Eutrophication is a global problem affecting many inland and estuarine waters. Many wetlands on the Swan Coast Plain, in Western Australia, have undergone increasing nutrient enrichment since European settlement of the region in the 1850’s. Problems such as algal blooms and nuisance swarms of non-biting midges (Diptera; Chironomidae) are the consequence of nutrient enrichment in many of these wetlands. The restoration of these degraded wetlands, especially with respect to reducing nutrient enrichment, requires a range of comprehensive and effective techniques including catchment management, diversion or treatment of surface inputs and treatment of enriched sediments. Nitrogen and phosphorus, especially phosphorus, are not the only factors controlling algal biomass in water bodies, but they are the only elements that can be removed efficiently and economically. Internal P cycling from wetland sediments can initiate and sustain eutrophication and related algal blooms and nuisance midge problems even after external sources are diverted or reduced. The aim of this study was to identify an effective material to reduce sediment phosphorus release and thereby the phosphorus concentration of the water column. It was also important to determine the impact of the selected amendment material on phytoplankton and larval midge (chironomid) communities. A range of experiments at increasing scales, from bench-top, to microcosm to outdoor mesocosm experiments were designed to test three hypotheses: 1) Materials which have a high P sorption capacity, over a wide range of P solution concentrations, and low P release rate, are potentially suitable agents to reduce P in wetlands with enriched sediments by inactivating sediment P; 2) A reduction in the abundance of cyanobacteria caused by increasing the N:P ratio of an aquatic ecosystem results in a reduction in the density of nuisance species of Chironomidae. 3) Successful amendment of enriched sediments reduces P in the water column thereby reducing the total phytoplankton biomass and the related density of nuisance species of Chironomidae. The adsorption and desorption experiments were carried out under a range of pH values and P concentrations, with a number of materials including fly ash, red mud, precipitated calcium carbonate, crushed limestone and lime to determine the maximum adsorption capacity and affinity of these materials. A rang of P concentrations (0-1000 µg/L) simulated the P concentration of the water column in a range of wetlands of differing trophic status. Poor fits to the Langmuir equation occurred with both red mud and fly ash due to their high P content. A good fit occurred with lime, with a high P removal rate (90%-96%) over the same range. Fly ash and red mud were eliminated from further investigation due to the possibility that they might release phosphorus rather than absorb when P concentrations in surrounding environment were less than 300 µg/L or 200 µg/L respectively (concentrations which can occur in eutrophic systems). Among the three lime-based, redox-insensitive materials tested in the second mesocosm experiments, precipitated calcium carbonate (PCC) possessed the highest maximum adsorption capacity and lowest desorption rate under a range of pH values (6.2, 7.2 and 10) and P concentrations (0-12 000 µg/L), followed by crushed limestone and lime. The different maximum absorption capacities of the three materials appears to be mainly attributed to their particle size (surface area). Lime was chosen as the amendment material for further investigation because it was the only one of the three available in sufficient quantities within the timeframe of this study. Microcosm experiments showed that lime was effective in reducing sediment P release from intact sediment cores, and the ratio of TN:TP in the treatment cores increased over time compared to the control cores (in which TN: TP decreased slightly). In the first mesocosm experiment a significantly higher density of larval midges was found in the treatments than in the controls. The treatments were aimed to increase N:P ratio in the systems to reduce cyanobacteria and, subsequently, larval midge densities. However even though cyanobacteria were eliminated from the treatments, the nitrogen addition appeared to result in higher phytoplankton biomass overall, which fuelled an increase in larval midge densities. In the second mesocosm experiment, the addition of lime to enriched sediments resulted in a reduction in P in the water column. This reduction was accompanied by a reduction in total phytoplankton biomass, the absence of cyanobacteria, and a less abundant and more species - diverse chironomid fauna in the treatment mesocosms. Sediment P fractionation undertaken for both the microcosm and mesocosm experiments showed that most of the phosphorus adsorbed by lime was in the labile fraction (NH3Cl extractable P and NaOH extractable P). Phosphorus in the HCl extractable fraction was also found to be higher in the treatments due to the presence of inert mineral P in the lime than the formation of new hydroxyapatite from adsorbed P. The two mesocosm experiments suggested that larval midges were non-selective feeders, responding to total phytoplankton biomass, rather than the presence of cyanobacteria. Dissolved oxygen and predation also influenced larval midge densities. In summary, although lime appeared to be a useful material for reducing P release from enriched sediments under controlled laboratory conditions, the effect under field conditions was not as definitive. Further work is required to more fully determine the conditions under which sediment remediation may be used as a means of controlling sediment P release and associated high densities of larval chironomids.

China¡¦s water pollution problem has been experienced remediation by Chinese government numerous times; however, not much improvement is seen so far. In addition, Chinese government admits that algae, nutrient and other water pollution problems will not be eliminated in short period of time. Therefore, this study examined the current situation of China¡¦s water bodies as well as the sources of the pollution, and then compared with the measures taken to the problems by the Chinese government. It is found that city and household sewage are the major factors; nevertheless, they haven been less regarded. Therefore, the government should not only maintain the past results of remediation, but also emphasize on strengthening on constructions of sewage discharge facilities and ensuring capital provided for sewage treatment plants in order to control the most water pollution sources into China¡¦s water bodies.

Around 70% of the world is covered with water but only 2.5% of it is freshwater and even less is available for the ecosystem and humanity. The limited available fresh water is facing increasing challenges from water pollutions and eutrophication is one of the major concerns worldwide. The reason of eutrophication is the presence of excessive amounts of phosphorus and nitrogen in water bodies, which may cause algal blooms and a variety of harms to aquatic ecosystem in association with algal blooms. Among these two components, phosphorus plays a major role in eutrophication control and recovery since atmospheric N2 can be fixed by biological nitrogen fixation (BNF) processes and is therefore of little meaning to control. In this study, we investigated for the first time the potential of using controlled growth of algae and, in particular, filamentous cyanobacterium Spirulina platensis, for eutrophic water restoration. This study investigated the algal cell growth, algal by-product production, and removal of phosphate by S. platensis at different phosphate levels in artificial wastewaters and eutrophic waters. Results indicate that S. platensis could remove 90.17% of phosphorus from artificial wastewaters containing 10 mg/L phosphate in a 16-day cultivation period. When tested for eutrophic water restoration, S. platensis was able to convert hypo-eutrophic, eutrophic, and meso-eutrophic waters to oligotrophic water. It was shown that by using 100- micron nylon mesh cloth we could keep biomass concentration to be lower than 0.30±0.02 g/L. In the meantime, light/dark tests indicate that the dissolved oxygen level would not go below the hypoxic level, i.e., 4 mg/L after a 12-hour dark period at biomass concentration up to 1 g/L. These results indicate that it is possible to use S. platensis for both control of point source discharge and eutrophic water restoration.

No description available.

No description available.

It was the purpose of this investigation to attempt to demonstrate if differences in eutrophic levels existed among selected areas of Garza-Little Elm, and to demonstrate the role that sediments play in affecting eutrophication.

O trabalho teve por objetivo avaliar a qualidade de água em viveiro de piscicultura com florescimento de cianobactérias e a toxicidade aguda (DL50-24h) de microcistina nas espécies matrinxã (Brycon cephalus) e tilápia nilótica (Oreochromis niloticus), bem como as alterações histológicas nas brânquias, rins e fígado nos peixes. Foi realizado o monitoramento da qualidade de água de um empreendimento piscícola localizado na cidade de Espírito Santo do Pinhal/SP, Brasil. Foram realizadas, em datas distintas, duas coletas de amostras de água contendo floração de microalgas, para análise da composição fitoplanctônica, determinação de toxinas e bioensaios toxicológicos em laboratório. Foram realizadas medições das variáveis físicas, químicas e biológicas da água, e determinação do estado trófico do viveiro monitorado. O viveiro apresentava-se hipereutrófico, com presença de cianotoxinas representadas por microcistinas com valores variando entre 229,2 e 147,4 µg/g. O florescimento de cianobactérias apresentou-se de composição mista, representado principalmente pelas espécies Anabaena circinalis, A. spiroides, Aphanocapsa sp., Microcystis aeruginosa, M. panniformis, M. viridis, M. cf. wesembergii, Pseudanabaena mucicola, entre outras espécies. Os resultados dos bioensaios com microcistina obtida do extrato bruto de fitoplâncton do florescimento não apresentaram letalidade para os peixes. Contudo, foram verificadas alterações em órgãos dos peixes testados, como a presença de depósitos hepatocelulares intracitoplasmáticos, degeneração vacuolar observada em epitélio tubular renal, e proliferação de epitélio de revestimento (hiperplasia) das brânquias, com casos de fusão total das lamelas secundárias, tanto para matrinxã como para tilápia nilótica. Extratos brutos de cianotoxina, em concentrações a partir de 125 mg/kg de peso corporal, injetados em peixes provocam efeitos deletérios com expressiva alteração nas brânquias, rins e fígado. / The aim of this study was to evaluate the water quality in fish earthpond with blooms of cyanobacterias and acute toxicity (DL50 - 24 hs) of microcystin in species (Brycon cephalus) and tilapia nilotica (Oreochromis niloticus) as well as histological changes in gills, kidney and liver in fish. Water quality monitoring was carryed out in a pisciculture in Espirito Santo do Pinhal city, SP, Brazil. There were two collections of water samples containing bloom of cyanobacteria for analysis of microalgae composition, toxin determination and toxicological bioassay in laboratory. Measurements of physical, chemical and biological variables were done and determination of trophic status of pond water were monitored. The results according to the trophic state index of samples taken showed hipereutrophic state for the pond water. Was evident the presence of cyanobacteria, represented by microcystins with values ranging from 229.2 to 147.4 µg/g. The bloom of cyanobacteria presented mixed composition, represented mainly by species Anabaena circinalis, Anabaena spiroides, Aphanocapsa sp., Microcystis aeruginosa, Microcystis panniformis, Microcystis viridis, Microcystis cf. Wesembergii, Pseudanabaena mucicola among others. The results of tests with crude extract of bloom cyanobacteria did not show mortality of fish. However, there were changes in cellular structures of fish tested as the presence of hepatocellular intracytoplasmatic deposit, vacuolar degeneration observed in renal tubular epithelium, and proliferation of epithelial lining (hyperplasia) of gills, with cases of total fusion of secondary lamellae for both tilapias and for matrinxã. Crude extract of cyanotoxins, in concentrations of 125 mg/kg of body weight, injected in fishes provoke deleterious effect with expressive changes in the gills, kidney and liver.

Internal loading of phosphorus (P) from lake sediments can delay the recovery of lakes from eutrophication for years to decades following decreases in external nutrient inputs. While internal P loading is a pervasive problem in freshwater systems, molecular speciation of P in benthic sediments of these systems remains poorly characterized. As different P species will exhibit different responses to changing sediment-water interface (SWI) geochemistry, quantifying P speciation in sediments is a critical step in understanding P dynamics in sediment-water systems. Here, various synchrotron-based techniques were employed to directly probe the bonding environments of P and iron (Fe) in natural and experimentally manipulated lake sediments in order to link chemical speciation to chemical behavior and to identify the geochemical drivers that mediate this linkage. We manipulated SWI redox conditions in mesocosm experiments to investigate the impacts of prolonged anoxia and redox oscillations on P mobility and speciation in sediments. Mesocosm experiments demonstrate that oscillating redox conditions near the SWI may drive accelerated P release from sediments relative to uninterrupted reducing conditions. Sediment P is found to be predominantly associated with Fe oxyhydroxides, calcium carbonate, and apatite minerals in three shallow hyper/eutrophic lakes in northern Vermont. In Missisquoi Bay and Lake Carmi, Fe redox cycling controls P mobility via precipitation and dissolution of Fe oxyhydroxides. In the hypereutrophic Shelburne Pond, the presence of Fe sulfides precludes redox-driven P cycling and P mobility is instead dominated by organic matter mineralization. Our results demonstrate that internal P loading can manifest differently in similar shallow lake systems due to differences in lake configuration, sediment P and Fe speciation, and organic content of sediments. This work demonstrates the potential utility, as well as the limitations, of P K- edge X-ray absorption near edge structure spectroscopy in determining sediment P speciation in freshwater lakes.

Lake Waikare is a large, shallow eutrophic lake devoid of submerged macrophytes. I investigated potential methods for re-establishing submerged macrophytes in the lake. Specifically, I subjected charophyte (Chara corallina) plantlets to two treatments of exposure in the lake (in areas exposed and sheltered from wind) to test for survival and growth under these conditions, and inside and outside fish exclosures to test for growth and survival in the presence of fish. While plantlets grew outside the exclosures in winter, their accumulated biomass over 21 days was less than protected plantlets. In winter, the accumulated biomass was lower outside than inside exclosures (by ~40%) at the sheltered site and was lower outside than inside exclosures (by 43%) at the exposed site. Overall, growth rates in winter were higher at the sheltered site (compared to the exposed site) by ~7%. In summer, charophyte accumulated biomass inside the exclosures increased by 85%, while at the sheltered site accumulated biomass increased by 58%. Outside the exclosures in summer the plantlets were completely removed at both sites. Overall, growth rates where higher at the exposed site than the sheltered site by 31%. Fish were responsible for the partial removal of plantlets in winter and total removal of plantlets in summer, and therefore affect the survival and growth of charophytes in Lake Waikare. The embayment at the sheltered site provides the best location in winter for re-establishment of charophytes from oospores because better growth rates were obtained there, and its sheltered location provides protection from severe wave action found at the exposed site. Oospores did not germinate after being submersed in the lake for 90 days due to heavy sedimentation. To induce an improvement in the present light climate, Alum was tested to determine its effectiveness and longevity for settling lake sediments to allow charophytes to establish and grow. Examining the settling rates of Lake Waikare sediments and water treated with Alum over a range of suspended sediment concentrations and time intervals, sediments settled faster with Alum than without for at least 15 days (at 200 g l^1 suspended sediment concentration) and it remained active to 60 days but at reduced effectiveness. At the other concentrations tested (100 g l^1 and 300 g l^1 suspended sediment concentration), Alum responses were insignificant. An improved light climate achieved by fish removal or Alum treatment will likely not be sufficient to permit the re-establishment of submerged macrophytes due to the turbid, algal-dominated state of the lake. The present nutrient and sediment levels, wave climate and fish influence must be mitigated so charophyte plantlets can be established.

O trabalho teve por objetivo avaliar a qualidade de água em viveiro de piscicultura com florescimento de cianobactérias e a toxicidade aguda (DL50-24h) de microcistina nas espécies matrinxã (Brycon cephalus) e tilápia nilótica (Oreochromis niloticus), bem como as alterações histológicas nas brânquias, rins e fígado nos peixes. Foi realizado o monitoramento da qualidade de água de um empreendimento piscícola localizado na cidade de Espírito Santo do Pinhal/SP, Brasil. Foram realizadas, em datas distintas, duas coletas de amostras de água contendo floração de microalgas, para análise da composição fitoplanctônica, determinação de toxinas e bioensaios toxicológicos em laboratório. Foram realizadas medições das variáveis físicas, químicas e biológicas da água, e determinação do estado trófico do viveiro monitorado. O viveiro apresentava-se hipereutrófico, com presença de cianotoxinas representadas por microcistinas com valores variando entre 229,2 e 147,4 µg/g. O florescimento de cianobactérias apresentou-se de composição mista, representado principalmente pelas espécies Anabaena circinalis, A. spiroides, Aphanocapsa sp., Microcystis aeruginosa, M. panniformis, M. viridis, M. cf. wesembergii, Pseudanabaena mucicola, entre outras espécies. Os resultados dos bioensaios com microcistina obtida do extrato bruto de fitoplâncton do florescimento não apresentaram letalidade para os peixes. Contudo, foram verificadas alterações em órgãos dos peixes testados, como a presença de depósitos hepatocelulares intracitoplasmáticos, degeneração vacuolar observada em epitélio tubular renal, e proliferação de epitélio de revestimento (hiperplasia) das brânquias, com casos de fusão total das lamelas secundárias, tanto para matrinxã como para tilápia nilótica. Extratos brutos de cianotoxina, em concentrações a partir de 125 mg/kg de peso corporal, injetados em peixes provocam efeitos deletérios com expressiva alteração nas brânquias, rins e fígado. / The aim of this study was to evaluate the water quality in fish earthpond with blooms of cyanobacterias and acute toxicity (DL50 - 24 hs) of microcystin in species (Brycon cephalus) and tilapia nilotica (Oreochromis niloticus) as well as histological changes in gills, kidney and liver in fish. Water quality monitoring was carryed out in a pisciculture in Espirito Santo do Pinhal city, SP, Brazil. There were two collections of water samples containing bloom of cyanobacteria for analysis of microalgae composition, toxin determination and toxicological bioassay in laboratory. Measurements of physical, chemical and biological variables were done and determination of trophic status of pond water were monitored. The results according to the trophic state index of samples taken showed hipereutrophic state for the pond water. Was evident the presence of cyanobacteria, represented by microcystins with values ranging from 229.2 to 147.4 µg/g. The bloom of cyanobacteria presented mixed composition, represented mainly by species Anabaena circinalis, Anabaena spiroides, Aphanocapsa sp., Microcystis aeruginosa, Microcystis panniformis, Microcystis viridis, Microcystis cf. Wesembergii, Pseudanabaena mucicola among others. The results of tests with crude extract of bloom cyanobacteria did not show mortality of fish. However, there were changes in cellular structures of fish tested as the presence of hepatocellular intracytoplasmatic deposit, vacuolar degeneration observed in renal tubular epithelium, and proliferation of epithelial lining (hyperplasia) of gills, with cases of total fusion of secondary lamellae for both tilapias and for matrinxã. Crude extract of cyanotoxins, in concentrations of 125 mg/kg of body weight, injected in fishes provoke deleterious effect with expressive changes in the gills, kidney and liver.