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1.
Sci Total Environ ; 751: 141618, 2021 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-33167190

RESUMO

Some wastewater sources, such as agricultural waste and runoff, and industrial sewage, can degrade water quality. This study summarises the sources and corresponding mechanisms that trigger eutrophication in lakes. Additionally, the trophic status index and water quality index (WQI) which are effective tools for evaluating the degree of eutrophication of lakes, have been discussed. This study also explores the main nutrients (nitrogen and phosphorus) driving transformations in the water body and sediment. Lake Erhai was used as a case study, and it was found to be in a mesotrophic state, with N and P co-limitation before 2006, and only P limitation since 2006. Finally, effective measures to maintain sustainable development in the watershed are proposed, along with a framework for an early warning system adopting the latest technologies (geographic information systems (GIS), remote sensing (RS)) for preventing eutrophication.


Assuntos
Eutrofização , Lagos , China , Monitoramento Ambiental , Nitrogênio/análise , Fósforo/análise , Qualidade da Água
2.
Sci Total Environ ; 751: 141869, 2021 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-32882542

RESUMO

Black bloom occurs frequently in eutrophic waters. We investigated the conditions promoted the formation of black bloom via in-situ measurement in two aquatic microcosms and the effects of black bloom on the bacterial community composition. Although larger changes in dissolved oxygen (DO) were detected in the Hydrilla verticillata-dominated microcosm over the 90-day simulation, black bloom occurred more readily in the phytoplankton-dominated than macrophyte-dominated microcosm under conditions of O2 depletion and temperature above 30 °C. The sediment bacterial community composition shifted after black bloom; the relative abundance of Thiobacillus and Sideroxydans, which oxidize iron (Fe) and sulfur (S), decreased by 47% and 48%, respectively, in the phytoplankton-dominated microcosm and by 18% and 20% in the macrophyte-dominated microcosm. By contrast, Desulfatiglans increased by 13% and 19%, respectively, after black bloom. Furthermore, inter-taxa correlations remarkably changed according to co-occurrence network analysis. Thirty-six different taxa from the phylum to the genus level were identified as biomarkers of sediments collected before and after the black bloom event. Most of these biomarkers are related to Fe/S cycling in aquatic ecosystems.


Assuntos
Sedimentos Geológicos , Ferro , Bactérias , Ecossistema , Eutrofização , Ferro/análise , Lagos , Enxofre
3.
J Environ Sci (China) ; 99: 143-150, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33183691

RESUMO

Phosphorus is a vital nutrient for algal growth, thus, a better understanding of phosphorus availability is essential to mitigate harmful algal blooms in lakes. Wind waves are a ubiquitous characteristic of lake ecosystems. However, its effects on the cycling of organic phosphorus and its usage by phytoplankton remain poorly elucidated in shallow eutrophic lakes. A mesocosm experiment was carried out to investigate the responses of alkaline phosphatase activity fractions to wind waves in large, shallow, eutrophic Lake Taihu. Results showed that wind-driven waves induced the release of alkaline phosphatase and phosphorus from the sediment, and dramatically enhanced phytoplanktonic alkaline phosphatase activity. However, compared to the calm conditions, bacterial and dissolved alkaline phosphatase activity decreased in wind-wave conditions. Consistently, the gene copies of Microcystis phoX increased but bacterial phoX decreased under wind-wave conditions. The ecological effects of these waves on phosphorus and phytoplankton likely accelerated the biogeochemical cycling of phosphorus and promoted phytoplankton production in Lake Taihu. This study provides an improved current understanding of phosphorus availability and the phosphorus strategies of plankton in shallow, eutrophic lakes.


Assuntos
Lagos , Fósforo , Fosfatase Alcalina , China , Ecossistema , Monitoramento Ambiental , Eutrofização , Fósforo/análise , Vento
4.
J Environ Sci (China) ; 99: 187-195, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33183696

RESUMO

Periodically hydrologic alterations driven by seasonal change and water storage capacity management strongly modify physicochemical properties and chlorophyll-a (Chl-a) and their interactions in dam-induced lakes. However, the extent and magnitude of these changes still remain unclear. This study aimed to determine the effects of periodically hydrologic alterations on physicochemical variables and Chl-a in the dam-induced urban Hanfeng Lake, upstream of Three Gorges Reservoir. Shifts in Chl-a and 13 physicochemical variables were recorded monthly in the lake from January 2013 to December 2014. Chl-a was neither seasonal nor inter-annual differences while a few physical variables such as flow velocity (V) exhibited significantly seasonal variabilities, and chemical variables like total nitrogen (TN), nitrate-nitrogen (NO3-N), total phosphorus (TP), dissolved silica (DSi) were markedly inter-annual differences. Higher TN:TP (40:1) and lower NO3-N:DSi (0.8:1) relative to balanced stoichiometric ratios suggested changes in composition of phytoplankton communities and potentially increased proportion of diatom in Hanfeng Lake. Chl-a was predicable by combination of dissolved oxygen (DO), TN and DSi in dry season, and by V alone in wet season. During the whole study period, Chl-a was solely negatively correlated with TN:TP, indicating decline in N concentration and increase in P could therefore increase Chl-a. Our results highlight pronounced decoupling of linkages between Chl-a and physicochemical variables affected by periodically hydrologic alterations in dam-induced aquatic systems.


Assuntos
Eutrofização , Lagos , China , Clorofila/análise , Clorofila A , Monitoramento Ambiental , Nitrogênio/análise , Fósforo/análise
5.
Sci Total Environ ; 752: 141262, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-32889253

RESUMO

This study evaluates spatiotemporal variability in the behavior of septic system derived nutrients in a sandy nearshore aquifer and their discharge to a large lake. A groundwater nutrient-rich plume was monitored over a two-year period with the septic system origin of the plume confirmed using artificial sweeteners. High temporal variability in NO3-N attenuation in the nearshore aquifer prior to discharge to the lake (42-96%) reveals the complex behavior of NO3-N and potential importance of changing hydrological and geochemical conditions in controlling NO3-N discharge to the lake. While PO4-P was retarded in the nearshore aquifer, the PO4-P plume extended over 90 m downgradient of the septic system. It was estimated that the PO4-P plume may reach the lake within 10 years and represents a legacy issue whereby PO4-P loads to the lake may increase over time. To provide broader assessment of the contribution of septic systems to P and N loads to a large lake, a regional scale geospatial model was developed that considers the locations of individual septic systems along the Canadian Lake Erie shoreline. The estimated P and N loads indicate that septic systems along the shoreline are only a minor contributor to the annual P and N loads to Lake Erie. However, it is possible that nutrients from septic systems may contribute to localized algal blooms in shoreline areas with high septic system density. In addition, disproportionate P and N loads in discharging groundwater may change the N:P ratio in nearshore waters and promote growth of harmful cyanobacteria. The study provides new insights into factors controlling the function of the reaction zone near the groundwater-lake interface including its impact on groundwater-derived nutrient inputs to large lakes. Further, the study findings are needed to inform septic system and nutrient management programs aimed at reducing lake eutrophication.


Assuntos
Água Subterrânea , Lagos , Canadá , Monitoramento Ambiental , Eutrofização , Nitrogênio/análise , Nutrientes , Fósforo/análise
6.
Sci Total Environ ; 753: 141821, 2021 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-32891993

RESUMO

Intense human disturbance has made algal bloom a prominent environmental problem in gate-controlled urban water bodies. Urban water bodies present the characteristics of natural rivers and lakes simultaneously, whose algal blooms may manifest multi-factor interactions. Hence, effective regulation strategies require a multi-factor analysis to understand local blooming mechanisms. This study designed a holistic multi-factor analysis framework by integrating five data mining techniques. First, the Kolmogorov-Smirnov test was conducted to screen out the possible explanatory variables. Then, correlation analyses and principal component analyses were performed to identify variable collinearity and mutual causality, respectively. After collinearity and mutual causality were treated prudently by using orthogonalization and instrumental variables, multilinear regression can be properly conducted to quantify factor contributions to algae growth. Lastly, a decision tree was used innovatively to depict the limiting threshold curves of each driving factor that restricts algae growth under different circumstances. The driving factors, their contributions, and the limiting threshold curves compose the complete blooming mechanisms, thus providing a clear direction for the targeted regulation task. A typical case study was performed in Suzhou, a Chinese city with an intricate gate-controlled river network. Results confirmed that climatic factors (i.e., water temperature and solar radiation), hydrodynamic factors (i.e., flow velocity), nutrients (i.e., phosphorus and nitrogen), and external loadings contributed 49.3%, 21.7%, 21.3%, and 7.7%, respectively, to algae growth. These results indicate that a joint regulation strategy is urgently required. Future studies can focus on coupling the revealed mechanisms with an ecological model to provide a comprehensive toolkit for the optimization of an adaptive joint regulation plan under the background of global warming.


Assuntos
Monitoramento Ambiental , Eutrofização , China , Cidades , Mineração de Dados , Análise Fatorial , Humanos , Lagos , Fósforo/análise
7.
Sci Total Environ ; 753: 141985, 2021 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-32892000

RESUMO

Global freshwater lakes are changing due to human activities and climate change. Unfortunately, sufficient long-term monitoring is lacking for most lakes. However, lake sedimentary archives can extend the instrumental record and reveal historical environmental trends. In particular, sedimentary DNA analysis of lacustrine sediment cores can aid the reconstruction of past trends in eukaryotic algal and cyanobacterial communities, as was conducted in this study for Lake Chaohu in China. The results presented here indicate that the construction of the Chaohu Dam in 1963 is associated with decreased richness of eukaryotic algal and cyanobacterial communities. Several groups, including the eukaryotic algal taxa, Chlorophyceae, and cyanobacterial groups like Dolichospermum, Microcystis, Planktothricoides, Cyanobium, Pseudanabaena, and Synechococcus, increased in abundance following inferred historical nutrient enrichment. Nutrient concentrations and hydrologic conditions were further implicated as the dominant controls on communities based on Random Forest and generalized additive modeling statistical analyses. In particular, significant increases in lake hydraulic residence times after the construction of the Chaohu Dam were significantly associated with altered biological community structures. Further, phosphorus enrichment was positively associated with increased richness and diversity of these communities following the 1980s. In addition, effects from increased atmospheric temperatures on eukaryotic algal and cyanobacterial communities were apparent. Here, high-throughput sequencing analysis of sedimentary DNA allowed the inference of long-term biodiversity dynamics of Lake Chaohu. These results underscore the important impacts of anthropogenic activities and climate change on aquatic ecosystems at the decadal scale.


Assuntos
Mudança Climática , Lagos , China , DNA , Ecossistema , Eucariotos , Eutrofização , Atividades Humanas , Humanos
8.
Nat Commun ; 11(1): 5154, 2020 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-33056993

RESUMO

Blue carbon (C) ecosystems are among the most effective C sinks of the biosphere, but methane (CH4) emissions can offset their climate cooling effect. Drivers of CH4 emissions from blue C ecosystems and effects of global change are poorly understood. Here we test for the effects of sea level rise (SLR) and its interactions with elevated atmospheric CO2, eutrophication, and plant community composition on CH4 emissions from an estuarine tidal wetland. Changes in CH4 emissions with SLR are primarily mediated by shifts in plant community composition and associated plant traits that determine both the direction and magnitude of SLR effects on CH4 emissions. We furthermore show strong stimulation of CH4 emissions by elevated atmospheric CO2, whereas effects of eutrophication are not significant. Overall, our findings demonstrate a high sensitivity of CH4 emissions to global change with important implications for modeling greenhouse-gas dynamics of blue C ecosystems.


Assuntos
Ciclo do Carbono , Dióxido de Carbono/metabolismo , Metano/metabolismo , Plantas/metabolismo , Elevação do Nível do Mar , Atmosfera/química , Eutrofização , Efeito Estufa , Áreas Alagadas
9.
Nat Commun ; 11(1): 5375, 2020 10 23.
Artigo em Inglês | MEDLINE | ID: mdl-33097736

RESUMO

Eutrophication is a widespread environmental change that usually reduces the stabilizing effect of plant diversity on productivity in local communities. Whether this effect is scale dependent remains to be elucidated. Here, we determine the relationship between plant diversity and temporal stability of productivity for 243 plant communities from 42 grasslands across the globe and quantify the effect of chronic fertilization on these relationships. Unfertilized local communities with more plant species exhibit greater asynchronous dynamics among species in response to natural environmental fluctuations, resulting in greater local stability (alpha stability). Moreover, neighborhood communities that have greater spatial variation in plant species composition within sites (higher beta diversity) have greater spatial asynchrony of productivity among communities, resulting in greater stability at the larger scale (gamma stability). Importantly, fertilization consistently weakens the contribution of plant diversity to both of these stabilizing mechanisms, thus diminishing the positive effect of biodiversity on stability at differing spatial scales. Our findings suggest that preserving grassland functional stability requires conservation of plant diversity within and among ecological communities.


Assuntos
Biota , Ecossistema , Eutrofização , Pradaria , Biodiversidade , Biomassa , Fertilização , Modelos Biológicos , Plantas
10.
Huan Jing Ke Xue ; 41(11): 4914-4923, 2020 Nov 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124235

RESUMO

Using daily survey and monitoring "black water event" (BWE) results in the sensitive area of Lake Taihu from April to October, 2009-2018, as well as the BWE analyzed data for relative meteorological, hydrological, chemical, and algal bloom conditions, the characteristics and yearly differences of BWEs were summarized. A BWE control strategy was suggested. There were 75 BWE occurrences detected in the past 10 years. The average area of a BWE was 1.35 km2, with a maximum area of 9.20 km2. The BWEs lasted for an average of three days, while the longest lasted 16 days. The BWEs significantly increased organic matter, total nitrogen, total phosphorus, ammonia, and sulfate, among others. All the BWEs occurred at water temperatures over 20℃. All the BWE occurrences started between May and September. The yearly BWE intensity (BWEI) varied significantly among years, with the strongest intensity in 2017 and the second strongest in 2018. The BWEI was significantly positively related to yearly algal bloom intensity (ABI) and average daily water temperature from May to September, while there was no significant relationship with major nutrient indicators. This suggests that climatic variation among years will significantly influence the risk of a BWE in Lake Taihu. The occurrence of a BWE was significantly influenced by a polluted river mouth. Almost all the BWEs occurred near river mouths, except for five macrophyte-related BWEs. This suggests that sediment pollution and its resuspension could be strongly related to the occurrence of a BWE. When considering degradation factors, a BWE could be classified as an algal-related BWE and a macrophyte-related BWE. The algal-related BWE could be further classified into three types:river-related BWE, bloom transport BWE, and local origin BWE. This research suggests that algal bloom control will be the fundamental countermeasure to decrease the risk of a BWE. Bloom abatement treatments, including mechanical bloom cleaning, water current adjustment engineering, coast-away bloom cleaning engineering, mechanical aeration treatment, and sediment dredging near river mouths would be effective methods to abate the risk of a BWE.


Assuntos
Lagos , Água , China , Monitoramento Ambiental , Eutrofização , Fósforo/análise
11.
Huan Jing Ke Xue ; 41(9): 4030-4041, 2020 Sep 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124283

RESUMO

In spring and summer of 2018, 26 lakes in the middle and lower reaches of the Yangtze River were studied to determine the temporal and spatial characteristics of nitrogen and phosphorus ratios (TN/TP) and their influencing factors. The differences in nitrogen and phosphorus ratios in different types of lakes (including water-psaaing lakes, deep reservoirs and eutrophic lakes) and in different seasons were analyzed in terms of the sources of the lakes, lake depth, suspended particulate matter concentrations, and phytoplankton levels. The average TN/TP was 21.52±14.28 in spring and 21.73±23.78 in summer. The TN/TP varied significantly in different types of lakes. The TN/TP ratios in water-passing lakes, deep reservoirs and eutrophic lakes were 20.41±9.25, 40.97±33.37, and 14.38±7.40 during spring, and were 22.62±6.48, 96.38±45.91, and 10.91±4.44 during summer, respectively. The TN/TP of the water-passing lakes and deep reservoirs increased significantly in summer, while that of the eutrophic lakes decreased significantly, which indicates that TN/TP changes and lake nutritional status are closely related. The source of nutrients in lakes and reservoirs affects the TN/TP. The TN/TP of lakes and reservoirs had a significant correlation with the lake depth in both spring and summer, indicating that lake depth is a key factor affecting the ratio of nitrogen and phosphorus. In addition, in eutrophic lakes with higher absolute nutrient concentrations, TN/TP has less effect on phytoplankton, while in deep-water lakes with lower absolute nutrient concentrations, TN/TP can determine the growth of phytoplankton limited by phosphorus. Therefore, the governance strategy of lakes in the middle and lower reaches of the Yangtze River should prioritize phosphorus control. Local digging, controlling non-point source pollution, sediment dredging, and changing fishery production methods can be applied to improve the ecological quality of the eutrophic lakes.


Assuntos
Lagos , Fósforo , China , Monitoramento Ambiental , Eutrofização , Nitrogênio/análise , Fósforo/análise , Rios
12.
Huan Jing Ke Xue ; 41(9): 4042-4052, 2020 Sep 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124284

RESUMO

Eutrophication of shallow lakes in the middle and lower reaches of the Yangtze River has become an increasingly serious problem. In this study, we investigated the temporal and spatial variations in nutrient loads (nitrogen, N and phosphorus, P) in the Changdang Lake Catchment located to the northwest of Lake Taihu through field sampling and laboratory analysis in 2016-2017. The results show the severity of the N and P pollution in the Changdang Lake catchment. The mean river water concentrations of TN, NO3--N, NH4+-N, TP, Chla, and permanganate index are (3.70±0.76) mg ·L-1, (1.81±0.42) mg ·L-1, (1.03±0.61) mg ·L-1, (0.38±0.31) mg ·L-1, (25.74±37.00) µg ·L-1, and (6.35±0.81) mg ·L-1, respectively. N pollution in the river is more severe in winter and spring than in summer and autumn whereas P pollution in the river is worse in autumn and winter than in spring and summer. Spatially, the magnitude of river N and P pollution follows the order of northern > northwestern > southern > eastern part of the study area. The rivers are in a state of moderate to severe eutrophication. The mean lake water concentrations of TN, NO3--N, NH4+-N, TP, Chla, and permanganate index are (2.25±0.94) mg ·L-1, (0.98±0.47) mg ·L-1, (0.19±0.14) mg ·L-1, (0.11±0.03) mg ·L-1, (18.71±8.76) µg ·L-1, and (4.59±1.09) mg ·L-1, respectively. The water quality in Changdang Lake is categorized as worse than class Ⅲ for TN and TP concentrations, which show decreasing trends from the west to the east to the south of the lake. The lake is in a status of slight to moderate eutrophication. The lake water quality is affected by the combination of sewage discharge and non-point source pollutant losses. The inflow rivers including the Danjinlicao River, Tongji River, and Xuebu River are the dominant pollution sources for Changdang Lake. The Danjinlicao River transports 10-12 times the total N and P loads transported by Tongji and Xuebu rivers. Changes in land use and atmospheric deposition are the driving factors of the deterioration of water quality and eutrophication in the catchment.


Assuntos
Rios , Poluentes Químicos da Água , China , Monitoramento Ambiental , Eutrofização , Lagos , Nitrogênio/análise , Nutrientes , Fósforo/análise , Poluentes Químicos da Água/análise
13.
Huan Jing Ke Xue ; 41(9): 4053-4061, 2020 Sep 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124285

RESUMO

The decomposition of submerged macrophytes is generally associated with dramatic changes in the water environment, such as the large release of nutrients (e.g., nitrogen and phosphorus) and organic carbon to the surrounding waters, which may result in significant changes in phytoplankton community structure. In this study, Potamogeton crispus, physicochemical variables, and phytoplankton samples were collected in 14 shallow lakes in the middle and lower Jianghuai Plain in spring (growing period of P. crispus) and summer (decomposition phase of P. crispus) of 2018. The effects of the decline of P. crispus on water quality and phytoplankton community structure were quantified. The results showed that water transparency increased significantly in spring because the growth of P. crispus inhibits sediment resuspension and macrophytes can transport the nutrients from the water column to the sediment. The values of dissolved oxygen and pH also increased significantly due the photosynthesis by macrophytes. In contrast, the decomposition of P. crispus during summer months caused a significant increase in water turbidity and organic matter. There were considerable differences in phytoplankton biomass and cyanobacterial biomass in the sites with or without P. crispus, and the corresponding ratios of cyanobacterial biomass to the total algal biomass were 18.96% and 34.05%, respectively. Higher values of cyanobacterial biomass were observed with the decomposition of P. crispus than its counterpart in summer because ① the decomposition of macrophytes provided sufficient organic matter and nutrient (nitrogen and phosphorus) resources for cyanobacterial growth; ② P. crispus decline in summer significantly increased water turbidity, which makes cyanobacteria occupy a better ecological niche and more efficiently utilize nitrogen and phosphorus.


Assuntos
Potamogetonaceae , Biomassa , Eutrofização , Lagos , Nitrogênio , Fósforo , Fitoplâncton
14.
An Acad Bras Cienc ; 92(3): e20200758, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33111824

RESUMO

This study compares two mangroves with different land uses in the Jaguaribe River estuary, harboring large shrimp farms, and in the more pristine Pacotí River estuary. Normalized Difference Vegetation Index (NDVI) was used to compare the overall health of the forests. Measures of suspended matter (TSS), total (TP), particulate (PartP) and soluble reactive phosphorus (SRP) in the inflow and outflow waters of tidal channels draining the mangroves were performed during tidal cycles. NDVI varied from 0.65 in the Jaguaribe estuary to 0.85 in the Pacotí, suggesting the impact of shrimp farm effluents on mangrove canopy cover. The shrimp farm influenced site showed 10 times larger absolute ∑P (TP + PartP + SRP) = 1.2-5.2 kg.hr-1) flux than the pristine site (∑P = 0.22 kg.hr-1). Tidal balances showed smaller retentions of the total influx: 28-54%; 44-45%; 38-65% and 8-53% for TSS; TP; SRP; and PartP respectively, in the shrimp farm influenced site to over 93% of the total tidal input of TSS and all P fractions in the pristine mangrove. This suggests that mangrove phosphorus accumulation is decreased in the forest with lower NDVI and limits mangrove's potential as a natural barrier to the nutrient transport to adjacent estuarine and coastal waters.


Assuntos
Eutrofização , Fósforo , Animais , Aquicultura , Brasil , Monitoramento Ambiental , Fósforo/análise
15.
Sci Total Environ ; 748: 142309, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-33113670

RESUMO

Extracellular polymeric substances (EPSs), which composed of different organic components, play an important role in the formation of mucilaginous cyanobacterial bloom. However, how the phylogeny of microbial community coupling with the degradation of EPS matrixes remains unclear. A better understanding of the dynamic process not only give insight into the carbon cycling in the phycosphere, but also provide a new approach for controlling the cyanobacteria bloom. In this study, fractionated EPSs were prepared as a carbon source to enrich different particle size microorganisms. Changes of organic components in EPSs and microbial communities in the degradation process were investigated using Fluorescence excitation and emission matrix (EEM) and Illumina sequencing. The results showed that it is the change of organic components in the degradation process that causes the microbial community to follow a certain succession law. Size-fractionated microorganisms exhibited different hydrolytic activities when interacting with macromolecules, but they did not present different phylogenetic compositions. The changes of humic-like C1 and tryptophan-like C3 in EPSs were significantly correlated to the variations of microbial community composition and diversity. Tightly-bound EPSs (TB-EPSs) contained more low molecular single carbon compounds and were more easily utilized by more diverse microorganisms. Betaproteobacteria, Firmicute, Alphaproteobacteria, Sphingobacteria and Actinobacter were significantly correlated with the changes of organic maters through the humification process. Meanwhile, loosely-bound EPSs (LB-EPSs), which composed of more macromolecules, were more affiliated to a functional organized microbial community. When Gammaproteobacteria and Betaproteobacteria were involved in LB-EPS degradation as indicators, the polysaccharide structures changed dramatically. And the content of some small molecules was briefly increased during the degradation process. Therefore, in order to prevent algal bloom from reducing cellular aggregation by decreasing viscous EPSs, specialized microbial communities should be considered in the phycosphere.


Assuntos
Cianobactérias , Matriz Extracelular de Substâncias Poliméricas , Eutrofização , Filogenia , Polissacarídeos
16.
J Environ Qual ; 49(5): 1203-1224, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33016450

RESUMO

Phosphorus (P) losses from nonpoint sources into surface water resources through surface runoff and tile drainage play a significant role in eutrophication. Accordingly, the number of studies involving the modeling of agricultural P losses, the uncertainties of such models, and the best management practices (BMPs) supported by the modeling of hypothetical P loss reduction scenarios has increased significantly around the world. Many improvements have been made to these models: separate manure P pools, variable source areas allowing the determination of critical source areas of P loss, analyses of modeling uncertainties, and understanding of legacy P. However, several elements are still missing or have yet to be sufficiently addressed: the incorporation of preferential flow into models, the modification of P sorption-desorption processes considering recent research data (e.g., pedotransfer functions for labile, active, or stable P, along with P sorption coefficients), BMP parameterization, and scale-up issues, as well as stakeholder-scientist and experimentalist-modeler interactions. The accuracy of P loss modeling can be improved by (a) incorporating dynamic P sorption-desorption processes and new P subroutines for direct P loss from manure, fertilizer, and dung, (b) modeling preferential flow, connectivity between field and adjacent water bodies, and P in-stream processes, (c) including an assessment of model uncertainty, (d) integrating field and watershed models for BMP calibration and scaling field results up to larger areas, and (e) building a holistic interaction between stakeholders, experimentalists, and modelers.


Assuntos
Agricultura , Fósforo , Eutrofização , Fertilizantes , Esterco
17.
Bull Environ Contam Toxicol ; 105(5): 742-749, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33000334

RESUMO

Inland lakes are important ecosystems for the carbon cycle at both regional and global scales. However, a knowledge gap still exists about the correlations between the partial pressure of CO2 (pCO2) and nutrient dynamics in lakes. In this study, we analysed the long-term dynamics of nutrient and pCO2 in Taihu Lake. Strong spatial heterogeneity was observed with highest nutrient concentrations occurring in the River mouth and significant lower concentrations (p < 0.01) occurring in East Taihu and Other zone. For pCO2, the average values were 1136.81 ± 1240.16 µatm, 433.07 ± 305.45 µatm, and 487.05 ± 414.02 µatm in Rive mouth, East Taihu, and Other zone, respectively. Statistical analysis revealed that pCO2 was significantly and positively related to nutrient (TN: total nitrogen and NH4+: ammonium) concentrations (p < 0.01), but negatively related to Chla (Chlorophyll a) concentrations in River mouth and Other zone (p < 0.01). The parallelism of nutrient concentrations and pCO2 in Taihu Lake highlights the dual effects of external pollution inputs from the surrounding catchment. In addition, progressive mitigation was found for not only nutrients but also pCO2, which was attributed to the previous effort in the environmental protections in Taihu Lake basin. Our results also suggest the importance of long-term monitoring for the future assessment of anthropogenic impacts on nutrient and CO2 dynamics in freshwater lakes.


Assuntos
Dióxido de Carbono/análise , Monitoramento Ambiental/métodos , Lagos/química , Nitrogênio/análise , Fósforo/análise , Poluentes Químicos da Água/análise , China , Clorofila A/análise , Ecossistema , Eutrofização , Rios/química
18.
Mar Environ Res ; 162: 105177, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33080558

RESUMO

Nitric oxide (NO) has been identified as a key physiological modulator and signaling molecule in animals and plants. However, due to its high reactivity, our knowledge of its production and consumption pathways in the ocean remain limited. Laboratory experiments showed that Ulva prolifera can produce NO, producing as much as 0.44 ± 0.04 nmol h-1 g-1. During the growth period, U. prolifera released NO, but during the decay period NO was absorbed by U. prolifera and bacteria. Furthermore, field investigations examined NO concentrations in the coastal waters of the Yellow Sea off Qingdao, where the U. prolifera green tide occurred in summer 2018. The average concentrations of NO in the surface seawater were 70.2 ± 38.2 pmol L-1 and 18.9 ± 10.3 pmol L-1 in the late- and after-bloom periods, respectively. NO release by U. prolifera was the primary contributor to the high NO concentrations during the late-bloom period. The study area was a net source of NO to the atmosphere during the study period, with average NO sea-air fluxes from the Qingdao coastal waters being 1.5 × 10-12 mol m-2 s-1 and 0.4 × 10-12 mol m-2 s-1 in the late- and after-bloom periods, respectively. This study concluded that the coastal waters of the Yellow Sea off Qingdao contributed more NO to the atmosphere during the bloom of U. prolifera than afterward.


Assuntos
Ulva , China , Surtos de Doenças , Eutrofização , Óxido Nítrico , Água do Mar
19.
Mar Environ Res ; 160: 104986, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32907724

RESUMO

Although eutrophication is considered a major driver for global seagrass loss with aquaculture effluents being a main factor, little is known about the effect on seagrass meadows in eastern Asia and their resilience to long-term nutrient impact. Seagrass meadows impacted by land-based aquaculture since the 1990s, were visited in 2008/2009 and revisited after another 9 years of effluent exposure. During that period seagrass aboveground biomass declined by 87%. Species diversity decreased with increasing effluent exposure. A δ15N of 9.0‰ of seagrass leaves and additional biogeochemical and biological indicators identify pond effluents as the driver of the observed eutrophication. When continuously exposed to dissolved inorganic nitrogen (DIN) concentrations exceeding a calculated threshold of 8 µM DIN seagrass meadows will disappear. Chronic nutrient pollution from aquaculture effluents can lead to a reduction of biodiversity and ultimately to a complete loss of seagrasses along the aquaculture-dominated coasts in E and SE Asia.


Assuntos
Aquicultura , Eutrofização , Nitrogênio , Biodiversidade , Biomassa
20.
Mar Environ Res ; 161: 105128, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32916642

RESUMO

Coastal lagoons are often characterized by eutrophic conditions which are known to impair the structure and functioning of both pelagic and benthic compartments. However, the manner in which eutrophication triggers a series of cascade effects in the whole food web in coastal lagoons has received little attention. Using stable isotope (SI) analyses, we investigated the food web structure in the hypertrophic lagoon of Yundang (Xiamen, China) in two periods of the year characterized by the recurrent alternation of Ulva lactuca and phytoplankton blooms in the cool (March) and warm (September) seasons, respectively. Large temporal fluctuations in the dominance of primary producers (i.e. macroalgae vs. phytoplankton) and, thus, in the available food items, were reflected in major changes in the diet and SI signals of several primary consumers, such as the amphipod Grandidierella japonica, the polychaetes Neanthes japonica and Capitella capitata, and omnivorous fishes (i.e. Mugil cephalus, Oreochromis niloticus, and Sardinella zunasi), while these changes were limited in top carnivorous fishes, such as Lateolabrax japonicus. Furthermore, reduced macrozoobenthic abundance available for omnivores in September was found to force omnivores to switch their feeding habits to those of herbivores. The present study provides evidence that the periodical alternation of macroalgal and phytoplankton blooms throughout the year strongly affect the relations among different trophic levels leading to a cascading effect across the whole food web and to major changes in the lagoon's food web structure. Importantly, our study shows that the lagoon's food web structure under persistent eutrophic conditions can still cope with seasonal changes in primary energy source type from macroalgae to microalgae due to the ability of omnivorous fishes to conduit different food sources up to the highest trophic levels. Thus, this study suggests that in such a highly variable eutrophic system, omnivores play a central role in the lagoon's functioning, and help to sustain the biological resources and the ecosystem services provided by the lagoon.


Assuntos
Ecossistema , Cadeia Alimentar , Animais , China , Eutrofização , Fitoplâncton
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