Trophic State Index Research Articles

Mapping the trophic state index of eastern lakes in China using an empirical model and Sentinel-2 imagery data

Lake eutrophication has become a critical environmental issue due to the global effects of anthropogenic activities and climate change, and has been comprehensively studied for many years. A series of models and indicators have been proposed to assess the trophic state of lakes. The trophic state index (TSI) is a synthetic index that integrates chlorophyll-a, water clarity, and total phosphorus and is widely used to evaluate the trophic state of aquatic environments. In this study, we collected in situ lake samples (N = 431) from typical lakes to match Sentinel-2 MultiSpectral Instrument (MSI) imagery data using the Case 2 Regional Coast Color processor. Then we developed a new empirical model, TSI = –34.04 × (band 4/band 5) – 1.114 × (band 1/band 4) + 97.376). This model is valid for all of China, with good performance and few errors (RMSE = 7.36; MAE = 6.25) for the validation dataset. Recognizing that over 94% of the Chinese population located along eastern watersheds and large lakes have competing water uses, and given the TSI model on the seasonal scales, we further estimated the mean TSI and trophic state in eastern Chinese lakes (>100 km2) from 2019 to 2020. The results revealed that more lakes were eutrophic in autumn (94.28%) than in spring (>77.14%), indicating a serious eutrophication of eastern lakes. Although the eastern lakes have been studied in more detail, this study found that eutrophication still has markedly negative impacts on lake ecosystems. In addition, no significant improvement was observed in spring, most likely due to the months of curfew/lockdown from January 2020 onwards due to COVID-19. This may be due to the enrichment of nutrients deposited in sediment or watershed soil, which can be characterized as “autochthonous sources” of lake eutrophication, over decades with high rates of economic development. This study demonstrates the applicability of Sentinel-2 MSI data to monitor lake eutrophication as well as the feasibility of blue/red and red/red edge combinations. The framework and TSI model used bands available on MSI sensors to develop a novel approach for generating historical eutrophication data for large-scale evaluation of and decision-making related aquatic environmental changes, even in poorly studied areas.

Modelling of Greek Lakes Water Quality Using Earth Observation in the Framework of the Water Framework Directive (WFD)

Given the great importance of lakes in Earth’s environment and human life, continuous water quality (WQ) monitoring within the frame of the Water Framework Directive (WFD) is the most crucial aspect for lake management. In this study, Earth Observation (EO) data from Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Landsat 8 Operational Land Imager (OLI) sensors have been combined with co-orbital in situ measurements from 50 lakes located in Greece with the main objective of delivering robust WQ assessment models. Correlation analysis among in situ co-orbital WQ data (Chlorophylla, Secchi depths, Total phosphorus-TP-) contributed to distinguishing their inter-relationships and improving the WQ models’ accuracy. Subsequently, stepwise multiple regression analysis (MLR) of the available TP and Secchi depth datasets was implemented to explore the potential to establish optimal quantitative models regardless of lake characteristics. Then, further MLR analysis concerning whether the lakes are natural or artificial was conducted with the basic aim of generating different remote sensing derived models for different types of lakes, while their combination was further utilized to assess their trophic status. Correlation matrix results showed a high and positive relationship between TP and Chlorophyll-a (0.85), whereas high negative relationships were found between Secchi depth with TP (−0.84) and Chlorophyll-a (−0.83). MLRs among Landsat data and Secchi depths resulted in 3 optimal models concerning the assessment of Secchi depth of all lakes (Secchigeneral; R = 0.78; RMSE = 0.24 m), natural (Secchinatural; R = 0.95; RMSE = 0.14 m) and artificial (Secchiartificial; R = 0.62; RMSE = 0.1 m), with reliable accuracy. Study findings showed that TP-related MLR analyses failed to deliver a statistically acceptable model for the reservoirs; nevertheless, they delivered a robust TPgeneral (R = 0.71; RMSE = 1.41 mg/L) and TPnatural model (R = 0.93; RMSE = 1.43 mg/L). Subsequently, trophic status classification was conducted herein, calculating Carlson’s Trophic State Index (TSI) initially throughout all lakes and then oriented toward natural-only and artificial-only lakes. Those three types of TSI (general, natural, artificial) were calculated based on previously published satellite-derived Chlorophyll-a (Chl-a) assessment models and the hereby specially designed WQ models (Secchi depth, TP). The higher deviation of satellite-derived TSI values in relation to in situ ones was detected in reservoirs and shallower lakes (mean depth < 5 m), indicating noticeable divergences among natural and artificial lakes. All in all, the study findings provide important support toward the perpetual WQ monitoring and trophic status prediction of Greek lakes and, by extension, their sustainable management, particularly in cases when ground truth data is limited.

Eutrophication decrease compositional dissimilarity in freshwater plankton communities

Human activities, such as land use change and eutrophication, threaten freshwater biodiversity and ecosystem function. In this study, we examined both the α- and β-diversity of plankton communities, that is, bacteria/prokaryotic algae, eukaryotic algae, and zooplankton/metazoans, using both classical microscopy and high-throughput sequencing methods across 40 lakes of the Yangtze River Basin. The spatial variations in plankton communities were explained by environmental variables such as trophic status index (TSI) and environmental heterogeneity according to non-metric multidimensional scaling analyses, mantel tests, and structural equation model. Our results showed that the compositional dissimilarities of bacteria, cyanobacteria, eukaryotic algae, and metazoans all decreased with the increasing TSI values, and were significantly positively related to environmental dissimilarity. Both the species richness and compositional dissimilarity of zooplankton had positive effects on zooplankton/phytoplankton biomass ratio. Zooplankton diversity was not directly affected by TSI and environmental dissimilarity; however, it was indirectly affected by the biotic interactions with cyanobacteria or eukaryotic algae. In addition, there were significant positive relationships between bacteria/cyanobacteria and eukaryotic algae dissimilarities. Our results indicated that increased trophic status and decreased environmental dissimilarity as consequences of eutrophication may weaken the trophic cascading effects of planktonic food chain via reducing the top-down effects of zooplankton on phytoplankton.

Evaluation of trophic state for inland waters through combining Forel-Ule Index and inherent optical properties

Eutrophication is a severe environmental pollution problem for inland waters and poses significant threats to the water safety. Monitoring trophic state of inland waters using optical remote sensing generally requires the inversion of water quality parameters, such as chlorophyll-a, secchi depth, etc. However, the accurate inversion of these individual indicators remains challenging, while the associated retrieval errors can propagate and degrade the evaluation of trophic state. Hence, we proposed a novel monitoring method by developing a Trophic State Index (TSI) based on optical remote-sensing parameters, i.e., Forel-Ule index (FUI) and non-water absorption coefficient at 674 nm (referred to as at−w(674)) retrieved from Sentinel-3 Ocean and Land Color Instrument (OLCI) imagery. The estimated TSI showed favorable correspondence with observed water quality data, including coefficient of determination (r2 = 0.91), root mean squared error (RMSE = 5.54), and mean absolute percentage error (MAPE = 10.69%). Using the Sentinel-3 OLCI data, the proposed method also had very good performance in the field spectrum (MAPE = 5.25 % , RMSE = 3.36). The monthly trophic state evaluation also showed congruence (MAPE = 12.51 % , RMSE = 6.41) with surface water quality monthly report (SWQMR) from the Ministry of Environment and Ecology of the People's Republic of China. The monthly TSI showed favorable agreement for 23 ungauged lakes (RMSE = 7.26, MAPE = 12.78%), indicating potential utility for regional lake water quality monitoring. The proposed method was then applied to 47 other large (>50 km2) water bodies in the Middle-and-Lower watershed of Yangtze River and the Huaihe watershed to evaluate the spatial and temporal variation of trophic state from 2016 to 2020. The TSI results revealed several lakes, such as Lake Honghu and Lake Luoma, with rapidly deteriorating water quality during the study period, while other lakes show relative improvement (e.g., Xiashan Reservoir), indicating unbalanced environmental pressure over the region. Overall, this study showed promising performance and potential for satellite-based monitoring of regional aquatic environments.

Perception of the local community: What is their relationship with environmental quality indicators of reservoirs?

Evaluating the conservation of aquatic ecosystems, especially those which serve to supply, has been carried out using a variety of tools. However, the perception of water quality by the local community which lives in direct contact with water resources has not been considered with enough importance. This study analysed the relationship between the conservation status of reservoirs as perceived by the local community and their conservation status according to physical, chemical, and biological indicators. To do so, we calculated the Trophic State Index (TSI) of the reservoirs, the diversity and richness of benthic macroinvertebrate and we analysed the human influence in the riparian zone. Thus, we created the Community Conservation Perception Index (CCPI) to quantitatively associate the perception of the local community with environmental quality indicators (TSI, diversity, richness and anthropogenic influences in the riparian zone). We found that interviewee perception of reservoir conservation (using the CCPI) was related to trophic state, richness and diversity of benthic macroinvertebrate, and the presence of residences and agriculture in the riparian zone. It is necessary to consider the environmental perception of the local community as a relevant factor in management programmes and the conservation of ecosystems, even if artificial, as is the case with reservoirs. These communities can significantly contribute to maintaining the environmental quality through their performance in participatory management in projects such as: participating in the investigation of pollution in reservoirs, collecting parameters related to water quality, and community action in designing conservation strategies.

Temporal dependence of chlorophyll a–nutrient relationships in Lake Taihu: Drivers and management implications

Eutrophication and its associated algal blooms are principal environmental challenges confronting lakes worldwide. The empirical relationships between nutrient (total nitrogen, TN; total phosphorus, TP) and chlorophyll a (Chla) level are widely used as a theoretical basis for lake eutrophication management. Here, seasonal environmental variables and Chla from 2005 to 2020 in Chinese shallow eutrophic Lake Taihu were examined and Chla-nutrient equations in the entire period and annually from 2005 to 2020 were explored using 95% quantile regression model. The results showed robust linear relationships of logChla-logTN and logChla-logTP in the vast majority of cases. Based on Chla-nutrient equations in the entire study period, 0.69 mg/L TN and 52 μg/L TP are recommended as nutrient threshold in Lake Taihu. Furthermore, the results revealed increasing Chla sensitivity to nutrient for each study month (i.e. February, May, August, and November) from 2005 to 2020, whose drivers included increase in water temperature and water level, decrease in wind speed, mass ratio of nitrogen to phosphorus, and grazing effect. It is noteworthy that atmospheric stilling is likely to be the key climatic factor promoting annual peak Chla in Lake Taihu. For one, the deviations of the sub-index of Trophic State Index indicated that light is a critical limiting factor of summer Chla in Lake Taihu. For another, calmer water mainly due to atmospheric stilling decreased near 40% non-algal turbidity and a substantially increased buoyant cyanobacteria during the study period, improving phytoplankton “light niche”. Thus, increasing algal sensitivity to nutrient occurred until the additional algal-turbidity induce further light limitations or the exhaustion of TN (or TP) cause nutrient limitation. Given atmospheric stilling is a global phenomenon, this study would affect future algal bloom mitigation efforts in shallow lakes as temperature is always the focus in the recent literatures on global climate change.

Application of WQIEUT and TSIKO for comprehensive water quality assessment immediately after the construction of the Yeongju Multipurpose Dam in the Naeseong Stream Basin, Republic of Korea

This study evaluated changes in the aquatic environment and river water quality due to the construction of the Yeongju Multipurpose Dam (YMD) in the Naeseong Stream Basin, Republic of Korea, over eight years. This study evaluated water quality characteristics immediately after dam construction in the target area with aquatic environmental values and important water quality parameters using classification schemes. The drastic formation of new lentic systems in the upstream dammed pool presented exponential algal growth and high potential availability of nitrogenous compounds depending on seasonally. The results of the river system analyzed with the water quality index focused on eutrophication (WQIEUT) and trophic state index of the Republic of Korea (TSIKO) provided adequate complementary information for specific water quality background within the extensive basin for future management. From the results, inflow and accumulation of anthropogenic organic matter as potential eutrophic factors in the upstream dammed pool were significant in the short-term period. However, the downstream lotic systems adjacent to the dam presented the temporary disturbance by physical factors. Furthermore, potential microbial factors were significant in the outlet in the basin depending on seasonally. These results using classification schemes can aid accessible decision-making for water quality management to prevent eutrophication in the dammed pool of upstream or best management practices (BMP) with microbial source tracking (MST) approaches in the downstream area.

Effects of the Three Gorges Reservoir Operation on Vertical Distribution of Chlorophyll a and Environmental Factors in Tributaries

The hydrodynamics and environmental factors in the Xiangxi River (XXR) and Shennong River (SNR), which are tributaries of the Three Gorges Reservoir (TGR), were monitored from July to August (the low water level period) and in October (the impoundment period) in 2018. The vertical distribution characteristics of chlorophyll a and other indicators of the two tributaries were analyzed during the different operation periods, and the factors that affected the vertical distribution in each period were discussed. The results showed that the vertical distribution of dissolved oxygen, water temperature, pH value, and chlorophyll a of the XXR and SNR during the low water level period was relatively consistent. The indexes 0-10 m (0-5 m for chlorophyll a) from the surface of the XXR and SNR, respectively, showed significant stratification and decreased with increasing water depth; the stability index of thermal stratification (RWCS/H) was 13.71-29.07 m-1, which was stable. After the water depth reached 10 m (5 m for chlorophyll a), the indexes tended to be stable along the water depth. During the impoundment period, there was no obvious stratification for each index; the stability index of thermal stratification was 0-0.5 m-1, the stability of the water body was weak, and the vertical variation of each index was relatively stable. The comprehensive trophic state index (TLI) of the XXR and SNR were 55 and 53 during the low water level period, respectively, indicating that they were in a slightly eutrophic state, and 39 and 46 during the impoundment period, respectively, indicating a mesotrophic state. Linear regression analysis showed that chlorophyll a, dissolved oxygen, water temperature, and pH in the two tributaries were significantly correlated in the vertical direction in the low water level period, indicating that dissolved oxygen, water temperature stratification, and pH were important factors affecting the vertical distribution of chlorophyll a. During the impoundment period, a large amount of backflow from the Yangtze River, a large fluctuation in tributary water level, and the decrease in RWCS/H were the important factors that affected the small vertical change in the water body. The enhancement of vertical mixing and the decrease in Zeu/Zmix were the key factors affecting the nutritional status of the water.

Performance Evaluation of Watershed Environment Governance—A Case Study of Taihu Basin

The rapid development of urbanization and industrialization brings a series of problems of environment governance, and several basins are facing huge pressure. This paper selects the Taihu basin in the Yangtze River Delta of China as the study area, establishes the DPSIR model to measure the water environment governance performance of the region (Cj), analyzes the causes of changes in the five subsystems (the governance performance of the subsystems is recorded as C1j,C2j,C3j,C4j,C5j), and uses the diagnostic model to identify the barrier factors that restrict the improvement of Cj in the last 5 years. The results show that during the study period, C1j of the driving force subsystem generally tends to increase and maintains a steady growth, which is closely linked to economic growth in the basin; C2j of the pressure subsystem increases with a small fluctuation, and the pollution generation still needs attention; in the state subsystem, C3j shows a large fluctuation, and varies significantly in a cyclical manner, corresponding to the short maintenance time and repeated treatment of pollution in the watershed; C4j of the impact subsystem shows an overall upward but a slightly slower trend, and it is related to the fact that the industrial structure of the basin still needs to be improved; and C5j of the response subsystem shows an overall upward trend and a slightly larger increase, and the multi-actor collaborative management has helped a lot. The main barrier factors include key cross-sections’ water quality compliance rate, the water quality compliance rate of key water function areas, water consumption per 10,000 yuan of industrial added value, and the lake trophic status index. Based on the results of the study, the article gives recommendations for watershed governance, such as controlling pollution generation, optimising industrial structure, using technological tools to help governance, sharing the cost of governance among multiple parties and strengthening supervision The findings help to make scientific environmental protection planning and policies of the study region. The research can also provide experience for other countries and regions in watershed governance.

Application of multiple indices to the evaluation of trophic and ecological status in a tropical macrotidal estuary (Equatorial Margin, Brazil)

ABSTRACT The Paciência river estuary (PRE) is an Amazonian estuary with relevant socio-economic importance; however, it is undergoing a continuous anthropogenic pressure such as the input of untreated domestic effluents. Hence, the phytoplankton community and trophic indices were analysed during three seasons in 2017 to assess the water quality and understand the degree of human influence in a macrotidal estuary. The trophic state of the PRE was determined by applying the trophic state index (TSI), trophic index, and Karydis trophic index, and ecological status by diversity metrics (diversity, evenness, richness, and dominance). Multivariate analysis indicated that TSI and dominance index were the most sensitive indices to changes in environmental conditions. The precipitation regime characterised the estuary in two different trophic scenarios. PRE was hypereutrophic in the dry season and mesotrophic in the rainy/transitional seasons based on the TSI. A high dominance index was recorded in the dry season with blooms of Thalassiosira rotula, reflecting an ecological disturbance. A higher phytoplankton diversity was recorded in the rainy/transitional seasons, indicating a tendency toward a lower stressed ecosystem. Therefore, understanding the trophic state variability in tropical estuaries and its response to changes in phytoplankton ecology is essential to support the management of coastal ecosystems.

Spatiotemporal Evaluation of Eutrophication State in The Hammar Marsh Using A Satellite-Based Model

Water pollution is now a major threat to the existence of living beings. Accordingly, Water quality monitoring is an important activity toward restoring water quality. As wetland eutrophication is one of the essential ecosystem elements, devastation of this element is a significant issue. The Trophic State Index (TSI) provides information about trophic condition of water bodies. This paper aims to conduct spatiotemporal monitoring for the eutrophication of the west part of Al-Hammar Marsh for the period 2013-2020. To this end, a satellite-based TSI computation model was developed and implemented by using a series of OLI Landsat satellite images. The results showed that there was no improvement in the eutrophication state in the marsh, the percentage of the low class of TSI decreased in 2015 and 2018 to 7.9% and 2.6% and increased in 2017 and 2020 to 39.8%, and 56.3%. In general, the TSI was in the poor class in all the considered periods. Fluctuation of quantity and quality of the inflow prevents restoring the eutrophication of the marsh because this process requires stability in the levels of inundation above the critical limits for the water depth and periods. Therefore, it is necessary to find suitable alternatives to provide water drainage in quantities and quality that ensure the sustainability of the marsh ecosystem.

Avaliação de qualidade de água superficial e intersticial: estudo de caso da Enseada do Saco da Mangueira

A enseada do Saco da Mangueira, situada nas margens do município do Rio Grande - RS, vem sofrendo ao longo dos anos, processos de poluição e contaminação associados ao seu significativo papel em atividades pesqueiras, industriais, de lazer, entre outras. Com base no exposto, esse trabalho tem por objetivo avaliar a qualidade da água da enseada do Saco da Mangueira, e para isto construir um testemunhador de sedimento de fundo a fim de permitir a extração da água intersticial para avaliação da sua qualidade juntamente com as águas de superfície e fundo, através da sua classificação e enquadramento com base na Resolução do CONAMA Nº 357 de 2005, além da classificação eutrófica pelo Índice do Estado Trófico, como forma de auxílio no planejamento e gestão dos recursos hídricos deste ecossistema. Foi realizada uma campanha amostral no dia 13 de fevereiro de 2020 na qual foram coletadas amostras de água em 6 locais distribuídos ao longo da região de estudo, sob estas foram avaliados parâmetros físicos, químicos e microbiológicos. Os resultados obtidos permitiram verificar que as águas do Saco da Mangueira encontram-se em condição ambiental da Classe 2 da Resolução do CONAMA 357/05, excetuando para coliformes em alguns locais. O Índice de Estado Trófico indicou que a enseada apresenta de baixa à intermediária quantidade de nutrientes, classificado de mesotrófico a oligotrófico. Deste modo, conclui-se que a enseada pode sofrer degradações associadas às diferentes fontes de entradas antrópicas, independente do seu enquadramento, o que reforça a necessidade de monitoramento contínuo da qualidade destas águas e uma gestão ambiental integrada.Palavras-chave: amostrador de água intersticial, parâmetros físico-químicos e microbiológicos, resolução do conama nº 357 de 2005, estuário, Laguna dos Patos. Construction of a testimony sampling for assessment of surface and interstitial water quality: case study of sacco da mangueira bay A B S T R A C TThe Saco da Mangueira bay, located on the banks of the municipality of Rio Grande - RS, has suffered over the years, processes of pollution and contamination associated with its significant role in fishing, industrial, leisure activities, among others. Based on the above, this work aims to evaluate the water quality of the Saco da Mangueira bay, and for this to build a bottom sediment sampler in order to allow the extraction of interstitial water to evaluate its quality together with the of surface and bottom, through its classification and framing based on CONAMA Resolution No. 357 of 2005, in addition to the eutrophic classification by the Trophic State Index, as a form of aid in the planning and management of the water resources of this ecosystem. A sampling campaign was carried out on February 13, 2020, in which water samples were collected at 6 locations distributed in the study region, under which physical, chemical and microbiological parameters were evaluated. The results obtained showed that the waters of Saco da Mangueira are in Class 2 environmental condition of CONAMA Resolution 357/05, except for coliforms in some places. The Trophic State Index indicated that the bay has a low to intermediate amount of nutrients, classified from mesotrophic to oligotrophic. Thus, it is concluded that the bay can suffer degradation associated with different sources of human inputs, regardless of its framework, which reinforces the need for continuous monitoring of the quality of these waters and an integrated environmental management.Keywords: interstitial water sampler, physicochemical and microbiological parameters, resolution of conama nº 357 of 2005, estuary, Laguna dos Patos.

Responses of plankton community to water environment changes in karst springs in Wuming Basin, Guangxi Province

近年来我国西南岩溶地区一些岩溶泉出现水生生态系统由草型向藻型转变的问题，但水化学监测却显示泉水水质依旧良好.岩溶泉的水质变化与水生生态系统退化不同步，故探寻岩溶泉水环境的变化以及浮游生物群落的响应，对全面掌握和客观评价泉水的健康状况具有重要意义.于2016年7月、2020年7月两个时期对广西武鸣盆地内4个岩溶泉进行了浮游生物调查和水环境监测.结果显示，4年后浮游生物检出种类和数量增加.浮游植物快速繁殖，总丰度由1.71×10⁵ cells/L上升至79.92×10⁵ cells/L，蓝藻门或绿藻门比例上升；浮游动物总丰度由264.28 ind./L降至137.25 ind./L，大型甲壳类浮游动物密度减少，部分泉口轮虫类密度增加.同时，优势种转变为更适应于富营养化环境的耐污种，或耐污种种类和数量上升.浮游生物的多样性与水体营养水平并未完全吻合.理化指标的水质评价结果显示，4个泉的水质仍属于I类或Ⅱ类，但综合营养状态指数显示营养状态均向富营养化方向发展，大部分泉基本已处于中-富营养水平.冗余分析结果显示，水温、pH、亚硝态氮、总磷、硝态氮浓度是影响岩溶泉浮游植物群落结构的主要环境因子.浮游动物群落结构与水温、亚硝态氮、氨氮和叶绿素a浓度显著相关.两个时期浮游生物对主要水环境因子的变化有了一定的响应.建议岩溶泉的水质评价依据理化指标的同时还应关注生物指标，多个指标的相互验证才能更全面的反映水体健康状况.同时，为使泉口以及区域地下水资源的可持续开发利用，建议对重要泉口划分泉域保护区，控制泉口污染物的输入，合理开发和管理地下水资源，对已转变的水生生态系统可考虑尽快进行生态修复.;The shift from a clear macrophyte-dominated state to a turbid algal-dominated state has been occurred in some karst springs of Southwest China in recent years, but hydrochemical monitoring still reveal good conditions. The trend of water quality in karst springs is not synchronous with the degradation of aquatic ecosystem. To understand comprehensively and evaluate objectively the health of the spring water, we discussed how plankton community responds to water environment. Plankton investigation and physicochemical parameters monitoring have been conducted at four karst springs of the Wuming Basin, Guangxi province, in July 2016 and July 2020, respectively. The results showed that the number of species and density of plankton detected have increased 4 years later. Reproduced rapidly, the phytoplankton abundance of those all springs increased from 1.71×10⁵ cells/L to 79.92×10⁵ cells/L. And the total abundance of zooplankton decreased from 264.28 ind./L to 137.25 ind./L. The proportion of Cyanophyta or Chlorophyta in each spring increased, while density of some large crustacean's species reduced. And density of Rotifer has increased in some springs. Furthermore, some dominant species have converted to the species typically found in the eutrophicated environment. The number of species tolerant to pollution has increased also. However, the plankton biodiversity does not fully coincide with trophic levels. The water quality based on physicochemical parameters were ranked as either category I or II, while the comprehensive trophic state index of all springs has raised gradually. And most springs has been polluted in middle -heavy eutrophication level. Result from Redundancy analysis showed that phytoplankton communities were significantly related to water temperature (WT), pH, nitrite nitrogen (NO^-₂-N), total phosphorus and nitrate nitrogen. The main environmental factors affecting the zooplankton community structure were WT, NO^-₂-N, ammonia nitrogen and chlorophyll-a. The plankton has responded to changes of the major water environmental factors. We suggest that water quality evaluation of karst spring should be combined with the physicochemical parameters and biological indicators. Multiple indexes could more comprehensively reflect the health state of water. Lastly, in order to develop groundwater sustainably, it is suggested to divide spring protection areas for important springs, take measures to prevent springs from being polluted, and reasonably manage and develop groundwater resources. Ecological restoration should be conducted for the damaged aquatic ecosystem as soon as possible.

English

The untreated disposal of wastewater in the coastal environment leads to growth of harmful algal blooms which risks the coastal ecology and human health. The harmful algal bloom can destroy aquatic natural life by reducing dissolved oxygen concentration. This study aimed to evaluate the eutrophication status at the Boseong county, Beolgyo village estuary, considering different water quality parameters. Furthermore, this study also investigated the effect of land use activates the estuarine water environment. The date of the acquisition for the Landsat 8 high-resolution satellite images were four different events i.e., 11th March, 2019, 15th June, 2019, 19th September, 2019, and 8 th December, 2019 in four different seasons such as Spring, Summer, Fall, and Winter respectively for selected study region. Land use and land cover were extracted on the basis of accuracy’s percentage and the Kappa coefficient. Concentrations of water quality parameters such as Chlorophyll-a (Chla), Total Phosphorous (TP), Transparency of Sechi Depth (TSD) were extracted using Carlson Trophic State Index (CTSI). The study found that the overall value of the CTSI is classified under the medium eutrophication state in summer and autumn season (CTSI~60-70). While it falls in the light eutrophic state in winter and spring seasons (CTSI~50-60). The value of TSI for all studied nutrients is the higher nearby cropping area as well as land settlements. The spatial variation of the trophic index in the study region aided strong evidence to be detected over the area’s adjutant to agrarian farming and urban habitats. The study concludes that the TSI could be used as a simple management tool to classify individual water ecosystems into broad classification that represent their water quality health.

Seasonal dynamics of phytoplankton and its relationship with environmental factors in Lake Hulun

为探究呼伦湖浮游植物群落的季节变化特征及其与环境因子的关系，本研究分别于2019年3、5—10月对呼伦湖浮游植物的种类、细胞密度和生物量及湖水水质进行调查.结果显示，共鉴定出120种浮游植物，隶属于7门72属.从浮游植物群落季节组成差异上来看，春季绿藻门种类数最多，其次是硅藻门、蓝藻门；夏秋季绿藻门种类数最多，蓝藻门次之；冬季硅藻门种类数最多，绿藻门次之.呼伦湖浮游植物优势种主要为硅藻门的梅尼小环藻（Cyclotella meneghiniana）、蓝藻门的卷曲长孢藻（Anabaena circinalis）和细小平裂藻（Merismopedia minima），种类数在春季最多，秋冬季最少.浮游植物细胞密度在春季（123.52×10⁴ cells/L）和冬季（16.41×10⁴ cells/L）较夏季（280.80×10⁴ cells/L）和秋季（380.63×10⁴ cells/L）低，春冬季绿藻门细胞密度最高，夏秋季蓝藻门细胞密度最高.就浮游植物生物量而言，夏季（0.38 mg/L）最大，其次是秋季（0.26 mg/L）和春季（0.24 mg/L），冬季（0.13 mg/L）最小.香农-威纳（Shannon-Wiener）多样性指数、均匀度指数和综合营养状态指数均表明呼伦湖水体处于中营养状态.冗余分析（RDA）表明：水温、叶绿素a、pH和营养盐浓度是影响呼伦湖浮游植物群落分布的主要环境因子.;To understand the phytoplankton community characteristics and its relationships with environmental factors, we investigated the species, abundance and biomass of phytoplankton and environmental factors at eight sampling sites in Lake Hulun during March and from May to October of 2019. The results showed that:A total of 120 phytoplankton species were identified, belonging to 7 plyla and 72 genera. In terms of the seasonal composition of the phytoplankton community, Chlorophyta was the dominant groups in spring, followed by Bacillariophyta and Cyanophyta. The number of Chlorophyta was the largest in summer and autumn, followed by Cyanophyta. Bacillariophyta was the dominant group in winter, followed by Chlorophyta. The dominant species of phytoplankton in Lake Hulun were Cyclotella meneghiniana of Bacillariophyta, Anabaena circinalis and Merismopedia minima of Cyanophyta. The number of the dominant species was the most in spring and the least in autumn and winter. The phytoplankton abundance in spring (123.52×10⁴ cells/L) and winter (16.41×10⁴ cells/L) was lower than that in summer (280.80×10⁴ cells/L) and autumn (380.63×10⁴ cells/L). The abundance of Chlorophyta was the highest in spring and winter, and the abundance of Cyanophyta was the highest in summer and autumn. In terms of phytoplankton biomass, summer (0.38 mg/L) had the largest, followed by autumn (0.26 mg/L) and spring (0.24 mg/L), and winter (0.13 mg/L) had the smallest. Shannon-Wiener diversity index, evenness index J and comprehensive trophic state index all indicated that Lake Hulun was in mesotrophic condition. Redundancy analysis of phytoplankton abundance and water environmental factors showed that water temperature, chlorophyll-a, pH and nitrogen and phosphorus nutrients were the main environmental factors that affected the distribution of the phytoplankton community in Lake Hulun.

Avaliação trófica de quatro reservatórios tropicais usando gêneros fitoplanctônicos

Abstract: Aim Monitoring the trophic state of reservoirs requires indices that provide a quick report of the ecosystem to decision makers. This study aimed to develop a system of trophic status indicators for tropical mountain reservoirs using phytoplankton genera. Methods Between 2004 and 2010, four reservoirs for water supply in Bogotá (Colombia), which have different trophic statuses and hydraulic management, were monitored. Samples were collected for the analysis of physical and chemical variables and phytoplankton community. Through multivariate analysis, the significance of the relationships between environmental variables and phytoplankton species and genera was established. Subsequently, trophic indices were proposed as relevant variables. The global trophic index was calculated as the sum of the partial indices. Results Analysis of the main components showed that reservoirs varied chemically depending on trophic status. Phytoplankton were composed of 63 genera, 59% of which were present in the four reservoirs. Although the physical characteristics of water, such as temperature and total solids content, explained a large part of the variation in the genera, a significant relationship between the genera and variables related to trophic state was observed in each reservoir. The multivariate analyses grouping the data by genera showed a behavior similar to the analysis using information at the species level. Plankton indices of trophic state were developed for phosphorus (TP), total Kjeldahl nitrogen (TKN), total organic carbon (TOC), and Secchi disk (SD) using data grouped by genera. The indices were significantly correlated with the values of each variable in each reservoir. Linear regression models showed a significant prediction of chlorophyll-a using TP, TKN, and SD indices in the three reservoirs with the highest trophic level. In addition, the global index showed a significant relationship with variables related to the trophic state. Conclusions Phytoplankton data at the genus level can be used to assess trophic status. The models for SD, TP, and TKN could be used as indicators of the trophic status of the studied reservoirs.

Water Quality Assessment and Eutrophic Classification of Hanoi Lakes Using Different Indices

The trophic levels in urban lakes are typically based on the forms of nutrition and phytoplankton communities in the lakes. In this study, comparisons between eutrophication indices and the water quality index (VN-WQI) were used to classify the water quality of 20 lakes in Hanoi, Vietnam. The results showed that the water quality ranged from very bad to poor. High levels of the eutrophication phenomenon in terms of total N and P were observed in all sampling sites. Cyanobacteria was the dominate algae phylum making up 65.78% of the total population, whereas Chlorophyta (including 19 genera) was the most diverse phylum. The density of the algae was 5,000-14,000 cells mL-1 and the chlorophyll-a level was 10-40 µg L-1. Based on this information, the water quality levels in the lakes were classified from eutrophic to polytrophic. The Trophic Status Index (TSI) and Trophic Level Index (TLI) values ​​were 66.9-86.0 and 54.4-76.0 points, respectively, corresponding from eutrophic to extreme-trophic. Classifications based on algae community structure indices were from oligotrophic to eutrophic, similar and consistent with the TLI classifications. According to the results in this study, the TLI was found to be more accurate and precise than the other indices. It is recommended that the TLI is an applicable tool to classify eutrophication in urban lakes.

The Trophic Status and Fish Potential Yield of Ayamaru Lake in West Papua, Indonesia

Ayamaru lake is a shallow lake located in the Maybrat district, West Papua which has a significant role in supporting the water supply, transportation, tourism, fisheries, and transit area for the migratory bird. The data and information of the trophic status and the fish potential yield in this lake should be understood before making any decisions for effective resource management to enhance fish production. The study was conducted in March and July 2019 in five sampling sites of Ayamaru lake, West Papua. Three water quality parameters were sampled for this study namely transparency, chlorophyll-a, and total phosphate. Moreover, these three parameters were used to calculate the Trophic State Index (TSI) and Fish Potential Yield. The result showed that based on the TSI value, the Ayamaru lake was categorized as a mesotrophic lake supported by its clear water. This waterbody has a fish potential yield of 56.33 kg/ha/year or 55.2 ton/year.

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.

Exploring the potential of small water bodies as an integrative management tool for fisheries production

AbstractUnderstanding the potential of small water bodies (SWBs) will open greater opportunities in investment towards increased food and energy production. This study established the carrying capacity for fisheries development in SWBs in eight counties in Central and seven counties in Western Kenya. The carrying capacity of SWBs was calculated using socio‐economic index (SI), trophic status index (TSI), and summaries of socio‐economic and limnological data from 74 SWBs. The central region had a potential of 72,447 t in 37 sampled SWBs, whereas that of the western region had only 447 t in a similar number of sampled sites that forms part of the total national aquaculture potential. The higher potential in the central region is attributed to the relatively larger hydroelectric dams located in the area. To boost production in SWBs with low carrying capacities, restocking with native endemic fish species, which require limited or no supplementary feeding, is recommended. However, in SWBs, where depths reach 3.0 m or more, which optimises on intensive feeding and good water circulation, cage culture reared fish coupled with a strong local community association would be recommended. The indexing holistic approach herein forms an integrative management tool for fisheries production.