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At least 127 records · Page 7Linked to original sources
PubMed2000

Suspended chlorophyll in the River Nene, a small nutrient-rich river in eastern England: long-term and spatial trends.

The distribution of suspended algae was investigated in a 69-km length of a small lowland river in the UK, the Nene, using chlorophyll as a measure of biomass. Variations in chlorophyll data collected between 1975 and 1996 by water management organisations at a downstream site (km 91.7) were evaluated against a range of physical and chemical variables. Interpretation was aided by additional sampling at eight sites on the main river (including km 91.7) and three tributaries between 1994 and 1996. Significant inter-year variation was evident in all data and was most pronounced in discharge. The latter half of the 22-year period had significantly higher temperature and light and significantly lower ammonia concentrations. Discharge, temperature and light were significant predictors of chlorophyll concentration, particularly between January and June, and spring chlorophyll maxima ranged from 106 to 276 microg l(-1). Summer chlorophyll concentrations were generally low relative to spring peaks. Some summers, however, had very low chlorophyll concentrations (average < 10 microg l(-1)) which were independent of the controlling factors at other times and inter-year variation in submerged macrophyte abundance is proposed as a causal factor for their occurrence. Spring chlorophyll peaks occurred earlier and had smaller amplitude at downstream sites compared to those further upstream. Average spring chlorophyll concentration (April-June) increased significantly between km 22.4 and 43.9, thereafter remaining high to km 91.7. Spatial trends were attributed to changes in channel morphology, retention time and longitudinal variations in velocity and temperature.

Biomass↗
PubMed2005

Nest placement of the giant Amazon river turtle, Podocnemis expansa, in the Araguaia River, Goiás State, Brazil.

The giant Amazon river turtle (Podocnemis expansa) nests on extensive sand bars on the margins and interior of the channel during the dry season. The high concentration of nests in specific points of certain beaches indicates that the selection of nest placement is not random but is related to some geological aspects, such as bar margin inclination and presence of a high, sandy platform. The presence of access channels to high platform points or ramp morphology are decisive factors in the choice of nesting areas. The eroded and escarped margins of the beaches hinder the Amazon river turtle arriving at the most suitable places for nesting. Through the years, changes in beach morphology can alter nest distribution.

Animals↗
PubMed2003

Comparative susceptibility of two races of Salmo salar (Baltic Lule river and Atlantic Conon river strains) to infection with Gyrodactylus salaris.

The susceptibility of various races of salmonids towards infections with the skin parasitic monogenean Gyrodactylus salaris Malmberg, 1957, differs markedly. Norwegian and Scottish salmon strains are known as extremely susceptible to infection, whereas Baltic salmon races such as the Neva strain (Russian origin) and the Indals river (Swedish origin) salmon have been characterized as relatively resistant. However, the status of the many other Baltic strains has remained unknown. The present study reports on the susceptibility of the Baltic salmon from the Swedish river Lule. It was shown that this strain is susceptible to infection but to a lesser extent than the Scottish salmon. Further studies showed that injection of immuno-suppressants (dexamethasone) greatly increased population growth of G. salaris on Scottish salmon but not on the Baltic salmon. Mucous cell density on fins differed between strains, and a general trend to decreased cell density on infected fish 8 wk post-infection, compared to uninfected fish, was observed. The largest decrease in mucous cell density following infection was seen in the most resistant fish. After administration of immuno-suppressants, this decrease in mucous cell density was inhibited in the Scottish salmon but not in the Baltic salmon. Thus, there seems to be a relationship between the fishes' ability to discard mucous cells and the ability to resist infections with Gyrodactylus salaris. Although the Lule salmon seems more susceptible to infection compared to previous reports on the Neva salmon, the results support the notion that Baltic salmon strains are generally more resistant than East Atlantic salmon.

Animals↗
PubMed2003

Mercury in the Moji-Guaçu river basin, S.P-Brazil: the link between marginal lagoons and river contribution, assessed by 210Pb dating profiles.

Total mercury content was evaluated in water and suspended sediment samples of the Moji-Guaçu river and in water and bottom sediment of its 3 marginal lagoons (Catingueiro, Barrinha, and Rio das Pedras), located downstream of the sampling point in the main channel. In all situations, low Hg concentrations were found in suspended and bottom sediments. Aluminum was used as a geochemical tracer to normalize the Hg concentrations in the sediment cores from the Rio das Pedras lagoon (r = 0.92). It was estimated that the Moji-Guaçu river transports up to 19 kg Hg yr(-1), 65% in the dissolved form and 35% adsorbed onto particulate matter. Following an acute toxic stage observed in the years 1970-1980, the basin has been restored to its original conditions mainly by natural recovery and a general reduction in Hg input to the ecosystem.

Brazil↗
PubMedDate not supplied

[Limnetic zooplankton run-off a high-head dam and their fate in a river with high current velocity (case of the Krasnoiarsk hydroelectric power station on the Yenisei river].

The vertical distribution of net zooplankton in head-water of Krasnoyarsk hydroelectric power station and its horizontal distribution in the tail-water were studied during two years in winter and summer seasons. In order to distinguish living and dead individuals the special staining was used. It was revealed that on average 77% of living plankton pass through high-head dam with deep water scoop to the tailwater. While passing through dam aggregates some individuals of the reservoir plankton are traumatized and die, that results in some increase of portion of dead individuals in the tail water near dam (from 3 to 6%). Alive zooplankton passed through the dam aggregates is eliminated under the Upper Yenisei highly turbulent conditions. There is approximately 10% of it in 32 km from the dam if compare with biomass in 20-40 m layer of reservoir, the portion of dead increases to 11%. The biomass of zooplankton suspended in the water column of the tail-water sometimes increases (till > 1 g/m3) due to large Copepoda Heteroscope borealis, which inhabits near-bottom and near-shore river zones and can be found in the central part of the river during reproductive period. Limnetic zooplankton from the reservoir cannot be considered as important food for planktivores in the tail-water.

Animals↗
PubMed2006

Flow-specific trends in river-water quality resulting from the effects of the Clean Air Act in three mesoscale, forested river basins in the northeastern United States through 2002.

Two new methods for assessing temporal trends in stream-solute concentrations at specific streamflow ranges were applied to long (40 to 50-year) but sparse (bi-weekly to quarterly sampling) stream-water quality data collected at three forested mesoscale basins along an atmospheric deposition gradient in the northeastern United States (one in north-central Pennsylvania, one in southeastern New York, and one in eastern Maine). The three data sets span the period since the implementation of the Clean Air Act in 1970 and its subsequent amendments. Declining sulfate (O4(2-)) trends since the mid 1960s were identified for all 3 rivers by one or more of the 4 methods of trend detection used. Flow-specific trends were assessed by segmenting the data sets into 3-year and 6-year blocks, then determining concentration-discharge relationships for each block. Declining sulfate (O4(2-)) trends at median flow were similar to trends determined using a Seasonal Kendall Tau test and Sen slope estimator. The trend of declining O4(2-) concentrations differed at high, median and low flow since the mid 1980s at YWC and NR, and at high and low flow at WR, but the trends leveled or reversed at high flow from 1999 through 2002. Trends for the period of record at high flows were similar to medium- and low-flow trends for Ca2++ Mg2+ concentrations at WR, non-significant at YWC, and were more negative at low flow than at high flow at NR; trends in nitrate (NO3-), and alkalinity (ALK) concentrations were different at different flow conditions, and in ways that are consistent with the hydrology and deposition history at each watershed. Quarterly sampling is adequate for assessing average-flow trends in the chemical parameters assessed over long time periods (approximately decades). However, with even a modest effort at sampling a range of flow conditions within each year, trends at specified flows for constituents with strong concentration-discharge relationships can be evaluated and may allow early detection of ecosystem response to climate change and pollution management strategies.

Acid Rain↗
PubMed2003

Cladocera fauna composition in a river-lagoon system of the Upper Paraná River floodplain, with a new record for Brazil.

Cladocera communities were studied in lotic and lentic environments of the Upper Paraná River floodplain, State of Mato Grosso do Sul, Brazil. A total of 63 species of Cladocera were identified in 108 samples. Of these, 24 species are considered new records for that floodplain, and one is a new record for Brazil. Chydoridae was the most representative family with 19 genera and 39 species.

Animals↗
PubMed2005

Reproductive seasonality of fishes from a lotic stretch of the Grande River, high Paraná river basin, Brazil.

We searched for correlations between water level, rainfall, temperature, and reproductive activity of fishes in a lotic stretch of the Grande River below the Volta Grande Dam. Gillnets were used to catch the fish on six field journeys made bimonthly between April 1998 and February 1999. Fish gonads were classified according to maturation grade and the amount of mature or spent gonads was correlated with rainfall and air temperature. Most fish species showed seasonal reproduction (between October and February). The relative frequency of fully mature and spent gonads significantly correlated with rainfall (Spearman r = 0.94, p = 0.005) and air temperature (r = 0.84, p = 0.036), showing the importance of these factors in regulating the reproductive cycle of fishes in this location. Nevertheless, dam operation resulted in minimal water level variation that did not significantly correlate with reproductive activity (r = -0.43, p = 0.396).

Animals↗
PubMed2006

Effect of different river water quality model concepts used for river basin management decisions.

n this research the applicability of two different water quality concepts, a QUAL2E-based and a RWQM1-based water quality model is evaluated in terms of management decisions. The Dender river in Belgium serves as a case study for the application of the methodology. By using sensitivity analysis on both model concepts the important processes are revealed. Further, the differences between the predictions for a future scenario are analysed. The scenario chosen here is a reduction in fertiliser use of 90%, which reduces the diffuse pollution. This way, the advantages or disadvantages of using one concept against the other for this scenario are formulated. It was found that the QUAL-based models are more focussing on algae processes while the RWQM1 also takes into account processes in the sediment. Further the QUAL-based models are easier to calibrate, especially when only a small amount of data is available. Both concepts lead to more or less the same conclusions. However for some periods the differences become important and to reduce the uncertainty in those periods, more efforts should be spent in calibration and in better detection of parameters concerning sediment processes and diffusion.

Belgium↗
PubMed2001

Halogenated organic contaminants in sediments of the Havel and Spree rivers (Germany). Part 5 of organic compounds as contaminants of the Elbe river and its tributaries.

To give a detailed and comprehensive view on the state of pollution of the Havel and Spree rivers nontarget screening as well as quantitative (target) analyses were applied to anoxic sedimentsamples. Based on nontarget GC/MS analysis a significant contribution to the anthropogenic contamination could be attributed to halogenated compounds. Three groups of contaminants corresponding either to diffuse or local contamination could be distinguished. Several commonly observable compounds including pentachloroanisol, polychlorinated biphenyles, 2,4-dichlorobenzoic acid, and chlorinated benzenes were detected with a distribution reflecting the contribution of nonpoint source emissions. A second group of chlorinated as well as brominated compounds was attributed to a strong point source emission at the Teltow Canal. At the sampling locations influenced by this point source the amount of mono- and dibrominated naphthalenes, chlorinated naphthalenes, and hexachlorocyclohexanes as well as DDT- and methoxychlor-related compounds increased significantly as compared to the background concentrations. A third group of halogen compounds emitted at this site consisted of the pesticides bromopropylate, methoxychlor, and chlorfensone as well as specific brominated aromatics including 2,4,6-tribromoaniline, 4,4'-dibromobenzophenone, and brominated benzenes. In addition, tetrabromochlorotoluenes, tribromodichlorotoluenes, dibromotrichlorotoluenes, and 2,2-bis(4-bromophenyl)acetic acid isopropyl ester were identified and are reported for the first time as environmental contaminants. The amounts of brominated compounds detected in Teltow Canal sediments occurred at a similar concentration level as their chlorinated analogues. Therefore, investigations on the occurrence of such a broad spectrum of brominated compounds as established in this work are presumably required more frequently to assess the environmental impact of this type of emissions.

DDT↗
PubMed1988

Seasonal distribution of Aeromonas hydrophila in river water and isolation from river fish.

The seasonal distribution of Aeromonas hydrophila in water and recovery rate from live river fish was investigated. The highest isolation rates of A. hydrophila occurred in water during the late winter followed by a progressive decline in density during the summer and monsoon seasons. The organism was recovered from fish throughout the period from which it was concluded that they form a reservoir which is unrelated to their density in water. The enterotoxigenicity of some environmental strains was tested in suckling mice and rabbit ileal loop.

Aeromonas↗
PubMed2001

From river to ridge: a blueprint for sustainable management in the Georges River catchment.

Research on sustainable transport and water projects, conducted in North America during 1999, identified four key considerations common to a number of projects. These four considerations are the preconditions necessary to achieve sustainability in a given location. These preconditions (BAPP) are boundary definition, administrative alignment, protection of non-urban lands, and the participation of all interested parties. This paper considers the perceived attitudes of various catchment stakeholders and focuses on planners and planning. The results of questionnaire surveys based on BAPP concepts suggest that local government is perceived as having the highest priority for protection of riparian lands and waterways (as individual Councils and Regional Organisations of Councils). Thus local government is the preferred arena for coordination, responsibility and jurisdiction of waterways and riparian land. The opportunity exists to examine the differing roles of local and state government. The paper concludes by outlining the implications of this research for land use planning and institutional structures in sustainable river management.

Agriculture↗
PubMed2002

Environmental water in a regulated river system: the Murrumbidgee River planning approach to the determination of environmental needs.

The major platform of the Council of Australian Governments (COAG) water reform program is the equitable and sustainable sharing of surface and groundwater resources between the environment and consumptive water users. In the regulated section of the Murrumbidgee River below Burrinjuck Dam, approximately 2,800 GL of the available surface water (4,300 GL) is diverted or extracted for irrigation uses in the Murrumbidgee Irrigation Area and Districts, and in the Coleambally Irrigation Area. Environmental flow rules have been developed for the Murrumbidgee which provide for an allocation of water to the environment but on the basis of no more than a 10% impact on farm-gate income of irrigation farmers. This provision limits the volume of water that can be used for environmental purposes, so the most effective use must be made of it. To identify and quantify the benefits to the environment of this limited additional volume of water and to determine the most effective use of the water, an "environmental spreadsheet matrix" has been developed. This paper outlines the development and use of the matrix in the planned implementation of flow regimes appropriate to the protection and enhancement of riparian and aquatic ecosystems and ecological processes.

Australia↗
PubMedDate not supplied

[Viral flora (coliphages and human enteroviruses) found in river water after an urban district (Saint-Etienne). I. Comparative study of four simple and inexpensive methods for concentration and isolation of river-water viruses (author's transl)].

Four methods for the concentration of human enteroviruses in the waters of the river Furan were surveyed: the original method described by WALLIS, of adsorption of viruses on PE-60 polyelectrolyte; a modified version of the Wallis method; a method using a different polyelectrolyte available in France, the POE; the two-phase system described by SHUVAL. The best results were obtained when using the method of adsorption on polyelectrolytes, and the second method was finally chosen for field surveys.

Adsorption↗
PubMed2003

Endoparasite infracommunities of Hemisorubim platyrhynchos (Valenciennes, 1840) (Pisces: Pimelodidae) of the Baía River, Upper Parana River floodplain, Brazil: specific composition and ecological aspects.

Parasites of 136 specimens of Hemisorubim platyrhynchos, popularly called jurupoca, were analyzed. Fourteen parasite species were recorded: four digeneans (Crocodilicola pseudostoma, one Gorgoderidae species, Sanguinicola platyrhynchi, and Sphincterodiplostomum sp.); three cestodes (Goezeella paranaensis, Spatulifer maringaensis, and Mariauxiella piscatorum); five nematodes (Contracaecum Type 1 larvae of Moravec, Kohn, & Fernandes, 1993; Contracaecum Type 2 larvae of Moravec, Kohn, & Fernandes, 1993; Cucullanus (Cucullanus) zungaro; Eustrongylides ignotus; and Goezia sp.); one acanthocephalan (Quadrigyrus machadoi), and one pentastomid (Sebekia sp.). Most of the helminth specimens were found in larval stages, confirming that H. platyrhynchos is a significant source of their transmission. No dominance was reported. With the exception of Contracaecum Type 2 (featuring random dispersion), the species had a clumped pattern of dispersion in the host sample. Evidence of competition among parasite species was not reported. Several species of parasites were correlated with host size and sex. This fact may be explained by increase in food content and possible behavioral modifications of male and female hosts. Infracommunity diversity was not related to host size or sex.

Animals↗