Eutrophication Process Research Articles

Litter decomposition in European coniferous and broadleaf forests under experimentally elevated acidity and nitrogen addition

Atmospheric sulfur (S) and nitrogen (N) deposition has impacted many regions across the Northern Hemisphere inducing acidification and eutrophication of terrestrial ecosystems. However, acidification and eutrophication processes may differently impact litter decomposition and thus soil carbon (C) dynamics. We performed a field soil chemistry manipulation in two mountainous temperate forest stands (Picea abies and Fagus sylvatica) historically affected by acid (S and N) deposition. In each stand, four treatments were established: control, acid addition (H2SO4 – 50 kg S·ha− 1·year− 1), N addition (NH4NO3 – 50 kg N·ha− 1·year− 1) and their combination. In fourth year of manipulation, we established litter decomposition experiment. Litter bags of contrasting quality and origin (green tea, rooibos tea, spruce needles and beech leaves), in total 1536 samples, were buried below the organic layer and left to decompose up to 24 months. Retrieved samples were analysed for mass loss, C/N, and concentration of CuO oxidation lignin. Data were complemented by monitoring soil water pH and soil CO2 efflux. Acid additions decreased soil water pH, soil respiration and suppressed decomposition of the high-quality litter (green tea) in both stands, whereas mass loss of remaining litter was reduced only in the spruce stand. Nitrogen treatments, when coupled with decreasing soil water pH, constrained needle decomposition in the naturally more acidic spruce stand. Our study demonstrates a suppressing effect of soil acidity on decomposition processes and soil C dynamics. The effect of N addition, as a nutrient, was insignificant, likely because of previous ecosystem adaptation to historical N loadings.

Hotspot analysis of spatial distribution of algae blooms in small and medium water bodies.

Intensive land use favors eutrophication processes and algae bloom proliferation in freshwaters, which is considered to be one of the main environmental issues worldwide. In general, and particularly in South America, inland water monitoring only covers the main water bodies due to the high costs and efforts involved. In order to improve the coverage of spatial and temporal of algae bloom monitoring, remote sensing serves as an alternative tool. Thereby, the analysis of significant spatial clusters of high values (hotspots) and low values (coldspots) of chlorophyll-a has been applied in coastal studies; however, at present, there are no studies in freshwaters. In this study, Getis-Ord Gi* hotspot analysis was applied to detect spatial distribution patterns of algae bloom dynamics in small- and medium-sized freshwater bodies. Four in situ samplings were carried out in five suburban lakes of Uruguay, in agreement with the satellite capture. Total and cyanobacterial chlorophyll-a concentration, and suspended solids were evaluated. Linear models were developed by combining pre-established indexes with additional Sentinel-2 spectral bands and in situ data. The relationship between red and red edge regions allowed mapping the chlorophyll-a in the study lakes with an adjustment of R2 = 0.83. Hotspot analysis was performed with the selected linear model, and significant chlorophyll-a variability within each lake was successfully detected. The novel application of hotspots analyses presented in this work represents a contribution to advance knowledge in the remote detection of algae bloom dynamics and improve monitoring capabilities of inland water bodies.

Determination of Changes in the Quality of Surface Water in the River—Reservoir System

Assessing the changing parameters of water quality at different points in the river–reservoir system can help prevent river pollution and implement remedial policies. It is also crucial in modeling water resources. Multivariate statistical analysis is useful for the analysis of changes in surface water quality. It helps to identify indicators that may be responsible for the eutrophication process of a reservoir. Additionally, the analysis of the water quality profile and the water quality index (WQI) is useful in assessing water pollution. These tools can support and verify the results of a multivariate statistical analysis. In this study, changes in water quality parameters of the Turawa reservoir (TR), and the Mała Panew river at the point below the Turawa reservoir (bTR) and above the Turawa reservoir (aTR), were analyzed. The analyzed period was from 2019 to 2020 (360 samples were analyzed). It was found that TN, NO2-N, and NO3-N decreased after passing through the Turawa reservoir. Nevertheless, principal component analysis (PCA) and redundancy analysis (RDA) showed that NO2-N and NO3-N contribute to the observed variability of the water quality in the river-reservoir system. PCA showed that pH and PO4-P had a lower impact on the water quality in the reservoir than nitrogen compounds. Additionally, RDA proved that the values of the NO3-N and NO2-N indicators obtained the highest values at the aTR point, PO4-P at the bTR, and pH at the TR. This allows the conclusion that the Turawa reservoir reduced the concentration of NO2-N and NO3-N in comparison with the concentration of these compounds flowing into the reservoir. PCA and RDA showed that both parameters (NO2-N and NO3-N) may be responsible for the eutrophication process of the Turawa reservoir. The analysis of short-term changes in water quality data may reveal additional sources of water pollution. High temperatures and alkaline reaction may cause the release of nitrogen and phosphorus compounds from sediments, which indicates an increased concentration of TP, PO4-P, and Norg in the waters at the TR point, and TP, PO4-P, and NH4-N concentrations at the bTR point. The water quality profile combined with PCA and RDA allows more effective monitoring for the needs of water management in the reservoir catchment area. The analyzed WQI for water below the reservoir (bTR) was lower than that of the reservoir water (TR), which indicates an improvement in water after passing through the reservoir.

The exacerbation of mercury methylation by Geobacter sulfurreducens PCA in a freshwater algae-bacteria symbiotic system throughout the lifetime of algae

Mine-polluted wastewater with mercury (Hg) poses severe environmental pollution since Hg(II) can be converted to highly neurotoxic methylmercury (MeHg) under anaerobic conditions. Previous studies on Hg methylation have focused on aquatic sediments, but few have investigated the MeHg formation in water layers containing algae. In this study, we investigated the dynamic effect of algae on Hg methylation throughout the lifetime of algae. We found that Chlorella pyrenoidosa was a non-methylating alga and exhibited good tolerance to Hg stress (1–20 μg/L); thus Hg(II) could not inhibit the process of eutrophication. However, the presence of C. pyrenoidosa significantly enhanced the Hg methylation by Geobacter sulfurreducens PCA. Compared to the control sample without algae, the MeHg production rate of algae-bacteria samples remarkably exacerbated by 62.3–188.3% with the algal growth period at cell densities of 1.5 × 106–25 × 106 cells/mL. The increase of algal organic matter and thiols with the algal growth period resulted in the exacerbation of MeHg production. The Hg methylation was also enhanced with the presence of dead algae, of which the enhancement was ~62.4% lower than that with the presence of live algae. Accordingly, the potential mechanism of Hg methylation in a freshwater algae-bacteria symbiotic system throughout the algal lifetime was proposed.

"Greenhouse gas dynamics in a coastal lagoon during the recovery of the macrophyte meadow (Mar Menor, SE Spain)".

The Mar Menor is a hypersaline coastal lagoon with salinity values ranging from 41.9 to 45.5. The system is subjected to a high anthropic pressure that causes an intense eutrophication process, followed by a recovery of the macrophyte meadows. This study focuses on the distribution of the main greenhouse gases (CO2, CH4 and N2O) and was carried out in the extreme seasonal conditions of winter and summer during the year 2018. Sediment-water-atmosphere exchanges and biochemical processes in the water column appeared to be the main factors to explain the variability of these gases. Dissolved Inorganic Carbon (DIC), CH4 and N2O benthic fluxes values obtained in this study, were of 91 ± 29 mmol m-2 d-1, 3.9 ± 1.9 μmol m-2 d-1 and -0.65 μmol m-2 d-1, respectively, along with an important seasonal variation observed, with an increase of DIC and CH4 benthic fluxes during the summer season. Mean values of partial pressure of CO2 (pCO2) in surface water were of 579 μatm in winter and 464 μatm in summer, therefore we can establish that the Mar Menor acts as a source of this gas emitting 3.3 ± 3.0 mmol CO2 m-2 d-1 to the atmosphere. In spite of this, the Mar Menor has a strong autotrophic behaviour partly due to the recovery of the macrophyte meadows, presenting an estimated NEP of 101 mmol m-2 d-1. Regarding to CH4, the mean fluxes to the atmosphere were of 8.0 ± 5.8 μmol m-2 d-1 and there was evidence of CH4 production in the water column that increased in summer. Last of all, in the case of N2O the system acts as a sink with values of -0.65 ± 0.5 μmol m-2 d-1, presenting an intake of N2O that is usually detected in pristine systems.

Method of the Assessment of the Eutrophication of the Waters of the Gulf of Taganrog of the Sea of Azov Subject to the External Load on the Water Area

Eutrophication of waters is a complex problem that is widespread all over the world. These process especially intensified during the last century because of the human activity which lead to the anthropogenic transformation of water reservoirs. The object of the study – the Gulf of Taganrog of the Sea of Azov – also subject to the processes of waters eutrophication. So the research evaluates the Gulf ecosystem from the standpoint of eutrophication. The method of such assessment was developed. It includes the regression analysis and mathematical modelling. The study showed the change in the type of eutrophication of a water body from the mehotrophic type to the eutrophic one; the estimation of the inflow of the concentrations of ammonium ion, nitrate and phosphate into the waters of the Gulf showed the sources that influence this income mostly; the natural load influences the ecosystem most.

Disturbance of Sustainability of the Reservoir Ecosystem: A Model Approach for Assessing and Forecasting the Long-term Process of Eutrophication

Disturbance of Sustainability of the Reservoir Ecosystem: A Model Approach for Assessing and Forecasting the Long-term Process of Eutrophication

Study of a hydrodynamic threshold system for controlling dinoflagellate blooms in reservoirs

Hydrodynamic conditions often affect the eutrophication process and play a key role in algal growth in reservoirs. A promising approach for controlling algal blooms in reservoirs is to create adverse hydrodynamic conditions by implementing reservoir operation strategies. However, research on this method is still nascent and does not support practical applications due to the lack of quantitative hydrodynamic thresholds. In this paper, field observations of algal growth from April 2015 to August 2016 were conducted, and a three-dimensional (3D) model that couples hydrodynamics and water temperatures for the Zipingpu Reservoir was established. Low flow velocities (V) and low Reynolds numbers (Re) in the Longchi tributary are favorable for dinoflagellate growth and accumulation, which can explain why dinoflagellate blooms are more likely to occur in the tributary. A temperature of 18-22°C is considered a precondition for Peridiniopsis penardii blooms, suggesting that freshwater dinoflagellate species may prefer lower temperatures than marine dinoflagellate species. Shallow mixing layer depth (Zmix) is conducive to Peridiniopsis penardii gathering in the upper water layers and promotes growth. The shallow euphotic layer depth (Zeu) was speculated to promote the dominance of this species by stimulating its heterotrophy and inhibiting other algal autotrophy. Furthermore, a boundary line analysis was introduced to characterize the relationships between algal biomass and hydrodynamic indicators. Thus, the thresholds for V, Re, and Zmix/Zeu were determined to be 0.034ms-1, 6.7×104, and 1.7, respectively. Either accelerating horizontal flow to exceed the thresholds of V and Re or facilitating vertical mixing to exceed the threshold of Zmix/Zeu can prevent dinoflagellate blooms. Therefore, the summarized hydrodynamic threshold system is suggested to be an effective standard for controlling dinoflagellate blooms in the reservoir. Moreover, this study can provide a useful reference for understanding the mechanism of freshwater dinoflagellate blooms.

Tracking historical chlorophyll-a change in the guanting reservoir, Northern China, based on landsat series inter-sensor normalization

ABSTRACT The Guanting Reservoir supplied drinking water to Beijing until 1997, following which the water quality of the reservoir deteriorated. The chlorophyll-a concentration (C chl-a ) of water is an important indicator of eutrophication. Therefore, changes in the C chl-a of the Guanting Reservoir should be monitored and analysed. For more than 30 years, the monitoring of C chl-a in inland waterbodies has only been possible using the Landsat 5 Thematic Mapper (TM), Landsat 7 Enhanced Thematic Mapper (ETM), and Landsat 8 Operational Land Imager (OLI). However, there are data consistency problems in monitoring C chl-a using these sensors. To address this issue, this study utilized inter-sensor normalization models of the different sensors and a unified C chl-a estimation model for Landsat series data with a long time span. After inter-sensor normalization, the mean relative error (MRE) of remote sensing reflectance (R rs) between OLI and TM/ETM+ was corrected to 1–5%. The unified model of C chl-a estimation employed the normalized ratio index of blue R B and near-infrared R NIR remote sensing reflectance: (R NIR – R B): (R NIR + R B). The MRE for estimating C chl-a was 25.7% and the root-mean-square error (RMSE) was 5.65 mg m–3. The C chl-a of the Guanting Reservoir was then estimated for years between 1985 and 2019. During this time, C chl-a had a distinct seasonal distribution trend; the annual changes go through four stages, and each period shows different change characteristics. This study is the first to systematically understand the history of chlorophyll-a changes in the Guanting Reservoir over the past 30 years and provides references data for its eutrophication process and management.

The eutrophication process of Nador’s lagoon (Morocco) evaluated by the Life Cycle Impact Assessment method

The Nador lagoon system of northeastern Morocco represents the largest regional paralic hydro-system between the Mediterranean Sea and the African continent. Due to its importance, this lagoon is one of the five Sites of Biological and Ecological Interest (SIBE) and was classified in 2005 as a protected site by the international Ramsar treatise. The Nador lagoon is subjected to eutrophic impacts due to pollutant releases from a wastewater plant, three major cities, an agricultural site, and to varied inputs carried by rivers draining the lagoon watershed. The NO2-, NO3-, NH4+, and PO43- contents of nine water samples collected during summer and winter times at different places in the lagoon were measured and translated in terms of the Redfield ratio (N/P) and the Aquatic Eutrophication Potential. The analyses show that N/P is less than 16 in terms of the Redfield ratio, which designates N as the limiting factor for the algal growth over the entire lagoon. However, one of the higher N/P ratios was obtained next to the releases of the Beni-Ensar city and near the outlets of the wastewater plant and the nearby Bouaroug creek. The aquatic eutrophication potential of the phosphorus compounds (AEP (P)) is systematically greater than the aquatic eutrophication potential of the nitrogen compounds (AEP (N)), whether in winter or summer, which confirms that nitrogen is the limiting factor for the local algal growth.

Long-term eutrophication and contamination of the central area of Sepetiba Bay (SW Brazil).

This work sheds light on the recent evolution (≈1915-2015AD) of Sepetiba Bay (SB; SE Brazil), a subtropical coastal lagoon on the southwestern Brazilian coast, based on a multiproxy approach. Variations in geochemical proxies as well as textural, mineralogical and geochronological data allow us to reconstruct temporally constrained changes in the depositional environments along the SP3 sediment core collected from the central area of SB. At the beginning of the twentieth century, the substrate of the study site was composed of coarse-grained sediments, largely sourced from felsic rocks of proximal areas and deposited under moderate to strong shallow marine hydrodynamics. Since the 1930s, the study area has undergone silting and received high contributions of materials from mafic rocks sourced by river basins. The SP3 core reveals a shallowing-upward sequence due to human-induced silting with significant eutrophication since the middle of 1970, which was caused by significant enrichment of organic matter that was provided by not only marine productivity but also continental and human waste. In addition, the sediments deposited after 1980 exhibit significant enrichment and are moderately to strongly polluted by Cd and Zn. Metals were dispersed by hydrodynamics from the source areas, but diagenetic processes promoted their retention in the sediments. The potential ecological risk index (PERI) indicates that the level of high (considerable) ecological risk is in sediments deposited in ≈1995 (30-32cm; subsurface). The applied methodology allowed us to understand the thickness of the bottom sediment affected by eutrophication processes and contaminants. Identical methodologies can be applied in other coastal zones, and can provide useful information to decision makers and stakeholders that manage those areas.

Feasibility Analysis of the Sustainability of the Tres Palos Coastal Lagoon: A Multifactorial Approach

We studied the cultural eutrophication process assessments of coastal lagoons by considering sociopolitical, socioeconomic, demographic, technological, and cultural factors, which represent indirect drivers exerting effects on the eutrophication process, causing changes on the trophic status. Multifactorial interactions in eutrophication processes make understanding their complex dynamics difficult, leading to unreliable assessments and, consequently, to unsustainable management actions. This, in turn, hinders the feasibility of coastal lagoon sustainability. We propose a method based on the evaluation of pathways derived from a multifactorial network, which represents the eutrophication process, with the aim of determining the feasibility of the sustainability of the Tres Palos coastal lagoon. Our findings revealed that most of the evaluations of relationships belonging to pathways were unfeasible due to reasons such as: there was no evidence of the existence of public policies, technological skills, and cultural factors; there was a lack of data related to human settlements around the lagoon and river, industrial waste, agricultural practices, and tourism. The preceding shortcomings hinder the feasibility of coastal lagoon sustainability under study. We suggest that assessments of cultural eutrophication processes that overlook sociopolitical, socioeconomic, technological, and cultural factors are limited and inadequate for supporting the feasibility of sustainable coastal lagoons.

Sedimentary record of nutrients and sources of organic matter in the Shuanglong reservoir, Dianchi watershed, China.

In the last few decades, the eutrophication of lakes has been a serious issue in the middle and lower reaches of the Yangtze River watershed. To explore the relationship between lake systems and anthropogenic activities, sediments were collected from the Shuanglong reservoir in the Dianchi watershed in Southwest China. Total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC), and the carbon isotopic ratio (δ13C) were analyzed in sediment cores to reconstruct the effects of natural succession and human activities on the past lacustrine environmental conditions. A reliable chronology of the sediment core was established by using the 210Pb dating technique, which indicated that the age span of the 70-cm sediment core is from the years 1871 to 2011. Above - 31 cm depth in the core, TN, TP, TOC, C/N, and δ13C increased significantly, indicating that eutrophication has occurred since the 1980s. By combining the indicators of δ13C and C/N, it was shown that terrestrial and lacustrine components were the main sources of organic matter (OM) in the reservoir, which was mostly controlled by terrestrial C3 plants and algae. Since the 1980s, increased sewage discharge, fish aquaculture, fertilizer application, population, and economic strength have sped up the eutrophication process, and the eutrophication was further intensified in 2001.

Оцінка стану Вармінсько-Мазурських озер у Польщі внаслідок процесу евтрофікації

The article is devoted to the study the origins and consequences of the eutrophication problem of Warmian-Masurian lakes of Voivodeship in Poland and to find the possible ways of its solution. Eutrophication, also known as hypertrophication is a process of enrichment of water bodies with nutrients, especially nitrogen and phosphorous that leads to algae and plants growth and results in inadequate supply of oxygen and loss of water quantity. Nowadays, the problem of eutrophication concerns not only Baltic countries, but also countries in the West Europe, the same as in whole world. The eutrophication problem also influences local landscape changes, because it is strictly associated with terrestrialization process, which is well-seen in the area of Warmian-Masurian Voivodeship. The aim of the work is to find the relationship between the eutrophication process and the environmental problems caused by them, as well as to find potential solutions and review the currently done ones, base on comparison of observations and literature sources. The work was mainly based on field observation, publications of researches, and the program of “lakes cleaning” in Szczytno and literature study, which confirmed the negative changes in structure of local associated with eutrophication and terrestrialization processes. To see the structural changes in the lakes as a result of the terrestrialization process, we compared their current state with old photographs of the area. Visible changes were found in the coastline, which was overgrown mainly with reeds and typhus, as well as former beaches, which were replaced by flora. To point out possible ways of solution, the program of “lakes cleaning” in Szczytno was used. The project was running for 3 years (from 2010 to 2013) and consisted of introducing of 71 tons of a polyaluminium coagulant under surveillance of scientists from the University of Warmia and Mazury. It was concluded that the changes of water bodies in the Warmian-Masurian Voivodeship are strongly associated with eutrophication process. To avoid and withdraw that processes there are many solutions, starting with the simplest to advanced ones what is well-seen in Szczytno Warmian-Masurian Voivodeship, where polyaluminium coagulant was used to “clean” the lake. Further research may focus on finding a variety of substances that can be used to mitigate and eliminate eutrophication without side effects, both for the environment and for humans.

Helminth’s assemblage of Trachemys dorbigni (Testudines: Emydidae) in southern Brazil: implications of anthropogenic environments and host’s genders

ABSTRACT The assemblage of helminths of Trachemys dorbigni was analyzed according two environments (rural and urban) and according to host’s gender. Thus, the helminths found were: Spiroxys contortus (Rudolphi, 1819), Falcaustra affinis (Leidy, 1856), Camallanus emydidius Mascarenhas & Müller, 2017, Dioctophyme renale (Goeze, 1782) (larvae), Eustrongylides sp. (larvae) (Nematoda), Telorchis corti (Stunkard, 1915), Telorchis achavali Mañé-Garzón & Holcman-Spector, 1973, Telorchis spp. (Digenea), Polystomoides rohdei Mañé-Garzón & Holcman-Spector,1968 and Neopolystoma sp. (Monogenoidea). Parasitological indices suggests that S. contortus, F. affinis, C. emydidius, T. corti and P. rohdei are species common in helminth assemblage of T. dorbigni in southern Brazil. Infection by Dioctophyme renale is typical of the urban area and suggest relation with eutrophication process and feedback of parasitic cycle in the freshwater urban environment. Parasitological indices of Neopolystoma sp. and T. achavali suggest to be occasional infections; whereas infection by Eustrongylides sp. could be considered accidental. About Telorchiidae, there was no co-occurrence of the species of this group for the examined hosts. In relation to host’s gender, it was observed that infections by S. contortus, F. affinis, C. emydidius and T. corti had higher rates in females, showing a more intimate association with the females of T. dorbigni. The results suggest that human impact on the environment could affect the infrapopulacional dynamics of parasite species influencing the presence and rates of infection of helminths or exacerbating heterogeneities related to host’s gender.

Evaluation of genotoxic potential induced by marine cage culture

BACKGROUND AND OBJECTIVES: The eutrophication process is increased by anthropogenic or aquaculture facilities in marine ecosystems. DNA damage biomarkers for fish species detect genotoxic parameters for ecological risk assessment. The aim of the present study was to determine genotoxic potential induced by marine cage culture in Iskenderun Bay on gilthead sea bream (Sparus aurata) using Comet assay. METHODS: This study was conducted at cage and reference stations of Iskenderun Bay, Northeastern Mediterranean in January 2017. The wild and cultured samples of S. aurata and water samples were collected from wild and fish farm. FINDING: The DNA damages at gill and liver cells of gilthead sea bream in the present study were observed with a higher level of DNA damage in gill cells compared to liver cells, and were determined at the low and minimal scale at the cage and reference stations, respectively. The present study demonstrated that the TP values were recorded at 0.020 and 0.016 mg/L in the cage and reference stations which are at border and below 0.020 mg/L. The DIN values were recorded at 0.097 and 0.075 mg/L in the cage and reference stations, which are at below 0.1 mg/L. The water bodies in the cage and reference stations exhibit Moderate/Mesotrophic water quality The correlations between physical-chemical parameters and DNA damage were shown that DIN, NH4-N, NO3-N and NO2-N in water revealed significant positive correlations with DNA damage levels in gill cells. CONCLUSION: The present study provides the first data set on genotoxic damage induced by marine cage culture in Iskenderun Bay on gilthead sea bream. The result of this research is an early warning for the marine system and further detailed research is needed to establish the source of the pollution and monitor environmental pollution.

Сток наносов и мутность воды основных притоков Ладожского озера

The vast catchment area of the Lake Ladoga is characterized by variety of underlying surface types and a complex hydrographic network. The processes of eutrophication of the southern littoral areas of the Lake Ladoga determine the relevance of assessing the removal of solid matter from the river flow to the estuaries of the tributaries of the Ladoga. Observations of sediment runoff of the main tributaries the Lake Ladoga were not carried out. In this regard, for each tributary were selected rivers-analogues the main criteria in the selection was the slope, the grain size of sediments and the catchment area (water availability). The modeling of annual solid runoff and turbidity of the Ladoga tributaries is based on an analytical formula for sediment flow by M.V. Shmakova and a stochastic model of annual solid runoff (M.V. Shmakova). According to the calculations, the annual flow of sediment entering the Ladoga water area is about 432 thousand t/year. The main sources of sediment are three major tributaries of the Lake Ladoga – the Svir, Volkhov and Vuoksa rivers, which account for 253 thousand t/year or 59 % of the total amount of sediment received in the lake. However, these watercourses have the smallest annual module solid flow, due to retention of sediment of backwater areas before hydroelectric dams on these rivers and as a consequence, a decrease in the overall sediment discharge. At the same time, the average annual solid runoff modulus for the Ladoga lake catchment area is 1.53 t/(km2·year), which corresponds well to the previous estimate of this value for the territory under consideration. The analysis of the annual module of solid runoff showed a good correspondence between the obtained values of this value and the conditions for the formation of solid runoff in the catchment, the characteristics of its soils.

Algal blooms and trophic state in a tropical estuary blocked by a dam (northeastern Brazil)

Abstract The Bacanga River Estuary is socioeconomically important due to artisanal fishing and aquaculture. It is blocked by a dam and is under human pressure along its drainage basin, intensifying the eutrophication process. This study reports on the occurrence of phytoplankton blooms and trophic state (TSI and TRIX) at six sampling sites during the annual cycle. The estuary was divided into downstream and upstream regions. Higher salinity, turbidity, depth, and lower dissolved oxygen levels were found downstream; whereas, high levels of chlorophyll a and nutrient concentrations were observed in both regions. There were blooms of Leptocylindrus danicus (1.45 × 106 cells L-1) and Skeletonema costatum (1.89 × 106 cells L-1) downstream; whereas phytoflagellate proliferation, such as those of Chlamydomonas sp. (13.17 × 106 cells L-1), Euglena gracilis (7.84 × 106 cells L-1), and Euglena proxima (1.03 × 106 cells L-1) were recorded upstream, with Chlamydomonas sp. as the discriminant species of this zone. Both trophic indices (TSI; TRIX) indicated elevated trophic conditions for the estuary, classifying it as hypereutrophic. Nevertheless, TSI only showed a significant relationship with some specific phytoplankton blooms. Thus, TSI seems to be the trophic index with a better response in the assessment of estuarine ecological functioning.

Application of the Contingent Valuation Method in Water Resources Protection

Abstract The option of using the contingent valuation method (CVM) to assess residents’ willingness to pay (WTP) for upgrading the quality of water resources in their communes is discussed in the article. Surveys were conducted using the direct interview method. The analysis included the application of CVM to examine the potential for financing projects that are focused on reducing the eutrophication process of the Baltic Sea, financing the construction of municipal sewage treatment plants in selected communes in Greece and Poland and financing the upgrade of sewage disposal and treatment standards in Śniadowo in north-eastern Poland. For authorities of a given area, the CVM is an instrument supporting the decision-making process regarding investments in water resources’ protection.

Unmanned aerial vehicle for eutrophication process monitoring in Timah Tasoh Dam, Perlis, Malaysia

Manual monitoring of the eutrophication status of water bodies such as a dam is a challenging task. Hence, drone technology can be used in assisting the monitoring work of any water bodies. This study was conducted to develop UAV-based remote sensing to derive indicators in lake water bodies. Four sampling points were chosen for testing where the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Turbidity Index (NDTI) were assessed. DJI Phantom 4 Pro drone was used for the aerial data acquisition. Ex-situ data were also acquired, such as nitrate concentration (N) and phosphate concentration (P). The hyperspectral UAV images were ortho-rectified and geo-referenced in Agisoft PhotoScan software and NDVI value estimation in ArcGIS. Results show the correlation between NDVI values and N and P concentration with coefficients values of 0.7079 for P concentration and 0.7004 for N concentration, respectively. This study confirmed the applicability of remote sensing for water resource management using UAVs, characterized as a quick and easy methodology.