Trophic State Index Research Articles

Seasonal Dynamics and Environmental Drivers of Phytoplankton in the Albufera Coastal Lagoon (Valencia, Spain)

The Albufera of Valencia is a hypereutrophic, oligohaline lagoon that has experienced significant changes in phytoplankton composition and state in recent decades due to human activities. These activities affect phytoplankton biomass and community structure, which are key indicators of ecosystem health. In this study, phytoplankton samples from the lagoon were analyzed to identify dominant groups and genera, and their seasonal cycles were determined using biovolume measurements with the Utermöhl method. Various environmental variables were also measured. Diversity was assessed using richness, equitability, and the Shannon–Wiener index. Canonical Correspondence Analysis (CCA) and Pearson correlation revealed that temperature and phosphorus significantly influence phytoplankton abundance. A species that exhibited seasonal abundance, resulting in a change in the lagoon’s color from green to brown, was identified. Water quality was assessed using the trophic state index, indicating that the lagoon is in poor condition and hyper-eutrophic. Cyanobacteria were the most dominant group, peaking in November, contrary to previous studies, followed by Chlorophyceae and Bacillariophyceae. Phytoplankton are vital bioindicators for assessing ecosystem health, underscoring the need for further research in this area.

Monitoring of Temporal and Spatial Variation of Water Quality in Agricultural Reservoir During Summer

ABSTRACTThis study investigated the spatiotemporal dynamics of water quality in a small‐scale agricultural reservoir, the Bangok Reservoir, during the summer. The study is motivated by the increasing importance of preserving river ecosystems, ensuring irrigation water quality and expanding agricultural water use. Seven water quality parameters were monitored at multiple points from July to October 2020, and Spearman correlation analysis was conducted to understand their spatial relationships. The results revealed that the Bangok Reservoir had reached a hypertrophic state, indicating excessive nutrient levels. While heavy rainfall and dilution effects posed challenges for accurate analysis, significant correlations were observed between chlorophyll‐a and total phosphorus, as well as between dissolved oxygen and pH. The trophic state index of Korea (TSIKO) indicated conditions favourable for algal growth due to phosphorus abundance. Higher concentrations of pollutants were found upstream, which was likely attributed to the inflow of livestock manure during rainfall and shallow water mixing. The study recommends the implementation of algae removal and reduction facilities in the upstream areas of the reservoir. These findings provide essential data for ongoing research on water quality in small‐scale agricultural reservoirs and emphasize the importance of continuous monitoring for better environmental management.

Water quality and eutrophication status of the Zarivar Wetland (Iran)

Wetlands are critically impacted by a variety of pollutants, primarily due to their position at the terminus of both surface and subsurface water flows. This study aims to assess the eutrophication status of Zarivar Wetland, situated in Kurdistan Province, Iran. To evaluate the eutrophication levels, the research employed the Iranian Water Quality Index for Surface Water Resources-Conventional Parameters (IRWQISC) and the Carlson’s Trophic State Index (TSI) during two sampling periods in July and September 2021. The findings indicate that in July, the wetland exhibited an upper-mesotrophic condition, with an average Carlson index value of 52.2, while in September, it transitioned to both upper-mesotrophic and eutrophic conditions, reflected by an average Carlson index value of 60.17. The zoned map of the eutrophication index identified domestic sewage from Marivan city as a significant contributor to elevated eutrophication levels in the southeastern region. Additionally, runoff from irrigated agricultural lands, orchards, and domestic wastewater from surrounding villages contributed to heightened eutrophication in the northeastern and eastern areas of the wetland. A comparative analysis of water quality between July and September 2021 revealed IRWQISC values ranging from 3.57 to 9.72 in July and from 2.63 to 4.72 in September, categorizing them as relatively good and good, respectively. To safeguard Zarivar Wetland, it is recommended to implement measures that prevent livestock waste discharge into the wetland, manage urban and rural sewage systems, control agricultural runoff, and optimize fertilizer application practices.

Evaluation of the primary production and maximum fish production in Salman Farsi Reservoir, Fars Province, Iran

Primary production in water bodies corresponds to their fish production capacity. Aquaculture planning for water resources is conducted based on specific geographical conditions and their internal and external factors. Understanding the fish production capacity of lakes enables predictions for exploitation (fishing) and restoration of reserves. This research aims to estimate the primary production of the Salman Farsi Reservoir, Fars Province, on the Ghare Aghaj River, to evaluate fish production capacity and plan aquaculture development. Sampling was conducted to measure dissolved oxygen, water temperature, pH, conductivity, transparency, total phosphorus, total nitrogen, and chlorophyll-a in three transversal sections along the side, surface, and deep areas of the open water, with three repetitions in four seasons during 2023 – 2024. Trophic conditions were estimated using Trophic Status Index (TSI) models. Total production of the lake was calculated using the Brämick-Lemke and Koeschel models, while fish production was calculated using the Brämick-Lemke and Downing models. The annual average of dissolved oxygen, transparency, electrical conductivity, pH, total phosphorus, total nitrogen, and chlorophyll-a concentration in the lake was 8.2 ppm, 4.1 meters, 1387 μS/cm, 8.3, 0.174 ppm, 4.50 ppm, and 1.38 ppm, respectively. The average TSI based on transparency, phosphorus, chlorophyll-a, and Carlson’s index was 40, 78, 33, and 50. The initial production size in the lake was estimated 292 gC.m-²y-1. Fish production capacity was calculated based on primary production at 39 Kg.ha-1.y-1 and based on phosphorus at 33 Kg.ha-1.y-1, with an average of 36 Kg.ha-1.y-1. Considering the 2000-hectare livable area for fish in the lake, the total fish production this year was estimated at 71.8 tons. Under current lake conditions, the allowable fishing size was estimated to be 7 to 11 tons of fish per year. Determining the production capacity and trophic level can help maximize exploitation while minimizing ecological impacts and potential risks associated with restocking and fishing, such as the introduction of excessive juvenile fish into the lake.

Geospatial Assessment of Trophic Status From a Dam Under Significant Agricultural Drainage at the Mid-Anatolia, Türkiye

The population of Anatolia is continuously growing and developing and it is under the deep influence of global warming. It is increasingly evident that more fresh water will be needed for drinking, irrigation and domestic use. This study aims to assess the water quality and trophic status of a dam (Bayramhacılı dam lake) under excessive agricultural irrigation threat using spatial and multivariate statistical analysis. In the study, the periodic changes in the eutrophic state of the dam lake were determined using global index categories, Carlson Trophic Status Index (CTSI = 66.7), Burns Trophic Level Index (BTLI = 6.4), and Shu Trophic State Index (STSI = 65.6). The two periodical averages of total phosphorus (TP), total nitrogen (TN), biological oxygen demand (BOD), (chemical oxygen demand (COD) and chlorophyll a (Chl_a) concentrations, which serve as an indicator of anthropogenic nutrient input, were determined to be 0.23, 31.28, 1.83, 8.99 and 48.1 µg/L, respectively. Trophic index distribution maps demonstrate that the dam’s surface water displays considerable alterations, particularly during the dry season. This evidence supports the implementation of a local management model that addresses the issue of eutrophication. It is therefore imperative that on-site measures are taken without delay.

Morpho-functional groups as an efficient tool for monitoring and management of the Billings reservoir (São Paulo, Brazil)

This research applied the Morphology-Based Functional Groups (MBFGs) combined with classical approaches, such as community descriptor species and phytoplankton classes in the Billings reservoir. This local is the largest freshwater reservoir in the metropolitan region of São Paulo that has around 22 million inhabitants. Two sampling stations differing in predominant uses were studied: Rio Grande, classified as mesotrophic, and Central Body, as super and hypereutrophic. The phytoplankton and limnological variables were collected over six months (n=12). The trophic state index was calculated using phosphorus concentrations. Three canonical correspondence analyses were calculated aiming to examine the effect of environmental variables on the phytoplankton structure from each classification method (descriptor species, classes, and MBFGs), identifying the influence of environmental variables (independent variables) on the abundance patterns of the phytoplankton community (dependent variables). The highest concentrations of chlorophyll a and phytoplankton density were recorded at the site with the highest concentrations of total phosphorous (average of 99.86 μg/L in Central Body). This site was also associated with the highest electrical conductivity, total dissolved solids, turbidity, and concentrations of total nitrogen and chlorophyll a. The main factors associated with phytoplankton distribution were the trophic state and the operational system. It was concluded that the phytoplankton approach through MBFG efficiently responds to fluctuations in the ecological attributes of phytoplankton, and because they are based on morphological features, MBFG reduces the complexity of identifying and classifying organisms at a specific level.

Limnological Characteristics of Inland, Glacial Lakes on the Horseshoe Island (Antarctica)

Antarctica is a continent with extreme climatic conditions, with many lakes and ponds with ecological status varying from ultra-oligotrophic to hypereutrophic. Horseshoe Island is situated in Marguerite Bay, in the western Antarctic Peninsula. In this research, we purpose to determine the limnological characteristics of four lakes on Horseshoe Island (Col 1, Col 2, Skua and Zano). Water samples were taken once (during the summer period) from one station in each of the lakes for chemical analysis. The Trophic State Index (TSI) was calculated based on Secchi depth, chlorophyll-a, and total phosphorus concentrations. Phytoplankton were sampled from the same stations, except for Lake Zano, because of the ice cover. Phytoplankton community indice (Q) was calculated. Total phosphorus concentration for Lake Col 1, Col 2, Skua and Zano were measured as 0.6, 0.65, 3.0, 4.6 mg/m3, respectively. Based on total phosphorus, these four lentic systems are oligotrophic. TSI values pointed out oligotrophy and mesotrophy in the lakes. Lake Skua was found to be excellent quality (0.59 mg/l) while Lake Col 1 (0.72 mg/l) and Lake Col 2 (0.68 mg/l) were found to be good quality according to total phytoplankton biomass. The ecological status of the lakes is prediction to be of medium quality based on cyanobacteria biomass. This may be due to the rapid increase of Cyanobacteria in the short summer period as well as nutrient enrichment. Based on the Q indice, Lake Skua (4.2) is of excellent quality, Lake Col 2 (4) is of good quality, and Lake Col 1 (2.73) is of moderate quality in ice-free period. Because these lakes are under stressors such as climatic pressure (duration of ice cover) and natural eutrophication processes, regular monitoring of the lakes on the Antarctic continent is recommended.

Assessing water quality and land use impact in the Itanhém River basin: a study between the cities of Teixeira de Freitas and Alcobaça, Bahia

ABSTRACT Land use and occupation play a crucial role in shaping the physical and chemical properties of water. Like this study aimed to analyze the water quality parameters of a stretch the Itanhém River and relate this quality with the land use and occupation . To this end, samples were collected from seven strategically chosen points,identifying the physical-chemical variables necessary to obtain the Water Quality Index (WQI), . The Florestal Forum database was applied to analyze land use. The results showed that the body of water studied obtained values of thermotolerant coliforms and total phosphorus higher than the maximum values, WQI values that ranged between bad and good, and the Trophic State Index (TSI), it was identified as hypereutrophic was characterized the presence of pastures (both dirty and clean). Therefore, adequate management of water resources at the local level is necessary, as are agricultural, forestry, and sanitation activities.

Assessment of ecological status of Damsa Dam (Nevşehir, Türkiye) using trophic classification indexes, geospatial and statistical techniques

In this study, the water quality and trophic status of Damsa reservoir were evaluated using spatial and multivariate statistical analysis. When the thematic spatial distribution maps created for each parameter were analysed, it was determined that the water quality of Damsa Dam was class I water (very good) in terms of temperature, pH and dissolved oxygen and class III water (moderate) in terms of total N concentration. In the study, the changes on eutrophic status were analysed by global index categorisations and it was determined that Carlson trophic status index was CTSI=66.6, Burns trophic level index was BTLI=6.2 and Shu trophic status index was STSI=64.7. The results showed that Damsa Reservoir can reach the limits of ‘eutrophic’ according to CTSI classification scale, ‘eutrophic’ according to STSI classification scale and ‘hypereutrophic’ according to TLI classification scale. For this reason, the water quality of Damsa reservoir should be monitored continuously in certain periods and necessary interventions should be made in case of pollution.

Rotifers as indicators of trophic state in small water bodies with different catchments (field vs. forest)

AbstractCurrent methods for assessing lake trophic status using zooplankton are well-established, but there is a lack of approaches for small, shallow water bodies. This study addresses the gap by analyzing rotifer communities across 100 ponds in different catchment areas (field and forest). We hypothesized that the Rotifer Trophic State Index (TSIROT) is an effective tool for assessing trophic state, yielding comparable results to the Carlson TSI index. We also proposed that variations in physical and chemical parameters would significantly affect rotifer composition, impacting the trophic state assessment. Field ponds, exposed to agricultural runoff, exhibited higher trophic states and a predominance of detritivorous species. In contrast, forest ponds, with extensive macrophyte coverage, maintained lower trophic states and supported diverse algivorous species, particularly of littoral and mesotrophic origin. This confirmed our hypothesis that catchment type strongly influences trophic state and rotifer communities. We demonstrated that rotifer traits—abundance, species diversity, habitat type preferences and proportions of eutrophic versus mesotrophic species—along with TSIROT, are effective in assessing water quality in ponds. Overall, the results validate TSIROT as a reliable tool for small water bodies, comparable to Carlson’s TSI index, and highlight the importance of catchment type in influencing water quality.

Assessment of water quality and trophic state using a multipara-metric index-based approach for Lake Guineo, Lake Carraizo and Lake Cidra, Puerto Rico

To ensure a safe drinking water supply, it is necessary to protect water quality. The proposed project aims to understand water quality data analyzed from a temporal and spatial perspective on the following physiochemical parameters: DO, pH, temperature, Secchi disc turbidity, conductivity, nitrate, chlorophyll α & phosphate. The results provide information to evaluate the status of the water quality and its suitability for human consumption. These variables related to the general characteristics of water quality and trophic level were used for calculation of a water quality index (WQI) and trophic state index (TSI) to assess 3 lakes in Puerto Rico: Lake Cidra, Lake Carraizo and Lake Guineo. Presence or absence of macrophytes were monitored during six months in the three reservoirs in Puerto Rico as well as the parameters mentioned above. The objective of this investigation is to discuss the trophic state and water quality in 3 different trophic state reservoirs in Puerto Rico. Results were correlated with the density of the macrophyte species, Eichhornia crassipes. Variations of water in situ multiparametric sampling were recorded for 6 months. Thus, integrating components that define the status of reservoirs using multiparameter measurements from various perspectives; a better diagnosis is expected regarding the water quality assessment. This investigation aims to undertake a comprehensive study of water quality by implementing the WQI and TSI indices, considering physical, chemical, and biological parameters with respect to eutrophication and ecological considerations for three reservoirs in the Puerto Rico, providing information regarding the quality of water and trophic state of the chosen reservoirs. Overall WQI results revealed that the water quality improved after the Hurricane Fiona’s occurrence. Trophic State Index after the hurricane showed slight fluctuations in the reservoirs.

Trophic status analysis and nutrient source allocation in urban lakes of Dhaka, Bangladesh: a comprehensive approach to eutrophication monitoring.

Urban lakes are vital to ecosystems, providing essential services and recreational spaces in densely populated megacities. However, rapid urbanization and anthropogenic activities, particularly eutrophication driven by macronutrient accumulation, severely threaten these water bodies. This study underscores the critical need for continuous trophic state monitoring to sustain fish, wildlife, and plant ecosystems. The trophic status of Dhanmondi, Gulshan, and Banani Lakes in Dhaka City, Bangladesh, was assessed using Carlson's Trophic State Index (CTSI) and Burn's Trophic Level Index (BTLI), based on chlorophyll a (Chl-a), total phosphorus (TP), Secchi disc depth (SD), and total nitrogen (TN). Water samples from five sites per lake were analyzed for physicochemical parameters from June 2023 to May 2024, revealing monthly and seasonal variations. The study revealed that Dhanmondi Lake's CTSI ranged from 69.3 to 79.5 (June 2023 to March 2024), indicating initial "Eutrophic" conditions progressing to "Hypereutrophic." Gulshan Lake consistently showed "Hypereutrophic" conditions, with CTSI values between 84.1 and 97.3. Banani Lake was "Eutrophic" in June and July 2023, transitioning to "Hypereutrophic" from August 2023 to May 2024 (84.1-97.7). The Trophic Level Index (TLI) showed the "Hypereutrophic" status with a progressive monthly escalation for all the lakes. The Water Quality Index (WQI) categorized the lakes as "Poor" to "Very Poor" from June to August 2023, becoming "Unsuitable" from September 2023 to May 2024, indicating significant anthropogenic stress. Principal component analysis (PCA) identified nutrient infiltration, soil erosion, waste discharge, and organic residue accumulation as key pollution drivers. The study advocates for a multi-sectoral strategy to regulate nutrient loading and mitigate eutrophication, emphasizing best management practices for urban lake conservation.

Biotic aspects of suspended solid reduction in sedimentation ponds

The reduction of suspended solids is an important aspect of water management, especially in the mining industry. The ecological potential of sedimentation ponds has been identified, but many aspects of the coexistence of ecological and technological functions of these reservoirs are still unresolved. The aim of the study was to determine the effectiveness of suspended solid reduction in an open pit mine drainage system under the influence of biotic factors, including fish, taking into account the hydrochemical background. The dynamics of biotic factors and the sedimentation process were identified using the normalized total suspended solid reduction index (TE) and the trophic group status (TGS) indices of planktivorous, benthivorous, and carnivorous fish. The hydrochemical background in both ponds provided similar habitat conditions for biota and suspended solid reduction. Although a moderately trophic ecosystem has developed, the typical relationship between water transparency (SDD) and chlorophyll a concentration characteristic of natural waters was not observed. The sedimentation complex was found to be highly effective in reducing total suspended solids by 89–93%. Spatial variation of sedimentation rates was related to the ichthyobiotic factor, mainly to the biomass of bentophages and the status of this trophic group in the fish community. Stable relationships in the structure of the ichthyofauna with a balanced proportion of planktivorous fishes favored the sedimentation process. The results obtained are part of the development of research on the possibility of combining the technological function of artificial ponds with other applications and ecological benefits for industrialized areas.

Particle-attached bacterial communities are more susceptible to seasonal environmental fluctuations in mesotrophic than eutrophic tropical reservoirs.

Particle-attached bacterial (PAB) communities play pivotal roles in water organic matter decomposition, nutrient cycling, and the natural self-purification processes. However, we know little about their responses to seasonal environmental fluctuations, under eutrophication in reservoir ecosystems. In this study, we studied the shifts of PAB communities to seasonal environmental fluctuations in tropical China. Trophic state index (TSI) indicated that the studied reservoirs ranged from mesotrophic to eutrophic state with a gradual increase in TSI from 31 to 58. In eutrophic reservoirs, Cyanobacteria, especially Raphidiopsis raciborskii, significantly increased in its relative abundance from wet to dry season, but Synechococcales and Microcystaceae decreased. In contrast, the relative abundance of Clostridia, Bacilli, Coriobacteriia, Enterobacteriales, and Vibrionales were more susceptible to seasonal environmental fluctuations in mesotrophic than eutrophic reservoirs. PAB co-occurrence relationships in mesotrophic reservoirs varied more greatly in response to seasonal environmental fluctuations, compared with eutrophic reservoirs, in terms of topological properties of connectedness, average degree, robustness and vulnerability. Our results further demonstrated that the seasonal stability of PAB co-occurrence relationships was strongly correlative with TSI through mediating key bacterial taxa and community biodiversity. We proposed that eutrophication dramatically reduced the seasonal variation of PAB community compositions and co-occurring relationships in reservoir ecosystems.

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.

Inter-annual variability in the phytoplankton abundance and community structure of a tropical monsoonal estuary in response to variable monsoonal patterns

The study elucidates the inter-annual and seasonal variability in the phytoplankton abundance and community structure concurrent to variable rainfall patterns in Chettuva, a tropical monsoonal estuary along the southwest coast of India. The phytoplankton community exhibited statistically significant inter-annual variation with a 1.2-fold increase in abundance (av. 19.44 ×104cellsL−1) in 2021 in comparison with 2019 (av. 15.30 ×104cellsL−1). A total of 87 phytoplankton species were observed during the study, among which Bacillariophyceae dominated with 52 species, followed by Dinophyceae (20 species), and to a lesser extent by Chlorophyceae (11 species) and Cyanophyceae (2 species). Phytoplankton community structure also showed variation, with 71 species contributing to the diversity in 2021 and 62 species in 2019. Though Bacillariophycea dominated during both years, the community was more diverse in 2021comparatively a more saline year Biddulphia sp. Coscinodiscus sp., Cyclotella striata, Melosira sulcata, Pleurosigma sp., and Skeletonema costatum were the diatoms common to both the years, though with varied abundance. Dinophyceae did not show a conspicuous change in community structure in both years, with mostly the same species contributing to the total phytoplankton population but showed slight variation in abundance. Cyanophycea was observed exclusively during the year 2021. The abundance and community structure of the species varied from year to year, but they also changed seasonally, with lower numbers observed during the monsoon compared to the post-monsoon period in both years. CCA analysis identified two groups of phytoplankton assemblages in relation to the prevailing environmental conditions. The Group I species preferred lower temperature and salinity and elevated nutrient concentrations and they dominated during the monsoon season. Group II species preferred high saline well oxygenated, nutrient-poor waters and they dominated during the post-monsoon. Furthermore, the trophic state index analysis indicated mesotrophic conditions during the monsoon, while eutrophic conditions were observed in the post-monsoon period.

The future of algal blooms in lakes globally is in our hands

Lakes are fundamental to society and nature, yet they are currently exposed to excessive nutrients and climate change, resulting in algal blooms. In the future, this may change, but how and where still needs more scientific attention. Here, we explore future trends in algal blooms in lakes globally for >3500 ‘representative lakes’ for the year 2050, considering the attribution of both nutrient and climate factors. We soft-coupled a process-based lake ecosystem model (PCLake+) with a watershed nutrient model (MARINA-Multi) to assess trends in algal blooms in terms of the Trophic State Index for chlorophyll-a (TSI-Chla). Globally between 2010 and 2050, we show a rising trend in algal blooms under fossil-fuelled development (TSI-Chla increase in 91 % of lakes) and a declining trend under sustainable development (TSI-Chla decrease in 63 % of lakes). These changes are significantly attributed to nutrients. While not always significant, climate change attributions point to being unfavourable for lakes in 2050, exacerbating lake water quality. Our study stresses prioritising responsible nutrient and climate management on policy agendas. This implies that the future of algal blooms in lakes is in our hands.

Classifying eutrophication spatio-temporal dynamics in river systems using deep learning technique

Eutrophication is a major cause of water quality degradation in South Korea, owing to severe algal blooms. To manage eutrophication, the South Korean government provided the Trophic State Index (TSIko), which was revised according to Carlson's TSI. The TSIko levels were simulated using mechanistic water quality modeling. However, the computational complexity of model parameter calibration and the nonlinearity of water quality kinetics complicate analyzing accurate eutrophication conditions. Deep learning models have been considered alternatives to numerical model approaches because they directly extract water quality variables without prior knowledge. In particular, the convolutional neural network (CNN) model showed robust feature extraction from the complex datasets. This study constructed and optimized a CNN model using water quality data from the Han, Guem, Yeongsan, and Nakdong Rivers in South Korea over nine years from 2014 to 2022 to classify the TSIko. The CNN model provided validation results using the statistical measurement of classification accuracy, known as the F1 score, which is the harmonic mean of precision and recall. The F1 scores were 0.922, 0.950, 0.964, and 0.896 for oligotrophic, mesotrophic, eutrophic, and hypertrophic statuses, respectively. The CNN model outperformed conventional machine learning models. Subsequently, a eutrophication map for the four major rivers was generated using the CNN model to simulate the spatial and temporal variations of the eutrophication index, mimicking high spatio-temporal eutrophic dynamics with respect to the mainstream and tributaries of the Yeongsan and Nakdong Rivers. Therefore, this study demonstrates the capability of the CNN model to analyze eutrophication conditions at various spatial and temporal scales of major rivers in South Korea.

Exploring the effects of climate change and urban policies on lake water quality using remote sensing and explainable artificial intelligence

Climate change and urban policies significantly impact lake water quality, especially in rapidly developing regions. Existing impact assessments are limited by the duration and resolution of water quality data, while long-term impacts and contributions of climate and socioeconomic drivers have rarely been quantified. In this study, we utilized remote sensing imagery to obtain high spatiotemporal resolution data and Explainable Artificial Intelligence (XAI) to reveal how the comprehensive impacts vary over time. We obtained Trophic State Index (TSI) data between 2000 and 2022 from remote sensing imagery. XAI was employed to elucidate the intricate connections between TSI and the multifaceted factors that encompass climate and socioeconomic dynamics. Six typical lakes in East China were selected for this study. Results showed that the TSI of these lakes had generally decreased over the past two decades, being typically higher in the littoral zones compared to the center. Moreover, higher temperatures increased lake TSI. Meanwhile, higher rainfall increased TSI through increased lake nutrient inputs from surrounding watersheds where agricultural and industrial activities are intensive. It was also found that economic development impacts on lake TSI shifted around 2013. Economic development caused severe negative effects on lake water quality before 2013, while this phenomenon decreased thereafter. This is attributed to the implementation of a series of green transformation policies in the region. This study demonstrates the long-term contribution of climate change and urban policies in driving lake water quality variations, and provides implications for policy makers to establish positive economic, social, and environmental linkages.

Long-term monitoring of water quality and phytoplankton community structure of Lake Manzala, Mediterranean Coast of Egypt

Coastal wetlands play a crucial role in supporting biodiversity, providing valuable ecosystem services, and contributing to the resilience of coastal ecosystems, making the preservation and restoration of these wetlands essential for sustainable development in coastal regions. This study focuses on Lake Manzala, a coastal wetland located on the Mediterranean Coast of Egypt, highlighting the significance of conserving and managing this unique environment. The objective of this research was to evaluate the water quality and phytoplankton structure of Lake Manzala and establish an updated long-term ecological database for the region, specifically evaluating the effectiveness of development plans that were carried out in 2017. Surface water samples were collected seasonally at eleven sites between 2010 to 2022. The findings revealed that prior to the development plans, the phytoplankton abundance in Lake Manzala exhibited high levels of eutrophication, characterized by increased abundance and species richness. The dominant phytoplankton classes in Lake Manzala were Bacillariophyceae, Chlorophyceae, and Cyanophyceae. Prior to development plans, they accounted for 46.5% and 45.0% respectively. Post-development, Bacillariophyceae increased to 62.8%, while Chlorophyceae decreased to 25.1%. Dinophyceae increased from 1.3% to 9.04%, while Cyanophyceae decreased from 6.1% to 1.6%. Based on the Trophic State Index for chlorophyll a, Lake Manzala underwent a shift from predominantly hypertrophic to eutrophic conditions. The study explored the relationship between biological factors and environmental conditions using principal component analysis, cluster analysis, and the modified water quality index (WQI). The results indicated positive signs of improvement in Lake Manzala during the post-development phase, as it transitioned from a poor to a moderate state. This research emphasizes the need for integrated land and water management approaches. By informing policy direction and development, this research underscores the importance of preserving and restoring ecosystems for the long-term well-being of both local communities and the global environment.