Determinação da Concentração de Clorofila-a por Sensoriamento Remoto no Reservatório de Chapéu d’Úvas (Mg), Brasil

Na atualidade, um grande impacto nos reservatórios de água doce é a eutrofização, que afeta diretamente o tratamento e uso da água para abastecimento público, navegação, fauna e flora aquática e impacto visual. A clorofila-a é um dos indicadores de estado trófico da água e pode ser determinada utilizando sensoriamento remoto. Desta forma, este estudo objetivou determinar a concentração de clorofila-a na barragem de Chapéu d’Uvas em Juiz de Fora (Brasil), um dos principais mananciais de abastecimento público da cidade. Através de um modelo utilizando imagens do satélite Sentinel-2 foi avaliado o comportamento espaço-temporal da concentração do componente, foi correlacionado com dados de pluviosidade, temperatura, evaporação e uso e ocupação do solo em torno da barragem. Também foi aplicado um modelo para determinar o índice de estado trófico, que apresenta o grau de trofia que o corpo hídrico se encontra, classificando Chapéu d’Uvas como estado mesotrófico. Os resultados se mostraram satisfatórios para a espacialização e análise temporal da concentração de clorofila-a, a correlação com os dados de evaporação nos permitiu observar uma compatibilidade direta com a concentração do componente e verificou-se valores de clorofila-a acima da média do reservatório nas regiões de entradas de água pelos riachos e próximos as margens com menos cobertura de vegetação.Determination of Chlorophyll-a Concentration from Remote Sensing in Chapéu d’Úvas Reservoir (State of Minas Gerais, Brazil) A B S T R A C TCurrently, one of the great impacts on the freshwater reservoirs is eutrophication, which directly affects the treatment and use of water for public water supply, navigation, aquatic fauna and flora and visual impact. Chlorophyll-a is one of the water trophic state indicators and it can be determined using remote sensing. Thus, this study aimed to determine chlorophyll-a concentration in Chapéu d’Uvas dam, in Juiz de Fora (Brazil), one of the main water sources of public water supply for the city. From a model that uses Sentinel-2 satellite images, the spatial-temporal behavior of that component concentration was evaluated and correlated with data regarding rainfall, temperature, evaporation, and soil use and occupation around the dam. A model was also applied to determine trophic state index, which presents the body of water trophic state, classifying Chapéu d’Uvas as mesotrophic state. The results were satisfactory regarding spatialization and temporal analysis of chlorophyll-a concentration. The correlation with evaporation data permitted us to observe a direct correspondence with the component concentration. Chlorophyll-a values higher than the reservoir average were found in creek inlets and near the shore with lower vegetal cover.Keywords: eutrophication, Sentinel-2, quality of water, inland waters, trophic state

Assessment of Water Quality Based on Trophic Status and Nutrients-Chlorophyll Empirical Models of Different Elevation Reservoirs

Water quality degradation is one of the most pressing environmental challenges in reservoirs around the world and makes the trophic status assessment of reservoirs essential for their restoration and sustainable use. The main aims of this study were to determine the spatial variations in water quality and trophic state of 204 South Korean reservoirs at different altitude levels. The results demonstrated mean total phosphorus (TP), chlorophyll-a (CHL-a), total suspended solids (TSS), organic matter indicators (chemical oxygen demand: COD; total organic carbon: TOC), water temperature (WT), and electrical conductivity (EC) remain consistently higher in the very lowland reservoirs (VLLR) than those in other altitudes, due to sedimentary or alluvial watersheds. The average TP and CHL-a levels in VLLR crossed the limit of the eutrophic water, symptomizing a moderate risk of cyanobacterial blooms. Empirical models were developed to identify critical variables controlling algal biomass and water clarity in reservoirs. The empirical analyses of all reservoir categories illustrated TP as a better predictor of CHL-a (R2 = 0.44, p < 0.01) than TN (R2 = 0.02, p < 0.05) as well as showed strong P-limitation based on TN:TP ratios. The algal productivity of VLLR (R2 = 0.61, p < 0.01) was limited by phosphorus, while highland reservoirs (HLR) were phosphorus (R2 = 0.23, p < 0.03) and light-limited (R2 = 0.31, p < 0.01). However, TSS showed a highly significant influence on water clarity compared to TP and algal CHL-a in all reservoirs. TP and TSS explained 47% and 34% of the variance in non-algal turbidity (NAT) in HLR. In contrast, the TP and TSS variances were 18% and 29% in midland reservoirs (MLR) and 32% and 20% in LLR. The trophic state index (TSI) of selected reservoirs varied between mesotrophic to eutrophic states as per TSI (TP), TSI (CHL-a), and TSI (SD). Mean TSI (CHL-a) indicated all reservoirs as eutrophic. Trophic state index deviation (TSID) assessment also complemented the phosphorus limitation characterized by the blue-green algae (BGA) domination in all reservoirs. Overall, reservoirs at varying altitudes reflect the multiplying impacts of anthropogenic factors on water quality, which can provide valuable insights into reservoir water quality management.

Trophic Status In Joto Reservoir, Lamongan

Waduk Joto merupakan waduk yang berada di Kabupaten Lamongan yang biasa digunakan oleh masyarakat sekitar untuk aktifitas sehari-hari. Selain itu aliran air waduk juga digunakan untuk kegiatan perikanan dan pertanian. Dalam pengelolaan suatu perairan yang lestari dan berkelanjutan diperlukan informasi dasar mengenai tingkat kesuburan perairan guna pemanfaatan yang tepat. Penelitian ini bertujuan untuk mengetahui kualitas air dan status kesuburan perairan di Waduk Joto Kabupaten Lamongan. Metode pengumpulan data menggunakan purposive random sampling pada tiga stasiun yaitu bagian inlet, tengah, dan outlet. Penentuan status kesuburan perairan berdasarkan perhitunganmenggunakan Carlson Trophic State Index (TSI). Pengambilan sampel air dilakukan dengan interval waktu satu bulan sekali selama 3 bulan pada bulan Desember 2020 sampai Februari 2021. Parameter yang diamati meliputi suhu, kecerahan, pH, salinitas, oksigen terlarut (DO), nitrat, total fosfat, klorofil-a. Hasil penelitian menunjukkan bahwa status kesuburan perairan Waduk Joto pada bulan Desember 2020 – Februari 2021 berdasarkan TSI Carlson termasuk dalam kategori perairan hipereutrofik dengan nilai sebesar 74. Disarankan untuk melakukan penelitian lanjutan pada musim yang berbeda untuk mengetahui status kesuburan perairan di musim kemarau.

Environmental Characterization of Two Ecologically Distinct Gangetic Oxbow Lakes Using Zooplankton Taxonomic Indices In Ecological Monitoring: A Comparative Approach

In recent years closed and seasonally open oxbow lakes and river floodplains are subjected to eutrophication due to disconnection from river that compromises the hydro-ecological functions. This requires systematic studies to assess the ecological health of the water bodies using different indices and suggest appropriate strategies to manage the resources. The zooplanktons are closely link with surrounding environment throughout their life cycles and change rapidly in their growth and population when changes occurs in the surrounding, hence act as potential indicator of eutrophication. The present study examined the assemblage pattern of zooplankton community and trophic state of two ecologically distinct oxbow lakes based on eco-hydrological characteristics and community structure of rotifers and planktonic crustaceans seasonally over a period of 2 years. Comprehensive trophic state index (mTSI), rotifer trophic state index (mTSIROT) and Crustacean based indices (TSICR) were used to assess the degree of eutrophication. The Kruskal-Wallis test confirmed the heterogeneity of the eco-hydrological factors between the oxbow lakes. A total of 68 zooplankton species were identified of which rotifers (69%), cladocerans (18%), copepods (3%), ostacods (3%) and protozoans (7%). Seasonal fluctuation of relative abundance and frequency of species in both lakes have been well presented. Both lakes showed transition from high meso-eutrophic to moderately eutrophic state with mTSI, mTSIrot and mTSIcr values of 54.90±11.71 and 56.95±15.64, 59.55±4.54 and 60.26±4.48, 55.79±4.76 and 60.00±4.03 in Khalsi (seasonally open) and Akaipur (closed) respectively. The Canonical Correspondence analysis (CCA) revealed water quality parameters comparison NO3-N, water temperature and pH have contributed more in enhancement of abundance of eutrophication indicator species Brachionus and Keratella. The TSIs values indicated a prompt aquaculture fisheries management measures like stocking of planktivorous fish (Labeo catla and Puntius sp.) for both the lakes before they reach in plunged state at which their restoration might become a challenge. An overview of worldwide use of rotifer and crustacean based indices in assessment of TSI has also been synthesized. The use of these zooplankton indices to evaluate the trophic status of the ecologically distinct lakes is highly recommended for water quality assessment and management. Based on this study strategies could be developed to plan and manage floodplain oxbow lakes for fisheries enhancement programme as well as as conservation of biodiversity.

Long-Term Water Quality Patterns in an Estuarine Reservoir and the Functional Changes in Relations of Trophic State Variables Depending on the Construction of Serial Weirs in Upstream Reaches

Water quality degradation is one of the major problems with artificial lakes in estuaries. Long-term spatiotemporal patterns of water quality in a South Korean estuarine reservoir were analyzed using seasonal datasets from 2002 to 2020, and some functional changes in relations of trophic state variables due to the construction of serial weirs in the upper river were also investigated. A total of 19 water quality parameters were used for the study, including indicators of organic matter, nutrients, suspended solids, water clarity, and fecal pollution. In addition, chlorophyll-a (CHL-a) was used to assess algal biomass. An empirical regression model, trophic state index deviation (TSID), and principal component analysis (PCA) were applied. Longitudinal fluctuations in nutrients, organic matter, sestonic CHL-a, and suspended solids were found along the axis of the riverine (Rz), transition (Tz), and lacustrine zones (Lz). The degradation of water quality was seasonally caused by resuspension of sediments, monsoon input due to rainfall inflow, and intensity of Asian monsoon, and was also related to intensive anthropic activities within the catchment. The empirical model and PCA showed that light availability was directly controlled by non-algal turbidity, which was a more important regulator of CHL-a than total nitrogen (TN) and total phosphorus (TP). The TSID supported our hypothesis on the non-algal turbidity. We also found that the construction of serial upper weirs influenced nutrient regime, TSS, CHL-a level, and trophic state in the estuarine reservoir, resulting in lower TP and TN but high CHL-a and high TN/TP ratios. The proportions of both dissolved color clay particles and blue-green algae in the TSID additionally increased. Overall, the long-term patterns of nutrients, suspended solids, and algal biomass changed due to seasonal runoff, turnover time, and reservoir zones along with anthropic impacts of the upper weir constructions, resulting in changes in trophic state variables and their mutual relations in the estuarine reservoir.

Controlling Eutrophication via Surface Aerators in Irregular-Shaped Urban Ponds

Surface aerators have often been introduced in urban ponds for esthetics, but their roles in remediating water quality are less understood. Effects of surface aerators on controlling eutrophication were examined in two urban ponds, in which anaerobic odors and cyanobacterial blooms had occurred and several aerators had been installed. In one of the ponds, a dramatic improvement in dissolved oxygen (DO) (from 1.8 to 8.1 mg L−1) and total phosphorus (TP) (from 1.6 to 0.4 mg L−1) was evident based on the comparison before and after the aeration. Although cyano-bloom did not occur, phytoplankton was dominated by cyanobacteria Microcystis species in both periods. Chlorophyll a (Chl-a) increased (from 29 to 51 μg L−1) and water transparency decreased (from 81 to 27 cm) after the aeration. In the other pond with an irregular shape, water quality was monitored two years after the installation to examine seasonal variation in trophic state and its spatial variation associated with aerator distribution. The water was mixed vertically well for the whole pond, as indicated by small surface-to-bottom differences in temperature. DO decreased in summer after rainfall but was always >5.7 mg L−1. Total nitrogen (TN) and TP were 0.8–2.3 and 0.03–0.07 mg L−1, respectively, and no cyano-blooms were observed across sites throughout the year. Phytoplankton was dominated by green algae and diatom species, which may be favored by the lower phosphorus level of the pond. Chl-a was higher and transparency was lower in the north side, which had more aerators and less shade from trees and buildings. These results suggest that surface aerators increased DO by vertical and horizontal mixing of water, reduced phosphorus release from sediment, and prevented cyano-bloom occurrence, but they did not improve Chl-a level and transparency. Rather, aeration can promote algal growth, and thus, additional purifying measures such as filtration and contact oxidation are required to further improve the trophic state of these ponds.

Spatiotemporal Variation on Water Quality and Trophic State of a Tropical Urban Reservoir: A Case Study of the Lake Paranoá-DF, Brazil

Nutrient enrichment and eutrophication are among the main problems that lead to the deterioration of water quality in lakes and reservoirs. In this study, spatial and temporal variations in the concentrations of organic and inorganic species of nitrogen and phosphorus in the water column of Lake Paranoá-DF (Brazil) were evaluated between 2016 and 2017. Seasonality was the main factor in the variations in concentrations of the investigated parameters. Additionally, we found differences in behavior for different nutrients and other variables that indicate different main sources of each nutrient as well as different biogeochemical processes predominating in each season. For example, the electrical conductivity (EC), dissolved silicon, PO43−, and NO3− showed mean concentrations significantly higher in the rainy season, indicating greater inputs in these periods (which is in part related to increasing soil leaching and runoff). Agricultural activities were the main source of NO3− and wastewater treatment plants (WWTP) proved to be the main source of nutrients, mainly NH4+ and all forms of phosphorus. These two allochthonous sources are also the determining factors of the trophic state and the degradation of the water quality of Lake Paranoá. The lake is in the transition process from a mesotrophic to a eutrophic condition.

Analysis of Factors Influencing the Trophic State of Drinking Water Reservoirs in Taiwan

Eutrophication is an environmental pollution problem that occurs in natural water bodies. Regression analyses with interaction terms are carried out to identify the factors influencing the Shimen, Mingde, and Fongshan Reservoirs in Taiwan. The results indicate that the main factor influencing these reservoirs is total phosphorus. In the Shimen and Mingde Reservoirs, the influence of total phosphorus, when interacting with other factors, on water quality trophic state is more serious than that of total phosphorus per se. This implies that the actual influence of total phosphorus on the eutrophic condition could be underestimated. Furthermore, there was no deterministic causality between climate and water quality variables. In addition, time lagged effects, or the influence of their interaction with other variables, were considered separately in this study to further determine the actual relationships between water trophic state and influencing factors. The influencing patterns for three reservoirs are different, because the type, size, and background environment of each reservoir are different. This is as expected, since it is difficult to predict eutrophication in reservoirs with a universal index or equation. However, the multiple linear regression model used in this study could be a suitable quick-to-use, case-by-case model option for this problem.