Eutrophication Assessment Research Articles

Assessment of the Trophic Status and Trend Using the Transitional Water Eutrophication Assessment Method: A Case Study from Venice Lagoon

The Transitional Water Eutrophication Assessment Method (TWEAM) is a multi-index set up for assessing the eutrophication risk and trend in transitional waters. It includes a selection of environmental variables, an ecological status indicator (i.e., Macrophyte Quality Index, MaQI) and the Transitional Water Quality Index (TWQI). Possible outcomes of the TWEAM include three trophic classes in terms of eutrophication risk: (i) eutrophic; (ii) non-eutrophic; (iii) mesotrophic. The method was applied on data collected at 28 stations in the Venice Lagoon over four triennial monitoring cycles (MC I-IV) in the period 2011–2022. The spatial variability and medium-term trend of eutrophication risk were investigated, highlighting a general improvement in trophic conditions over time, with a decrease in mesotrophic stations (representing 46% of total in MC-I and 25% in MC-IV) in favor of non-eutrophic stations (46% of total in MC-I and 73% in MC-IV). The main driver of observed positive changes is related to the colonization of sensitive macroalgae and aquatic angiosperms, resulting in an increase in the percentage of stations with MaQI in good/high ecological status from 25% in MC-I to 54% in MC-IV. Eutrophic sites showed a non-linear trend, particularly in choked areas of the central lagoon, with anthropogenic disturbances and low water renewal.

Remote Sensing Evaluation of Trophic Status in the Daihai Lake Based on Fuzzy Classification

Trophic state index (TSI) is a critical ecological and environmental issue in water resource management that has garnered significant attention. Given the complexity of optical characteristics in aquatic environments, this study employs fuzzy classification methods (FCM) and composite nutrient status indices to meticulously classify in-situ remote sensing reflectance data, aiming to develop evaluation models for different nutrient status categories to facilitate the assessment of the Daihai River in Inner Mongolia, China. Subsequently, we applied this model to MSI data to analyze the nutrient status of Daihai Lake from 2016 to 2021. Furthermore, a structural equation model (SEM) was utilized to explore the primary driving factors influencing nutrient status. The results indicated that the water bodies in Daihai Lake can be broadly classified into three categories, with the nutrient status models demonstrating robust performance for each category (R2 = 0.80, R2 = 0.83, and R2 = 0.74). Comparisons were made between nutrient status accuracies obtained through the NCM and FCM based on measured data, yielding R2 values of 0.74 and 0.85, respectively. Furthermore, the TSI results derived from MSI inversion were validated, with NCM achieving an R2 of 0.49, RMSE of 6.88, and MAPE of 10.36%, while FCM exhibited an R2 of 0.55, RMSE of 8.89, and MAPE of 13.18%. An SEM–based analysis revealed that over the long term, human activities exerted a more substantial impact on eutrophication in Daihai Lake, while climatic factors played an accelerating and reinforcing role. These results are consistent with prior research in the Daihai area, indicating a state of mild eutrophication and the potential of the fuzzy classification method and comprehensive trophic status index method in eutrophication assessment.

Ecological Potential of Freshwater Dam Reservoirs Based on Fish Index, First Evaluation in Poland

A pilot ichthyological index was developed for use within the Water Framework Directive in the area of Central and Eastern Europe for dam reservoirs, which are heavily modified water bodies. This is the first approach to assessing this water body type based on ichthyofauna in Poland. Various fishing gear types were used. The tested dam reservoirs were scattered throughout the country, from lowland to mountainous areas, with very diverse hydrological and morphological characteristics and pressure ranges based on the TSI index. In preliminary work, a correlation matrix with the TSI index’s pressure indicator was tested based on the abundance or biomass of fish species, fish families present, fishing gear used, and fishing depth range for a total of 588 cases. As a result of the tests carried out, the preliminary indicator was based on the ratio of the number of the two families Cyprinidae and Percidae. The correlation between the developed indicator and the pressure index was strong (r = 0.77; p < 0.001). The Percidae family exhibited a strong correlation with the most connections in the matrix. Based on the obtained results, the principle of using already confirmed relationships, such as the ratio between Cyprinidae and Percidae fish families, in the assessment of eutrophication was confirmed to be effective, guaranteeing the effective initial assessment of ecological potential.

Case study: Nutrients distribution and assessment of the current trophic status of Plastiras lake in Thessaly (central Greece) after tropical storm Daniel

Based on the interactions of three water quality variables, chlorophyll-a (Chl-a), secchi depth (SD – water transparency) and total phosphorus (TP), this study was aimed to assess the trophic state of Plastiras Lake through the modified method of Carlson's trophic state index (CTSI). Eutrophication is one of the most serious problems for water quality and CTSI is an important index for monitoring water quality status and eutrophication assessment. The classification scale for Trophic State Index (TSI) fluctuates from 0 to 100 and the results of this study showed that the mean TSI for Chl-a was 42.95, for SD was 45.50 and for TP was 75.15. The overall CTSI finally was 54.53. These show that Plastiras Lake is presently classified as mesotrophic to eutrophic which reflects the current levels of nutrients in the lake.

Comprehensive Assessment of Eutrophication and the Mechanisms Driving Phytoplankton Blooms in Multifunctional Reservoirs

Comprehensive Assessment of Eutrophication and the Mechanisms Driving Phytoplankton Blooms in Multifunctional Reservoirs

Black Sea Eutrophication Comparative Analysis of Intensity between Coastal and Offshore Waters

Eutrophication, driven by excessive nutrient enrichment from sources like agricultural runoff, industrial discharge, and urbanisation, has severely impacted the Black Sea since the 1980s. This study aimed to assess eutrophication dynamics in the Romanian Exclusive Economic Zone from 2020 to 2022 using the Black Sea Eutrophication Assessment Tool (BEAST), an integrated approach to the causes and effects of eutrophication. Data were collected from 68 stations during five oceanographic expeditions, analysing 617 water samples for nutrients, chlorophyll a, zooplankton species Noctiluca scintillans, and dissolved oxygen. Additionally, 179 zoobenthic and 251 phytobenthic community samples were collected. The results indicate that coastal waters exhibit higher nutrient levels and algal blooms compared to offshore waters, necessitating significant reductions in nutrient concentrations to achieve good environmental status. In transitional waters, within the Danube Delta Biosphere Reserve, a 55% reduction in inorganic phosphorus and a 43% reduction in inorganic nitrogen concentrations are required, while coastal waters need reductions of 38% and 37%, respectively. The study highlights the need for improved wastewater treatment, stricter agricultural runoff controls, and continuous monitoring. Effective ecosystem-based management strategies, integrated coastal zone management, and international cooperation are essential to mitigate eutrophication and promote the long-term health of the Black Sea ecosystem.

Assessment of the eutrophication status at Mediterranean sub-basin scale, within the European Marine Strategy Framework Directive

The aim of this work is to define harmonized reference conditions and assessment thresholds for selected criteria elements of the Marine Strategy Framework Directive (MSFD) Descriptor 5 (Eutrophication) in the Eastern Mediterranean Sea and to test if a tool for integrated assessment of the status of marine systems can be used as a common methodological approach. In this frame, we tested two statistical approaches in order to set threshold values for four criteria of Descriptor 5: nutrients, chlorophyll a, transparency and dissolved oxygen in the bottom waters. It is noteworthy that this work revealed the need to apply common procedures in data treatment and assessment evaluation. This is the first attempt to set common methods for the assessment of eutrophication in the Eastern Mediterranean, which is essential in marine environments, especially those shared by several countries. To this end, we have applied common criteria and metrics and established thresholds “Good” and “Moderate” for nutrients, chlorophyll a, transparency and dissolved oxygen in the bottom waters for the different Water Types of the Adriatic and Aegean Seas (I, II, IIIW, IIIE), based on datasets provided by Italy, Slovenia, Croatia and Greece. The selected criteria elements were common for all countries, providing a unified approach to GES assessment of two case study areas: the Adriatic Sea and the Saronikos Gulf. Dissolved Inorganic Nitrogen (DIN) threshold values of 15.6, 6.85, 1.61 and 2.11 μmol L−1 were set for the Water Types I, II, IIIW and IIIE, respectively.We also tested if an aggregation tool for GES assessment, such as Nested Environmental status Assessment Tool (NEAT), could be used as a common methodological approach. The comparison of NEAT with TRIX showed good comparability. In this end, NEAT can be used as a useful and much needed assessment tool for assessing eutrophication status of the marine.

Enabling comprehensive assessment of marine eutrophication impacts and their evaluation against regional safe operating space

PurposeNitrogen emissions from human activities are contributing to elevated levels of eutrophication in coastal ecosystems. Mechanisms involved in marine eutrophication show strong geographical variation. Existing life cycle impact assessment (LCIA) and absolute environmental sustainability assessment (AESA) methods for marine eutrophication do not adequately represent this variability, do not have a full global coverage, and suffer from other limitations, such as poor estimation of coastal residence times. This study aims to advance LCIA and AESA for marine eutrophication.MethodsWe aligned and combined recent advancements in marine eutrophication LCIA and AESA methods into one method. By re-running models underlying the combined methods and incorporating additional data sources, we included marine regions missing in previous methods and improved fate modeling, with the inclusion of denitrification and plant uptake in the air emission-terrestrial deposition pathway. To demonstrate and validate our method, we applied it in a case study.ResultsThe developed method allows the assessment of marine eutrophication impacts from emissions to soil, freshwater, and air at high resolution (0.083° and 2° × 2.5° for inland and air emissions, respectively) and spatial coverage (all ice-free global continents). In the case study, we demonstrate the added value of our method by showing that the now quantified spatial variability within spatial units, e.g., river basins, can be large and have a strong influence on the modeled marine eutrophication from the case study. Compared to existing methods, our method identifies larger occupations of safe operating space for marine eutrophication, mainly due to the high resolution of the coastal compartment, reflecting a more realistic areal extent of marine eutrophication impacts.ConclusionsAlthough limited by factors such as simulations based on a single reference year for modeling inland and air fate, our method is readily applicable to assess the marine eutrophication impact of nitrogen emitted to any environmental compartment and relate it to the safe operating space. With substantial advancement of existing approaches, our method improves the basis for decision-making for managing nitrogen and reducing emissions to levels within the safe operating space.

An innovative method based on Gaussian cloud distribution and sample information richness for eutrophication assessment of Yangtze's lakes and reservoirs under uncertainty.

The precise assessment of a water body's eutrophication status is essential for making informed decisions in water environment management. However, conventional approaches frequently fail to consider the randomness, fuzziness, and inherent hidden information of water quality indicators. These would result in an unreliable assessment. An enhanced method was proposed for the eutrophication assessment under uncertainty in this study. The multi-dimension gaussian cloud distribution was introduced to capture the randomness and fuzziness. The Shannon entropy based on various sample size and trophic levels was proposed to maximize valuable information hidden in the datasets. Twenty-seven significant lakes and reservoirs located in the Yangtze River Basin were selected to demonstrate the proposed method. The sensitivity and consistency were used to evaluate the accuracy of the proposed method. Results indicate that the proposed method has the capability to effectively assess the eutrophication status of lakes and reservoirs under uncertainty and that it has a better sensitivity since it can identify more than 33-50% trophic levels compared to the traditional methods. Further scenario experiments analysis revealed that the sample information richness, i.e., sample size and the number of trophic levels is of great significance to the accuracy/robustness of the method. Moreover, a sample size of 60 can offer the most favorable balance between accuracy/robustness and the monitoring expenses. These findings are crucial to optimizing the eutrophication assessment.

Comprehensive assessment of eutrophication in Tangxun Lake, a large urban lake in the middle reaches of the Yangtze River

Urban lakes play an important role in supporting the ecological environment and human society, yet increasing pollution poses a threat to water quality. Tangxun Lake, a typical Large urban lake in the middle reaches of the Yangtze River, has experienced cultural eutrophication in recent years; however, few studies have comprehensively examined the water quality of this lake. Therefore, we aimed to evaluate the water quality of the Tangxun Lake Basin using the Nemerow pollution index, principal component analysis (PCA), phytoplankton density and diversity, and the comprehensive trophic level index (TLI). Additionally, we analyzed the main influencing factors to provide a reference for the management of the aquatic environment of Tangxun Lake. The Nemerow pollution index evaluation showed that the annual degree of pollution in Tangxun Lake ranged from mild to heavy. The PCA results showed that the main pollution factors affecting water quality were total phosphorus (TP) and total nitrogen (TN). According to the results of TLI, the water in Tangxun Lake was moderately to severely eutrophic. Evaluation of algal cell density showed that Tangxun Lake was mesotrophic, and the phytoplankton diversity index showed that the eutrophication level was high. The degree of pollution in Tangxun Lake varied seasonally and was in the order of spring > winter > summer > autumn. The pollution in inner Tangxun Lake was relatively serious in spring, summer, and autumn, whereas that in outer Tangxun Lake was more serious in winter. This study provides a scientific basis for the comprehensive management of the ecological environment in the Tangxun Lake Basin.

Assessment of eutrophication in the Berdan River Basin (Türkiye) using various classification tools

Assessment of eutrophication in the Berdan River Basin (Türkiye) using various classification tools

An integrated trophic state assessment of a Mediterranean lagoon (Lake Manzala, Egypt) using chemical and rotifer indices

Lake eutrophication assessment is a metric that can contribute to increasing the effectiveness of future management strategies to control and reduce lake eutrophication problems. Therefore, this study aims to conduct an integrated assessment of the environmental state of Lake Manzala through chemical and biological indices of the lake eutrophication state (Trophic state index, TSI). Chemical trophic indices generally classify Lake Manzala from mesotrophic to hypertrophic. However, based on the rotifer indices results, the lake ranged between mesotrophic to eutrophic. Results indicated a significant correlation (p < 0.05) between TSI(TN), TSI(TP), TSI (chem) and TSIROT abundance, and TSIROT wet-mass. Moreover, total phosphorus (TP) and total nitrogen (TN) were the most important parameters that influenced on the rotifers, particularly in the east-south sector. The species that had the highest positive correlation with TN and TP were Brachionus quadridentatus, Philodina roseola, Brachionus calyciflorus, Lecane bulla, Keratella cochlearis, and Filinia longiseta. Based on chemical and biological indices, the water quality and ecological status of the northern and middle regions of the lake have relatively improved compared to previous periods due to the dredging and cleansing process that has been ongoing since 2017.

Geotechnologies in the Assessment of Eutrophication in the Barra Bonita Reservoir, São Paulo, Brazil

Objective: The objective of this study was to identify locations with higher eutrophication and, consequently, susceptible to the emergence of macrophytes in the Barra Bonita reservoir, SP. Theoretical background: The presence of macrophytes, such as Eichhornia crassipes, is influenced by ecological succession driven by human activities like introducing exotic species and discharging untreated nutrients. Effective management, including buffer zones, is suggested to reduce eutrophication, though some studies question their effectiveness on a large scale. Method: The analysis of the Normalized Difference Vegetation Index (NDVI) was conducted using remote sensing images obtained from Landsat 8 and 9 satellites. As a criterion for data acquisition, corresponding data for the study region were obtained over a one-year temporal scale with a maximum cloud cover of 0%. Results and conclusion: Analyzing the images, it is observable that the month of June 2023 exhibited areas with a higher vegetation index and, consequently, eutrophication processes. This trend gradually decreased in the months of August, September, and November. Research implications: The analysis of satellite images revealed specific patterns of eutrophication, suggesting a direct correlation between the geographical distribution of nutrients and the potential proliferation of macrophytes. Additionally, comparative studies of nutrient concentrations in tributaries indicate that urban pollution, besides affecting local water quality, contributed to eutrophication in the Barra Bonita reservoir. Originality/value: Through the NDVI, the eutrophication possibility in Barra Bonita’s Reservoir was evidentiated.

Water environmental capacity analysis and eutrophication assessment of water-supplied reservoirs

The protection of water quality in reservoirs, particularly those designated for water supply, has garnered increasing attention for environmental management purposes. In this paper, the Shuangxikou Reservoir in Yuyao was chosen as a case study. The pollutant load at various points within the reservoir was analyzed and its eutrophication level was evaluated through a combination of site surveys and regular monitoring. Additionally, a model trial algorithm was utilized to investigate the water environment capacity concerning key pollutant indicators such as COD, NH3-N, TN, and TP in Shuangxikou Reservoir. The results indicated that the nutrient level in Shuangxikou Reservoir fell within the mid-trophic range, with water quality being superior in the central region compared to other areas. However, when compared to the water quality target of Class II surface water mandated by water environment functional zoning, the current TN and TP content in the reservoir exceeds acceptable levels. Consequently, targeted measures are imperative to enhance water quality in the reservoir.

A first ecological coherent assessment of eutrophication across the North-East Atlantic waters (2015–2020)

This paper presents the outcomes of the fourth application of the Common Procedure for the Identification of the Eutrophication Status of the OSPAR Maritime Area (the “Common Procedure”), conducted for the period 2015–2020 for the North East Atlantic. Previously, OSPAR has assessed eutrophication based on national assessment areas and disparate approaches lacking a transparent and comparable basis. A more harmonized approach has now been achieved through development of ecologically relevant assessment areas defined by oceanographic criteria rather than international boundaries, allowing for consistent assessments across exclusive economic zones and acknowledging that eutrophication is a transboundary problem. Thresholds that were specific for those harmonized assessment areas and eutrophication parameters have been derived primarily from an ensemble modeling approach to determine pre-eutrophic conditions. Common assessment areas and harmonized thresholds have enabled, for the first time, an objective and comparable assessment of the eutrophication status of the whole OSPAR Maritime Area. This establishes a level playing field for managing eutrophication and a solid basis for deriving OSPAR nutrient reduction targets as a prerequisite for targeted and successful regional eutrophication management. This assessment shows that eutrophication problem areas persist, in particular along the continental coasts from France to Denmark/Sweden and in the Greater North Sea and the Bay of Biscay and Iberian coast. The main areas affected by eutrophication are the plumes and adjacent coastal areas in the Greater North Sea and Bay of Biscay/Iberian Coast, with riverine nutrient inputs remaining the major source of nutrient pollution. Approximately 6% (152,904 km2) of the OSPAR Maritime Area is eutrophic, with the impacted area supporting many important ecosystem services. Fifty-eight percent of river plume areas (eight assessment areas out of 14), 22% (five of 27) of the coastal areas and 10% (three of 17) of the shelf areas were classified as problem areas. Application of the current assessment process to historical data from the previous three OSPAR assessment periods shows a gradual improvement since 2000. However, the OSPAR 2010 objective “to combat eutrophication, with the ultimate aim of achieving and maintaining a healthy marine environment where anthropogenic eutrophication does not occur” has not yet been fully achieved. Further measures to reduce nutrient loads are needed to ensure long-term sustainability of our coastal waters.

Assessment of Eutrophication Using Trophic State Index and Water Quality Characteristics of Saemangeum Lake

Assessment of Eutrophication Using Trophic State Index and Water Quality Characteristics of Saemangeum Lake

Effect of submarine groundwater discharge on nutrient distribution and eutrophication in Liaodong Bay, China

Driven by the anthropogenic activities associated with coastal settlements, eutrophication has become a global issue. Submarine groundwater discharge (SGD) is a significant continuous pathway for transporting nutrients from land to coastal waters, but its influence on eutrophication in Liaodong Bay (LDB) has received limited attention. In this study, radium isotopes and nutrient data from coastal waters were analyzed to evaluate the SGD flux and its implications for potential eutrophication in LDB. We found that the mean concentrations of dissolved inorganic nitrogen (DIN), phosphorous (DIP), and silicate (DSi) in groundwater were higher than those of seawater and river water. Based on 223Ra and 228Ra mass balance models, the SGD fluxes were estimated to be (0.53–2.03) × 109 m3/d, of which the fresh SGD accounted for 4 %–15 %. SGD is a vital invisible source of nutrients, contributing more than 79 % of the total inputs of DIN, DIP, and DSi into LDB. With high DIN/DIP ratios (average=85.8) and large nutrient inputs, SGD may significantly drive the phosphorus limitation and eutrophication in LDB. This study shows that SGD-derived nutrient fluxes should be considered in the assessment of water eutrophication for the formulation of future environmental management protocols in coastal systems.

Seasonal assessment of water quality and eutrophication of the Tucuruí Hydroelectric plant reservoir, Pará, Brazil

No represamento de um rio, a hidrologia local sofre mudanças nas condições físico-químicas e biológica do meio aquático, podendo gerar significativos impactos ambientais. Dessa forma, este estudo teve por objetivo avaliar a qualidade da água do reservatório da Usina Hidrelétrica de Tucuruí (UHT) localizada no estado do Pará, a partir da utilização do Índice de Qualidade da Água (IQA) e do Índice de Estado Trófico (IET). A coleta de dados foi realizada no banco de dados da Secretaria de Meio Ambiente e Sustentabilidade do Estado do Pará. Os dados foram coletados para o ano de 2022, em dois períodos distintos, chuvoso e seco. Os dados foram analisados por meio de estatística descritiva e posterior elaboração de gráficos e tabelas, teste não paramétrico de Wilcoxon e interpolação espacial. A análise dos dados permitiu a elaboração de mapas com a identificação do nível de qualidade e trofia dos pontos de monitoramento a montante, a jusante e do reservatório da UHT. Os resultados indicaram que o IQA determinado nos dois períodos analisados (chuvoso e seco) apresentou maiores valores nos pontos amostrais dentro do reservatório e o menor valor no ponto a montante. O ambiente pode ser classificado como oligotrófico, caracterizado pela pobreza em nutrientes e por uma baixa taxa de produção de matéria orgânica.

Integrated assessment of eutrophication in the southern Black Sea waters, using the Nested Environmental Status Assessment Tool

This research deals with the land-based pressures on the southern Black Sea coast (Turkey), with the objective of assessing their eutrophication impacts. In this context, reference values of some of the eutrophication indicators were calculated, and eutrophication assessment was carried out for this area using the holistic approach NEAT (Nested Environmental Status Assessment Tool). In addition, correlations between NEAT results of coastal regions and pressure-impact analysis methods were investigated. In the determined Spatial Assessment Unit (SAU) areas, 9 indicators were evaluated according to the SAU surface, both with and without weighting by their size the overall assessment of the Turkish Black Sea coast is good (0.70) and moderate (0.57) environmental status, for non-weighting and weighting by SAUs, respectively, with a high confidence level. With this study, we concluded that the sensitivity of the assessment tool needs to be increased. Despite these results, an appropriate number of indicators to represent the water column should be added. It is important to include the phytoplankton variable in the evaluation in future studies. In addition, this study, which uses NEAT allows identifying problematic environmental areas that require attention and action from managers and policymakers.

Assessment of old eutrophication in the sediments of Marchica Lagoon (a post-restored lagoon, Mediterranean): The role of geochemistry and granulometry of the sediments

Assessment of old eutrophication in the sediments of Marchica Lagoon (a post-restored lagoon, Mediterranean): The role of geochemistry and granulometry of the sediments