Hydrobiological studies on the Tugela river system

Summary A chemical and biological survey of the Tugela river, Natal is described. Some relationships between physical and chemical conditions in the river and the geology and climate of the basin are indicated. The flora and fauna of the main river is described, and the zonation of species in the river, and seasonal variations in the communities at various stations in the zones are delineated.Some relationships between the physical and chemical conditions in the basin, and the distribution and seasonal variations of the biological communities are indicated. Comparisons are made with other rivers. It is concluded that the Tugela river as a type in Southern Africa, falls intermediate between temperate and sub-tropical conditions.     

Hydrobiological studies with reference to sudden fish mortality

Summary Hydrobiological investigation of Gandhisagar (Nagpur) was undertaken with a view to finding out the causes of sudden fish mortality. Extensive observations carried out for over a period of several weeks, prior to, during and after mortality, have led us to the conclusion that depletion of dissolved oxygen was the main cause of sudden fish mortality.The depletion of Oxygen was brought about by several factors, viz., the depletion of phytoplankton resulting in the lesser evolution of oxygen, the gradual increase in the zooplankton which reached the maximum on the day of the fish mortality, resulting in the increased consumption of Oxygen for respiratory purposes, and the decomposition of the bottom sludge which also consumed oxygen to a large measure for the purposes of Chemical oxidation.The changes that are normally correlated with the decrease in the phytoplankton, such as, (i) lowering of the pH (from 8.9 to 7.5), (ii) the decrease in the carbonate contents of the water and (iii) the increase in the bottom turbidity were also noticed. Causes of the depletion of phytoplankton have not been ascertained but may be due to the presence ofDaphnia in very large numbers. Other aspect of the problem is under investigation.Published with the permission of the Director.     

A water quality analysis system to evaluate the impact of agricultural activities on N outflow in river basins in Japan

We have developed a personal-computer-based water quality analysis system for river basins. The system estimates potential N outflow by model and calculates actual N outflow from monitoring data. For the former it uses the potential load factor method to estimate annual nitrogen load from various sources and runoff potential from each area of land in a basin. For the latter it analyzes water quality monitoring data in relation to meteorological data. We used the system to analyze N outflow in basins around Lake Kasumigaura and the Yahagi River in central Honshu, Japan. The land around Lake Kasumigaura is rather flat, and about 25% is periodically flooded for rice and lotus cultivation. The land around the Yahagi River is mountainous, and much less land is flooded. In the Yahagi River basin the actual N outflow agreed closely with the potential. However, the actual N outflow in the basin around Lake Kasumigaura was much less than the potential, suggesting that a large part of the N load is denitrified in flooded soils. This further indicates that a sequence of different land uses including flooded rice fields is an important factor determining N outflow in basins in Japan. On the basis of the above analyses, we incorporated a denitrification model into the system that enables us to estimate N balance in a designated basin; this system may be helpful in the formulation of scenarios of land use and soil management for improving water quality.     

A water quality analysis system to evaluate the impact of agricultural activities on N outflow in river basins in Japan

We have developed a personal-computer-based water quality analysis system for river basins. The system estimates potential N outflow by model and calculates actual N outflow from monitoring data. For the former it uses the potential load factor method to estimate annual nitrogen load from various sources and runoff potential from each area of land in a basin. For the latter it analyzes water quality monitoring data in relation to meteorological data. We used the system to analyze N outflow in basins around Lake Kasumigaura and the Yahagi River in central Honshu, Japan. The land around Lake Kasumigaura is rather flat, and about 25% is periodically flooded for rice and lotus cultivation. The land around the Yahagi River is mountainous, and much less land is flooded. In the Yahagi River basin the actual N outflow agreed closely with the potential. However, the actual N outflow in the basin around Lake Kasumigaura was much less than the potential, suggesting that a large part of the N load is denitrified in flooded soils. This further indicates that a sequence of different land uses including flooded rice fields is an important factor determining N outflow in basins in Japan. On the basis of the above analyses, we incorporated a denitrification model into the system that enables us to estimate N balance in a designated basin;this system may be helpful in the formulation of scenarios of land use andsoil management for improving water quality.     

Hydrobiological studies on the Tugela River system

Summary A survey of pollution in the Bushmans river, and a tributary, the Little Bushmans river in the vicinity of Estcourt, Natal, is described. The pollution arose mainly from wastes discharged from a boardmill, a milk-processing factory, and a sewage-disposal, irrigation farm. The effects of these effluents on the chemistry of the river waters, and on the biological communities in them is described.The communities at polluted stations have been classified in relation to the degree of pollution, and the equivalence of the classification with the systems described by other workers has been indicated. Differences observed between communities in normal and polluted stretches of the rivers are suggested as indices of pollution.     

Hydrobiological consequences of the addition of phosphate precipitants to inlet water of lakes

Summary In three model reservoirs (LUND, 1975) a method reducing bluegreen algal blooms in lakes was studied. Iron or aluminium were added to inlet waters for chemically binding the inflowing phosphorus.The research program, started in 1975, includes intensive monitoring of many chemical and hydrobiological variables, the determination of water and mass balances and since 1977 measurements or primary production rates with¹⁴C. In this paper only the results found in 1977 are discussed. An attempt is made to describe quantitatively how growth rates and changes in biomass are interconnected and how phosphorus precipitation changes these variables.In all reservoirs a large discrepancy was observed between the actual rate of increase in the algal population and the relative production rate. The latter appeared to be higher by one order of magnitude. The relative death rate due to grazing can account for the large difference between these growth rates only when selective grazing of zooplankton on phytoplankton is assumed.It can be concluded that treatment of inlet water with AVR, an aluminium salt, is unsuccessful in reducing algal development. Treatment with ironsulphate may be successful, but a reduction of the relative growth rates was not observed. The effects of grazing of zooplankton andDreissena polymorpha need further investigation.     

Hydrobiological studies on the Vaal River in the Vereeniging area

Summary This paper deals with the chemical, bacteriological and faunal studies on the muddy bottom deposits of the Vaal River near Vereeniging, in a 64 kilometre section where it is held back by a barrage. No significant sewage pollution or other forms of organic pollution were found to occur but pollution by copper and mineral oil was found at one sampling station. Attempts to relate chemical, bacteriological and faunal results were largely negative except that high sulphide figures were normally accompanied by higher counts of oligochaetes than usual. The pollution with copper and mineral oil practically eliminated the fauna but had no obvious effects on the bacteriological results. On the whole the bottom fauna was rather sparse and poor in variety. This was attributed mainly to the regular deposition of fine, clayey silt.

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Zusammenfassung Dieser Artikel enthält chemische, bakteriologische und faunale Studien über die schlammigen Bodensedimente des Vaal-Flusses nahe Vereeniging, in einer Entfernung von 64 Kilometern, wo er durch ein Stauwerk zurückgehalten wird. Es wurden keine nennenswerte Abwasserverunreinigung oder andere Formen organischer Verunreinigung angetroffen. Bei einer Stelle der Probenentnahme wurde jedoch Verunreinigung durch Kupfer and Mineralöl angetroffen. Versuche, Beziehungen zwischen den chemischen, bakteriologischen und faunalen Ergebnissen herzustellen, fiel weitgehend negativ aus, mit Ausnahme von dem hohen Sulphidgehalt, der meistens von einer größeren Anzahl Oligochaeten als gewöhnlich begleitet wurde. Die Verunreinigung durch Kupfer and Mineralöl schaltete praktisch die Fauna aus, hatte jedoch keine offensicht-liche Auswirkung auf die bakteriologischen Ergebnisse. Im großen und ganzen war die Bodenfauna ziemlich spärlich und wies keine großen Variationen auf. Dies war hauptsächlich zurückzuführen auf eine regelmäßige Ablagerung von feinem, tonartigem Material.

     

济南泉溪藻类及水质评价

调查了济南城内著名的黑虎泉、趵突泉、珍珠泉和五龙潭泉四大泉群中的藻类植物, 共计有80 种及变种, 分属于蓝、红、硅、裸、绿和轮藻门, 其中, 以硅藻门种类最丰富, 相对数量也占优势。根据藻类植物的分布, 利用指示生物法对泉水水质进行了定性初步评价, 结果表明, 济南的泉水较清洁。但是泉水涌出后的保洁和管理问题仍然较大, 需要重视。     

七项河流附着硅藻指数在东江的适用性评估

综合运用因子分析、聚类分析、箱型图分析等统计方法评估了河流附着硅藻生物指数(Biological Diatom Index,IBD)、硅藻营养化指数(Trophic Diatom Index,TDI)、斯雷德切克指数(Sládecˇek’s Index,SLA)、特定污染敏感指数(Specific Polluosensitivity Index,IPS)、硅藻属指数(Generic Diatom Index,IDG)、戴斯指数(Descy Index,DESCY)和欧盟硅藻指数(European Economic Community Index,CEE)在东江流域河流水质评价中的适用性。结果显示:SLA与IPS,CEE显著相关(P<0.05),CEE与TDI不相关,其余指标间均极显著相关(P<0.01)。SLA与13项水质理化指标均无相关性,TDI与含氯度(Cl)显著负相关,CEE与溶解氧(DO)、电导率(Cond.)、总氮(TN)显著正相关(P<0.05),其余指标与氨氮(NH4-N)、pH不存在线性相关,与五日生化需氧量(BOD5)、高锰酸盐指数(CODKMnO4)、亚硝氮(NO2-N)、硝氮(NO3-N),总磷(TP)具极显著相关性(P<0.01)。13项水质理化指标中主成分负荷贡献大于50%的八项理化参数DO、BOD5、CODKMnO4、TN、NO3-N、NO2-N、TP和SiO2将试验区水质分为四组。IPS、IBD、IDG和CEE与水质物化分类一致性较好。IPS、IBD、IDG和CEE的逐步判别分析(引入P=0.20,剔除P=0.25)显示IPS和CEE都只选出了NO2-N,分类判别的正确率分别为55.6%和48.1%;IBD引入了NO2-N,CODKMnO4和DO 3个解释变量,判别正确率74.1%;IDG引入BOD5和NO3-N两个变量,分组正确率63.0%。硅藻群落聚类显示,IBD和IDG在水质物化分类的箱型图中呈现出明显合理的趋势。以上研究表明IBD和IDG硅藻指数最适合用于东江河流水质生物监测与评价。     

Comparative performance of benthic diatom indices used to assess river water quality

Grazer-periphyton interactions were investigated in 11 laboratory streams holding a range of densities of three herbivore taxa during a 32-d experiment. Effects of grazers on algae were strongest with Dicosmoecus gilvipes caddisflies, intermediate with Juga silicula snails, and weakest with Baetis spp. mayflies. Algal standing crop, export, and gross primary production declined logarithmically with increasing grazer density. Algal turnover rate, however, increased with grazer abundance. At high densities of all grazers, responses in most algal parameters converged, suggesting that high grazing pressure, regardless of taxon, will similarly affect periphyton. Growth of both Dicosmoecus caddisflies and Juga snails was density-dependent, with the highest growth rates occurring at the lowest densities. Caddisflies displayed high growth rates but low efficiency in resource use. Snails had lower growth rates but were more efficient in resource use. The coexistence of Dicosmoecus and Juga, or other competing herbivores, in natural streams may be related to these fundamental differences in life history strategies.Department of Fisheries and Wildlife     

Response of diatom indices to simulated water quality improvements in a river

Various diatom indices are routinely used in European countries to monitor water quality in waterways. In order to assess their sensitivities and their integration interval after a sudden and lasting environmental change, epilithic diatom biofilms were transferred from several polluted rivers to an unpolluted stream. To monitor the changes of the index values, the biofilms were sampled in a first experiment 20 and 40 days after transfer, and in a second experiment 30 and 60 days after transfer. Sensitivities of the indices to the water quality improvement were assessed calculating the differences between the index values of the reference and the transferred assemblages. Some indices have intermediate sensitivities (BDI, GDI, ILM, SLA), others higher sensitivities (CEE, EPI, ROT, SPI, TDI). The integration interval of these indices was 40–60 days. Some differences were observed between the indices, but their results were homogeneous when compared to those obtained with other metrics such as Bray-Curtis or Chord distances, used to assess the difference between the transferred and the reference diatom assemblages. These other metrics showed that even after 60 days, the transferred assemblages still differed from the reference. This underlines that metrics do not have the same integration intervals and do not assess the same stresses; the choice of the metric used to assess water quality is of prime importance.     

Forest river plants and water quality in Ghana

River plants and water chemistry in wet and dry seasons were sampled in a wide range of rivers with variable catchments in the forest zone of Ghana, in order to examine the relationships between the floristic composition within the river and river water and catchment environmental variables.Plant species occurring in the river or on its seasonally flooded banks along 500 m sample stretches were listed in 26 sites. Sample species richness was low (1–17 species per sample, mean 5.9). Only nine species were recorded that are confined to rivers. Cluster analysis defined five floristic groups which differed in catchment area, geology, turbidity and dissolved minerals.Analysis of water chemistry variables by principal components analysis revealed a strong principal gradient (42% of total variance) related to annual rainfall with low ionic concentrations under high rainfall. The second component described seasonal differences in water chemistry. Nitrate and chloride were more concentrated in the dry season, but sulphate and calcium were more concentrated in the wet season.Catchments with higher forest cover yielded more oligotrophic and less turbid water. Catchment geology influenced water chemistry so that sandstone areas yielded clear water, and ancient peneplain areas with bauxitic soil were characterised by exceptionally low silicon concentrations.The association of macrophyte composition with river chemistry and catchment conditions was somewhat tenuous, due to the low number of species, but the low turbidity, oligotrophic rivers under high rainfall and with a high percentage of species-rich forest cover were the more species rich. Prediction of river water quality at the scale of this study are more readily made from a knowledge of catchment rainfall and forest cover than from assessments of river plant composition.     

Use of benthic diatom communities to evaluate water quality in rivers of southern Poland

Biological and chemical data were processed to estimate trophic stage and degree of pollution in several streams and rivers in southern Poland. The majority were eutrophic and some of them heavily polluted; only a few were oligo-mesotrophic. The differences in the water quality of the rivers were reflected by different types of diatom community and also by the values for some diatom indices, which were calculated using the latest version of the 'Omnidia' database software. Except for the Sládeček's index, all diatom indices correlated significantly with organic load (COD), oxygen concentration, conductivity and most of the measured ions. Some indices showed a significant negative correlation with trophic level (expressed by NH₄-N and PO₄-P). In general, IPS (Specific Pollution Sensitivity Index) and GDI (Generic Diatom Index) indices gave the best results. Among the investigated diatom communities, only a few taxa indicated oligo-mesotrophy and oligo-β-mesosaprobity. Most of the sites were characterised by a greater relative contribution of eutraphent and tolerant ones as well as α-mesosaprobic and polysaprobic diatoms. This study suggests that the structure of benthic diatom communities and diatom indices, especially GDI, can be applied for monitoring rivers in Poland. This revised version was published online in June 2006 with corrections to the Cover Date.     

水利工程对河流生态系统服务功能的影响评价方法初探

通过分析水利工程对河流生态系统服务功能的影响,建立了评价指标体系和定量化的评价方法．评价指标体系包括建立评价指标的原则、对河流生态系统服务功能的分类和指标确定等．本文将河流生态系统的服务功能分为四类即供水及与供水量相关的航运和水电功能、生态支持功能、调节控制功能和文化美学功能．依据不同的功能类型,应用以前的研究成果,针对水利工程产生的生态效应如生物多样性的变化和河流净化功能的变化,确定了不同的调度指标,并建立了相应的数量化评价方法,主要包括指效法和BOD-DO模型方法,这些方法特有助于对水利工程的生态环境效应进行深入的分析与评价。