Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 4.762
Filtrar
1.
Microbes Environ ; 35(1)2020.
Artigo em Inglês | MEDLINE | ID: mdl-31969532

RESUMO

The pmoA gene, encoding particulate methane monooxygenase in methanotrophs, and nirS and nirK genes, encoding bacterial nitrite reductases, were examined in the root and rhizosphere sediment of three common emergent macrophytes (Phragmites australis, Typha angustifolia, and Scirpus triqueter) and unvegetated sediment from eutrophic Wuliangsuhai Lake in China. Sequencing analyses indicated that 334 out of 351 cloned pmoA sequences were phylogenetically the most closely related to type I methanotrophs (Gammaproteobacteria), and Methylomonas denitrificans-like organisms accounted for 44.4% of the total community. In addition, 244 out of 250 cloned nirS gene sequences belonged to type I methanotrophs, and 31.2% of nirS genes were the most closely related to paddy rice soil clone SP-2-12 in Methylomonas of the total community. Three genera of type I methanotrophs, Methylomonas, Methylobacter, and Methylovulum, were common in both pmoA and nirS clone libraries in each sample. A quantitative PCR (qPCR) analysis demonstrated that the copy numbers of the nirS and nirK genes were significantly higher in rhizosphere sediments than in unvegetated sediments in P. australis and T. angustifolia plants. In the same sample, the nirS gene copy number was significantly higher than that of nirK. Furthermore, type I methanotrophs were localized in the root tissues according to catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). Thus, nirS-carrying type I methanotrophs were enriched in macrophyte root and rhizosphere sediment and are expected to play important roles in carbon/nitrogen cycles in a eutrophic wetland.


Assuntos
Eutrofização , Gammaproteobacteria/genética , Genes Bacterianos/genética , Magnoliopsida/microbiologia , Microbiologia do Solo , Áreas Alagadas , Proteínas de Bactérias/genética , China , Gammaproteobacteria/classificação , Gammaproteobacteria/metabolismo , Dosagem de Genes , Lagos/microbiologia , Metano/metabolismo , Nitrito Redutases/genética , Oxigenases/genética , Raízes de Plantas/microbiologia , Rizosfera
2.
J Environ Manage ; 258: 109989, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31929079

RESUMO

The chlorophyll-breakdown to pheophorbide is determined by biotic factors such as grazing (via chlorophyllide) or senescence (via pheophytin). So far, much of the information on chlorophyll-breakdown is available from sediments, but information from the water column is limited. This study addressed chlorophyll-breakdown-pathways (Chl-BP) on a seasonal basis from eight major ports (18-30 stations/port) representing freshwater, estuarine, and marine ecosystems. The distribution of chlorophyll and its breakdown fractions (pheophytin, pheophorbide) exhibited distinct spatial and seasonal variations. Fresh-water (except Haldia-port) and estuarine ports are characterized by high-biomass, high-pheophytin, and low-pheophorbide, whereas marine-ports by low-biomass (except Mangalore-port), low-pheophytin, and high-pheophorbide. Pheophytin and pheophorbide distribution were biomass independent and dependent, respectively. The pheophorbide: pheophytin ratio indicated a potential proxy for determining the dominant breakdown pathway, i.e., herbivory dominant (>1) or not dominant (<1). However, CHl-BP is taxa-specific and grazer's feeding habits. The ratios exhibited apparent differences between different ecosystems, i.e., the higher ratios in marine (up to 11.2) followed by estuarine (up to 0.9) and freshwater (up to 0.4; except Haldia) systems. The diatoms (preferred grazer diet) contribution to total phytoplankton was more in marine followed by estuarine and freshwater systems. The low and high ratios suggested the prevalence of chlorophyll-breakdown via senescence and grazing mode, respectively. We proposed that such scaling will have implications in the ballast water management - BWM (ballast tank conditions (eg. dark) during voyages, post-voyage discharge - including treated water using approved BWM systems, and the nature of ports, potential discharge point) and algal bloom research (e.g. understanding fate and in control measures).


Assuntos
Clorofila , Fitoplâncton , Ecossistema , Eutrofização , Água Doce
3.
Water Res ; 171: 115441, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31927090

RESUMO

This study is an analysis of relationships between microalgae (measured as chlorophyll a) and the fecal indicator bacteria enterococci. Microalgae blooms and enterococci exceedances have been occurring in Florida's recreational waterways for years. More recently, this has become a management concern as microalgae blooms have been attributed to potentially toxic cyanobacteria, and enterococci exceedances link to human infection/illness. Since both the microalgal blooms and bacterial exceedances occur in regions that receive managed freshwater releases from Lake Okeechobee, we hypothesized that both the blooms and exceedances are related to excess nutrients from the lake. Two experimental sites, on Lake Okeechobee and the St. Lucie River (downstream of the lake), plus a control site on the Loxahatchee River (which does not receive lake flow) were evaluated. The hypothesis was evaluated through three study components: 1) analysis of available long-term data from local environmental databases, 2) a year-long monthly sampling and analysis of chlorophyll a, enterococci, nutrients, and physical-chemical data, and 3) microcosm experiments with altered water/sediment conditions. Results support the hypothesis that excess nutrients play a role in both chlorophyll a and enterococci levels. For the St. Lucie River, analyses indicate that chlorophyll a correlated significantly with total Kjeldahl nitrogen (TKN) (R2 = 0.30, p = 0.008) and the strongest model for enterococci included nitrate-nitrite, TKN, total phosphorus, orthophosphorus, and turbidity in our long-term analysis (n = 39, R2 = 0.83, p ≤ 0.001). The microcosm results indicated that chlorophyll a and enterococci only persisted for 36 h in water from all sources, and that sediments from Lake Okeechobee may have allowed for sustained levels of chlorophyll a and enterococci levels. Overall similarities were observed in chlorophyll a and enterococci relationships with nutrient concentrations regardless of a Lake Okeechobee connection, as underscored by a study of flow out of the lake and downstream areas. This suggests that both nutrient-rich lake water and untreated surface water runoff contribute to microalgae blooms and enterococci exceedances in southeast Florida.


Assuntos
Lagos , Microalgas , Proliferação de Células , Clorofila , Clorofila A , Enterococcus , Monitoramento Ambiental , Eutrofização , Florida , Nitrogênio , Fósforo
4.
Chemosphere ; 242: 125272, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31896182

RESUMO

Eutrophication pollution seriously threatens the sustainable development of Lake Taihu, China. In order to identify the primary parameters of water quality and the potential pollution sources, the water quality dataset of Lake Taihu (2010-2014) was analyzed with the water quality index (WQI) and multivariate statistical analysis methods. Principle component analysis/factor analysis (PCA/FA) and correlation analysis screened out five significant water quality indicators, i.e. potassium permanganate index (CODMn), total nitrogen (TN), total phosphorus (TP), chloride ion (Cl-) and dissolved oxygen (DO), to represent the whole datasets and evaluate the water quality with WQI. Since northwestern of Lake Taihu was the most heavily polluted area, the parameters of the water quality were analyzed to further explore the potential sources and their contributions. Five potential pollution sources of northwestern lake were identified, and the contribution rate of each pollution source was calculated by the absolute principal component score-multiple linear regression (APCS-MLR) and positive matrix factorization (PMF) models. In brief, the PMF model was more suitable for pollution source apportionment of the northwestern lake, and the contribution rate was ranked as agricultural non-point source pollution (26.6%) > domestic sewage discharge (23.5%) > industrial wastewater discharge and atmospheric deposition (20.6%) > phytoplankton growth (16.0%) > rainfall or wind disturbance (13.4%). This study might provide useful information for the optimization of water quality management and pollution control strategies of Lake Taihu.


Assuntos
Monitoramento Ambiental/métodos , Lagos/química , Modelos Estatísticos , Poluentes Químicos da Água/análise , Qualidade da Água , China , Interpretação Estatística de Dados , Monitoramento Ambiental/estatística & dados numéricos , Eutrofização , Análise Fatorial , Modelos Lineares , Análise Multivariada , Análise de Componente Principal
5.
Water Res ; 170: 115331, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31811989

RESUMO

Inland lakes receive growing attentions on eutrophication and their roles in global carbon cycle. However, understanding how inland lakes contribute to global carbon cycle is seriously hampered due to a shortage of long-term records. This study investigated the carbon dioxide (CO2) flux from the Lake Taihu, a large (2400 km2) and shallow (mean depth 1.9 m) eutrophic lake in subtropical region, based on a long-term (2000-2015) measurement of the partial pressure of carbon dioxide (pCO2) at high spatiotemporal resolution. We found that the Lake Taihu was a significant source of atmospheric CO2 with an average CO2 emission flux at 18.2 ± 8.4 mmol m-2 d-1 (mean±1standard deviation) and a mean annual pCO2 value of 778 ± 169 µatm. The highest pCO2 and CO2 flux were observed in eutrophic zone with a high external input of carbon and nutrient, and the lowest in non-eutrophic zones with no direct external input of nutrient and carbon. A substantial seasonal pattern in pCO2 was observed, particularly in eutrophic pelagic area, and was significantly negatively correlated with chlorophyll a. Long-term measurement showed the interannual variation in annual lake CO2 dynamics, which was highly sensitive to human-induced nutrient input. Watershed input of carbon and nutrient leads to the high CO2 level, counterbalancing the in-lake primary production. All lines of evidence suggest that human activities may have predominate contribution to CO2 source in the Lake Taihu, and this mechanism might be widespread in global freshwater lakes.


Assuntos
Dióxido de Carbono , Lagos , Ciclo do Carbono , China , Clorofila A , Eutrofização , Humanos
6.
Water Res ; 170: 115287, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31812813

RESUMO

The functional diversity of two planktonic functional compartments, the nano-microphytoplankton and the mesozooplankton was used in order to better understand i) the drained marshes functioning and their related ecological functions, ii) the impacts of human control (replenishment) and human activities on the catchment basin (urbanization and catchment basin size). It was based on a monthly seasonal survey on 7 freshwater drained marshes. Both nano-microphyto- and mesozooplankton displayed high seasonal variations linked to the environmental fluctuations and human control on sea lock gates. Winter presented the lower biomasses of both compartments. Winter that is characterized by low water temperature, low light availability and high flood is actually related to the dominance of tychopelagic phytoplankton and K-strategists zooplankton. Spring and summer were characterized by i) the succession of pelagic large cells, small cells and then taxa with alternatives food strategies due to nitrogen limitation and phosphorous desorption from the sediment leading to eutrophication processes and ii) the dominance of r-strategists for mesozooplankton. The artificial summer replenishment acts positively on water quality by decreasing the eutrophication processes since the nitrogen inputs limit the proliferation of phytoplankton mixotrophs and diazotrophs and increase the ecological efficiency during the warm period. Both small and large catchment basins may lead to summer eutrophication processes in drained marshes since the largest ones imply higher hydrodynamic features at the root of large inputs of nitrogen nutrient favoring the phytoplankton development while the smallest ones exhibit hypoxia problems due to high proliferation of macrophytes. Urbanized marshes are less subjected to eutrophication during summer than non urbanized marshes due to more recurrent nutrient inputs from urban waste. However they exhibited a lower ecological efficiency. The results suggest that a better management of the hydrodynamics of such anthropogenic systems can avoid eutrophication risks on coastal areas.


Assuntos
Plâncton , Áreas Alagadas , Animais , Eutrofização , Atividades Humanas , Humanos , Fitoplâncton , Estações do Ano
7.
Water Environ Res ; 92(1): 26-34, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31424121

RESUMO

Dilution with low-nutrient Columbia River Water (CRW) has markedly improved Moses Lake quality for 42 years. There were two phases of CRW volume input, which proportionately lowered total phosphorus (TP). Initially, spring-summer inputs averaged 130 × 106 m3 during 1977-1988 reducing average TP from 152 to 65 µg/L in half the lake proximal to the inputs. That input represented 1.5 volumes of that half-lake volume. Inputs doubled through the mid-1990s, and nearly 2.5 times since 2000, decreasing TP to a 18-year average of 24 µg/L. Chlorophyll a (chl) decreased further from 18 µg/L during the early dilution years to about 6 µg/L as TP declined. Cyanobacteria biovolume declined to 57% of total biovolume during 1977-1988 from 98% before dilution. Less (65%) CRW water since 2016 led to higher TP (41 µg/L) and chl (18 µg/L) in 2018, while cyanobacteria averaged 87% of total biovolume. More TP and cyanobacteria in 2018 are attributed to more internal TP loading. Increased N:P ratios have possibly given more advantage to the non-N-fixing cyanobacteria Microcystis, which comprised 82% and 74% of maximum cyanobacteria biovolume in 2017 and 2018. PRACTITIONER POINTS: Lake total phosphorus (TP) was reduced 57% in the 1970s-1980s by adding large volumes of low-nutrient Columbia River water (CRW). Total P was further reduced by 65% since 2000 by more than doubling the earlier CRW input to an average spring-summer concentration of 24 µg/L. Less (65%) CRW during 2017-2018 led to higher lake TP (41 µg/L) and a worse cyanobacteria bloom in 2018. Microcystis, an non-nitrogen fixer, was the dominant cyanobacteria in 2017-2018 likely related to higher N:P ratios.


Assuntos
Lagos , Fósforo , China , Clorofila , Clorofila A , Monitoramento Ambiental , Eutrofização
8.
Waste Manag ; 102: 12-20, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31654875

RESUMO

The combination of increased maritime transportation and the sensitivity of the Baltic Sea makes it necessary to establish efficient, eco-friendly and profitable ship-generated waste management strategies. This study aims to identify best management practices for ship-generated nutrient-rich organic wastes, i.e. food waste and sewage, on the Baltic Sea. Ship-generated waste quantities and characteristics, maritime waste regulations, and disposal methods are reviewed and discussed according to the available literature for the Ports of Helsinki, Stockholm, Tallinn and Copenhagen Malmö, which are the most important and busiest ports on the Baltic Sea. Sorting onboard and separation of food waste from other waste sources such as sewage and grey water is a suitable solution that facilitates further treatment. However, this procedure demands special facilities and sufficient storage space. Aforementioned food waste can be delivered to port reception facilities (PRFs) and used to produce biogas at land. However, currently only food waste from ships operating in the EU may be used as input for biogas production, not international food waste. Grinding of food waste and discharge into the sea is still common practice. In addition, shipping companies can choose buffet type restaurants in order to reduce food waste generation. Grey wastewater is generally discharged into the sea, whereas sewage needs to be treated on board before discharge or delivered to PRFs for treatment. New MARPOL regulations for passenger ships on the Baltic Sea require advanced treatment of pollutant nutrients, nitrogen and phosphorus, before sewage discharge in order to combat eutrophication of this sensitive area.


Assuntos
Eliminação de Resíduos , Gerenciamento de Resíduos , Eutrofização , Alimentos , Esgotos , Navios
9.
Ambio ; 49(2): 460-474, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31278623

RESUMO

To tackle the symptoms of eutrophication in the open Baltic Sea and Finnish coastal waters, Finland has agreed to reduce both total nitrogen (TN) and total phosphorus (TP) inputs. Due to large investments in treatment of municipal and industrial wastewaters, TP loads started to decrease already in the mid-1970s and the respective TN loads in the mid-1990s. During the last two decades, much effort has been spent in decreasing the load originating from diffuse sources. Trend analyses in 1995-2016 showed that, despite various mitigation measures, riverine nutrient export has not substantially decreased, and especially the export from rivers draining agricultural lands remains high. In some areas TN concentrations and export were increasing and we found evidence that it was linked to ditching of peatlands. Several factors connected to climate/weather (e.g. temperature and precipitation) have counteracted the mitigation measures, and therefore Finland will not achieve the nutrient reduction targets by 2021.


Assuntos
Rios , Poluentes Químicos da Água , Países Bálticos , Monitoramento Ambiental , Eutrofização , Finlândia , Nitrogênio , Nutrientes , Oceanos e Mares , Fósforo , Água
10.
Water Environ Res ; 92(1): 138-148, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31486194

RESUMO

Nutrient enrichment facilitates algal outbreaks in eutrophic shallow lakes. To further understand the influence of various inorganic nutrient forms on cyanobacterial blooms, a nitrate (NO3 ), ammonium (NH4 ), and orthophosphate (PO4 ) amendment experiment was conducted in a large shallow lake of China (Lake Taihu) during summer. The results showed that the photosynthetic performance of phytoplankton responded more positively to phosphorus (P) than nitrogen (N), and NH4 addition stimulated higher algal photosynthetic activities in P-enriched waters. Individual inorganic N or PO4 addition significantly activated cyanobacteria and green algae. Meanwhile, the N plus P amendment promoted higher biomass of the planktonic microbial community, and the dual addition of NH4  + PO4 yielded the highest chlorophyll a concentration. NH4 additions provisionally promoted higher green algae than cyanobacteria biomass in the beginning, while cyanobacteria dominated again with increasing NH4 :PO4 ratios. These results revealed that increasing ammonium would enhance the increase in phytoplankton biomass in advance and prolong the duration of algal blooms. Hence, based on the control of P loading, the reduction in external inorganic N focusing on ammonium sources (such as ammonia N fertilizer) at the watershed scale would help to alleviate eutrophication and cyanobacterial blooms over the long term in Lake Taihu. PRACTITIONER POINTS: Ammonium addition stimulated higher algal photosynthetic activities in P-enriched waters. Individual inorganic N or PO4 addition significantly activated cyanobacteria and green algae. The dual addition of NH4  + PO4 yielded the highest chlorophyll a concentration. Increasing NH4 would enhance the increase in phytoplankton biomass in advance and prolong the duration of cyanobacterial blooms.


Assuntos
Cianobactérias , Lagos , Baías , Biomassa , China , Clorofila A , Eutrofização , Nitrogênio , Nutrientes , Fósforo , Fitoplâncton
11.
Ambio ; 49(1): 187-196, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31020610

RESUMO

This paper documents the changes that followed large nutrient (N and P) and organic matter input reductions to a major metropolitan marine bay, Boston Harbor (USA). Before input reduction, its N and P inputs fell in the upper range of the < 1-> 300 gN m-2 year-1 and < 0.1-> 40 gP m-2 year-1 for coastal systems. Elevated nutrient and organic matter inputs are recognized causes of coastal eutrophication. Treatment upgrades and then diversion of its wastewater discharges offshore, lowered its N, P, and organic C inputs by 80-90%. The input decreases lowered its trophic status from hypereutrophic to eutrophic-mesotrophic. With the reversal of hypereutrophication, pelagic production and phytoplankton biomass decreased, and the nitrogen limitation relative to phosphorus limitation increased. Benthic metabolism and dissolved inorganic N fluxes decreased, and benthic-pelagic coupling was altered. Bottom-water dissolved oxygen, already at healthy levels, increased, and seagrass expanded. Coastal management requires that the changes, following the nutrient and organic matter input reductions implemented to address eutrophication, be understood. Boston Harbor's recovery, because its water column was vertically well mixed and marine, was more pronounced than in many other systems.


Assuntos
Eutrofização , Águas Residuárias , Boston , Monitoramento Ambiental , Nitrogênio , Fósforo , Fitoplâncton
12.
Water Res ; 168: 115132, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31590035

RESUMO

Dissolved organic matter (DOM) plays important roles in the aquatic biogeochemical cycle and the global carbon cycle. However, it is highly spatially and temporally varied due to complex sources from the catchment (allochthonous) and from within the system (autochthonous). Satellite remote sensing provides the ability to monitor DOM and identify the spatio-temporal variations in lakes on a global or regional scale. In this study, field work was conducted in 55 lakes in August 2012 along the middle and lower reaches of the Yangtze River (MLR-YR), where most lakes were characterized by eutrophication due to intense human activities. The results showed that both colored DOM (CDOM) and total DOM differed significantly by and were linearly related to the human-induced trophic state index (TSI), with R2 = 0.41 and 0.61, respectively. Autochthonous substances by phytoplankton contributed to 38.5% of CDOM and 35.2% of DOM, and allochthonous terrestrial substance indexed by land cover change and aquaculture contributed to almost half, with 49.7% of CDOM and 49.8% of DOM. In total, human activities explained as much as 81.7% and 87.5% of the variations in CDOM and DOM, respectively. Finally, a flowchart for estimating DOM from satellite-derived TSI was proposed. This study has great significance for synchronously monitoring and managing aquatic environment quality in regional eutrophic lakes around the world.


Assuntos
Lagos , Rios , China , Monitoramento Ambiental , Eutrofização , Atividades Humanas , Humanos , Fitoplâncton
13.
Sci Total Environ ; 701: 134944, 2020 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-31715481

RESUMO

This study investigated responses of the submerged macrophyte Vallisneria natans to a water depth gradient of 0.3-1.5 m in shallow lakes, and examined changes of morphology, physiological parameters, leaf-epiphytic bacteria community, and water purifying ability. Results of the morphological and physiological parameters (shoot height, root length, total chlorophyll, contents of soluble protein (SP) and malondialdehyde, activities of superoxide dismutase, catalase, peroxidase, glutamine synthetase, and alkaline phosphatase) indicated that 0.9-1.2 m was the optimal water depth for planting. Vallisneria natans suffered photoinhibition at the shallow water depth of 0.3-0.6 m and lipid peroxidation damage in water 1.2-1.5 m deep. Microbial analyses indicated that at the water depth of 0.6 m, the accumulated cyanobacteria led to the suppression of microbial organics decomposition and nutrient metabolism in the leaf biofilms. The water quality indicators (chemical oxygen demand, total nitrogen, total phosphorus, and fluorescent dissolved organic matter) also confirmed that 0.9-1.2 m was the optimal planting depth of Vallisneria natans. The results of this study provided theoretical guidance and technical support for the restoration of submerged macrophytes in natural shallow lakes.


Assuntos
Biodegradação Ambiental , Hydrocharitaceae/fisiologia , Biofilmes , Clorofila , Eutrofização , Lagos , Nitrogênio , Fósforo
14.
Chemosphere ; 240: 124903, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31563100

RESUMO

Excessive nitrogen has been a global concern to cause lake eutrophication. The denitrification and anammox processes are considered to be effective biological pathways for nitrogen removal. Submerged macrophytes also play a key role in the nitrogen cycle of lakes. However, the mechanism of submerged macrophytes on regulating biological nitrogen removal pathways has not been well quantified. Therefore, this study investigated the impacts of submerged macrophytes on the community structures and abundance of the nirS-type denitrifiers and anammox bacteria in the rhizospheres. The qPCR results indicated that the abundance of two bacteria in the near-rhizospheres of submerged macrophytes was significantly lower than the root compartments and non-rhizospheres, while the concentrations of organic acids in the near-rhizospheres were higher than those of the root compartments and non-rhizospheres. Redundancy analysis results illustrated that concentrations of NO3--N, NO2--N, citric acid and oxalic acid were the key environmental indicators which had the significant impact on the microbial community. The concentrations of citric acid and oxalic acid were negatively correlated with the nirS-type denitrifiers abundance, and the oxalic acid concentrations were negatively correlated with the anammox bacteria abundance. These results indicated that submerged macrophytes could reduce the abundance of nirS-type denitrifiers and anammox bacteria by releasing organic acids. In addition, the highest diversity of denitrifier community were found in the rhizosphere of the Hydrilla verticillata, while the highest diversity of anammox community were found in the Potamogeton maackianus rhizosphere. These results indicate that the impacts of submerged macrophytes on the biological nitrogen removal pathways were species-dependent.


Assuntos
Biodegradação Ambiental , Desnitrificação/genética , Rizosfera , Microbiologia do Solo , Bactérias/metabolismo , Eutrofização , Hydrocharitaceae/metabolismo , Lagos/química , Nitrogênio/química , Ciclo do Nitrogênio , Compostos Orgânicos/metabolismo , Potamogetonaceae/microbiologia
15.
Water Res ; 171: 115391, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31865125

RESUMO

Excessive addition of nitrogen (N) has threatened aquatic ecosystems for decades. Traditional water quality and biological monitoring assessment tools are widely used for monitoring nutrient loads and ecosystem health, but most of these methods cannot distinguish between different types and sources of pollution. This is a challenge, particularly when dealing with non-point sources of anthropogenic nitrogen inputs into freshwater systems. Recent laboratory studies using stable isotopic ratios (δ15N and C/N) of aquatic macrophytes (duckweed: Spirodela spp.) have shown successful differentiation and mapping between different N-sources and further, showed abilities to act as early warning indicators for environmental N-loading. Therefore, the aim of this study was to field test the potential of stable isotopic values of transplanted Spirodela spp. to map temporal and spatial N-loading variation and determine the main sources of N-loading in two river systems in the Eastern Cape Province of South Africa, using previously grown, isotopically calibrated and transplanted Spirodela plants, collected over a 13-month sampling period. Nitrogen isotopic values (δ15N) of Spirodela plants traced environmental N-loading and identified pollution hotspots and sources through time and space over a wide range of nutrient gradients. δ15N isotopic values of Spirodela spp. provided detailed dynamics on N-loading, therefore supporting its utilisation in the biological monitoring of ecosystem health and the early detection of eutrophication in freshwater systems.


Assuntos
Ecossistema , Rios , Monitoramento Ambiental , Eutrofização , Água Doce , Nitrogênio , Nutrientes , África do Sul
16.
Chemosphere ; 239: 124702, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31520979

RESUMO

Restoration of submerged macrophytes is widely applied to counteract eutrophication in shallow lakes. However, proliferation and accumulation of filamentous algae (possessing free-floating and periphytic life forms) hamper growth of submerged macrophytes. Here, we explored factors triggering the excessive proliferation of filamentous algae during lake restoration using field investigations and laboratory experiments. Results showed that, compared with free-floating Oscillatoria sp. (FO), periphytic Oscillatoria sp. (PO) showed faster growth rate, greater photosynthetic capacities and higher phosphorus (P) affinity. Therefore, PO was physiologically competitively superior to FO under low P concentration and improved light conditions. And proliferation of filamentous algae was mainly manifested in periphytic life form. Besides, field results showed that density of filamentous algae in water column might be related to substrate types. Some macrophyte (Ceratophyllum oryzetorum and Potamogeton crispus) might provide proper substrates for proliferation of filamentous algae. Further physiological experiments found that Oscillatoria showed specific eco-physiological responses to different macrophyte species. Hydrilla verticillata and C. oryzetorum promoted growth and photosynthetic activity of Oscillatoria, while Potamogeton malaianus inhibited growth and P uptake of PO. Myriophyllum spicatum exhibited no impact on growth of Oscillatoria. Our results revealed the intrinsic (physiological differences between free-floating and periphytic life forms of filamentous algae) and extrinsic (different macrophytes) factors affect the proliferation of filamentous algae, which are important for guidance on planting of submerged macrophytes during lake restoration.


Assuntos
Recuperação e Remediação Ambiental/métodos , Eutrofização , Hydrocharitaceae/crescimento & desenvolvimento , Lagos , Potamogetonaceae/crescimento & desenvolvimento , Proliferação de Células , Cianobactérias , Citoesqueleto , Fotossíntese , Água
17.
Chemosphere ; 239: 124780, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31726528

RESUMO

Among several other eutrophication management tools, Phoslock®, a lanthanum modified bentonite (LMB) clay, is now frequently used. Concerns have been raised as to whether exposure to Phoslock®-treated water may lead to lanthanum accumulation/toxicity in both animals and humans. In the present experimental study, rats were administered lanthanum orally as either lanthanum carbonate, lanthanum chloride or Phoslock® at doses of either 0.5 or 17 mg/L during 10 weeks. Controls received vehicle. The gastrointestinal absorption and tissue distribution of lanthanum was investigated. Extremely strict measures were implemented to avoid cross-contamination between different tissues or animals. Results showed no differences in gastrointestinal absorption between the different compounds under study as reflected by the serum lanthanum levels and concentrations found in the brain, bone, heart, spleen, lung, kidney and testes. At sacrifice, significant but equally increased lanthanum concentrations versus vehicle were observed in the liver for the highest dose of each compound which however, remained several orders of magnitude below the liver lanthanum concentration previously measured after long-term therapeutic administration of lanthanum carbonate and for which no hepatotoxicity was noticed in humans. In conclusion, (i) the use of LMB does not pose a toxicity risk (ii) gastrointestinal absorption of lanthanum is minimal and independent on the type of the compound, (iii) with exception of the liver, no significant increase in lanthanum levels is observed in the various organs under study, (iv) based on previous studies, the slightly increased liver lanthanum levels observed in a worst case scenario do not hold any risk of hepatotoxicity.


Assuntos
Bentonita/toxicidade , Lantânio/farmacocinética , Purificação da Água/métodos , Animais , Eutrofização , Lantânio/toxicidade , Fígado/química , Fósforo , Ratos
18.
Sci Total Environ ; 698: 134328, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31783469

RESUMO

In eutrophic lacustrine ecosystems, drifting algal blooms are easily trapped by emergent macrophytes in downwind littoral zones, potentially altering carbon cycling processes; yet, knowledge remains limited about the mechanisms driving these changes. In this study, Microcystis and Phragmites, two dominant photosynthetic organisms in a hypereutrophic (Lake Taihu, China), were collected to simulate their co-decomposition processes. We demonstrate how molecular-level biomarkers could be used to elucidate the degradation dynamics of these two distinct organic forms in mixtures. Microcystis-derived carbon accelerated the decomposition rate of mixed systems (positive co-metabolism effect), rather than retarding it. The decomposition rate of TOC (total organic carbon) directly measured in the mixed treatments was 14% higher than when the two substrates were incubated alone. The use of specific fatty acid biomarkers facilitated more accurate tracking, demonstrating 1.09 times higher decomposition rates for Phragmites detritus in mixed treatments than in single Phragmites treatments. Furthermore, Microcystis showed 0.98 times higher decomposition rates in mixed treatments than in single treatments. The addition of Microcystis detritus to Phragmites detritus might meet microbial stoichiometric requirements, increasing the abundance of decomposing bacteria in Phragmites detritus, and accelerating decomposition rates, resulting in the co-metabolism of Microcystis and Phragmites carbon. Given the increasing occurrence of algal blooms in eutrophic lakes, the processes documented here might enhance greenhouse gas emissions from lakes with continued global climate warming.


Assuntos
Monitoramento Ambiental , Lagos/química , Poluentes da Água/análise , Biomarcadores , China , Ecossistema , Eutrofização , Sedimentos Geológicos , Microcystis
19.
Ecotoxicol Environ Saf ; 188: 109888, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31706242

RESUMO

Eutrophication can induce hypoxia/anoxia and rich organic matter at the sediment-water interface in surface waters. When eutrophic waters are impacted with mercury (Hg) pollution, methylmercury (MeHg) production ability (MPA) of surface sediment would increase and more MeHg might be produced. To tackle this risk, this study firstly collected samples of surface sediment and overlying water from a typical eutrophic lake-Taihu Lake. Then from a sediment-water simulation system, we demonstrated that eutrophic waters were able to methylate Hg spontaneously, and that sediment is the major Hg sink in the system. After the addition of HgCl2 solution (approximately 1 mg L-1 in the slurry), MeHg concentrations in the sediment increased by 11.7 times after 48 h. The subsequent column experiments proved that O2 nanobubbles could significantly decrease the MPA of surface sediment, by up to 48%. Furthermore, we found that O2 nanobubbles could remediate anoxia mainly by increasing dissolved oxygen (from 0 to 2.1 mg L-1), oxidation-reduction potentials (by 37% on average), and sulfate (by 31% on average) in the overlying water. In addition, O2 nanobubbles could also help decrease organic matter concentration, as was revealed by the decline of dissolved organic carbon in the overlying water (by up to 57%) and total organic carbon in surface sediment (by up to 37%). The remediation of anoxia and reduction of organic matter could contribute to the decrease of hgcA gene abundance (by up to 86%), and thus result in the reduction of MPA after the addition of O2 nanobubbles. This study revealed the risk of MeHg production in case Hg pollution occurs in eutrophic waters and proposed a feasible solution for MeHg remediation.


Assuntos
Recuperação e Remediação Ambiental/métodos , Sedimentos Geológicos/química , Compostos de Metilmercúrio/química , Oxigênio/química , Poluentes Químicos da Água/química , Eutrofização , Lagos/química , Mercúrio/análise , Mercúrio/química , Compostos de Metilmercúrio/análise , Compostos Orgânicos/análise , Compostos Orgânicos/química , Oxirredução , Oxigênio/análise , Poluentes Químicos da Água/análise
20.
J Environ Sci (China) ; 86: 175-186, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31787182

RESUMO

A comprehensive understanding of the complex biogeochemical interactions between organic matter and persistent contaminants in the suspended matter is vital for eco-efficient estuary recovery. However, little is known regarding aeration effects in suspended particulate aggregates. Therefore, this study aimed to investigate the effects of aeration on the suspended matter from a Tropical and Eutrophic estuarine environment. Anoxic water with 60 g/L of suspended particulate matter (SPM) was collected from Guanabara Bay, Rio de Janeiro, Brazil, transferred to experimental boxes and aerated for 61 days. SPM aggregates monitoring included abiotic variables measurements and, determination of total organic matter (TOM), biopolymers composition, bacterial activity, trace metals, and polycyclic aromatic hydrocarbons (PAHs) concentrations. The aeration enhanced dissolved oxygen (DO) concentration and the redox potential (Eh). However, from days 0 to 61 the predominant bacterial activities were denitrification and fermentation. Electron transport system activity increased after day 10, and aerobic activity was detected after day 19. In summary, aeration increased aerobic bacterial activity, lipids (LIP) and trace metal concentrations, although diminished protein/carbohydrate ratio and PAH concentration. Trace metals concentration (Ni, Pb, Cu, Cr, Mn, and Fe) were the highest on day 19 when the pH was 5.9. Copper presented toxic values (Cu > 20.0 µg/g). The pH showed a strong negative correlation with Eh (r = -0.94; p < 0.001). Acidic environment (pH ≤ 5.9) in marine ecosystems with high loads of toxic trace metals is unsafe for biota. Therefore, managers must be aware of the environmental and biological risks of introducing the aeration technique into a eutrophic marine environment.


Assuntos
Monitoramento Ambiental , Recuperação e Remediação Ambiental , Poluentes Químicos da Água/análise , Brasil , Estuários , Eutrofização , Metais , Hidrocarbonetos Policíclicos Aromáticos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA