Eutrophication In China Research Articles

Eutrophication causes microbial community homogenization via modulating generalist species

Eutrophication substantially influences the community structure of aquatic organisms and has become a major threat to biodiversity. However, whether eutrophication is linked to homogenization of microbial communities and the possible underlying mechanisms are poorly understood. Here, we studied bacterial and fungal communities from water and sediments of 40 shallow lakes in the Yangtze-Huaihe River basin, a representative area characterized by intensifying eutrophication in China, and further examined the beta diversity patterns and underlying mechanisms under eutrophication conditions. Our results indicate that eutrophication generally caused biotic homogenization of bacterial and fungal communities in both habitats showing decreased community variations for the sites with a higher trophic state index (TSI). In the two habitats, community dissimilarities were positively correlated with TSI changes for both taxonomic groups, while the local contribution to beta diversity (LCBD) remarkably declined with increasing TSI for the fungal community. These phenomena were consistent with the pivotal importance of the TSI in statistically accounting for beta diversity of bacterial and fungal communities in both habitats. In addition, we found that physicochemical factors such as water temperature and pH were also important for bacterial and fungal communities in water, while heavy metal elements were important for the communities in sediments. Interestingly, generalist species, rather than specialist species, were revealed to more dominantly affect the variations in beta diversity along the trophic gradient, which were quantified by Bray-Curtis dissimilarity and LCBD. Collectively, our findings reveal the importance of generalist species in contributing to the change of beta diversity of microbial communities along trophic gradients, which have profound implications for a comprehensive understanding of the effects of eutrophication on microbial community.

Employing extreme value theory to establish nutrient criteria in bay waters: A case study of Xiangshan Bay

The Yangtze River estuary and its surrounding seas have had the highest degree of eutrophication in China. Xiangshan Bay, located at the southern bank of the Yangtze River, is not immune from eutrophication, leading to the water quality below the control requirements for marine functional zoning. Clarifying the nutrient criteria is essential to alleviate eutrophication in Xiangshan Bay. We used a generalized Pareto distribution-based peaks over threshold model to analyze 2006–2018 survey data. Through calculation, inorganic nitrogen and reactive phosphate criteria in Xiangshan Bay at the five percentile are 0.443 mg/L and 0.025 mg/L, respectively. Additionally, we also obtained the corresponding confidence intervals. Rationality and sensitivity analyses of the calculation results proved the methods used in this study to be rational and reliable, providing a basis for subsequent monitoring and assessment of nutrient salts in bays.

Coastal eutrophication in China: Trend, sources, and ecological effects

Eutrophication in coastal waters caused by excess nutrient inputs has occurred widely on a global scale. Due to the rapid economic development over the last four decades, most of the Chinese coastal waters have experienced a eutrophic process. Major observed trends of coastal eutrophication include two periods, a slow development from the 1970s to 1990s and a fast development after 2000, with major contributions of increased nitrogen (N) and phosphorus (P) from river inputs, atmospheric deposition, and submarine groundwater discharge (SGD). Nutrient composition and stoichiometry have been significantly changed, including increased ammonium, bioavailable organic N and P, and asymmetric ratios between N, P and silicate (Si). Most of these changes were related to the rapid increases in population density, fertilizer application, sewage discharge, aquaculture and fossil fuel combustion, and have resulted in distinctly increased harmful algal blooms. Coastal eutrophication combined with the effects of climate change is projected to continually grow in coming decades. Targeted research is therefore needed on nitrogen reduction and control, potential adaptation strategies and the consequences for ecosystems and economic sustainability.

Implications of phosphorus partitioning at the suspended particle-water interface for lake eutrophication in China’s largest freshwater lake, Poyang Lake

Nutrient partition, especially for phosphorus (P), has been prominently changed that was caused by variation of river-lake relationship during the post-Three Gorges Reservoir and catchment alternations. Changes in proportion of total particulate phosphorus (TPP) and total dissolved phosphorus (TDP) might accelerate lake eutrophication, but limited attention has been paid to P partition over suspended particle (SP) levels. Data analysis showed that SP concentration presented a positive effect on TPP in wet season and soluble reactive phosphorus (SRP) in dry season, indicating seasonal physical and chemical variations. Based on this phenomenon, we proposed a hypothesis that the SP levels would affect TDP and TPP proportions by partition in aqueous-solid. It was found that using the parabola models to fit the sorption relationships of SRP and TDP (R2 > 0.6, p < 0.01), the maximum sorption capacity (Qmax) was 64.54 mg/kg and 60.52 mg/kg at 400 mg/L of SP level, respectively. In addition, the partition coefficients (KP) of TDP and SRP were logarithmically increased with SP levels, indicating that higher SP levels (>400 mg/L) would hinder the sorption process. Furthermore, enhancing turbulence lead to less sorption of SRP and TDP at high SP levels (>800 mg/L). The sorption of SRP and TDP related to the presence of Fe/Al oxy-hydroxides were enriched in the Fe/Al–P fraction (47% of TP). The findings of this study indicated that the low SP levels would increase P bioavailability for alga and is not conducive for lake eutrophication management.

Global Change Can Make Coastal Eutrophication Control in China More Difficult

AbstractFast socio‐economic development in agriculture and urbanization resulted in increasing nutrient export by rivers, causing coastal eutrophication in China. In addition, climate change may affect hydrology, and as a result, nutrient flows from land to sea. This study aims at a better understanding of how future socio‐economic and climatic changes may affect coastal eutrophication in China. We modeled river export of total dissolved nitrogen (TDN) and phosphorus (TDP) in 2050 for six scenarios combining socio‐economic pathways (SSPs) and Representative Concentration Pathways (RCPs). We used the newly developed MARINA 2.0 (Model to Assess River Inputs of Nutrients to seAs) model. We found that global change can make coastal eutrophication control in China more difficult. In 2050 coastal waters may be considerably more polluted or considerably cleaner than today depending on the SSP‐RCP scenarios. By 2050, river export of TDN and TDP is 52% and 56% higher than in 2012, respectively, in SSP3‐RCP8.5 (assuming large challenges for sustainable socio‐economic development, and severe climate change). In contrast, river export of nutrients could be 56% (TDN) and 85% (TDP) lower in 2050 than in 2012 in SSP1‐RCP2.6 (assuming sustainable socio‐economic development, and low climate change). Climate change alone may increase river export of nutrients considerably through hydrology: We calculate 24% higher river export of TDN and 16% higher TDP for the SSP2 scenario assuming severe climate change compared to the same scenario with low climate change (SSP2‐RCP8.5 vs. SSP2‐RCP2.6). Policies and relevant technologies combining improved nutrient management and climate mitigation may help to improve water quality in rivers and coastal waters of China.

Comparison of Community and Function of Dissimilatory Nitrate Reduction to Ammonium (DNRA) Bacteria in Chinese Shallow Lakes with Different Eutrophication Degrees

Dissimilatory nitrate reduction to ammonium (DNRA) plays an important role in controlling nitrogen (N) loading in lake ecosystems. However, studies on the linkage between DNRA bacterial community structure and lake eutrophication remain unclear. We examined the community and abundance of DNRA bacteria at six basins of four shallow lakes with different degrees of eutrophication in China. Measurements of the different forms of N and phosphorus (P) in the water column and interstitial water as well as total organic carbon (TOC) and sulfide in the sediments in summer (July 2016) were performed. The nutritional status of Lake Chaohu was more serious than that of the lakes in Wuhan, including Lake Qingling, Lake Houguan, and Lake Zhiyin by comparing geochemical and physical parameters. We found a higher abundance of the nrfA gene, which is a function gene of DNRA bacteria in sediments with higher contents of TOC and sulfide. Moreover, nitrate was a significant factor influencing the DNRA bacterial community structure. A significant difference of the DNRA bacterial community structure between Lake Chaohu and the lakes in Wuhan was discovered. Furthermore, DNRA bacterial abundance and community positively correlated with NH4+ and Chl a concentrations in Lake Chaohu, in which a percent abundance of dominant populations varied along eutrophication gradients. Overall, the abundance and community structure of the DNRA bacteria might be important regulators of eutrophication and cyanobacteria bloom in Lake Chaohu.

Management Strategies to Optimize Soil Phosphorus Utilization and Alleviate Environmental Risk in China.

In the last decade, crop production in China has dramatically improved due to greater phosphorus (P) input. As P fertilizer application rates increased from 88 to 123 kg PO ha yr during 2004 to 2014, total P use efficiency (total P output in crops as a percentage of total P input) dropped from 68 to 20%, leading to an accumulation of >90 kg PO ha in the soil each year. Phosphorus lost from agriculture is the second greatest contributor to waterbody eutrophication in China, accounting for 25% of total P losses in 2010; the main contributor is livestock husbandry. Given these problems, as well as the finite nature of P reserves, three strategies are proposed here to reduce P fertilizer application rates, improve P use efficiency, and minimize the environmental risk caused by P loss in China: (i) improving soil legacy P utilization by modifying cropping systems, rhizosphere management, or microbial engineering, (ii) increasing P use efficiency by reducing P fertilizer applications and minimizing P fertilizer fixation, and (iii) promoting the extension of soil P management strategies. For these management strategies to succeed in China, close cooperation should be established among farmers, scientists, and governments in the future.

How to avoid coastal eutrophication - a back-casting study for the North China Plain.

Eutrophication is a serious problem in Chinese seas. We explore possibilities to avoid coastal eutrophication without compromising food production in the North China Plain. We used the Model to Assess River Inputs of Nutrient to seAs (MARINA 1.0) for back-casting and scenario analysis. Avoiding coastal eutrophication by 2050 implies required reductions in river export of total nitrogen (TN) and phosphorus (TP) by 50-90% for the Hai, Huai and Huang rivers. We analyzed the potential to meet these targets in 54 scenarios assuming improvements in manure recycling, fertilizer application, animal feed and wastewater treatment. Results indicate that combining manure recycling while reducing synthetic fertilizer use are effective options to reduce nutrient inputs to seas. Without such options, direct discharge of manure are important sources of water pollution. In the 7-25 scenarios with the low eutrophication potential, 40-100% of the N and P in untreated manure is recycled on land to replace synthetic fertilizers. Our results can support the formulation of effective environmental policies to avoid coastal eutrophication in China.

Phosphorus retention and loss in three types of soils with implications for geographical pattern of eutrophication in China

AbstractPhosphorus (P) loss from soil to water bodies is an important process associated with eutrophication of lakes and reservoirs. Phosphorus concentration in China's waterbodies changes geographically, increasing substantially with latitude. It is assumed that the geographical pattern results from change in soil retention and loss features of P. To test this assumption, we designed a soil column leaching experiment to measure the P retention capacity of three common types of soils in China: red, black and loess. Results showed that red soil possessed a much higher P retention capacity than black and loess soils. Red soil retained P primarily through binding by aluminium and iron, with half of the total retained P contributed by iron binding. Phosphorus loss in all three soils was influenced by pH of the used acid solution and the leaching rate. Specifically, acidification tends to promote soil P loss, whereas leaching rate decreases P loss.

Insight into the spatial distribution of nutrient elements and sediments fraction analysis in Taihu Lake

Lake eutrophication in China is a serious issue and has raised urgent attention, which is required for a better understanding of the eutrophic status. Particularly, the eutrophication of shallow lakes has received public attention for shallow lakes are vulnerable to changes in eutrophic status due to the closer proximity with bottom lake sediments. Herein, a comprehensive investigation on the spatial distribution of nutrient elements (including carbon, nitrogen and phosphorus) was conducted in a typical large shallow lake Taihu Lake, and the internal patterns between the distribution and eutrophic status were analyzed. The results showed that the distributions of nutrient elements in surface sediment displayed spatial diversity in different regions. Zhushan Bay, East Taihu Lake and Dongjiaozui Bay hold distinguished pattern of nutrient contents due to the different geographical locations and economic pattern of adjacent areas. Specifically, the concentrations of total carbon and total nitrogen in East Taihu Lake were significantly higher than other areas, and total phosphorus content in Zhushan Bay was the highest. Furthermore, different phosphorus fractions in sediment and eutrophic indicators of water column were further analyzed to reveal the potential contribution of sediments to nutrient loadings of overlying water. The phosphorus fraction analysis suggested that calcium bounded phosphorus accounted for the main component. Correlation analysis revealed the internal relations among various characteristics in sediment or water, which indicated that microcystis blooms were accompany with excessive COD and phosphorus and depletion of dissolved oxygen. The results offered a comprehensive understanding of the lake eutrophic status and benefited further the study on the ecological status assessment.

Characteristics of bioavailable organic phosphorus in sediment and its contribution to lake eutrophication in China

This study aims to establish the relative importance of sediment organic phosphorus (Po) to the total P and the major classes of organic molecules that contribute to sediment Po, determined by measuring their susceptibility to enzymatic hydrolysis, across a suite of lakes ranging from oligotrophic to eutrophic status. The results showed that Po accounted for 21–60% of total P, and bioavailable Po accounted for 9–34% of Po in the sediments. The bioavailable Po includes mainly labile (H2O-Po) and moderately labile (NaOH-Po) P forms. For H2O-Po (accounting for only1.4% of Po), 53% (average) was labile monoester P, 28% was diester P and 17% was phytate-like P. For NaOH-Po (accounting for 9–33% of Po), 32% was labile monoester P, 33% was phytate-like P and 18% was diester P. The composition of bioavailable Po, determined by enzyme assays, was related to the lake nutrient levels, which implies that sediment bioavailable Po could act as an effective indicator for lake eutrophic status. With the increase of lake nutrient levels, bioavailable Po content and alkaline phosphatase activity in the sediment all increased, indicating that Po represents an important and bioavailable source of P that increases with eutrophication, and could contribute to internal loading and resistance of eutrophic lakes to remediation. This implies that eutrophic lakes would maintain long-term eutrophic status and algal bloom phenomena even after the external input of P was controlled and the total P concentration of water has declined. Thus, in order to reduce the release risk of sediment P more efficiently and effectively, sediment P control technique should focus not only on reducing the total P and inorganic P, but should also pay close attention to the removal of bioavailable Po.

Decreasing input–output balance by reducing chemical fertilizer input without yield loss in intensive cropping system in the Coastal Area of southeast Lake Dianchi, Yunnan Province, China

Overuse of chemical fertilizer and/or manure in agriculture is a principal factor in water eutrophication in China. Our previous study indicated that reducing chemical fertilizer input effectively decreased the soil nitrogen, phosphorus, and potassium in an intensive vegetable cropping system in the coastal area of southeast Lake Dianchi, China. This study aimed to decrease the input–output balance, namely the nutrient balance between input of fertilizer and output through vegetable harvesting, by reducing chemical fertilizer application without yield loss. A pot experiment was performed using chemical fertilizer with different amounts of N, P, and K on soils from six vegetable fields’ representative of the study area. High nitrate concentration in soils 2, 3, and 6 resulted in high N absorption from soil, and low N absorption from chemical fertilizer. Moreover, the responses of dry matter production to N absorbed from chemical fertilizer were less sensitive in soils 2, 3, and 6 than those in the other soils. Accordingly, reducing N input of chemical fertilizer did not decrease total N absorption or dry matter production, which should be the reason why reducing N input of chemical fertilizer did not reduce dry matter production in soils 2, 3, and 6. In the cases of soils 1, 4, and 5, reducing N input of chemical fertilizer reduced dry matter production, owing to lower levels of soil nitrate. This study should be helpful for reducing nutrient surplus from chemical fertilizer in the coastal area of southeast Lake Dianchi and other eutrophic agricultural areas in China.

Economic development influences on sediment-bound nitrogen and phosphorus accumulation of lakes in China.

China has been confronted with serious water quality deterioration concurrent with rapid socioeconomic progress during the past 40 years. Consequently, knowledge about economic growth and lake water quality dynamics is important to understand eutrophication processes. Objectives were to (i) reconstruct historical nutrient accumulation and the basin economic progress on burial flux (BF); (ii) determine forms and structures of nitrogen (N) and phosphorus (P) in sediment and water using six cores in three of the most severely eutrophic lake areas in China (i.e., Eastern Plain, Yunnan-Guizhou Plain, and Inner Mongolia-Xinjiang regions). Results suggest that BFs of total nitrogen (TN) continued to increase in sediment, whereas total phosphorus (TP) levels were consistent or only slightly increased, except in highly polluted lakes during the past decades. Similar results were observed for concentrations of nutrients in water (i.e., increased N/P). This historical distribution pattern was correlated to long-term fertilization practices of farmers in the watershed (N fertilization exceeds that of P) and was contingent upon pollution control policies (e.g., emphasized P whereas N was ignored). Vertical profiles of BFs indicated that lake nutrient accumulation included three stages in China. Nutrient accumulation started in the 1980s, accelerated from the 1990s, and then declined after 2000. Before the 1980s, nutrients were relatively low and stable, with nutrient inputs being controlled by natural processes. Thereafter, N- and P-bound sediments dramatically increased due to the increasing influence of anthropogenic processes. Nutrients were primarily derived from industries and domestic sewage. After 2000, BFs of nutrients were steady and even decreased, owing to implementation of watershed load reduction policies. The decreasing NaOH-extracted P (Fe/Al-P) and increasing organic phosphorus (OP) indicated that the source of exogenous pollution underwent a shift. Inputs of nutrients were predominantly from agricultural and domestic sewage, whereas industrial pollution has been gradually controlled in most of the watersheds. Historical nutrient dynamics suggest that the economy of China is growing at the expense of its aquatic ecological environments. Therefore, more attention to nutrient export to groundwater resulting from economic development is important for further aquatic ecosystem deterioration and eutrophication in China.

Distinguishing the Main Pollution Source an Efficient Way in Agricultural Non-Point Source Pollution Control

Agricultural non-point source (NPS) pollution is a growing environmental problem, contributing much to water eutrophication in China as well as in other parts of the world. NPS pollutants are heterogeneously distributed and discharged from agricultural lands and other sources, and extremely hard to control by technical measures. Hence, control of the water quality problems caused by agricultural NPS pollution becomes difficult if recommended best management practices (BMPs) can’t be well implemented. In this paper, current research progress related to distinguishing agricultural NPS pollution sources was reviewed. Three pivotal methods for identifying agricultural NPS pollution sources were introduced and the advantages and disadvantages of each approach were discussed. Finally suggestions were presented on better identifying agricultural NPS pollution sources in China.

The Fluctuation of Arsenic Levels in Lake Taihu

This study was conducted to investigate the arsenic levels in the waters of lake Taihu, a huge, shallow, and very important lake which has been suffered with serious eutrophication in China. Unexpected great difference was detected for arsenic levels between the collected water samples of three successive surveys in Taihu in May 2009, Fall 2009, and May 2010, with arsenic levels in May 2009 being more than tenfold of those in Fall 2009 and May 2010. Such difference in arsenic levels do not routinely happen like seasonal changes as reported in many other lakes of the world. Considering arsenic contents as well as some basic aquatic monitoring data of the lake, such great arsenic fluctuations were probably due to the effects of strong hydraulic turbulence in Taihu for its very shallow depth. The spatial distribution of arsenic in Taihu were similar, despite great difference of arsenic levels in the three successive surveys, indicating such differences did not come from arsenic external input around the lake. The sudden increase of arsenic levels in Taihu highlights the importance of stabilization or removing of arsenic in lake sediments so as to keep arsenic lower than the national hygiene standard of China.

Eutrophication of Lake Waters in China: Cost, Causes, and Control

Lake water eutrophication has become one of the most important factors impeding sustainable economic development in China. Knowledge of the current status of lake water eutrophication and determination of its mechanism are prerequisites to devising a sound solution to the problem. Based on reviewing the literature, this paper elaborates on the evolutional process and current state of shallow inland lake water eutrophication in China. The mechanism of lake water eutrophication is explored from nutrient sources. In light of the identified mechanism strategies are proposed to control and tackle lake water eutrophication. This review reveals that water eutrophication in most lakes was initiated in the 1980s when the national economy underwent rapid development. At present, the problem of water eutrophication is still serious, with frequent occurrence of damaging algal blooms, which have disrupted the normal supply of drinking water in shore cities. Each destructive bloom caused a direct economic loss valued at billions of yuan. Nonpoint pollution sources, namely, waste discharge from agricultural fields and nutrients released from floor deposits, are identified as the two major sources of nitrogen and phosphorus. Therefore, all control and rehabilitation measures of lake water eutrophication should target these nutrient sources. Biological measures are recommended to rehabilitate eutrophied lake waters and restore the lake ecosystem in order to bring the problem under control.

Control concept and countermeasures for shallow lakes’ eutrophication in China

Research on lake eutrophication in China began in the early 1970s, and many lakes in China are now known to be in meso-eutrophic status. Lake eutrophication has been showing a rapidly increasing trend since 2000. Investigations show that the main reasons for lake eutrophication include a fragile lake background environment, excessive nutrient loading into lakes, excessive human activities, ecological degeneration, weak environmental protection awareness, and lax lake management. Major mechanisms resulting from lake eutrophication include nutrient recycling imbalance, major changes in water chemistry (pH, oxygen, and carbon), lake ecosystem imbalance, and algal prevalence in lakes. Some concepts for controlling eutrophication should be persistently proposed, including lake catchment control, combination of pollutant source control with ecological restoration, protection of three important aspects (terrestrial ecology, lake coast zone, and submerged plant), and combination of lake management with regulation. Measures to control lake eutrophication should include pollution source control (i.e., optimize industrial structural adjustments in the lake catchment, reduce nitrogen and phosphorus emission amounts, and control endogenous pollution) and lake ecological restoration (i.e. establish a zone-lake buffer region and lakeside zone, protect regional vegetation, utilize hydrophytes in renovation technology); countermeasures for lake management should include implementing water quality management, identifying environmental and lake water goals, legislating and formulating laws and regulations to protect lakes, strengthening publicity and the education of people, increasing public awareness through participation in systems and mechanic innovations, establishing lake region management institutions, and ensuring implementation of governance and management measures.

Water eutrophication in China and the combating strategies

AbstractThis paper reviews the current eutrophication status of China's lakes. Details of the most eutrophic ‘Three Lakes’, i.e. Dianchi Lake, Taihu Lake and Chaohu Lake, are given. Based on an explanation of its causes, policies and technologies currently in practice in addition to research towards combating the eutrophication are illustrated using some specific cases. Finally, some management issues and long‐term combating strategies are discussed. Copyright © 2007 Society of Chemical Industry

Controlling non-point-source pollution by rural resource recycling. Nitrogen runoff in Tai Lake valley, China, as an example

Agricultural non-point-source (NPS) pollution is regarded as the dominant contributor to water quality degradation and eutrophication in China. Nitrogen (N) is a primary source of pollution in fresh water bodies. In this work a linear programming model was developed to simulate the effectiveness of different nitrogen runoff control policies, using Pinghu City in Tai Lake valley as an example. Four policy scenarios were tested: a tax at a rate equivalent to 50% of the cost of nitrogen fertilizer (S1); a ban on summer fertilizer applications to make the most use of fertilizer applied in the spring (S2); mandatory substitution of regular fertilizers by controlled-release fertilizers (S3); and a subsidy of US$300 ha−1 (RMB¥150 mu−1) for using compost (S4). The results indicate that all four policies would effectively reduce nitrogen runoff—by 9.8, 26.8, 14.4, and 80.0%, respectively. A subsidy for recycling domestic animal manure and utilizing compost had the most significant effect on the reduction of nitrogen runoff without reducing household income. This research suggests that measures to control agricultural NPS pollution should be combined with a policy to promote recycling of bio-resources and that financial support for NPS pollution control combined with bio-resource recycling should be regarded as one aspect of public investment in regional sustainable development.

An analysis of lake eutrophication in China

An account of the problems of lake eutrophication in China is given, drawing particularly upon recent survey data of 25 lakes and reservoirs scattered across the country. Measurement of physicochem...