urbanization versus water quality degradation on bats, in single city or single watershed case studies. Across North Carolina, USA, we used the standardized North American Bat Monitoring Program mobile transect protocol to survey bat activity in 2015 and 2016 at 41 sites. We collected statewide water quality and urban land cover data to disentangle the effects of urbanization and water quality degradation on bats at the landscape scale. We found that statewide, water quality degradation and urbanization were not correlated. We found that bats responded to water quality degradation and urbanization independently at the landscape scale. Eptesicus fuscus and Lasiurus cinereus negatively responded to water quality degradation. Lasiurus borealis and Perimyotis subflavus positively responded to water quality degradation. Lasionycteris noctivagans did not respond to water quality degradation but was more active in more urbanized areas. Tadarida brasiliensis positively responded to urbanization and was less active in areas with degraded water quality. We show that bat–water quality relationships found at the local scale are evident at a landscape scale. We confirm that bats are useful bioindicators for both urbanization and water quality degradation. We suggest that water quality can be used to predict the presence of bat species of conservation concern, such as P. subflavus, in areas where it has not been studied locally.     

Quercus ilex facing water stress: a functional equilibrium hypothesis

A boundary line analysis of the scatterplot relating pre-dawn leaf water potential to pre-dawn minus minimum leaf water potential was applied to study the efficiency of the Mediterranean evergreen oak species to buffer the effects of variability in water resources. The results are discussed in term of stomatal regulation and changes in soil-to-leaf hydraulic conductance of water flow, both induced by changes in leaf water potential. For this purpose, we used data for leaf water potential measured in three stands of Quercus ilex across a soil water availability gradient in Southern France, and two others obtained in California and Arizona for Quercus turbinella and Portugal for Quercus coccifera. A classification of plant responses from mesic to xeric sites is proposed.     

Nitrogen uptake in relation to water availability in wheat

Nitrogen uptake and distribution in wheat (Triticum aestivum L.) are dependent on environmental conditions and in particular on the water regime. Under Mediterranean conditions, where high water stress at the end of the crop cycle is frequent, nitrogen uptake can be reduced, affecting yield and quality of the grain. To disclose these relations a field experiment was carried out in Central Portugal. Wheat was grown on a clay soil (Vertisol) at three water treatments: rainfed (WO), with 80 mm of irrigation (W1) and with 50 mm and 70 mm irrigations (W2). All treatments received 50 kg ha^–1 of N prior to sowing and were top-dressed with 140 kg ha^–1 of N, splitted in two applications, Kjeldahl N was determined in green leaves (GL), yellow leaves (YL), stems (ST), chaff (CH) and grain (GR). N uptake after anthesis was 40% of the total in W2, but was not noticeable in the other two treatments. N concentrations in the total above-ground plant dry matter, and in both YL and ST were not very different according to treatment, but water availability increased grain-N concentration. It seems, therefore, that grain protein concentration and N uptake can be substantially increased by late irrigations.     

Forces affecting water imbibition inMacrotermes workers (Termitidae,Isoptera)

Summary Observations of putative drinking behaviour at soil surfaces by major workers ofMacrotermes subhyalinus andM. bellicosus suggested that unidirectionally arranged trichomes on the anterior hypopharynx exert capillarity on water in soil pores. To test this hypothesis thirsty major workers were placed on soil of relatively low water content. From the soil types tested we determined soil-moisture retention curves which represent graphically the water content of the soil and its corresponding capillary potential. The termites were able to obtain water from different types of clay soil against potentials in the range – 1.6 to – 1.9 bar. On sandy soil the capillary potential was found to be much higher (– 0.18 bar), i.e. closer to zero. Sandy soil has a very unfavourable water retention capacity, i.e. its water content is very low at low capillary potential, whereas clay soil retains much more water at low capillary potential. The ability of the termites to gain water from soils with relatively low water content is an important adaptive feature for survival in semi-arid areas.