Trophic Index Research Articles

Trophic niches of two predator fish cohabiting in the Algerian coastal ecosystem: Scorpaena porcus (Linnaeus, 1758) and Scorpaena notata (Rafinesque, 1810)

The diet of adult specimens of black scorpionfish Scorpaena porcus (Linnaeus, 1758) and small red scorpionfish Scorpaena notata (Rafinesque, 1810), collected from the Algerian coast was studied using different coefficients and trophic indexes. The inventory of ingested prey indicates that the focal species have a diverse diet that covers different zoological groups. Their feeding spectrum is mainly composed of brachyuran crabs and other crustaceans such as isopods and shrimp. Fish and molluscs are only occasionally ingested. The vacuity coefficient average exceeded the estimated rate of 40%. The observed monthly fluctuations revealed a seasonal alimentary rhythm. The foraging activity of the two scorpionfish decreases in summer, during gonad maturation. This decrease is highlighted by the increase in the vacuity coefficient and the decrease in the repletion index. Despite a similarity in the food bolus, the two co-occurring fish exhibit a specialized diet. This was observed especially in mature individuals. In conclusion, our results demonstrated a very strong overlap of niches between two scorpionfish species.

Avaliação trófica de quatro reservatórios tropicais usando gêneros fitoplanctônicos

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

English

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

Catch trends of bottom trawl fauna with an emphasis on prawns and stomatopods, off Goa, India

Catch trends of bottom trawl fauna off Goa, India were investigated at fortnightly intervals from February 2006 – May 2008 with the exception of June – October months (monsoon). Inter-comparison of faunal abundance data obtained during February to April months of 2006, 2007 and 2008 indicated that abundance during 2006 and 2008 were significantly higher as compared to 2007. Available fish landing data for the region also corroborated this trend. The dominance of sub-adults among stomatopods during post-monsoon season (November – January), juveniles and sub-adults among prawns during pre-monsoon (February – May), indicated recruitment to the fishery. Comparison with 40-year-old published data indicated significant reduction in the overall yield (P = 0.043; α = 0.05). Additionally, yields of 12 out of 15 fish groups across the demersal trophic spectrum decreased significantly (P = 0.031; α = 0.05). However, catches of miscellaneous species increased 17 times, and were dominated by pufferfishes. The profusion of pufferfish is attributed to the perennial breeding habit of these fishes combined with increased removal of potential predators such as sharks and catfishes. Marine Trophic Index (MTI) and Fishing-in-Balance Index (FiB) decreased at rates of 0.017 and 0.016 per decade, respectively, implying sustained fishing pressure over the next few decades that could lead to potential trophic cascade and dominance of resilient opportunistic species such as puffers.&nbsp

ОЦЕНКА ТРОФНОСТИ ОЗЕРА БАЙКАЛ С ИСПОЛЬЗОВАНИЕМ ДИСТАНЦИОННОГО ЗОНДИРОВАНИЯ

The existing models for assessing the trophicity indicators of water bodies are intended for specific water bodies, and adaptation is required for their use with regard to others. Another problem is the lack of approaches in remote monitoring to the development of an integral indicator of the trophicity of water bodies. The purpose of this study is to develop models for calculating biotic and abiotic indicators for assessing the state of a reservoir, as well as an integral indicator of its trophicity. To achieve this goal, the tasks were set to compare the possibilities of using satellite images to assess water bodies, to calculate the trophic indicators of Lake Baikal according to existing models, adapting them, if necessary, to develop models for calculating biotic and abiotic indicators, to develop an integral assessment of the trophicity of Lake Baikal, and describe the algorithm for obtaining it. The object of the study is Lake Baikal. The subject of the study is the assessment of the reservoir’s trophicity. In terms of theoretical and methodological basis, the study relies on research works of Russian and foreign authors in the field of assessing the trophicity of water bodies, geographic information systems (GIS) as well as Earth remote sensing data (ERS). The methods of spatial analysis and correlation-regression analysis were used. The empirical and information-statistical bases of the work include statistical and analytical publications in the press on the topic under study, statistical data of the Russian Federation, foreign statistics, data from seminars and conferences on the problems of assessing the trophicity of water bodies, and the use of GIS and remote sensing data in assessing the state of water bodies. The scientific and practical novelty and significance of the results obtained lie in the development of an algorithm for assessing the trophicity of the reservoir using GIS and remote sensing. The parameters of models for calculating the Secchi disk transparency and chlorophyll-a concentration have been estimated. It is proposed to use rank assessment for express evaluation of the trophicity of water bodies, and an appropriate scale has been developed to determine the type of trophicity of the reservoir. An algorithm for estimating the trophicity of the reservoir is described.

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

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

A bacterial index to estimate lake trophic level: National scale validation

Lakes and their catchments have been subjected to centuries to millennia of exploitation by humans. Efficient monitoring methods are required to promote proactive protection and management. Traditional monitoring is time consuming and expensive, which limits the number of lakes monitored. Lake surface sediments provide a temporally integrated representation of environmental conditions and contain high microbial biomass. Based on these attributes, we hypothesized that bacteria associated with lake trophic states could be identified and used to develop an index that would not be confounded by non-nutrient stressor gradients. Metabarcoding (16S rRNA gene) was used to assess bacterial communities present in surface sediments from 259 non-saline lakes in New Zealand encompassing a range of trophic states from alpine microtrophic lakes to lowland hypertrophic lakes. A subset of lakes (n = 96) with monitoring data was used to identify indicator amplicon sequence variants (ASVs) associated with different trophic states. A total of 10,888 indicator taxa were identified and used to develop a Sediment Bacterial Trophic Index (SBTI), which signficantly correlated (r2 = 0.842, P < 0.001) with the Trophic Lake Index. The SBTI was then derived for the remaining 163 lakes, providing new knowledge of the trophic state of these unmonitored lakes. This new, robust DNA-based tool provides a rapid and cost-effective method that will allow a greater number of lakes to be monitored and more effectively managed in New Zealand and globally. The SBTI could also be applied in a paleolimnological context to investigate changes in trophic status over centuries to millennia.

Ecological Parameters of Water Bodies in the Northern Part of the Upper Volga Region with River Flow Regulations

The regulation of river flow in the Volga basin has caused irreversible changes to aquatic ecosystems. The transformation of the Volga into a cascade of hydraulic structures with a non-flow regime has resulted in a decrease in depth and flow, and an increase in the temperature and concentration of chemical elements, which has induced the process of eutrophication. The change in the species diversity of aquatic organisms under conditions of intense eutrophication was studied on models of water bodies from the Volga basin; the Kostroma section of the Gorky reservoir (Kostroma spill and the middle river section), and lakes Galichskoe and Chukhlomskoe were studied. Rheophilic biocenosis was replaced by a limnophilic one, the migration paths of fish were disrupted, and population characteristics were changed. In accordance with environmental conditions, the level of primary production and the calculated Carlson trophic index (TSI) and Broth-proposed index (ITS) (1987), the water bodies of the northern part of the upper Volga region are classified as follows: the middle river section of the Gorky reservoir is mesotrophic-eutrophic (TSI = 55.2, ITS = 16.2); the Kostroma spill is eutrophic with a tendency to hypertrophy (TSI = 67.4, ITS = 6.8); Lake Galichskoe is eutrophic with a tendency to dystrophy (TSI = 63.2, ITS = 8.4), and Lake Chukhlomskoe is hypertrophic with a tendency to dystrophy (TSI = 77.4, ITS = 8.0). In addition, frequent fluctuations in water level, reaching 1 m, have had an adverse effect on inhabitants of the littoral zone including the spawning fish, which may lead to disappearance of some of the region’s most sensitive species.

Phytoplankton and water quality of Lake Kuchane (Pskov region, Russia)

The phytoplankton communities of Lake Kuchane, located in the Mikhailovskoye Museum-Reserve, were studied during different 2016–2017 seasons for the first time. 213 specific and intraspecific taxa from 9 phylums were identified in the phytoplankton, namely: Bacillariophyta, Chlorophyta, Chrysophyta, Euglenophyta, Cyanobacteria, Dinophyta, Cryptophyta, Charophyta, and Xanthophyta. The ratio of the main phylums of microalgae during the studied seasons was similar. The floristic complex of the lake's algoflora consisted of diatoms (36.6%), green (27.2%) and golden (10.8%) algae. Most of the phytoplankton genera contained one species taxon only. The specific composition of the phytoplankton community in 2017 was similar from spring to autumn. The minimum specific similarity of the phytoplankton communities was noted in July, 2016, and August, 2017. According to the level of biomass of planktonic algae, the lake belongs to oligotrophic water bodies. The planktonic algoflora of Lake Kuchane is characterized by the predominance of cosmopolitan freshwater forms of microalgae. In relation to pH, the predominant representatives preferred slightly alkaline waters. The Milius trophic index varied in the range 18.0–39.6 with a maximum value in summer. The Pantle–Bukk saprobity index almost did not change during the entire study. The waters of Lake Kuchane corresponded to the betamesosaprobic self-purification zone, quality class III.

Trophic status assessment of Central Eastern Adriatic Sea using water quality variables and loading capacity concept for estuaries

The temporal and spatial variability of pollution pressures of the coastal waters resulting from river discharges is the main cause of eutrophication along the coastline. This study aims to assess the water quality and trophic state of Kastela Bay and the river Jadro estuary located in the Croatian central Adriatic Sea. The trophic assessment is classified using the composite trophic status index (TRIX), originally developed for Italian coastal waters and modified for the eastern central Adriatic Sea using data series from 2012 to 2019 from 13 stations. The impact coming from the river Jadro estuary is analyzed using the loading capacity concept to examine the exchange flows and loading dynamics of nutrients discharged in the Kastela Bay. The results show that the trophic index is larger within the river Jadro estuary and maintains the increased values in the surface layer throughout Kastela Bay. The presented loading capacity concept, accounting for the exchange flows in transitional waters, may help better understand the trophic dynamics of the receiving waters. The loading capacity is changing with the river flow and daily loads from measurements can be used to assess the pattern of impairment.

TROPHIC STATUS OF A TROPICAL COASTAL LAGOON IN MARGARITA ISLAND, VENEZUELA

Punta de Piedras Lagoon is a coastal lagoon located south of Margarita Island, in the Venezuelan Caribbean Sea. This lagoon has ecological and economic importance for the inhabitants of nearby communities. Currently, the urban and industrial development in its surroundings represents a potential source of pollutants, providing concentrations of nutrients that could affect the ecological balance of the area. The trophic status of Punta de Piedras Lagoon was evaluated using various trophic indices. The concentrations of chlorophyll-a and nutrients (ammonium, nitrites, nitrates, and orthophosphates) were estimated in 10 stations with a monthly frequency from February 2005 to January 2006. These data were used to estimate the trophic condition based on the Karydis and TRIX trophic indices, and by comparison with Organization for Economic Co-operation and Development reference values. It was found that Punta de Piedras lagoon presented mesotrophic conditions in most of the water body having considerable differences between indices. The values of the closest station to Paseo Esther Gil corresponded to eutrophic waters. However, the circulation and residence time of water allow an exchange with the adjacent sea, which prevents the eutrophication process in the lagoon.

Nineteen Years of Trophic State Variation in Large Lakes of the Yangtze River Delta Region Derived from MODIS Images

The Yangtze River Delta (YRD) is one of the regions with the most intensive human activities. The eutrophication of lakes in this area is becoming increasingly serious with consequent negative impacts on the water supply of the surrounding cities. But the spatial-temporal characteristics and driving factors of the trophic state of the lake in this region are still not clearly addressed. In this study, a semi-analytical algorithm for estimating the trophic index (TSI) using particle absorption at 645 nm based on MODIS images is proposed to monitor and evaluate the trophic state of 41 large lakes (larger than 10 km2) in the YRD from 2002 to 2020. The performance of the proposed algorithm is evaluated using an independent dataset. Results showed that the root-mean-square error (RMSE) of the algorithm is less than 6 and the mean absolute percentage error (MAPE) does not exceed 8%, indicating that it can be applied for remotely deriving the TSI in the YRD. The spatial-temporal patterns revealed that there were significantly more lakes with moderate eutrophication in the Lower Yangtze River (LYR) than in the Lower Huaihe River (LHR). The overall average value of the TSI reaches a maximum in summer and a minimum in winter. The TSI value in the YRD over the period 2002–2020 showed a downward trend, especially after 2013. Individually, 33 lakes showed a downward trend and 8 lakes showed an upward trend. Furthermore, marked seasonal and interannual temporal variations can be clearly observed in the LYR and LHR and the sum of the variance contributions of seasonal and interannual components is more than 50%. Multiple linear regression analysis showed that human activities can explain 65% of the variation in the lake TSI in the YRD.

Hyper-Nutrient Enrichment Status in the Sabalan Lake, Iran

Lakes/reservoirs are rapidly deteriorating from cultural eutrophication due to anthropogenic factors. In this study, we aimed to (1) explore nutrient levels in the Sabalan dam reservoir (SDR) of northwest Iran, (2) determine the reservoir water fertility using the total phosphorus (TP) based and total nitrogen (TN) based Carlson trophic state indices, and (3) specify primary limiting factors for the reservoir eutrophication. Our field observations showed a state of hyper-nutrient enrichment in the SDR. The highest variation of TN in the reservoir water column happened when the reservoir was severely stratified (in August) while the highest variation of TP took place when the thermocline was attenuated with the deepening of the epilimnion (in October). Both TP and TN based trophic indicators classified the SDR as a hypereutrophic lake. TN:TP molar ratio averaged at the epilimnion indicated a P–deficiency in the reservoir during warm months whilst it suggested a co–deficiency of P and N in cold months. Given the hyper-nutrient enrichment state in the reservoir, other drivers such as water residence time (WRT) can also act as the main contributor of eutrophication in the SDR. We found that WRT in the SDR varied from hundreds to thousands of days, which was much longer than that of other reservoirs/lakes with the same and even much greater storage capacity. Therefore, both hyper-nutrient enrichment and WRT mainly controlled eutrophication in the reservoir. Given time consuming and expensive management practices for reducing nutrients in the watershed, changes in the SDR operation are suggested to somewhat recover its hypereutrophic state in the short-term. However, strategic long-term recovery plans are required to reduce the transition of nutrients from the watershed to the SDR.

Ecological assessment of Burç Reservoir’s surface water (Turkey) using phytoplankton metrics and multivariate approach

The present study aimed to elucidate relationships between phytoplankton species and stressors using multivariate approaches and assess the environmental condition of Burç Reservoir?s surface water using phytoplankton metrics from September 2018 to August 2019 according to implementations of the Water Framework Directive. Burç Reservoir had a characteristic of a warm monomictic pattern. Phytoplankton functional groups (E, F, J, LO, LM, MP , P, S1 , T, and W1 ) were found in the reservoir. A significant difference was found in total biovolume values changed from 2.28 mm3 /L in November 2018 to 0.51 mm3 /L in February 2019. The first two axes of canonical correspondence analysis explained 99.2% of relationships between stressors and phytoplankton assemblages. Explanatory factors such as electrical conductivity (EC), nitrate (NO3 -N), total nitrogen (TN), water temperature, calcium (Ca+2), precipitation, total organic carbon (TOC), ortho-phosphate (o-PO4 ), and total phosphorus (TP) significantly drove the spatiotemporal distribution of phytoplankton. Weighted average regression resulted that phytoplankton species such as Gymnodinium saginatum, Snowella lacustris, Ceratium hirundinella, and Pseudanabaena limnetica were closely associated with high TP, while Fragilaria capucina, Navicula trivialis, Cymbella aspera, Ulnaria biceps, Nitzschia palea, and Pseudopediastrum boryanum closely related to the EC. Carlson's trophic state index indicated that Burç Reservoir mainly has a eutrophic characteristic with the assessment of chlorophyll a, total phosphorus, and Secchi disk depth, while it had a eu-hypertrophic according to the OECD classification. Results of the modified PTI-phytoplankton trophic index (mean = 2.37), the Med-PTI Mediterranean phytoplankton trophic index (mean = 1.96), and the Q assemblage index (mean = 2.58) indicated a moderate ecological status of Burç Reservoir. The present study confirmed that phytoplankton assemblages are closely integrated with the environmental condition of Burç Reservoir, which could be assessed by using the PTI and Med-PTI.

Contaminants and heavy metals along the mangrove area of Dongzhai Harbor, China: distribution and assessment

In recent decades, higher-place shrimp ponds are prevalent in coastal areas of developing countries. However, shrimp aquaculture has a growing negative impact on mangrove wetland ecosystems. Mangroves located in Dongzhai harbor are under threat continuously of this commercialization. Therefore, a comprehensive analysis of contaminants and heavy metals is necessary for Dongzhai harbor, considering the mangrove area was declined and ecological services offered to the coastal communities with an insight for future restoration activities. In this study, pond effluents (Total Nitrogen (TN), Ammonia Nitrogen (AN), Total phosphorus (TP), Chemical Oxygen Demond (COD)) and heavy metals (Cd, Cu, Pb, Zn) were monitored in Dongzhai harbor yearly between 2013 and 2017. The results showed that the contents of Cd, Cu, Pb, and Zn were far lower than the standards. However, the main contaminants were organic matter and nitrogen. Maximum values of COD and TN were 26.10 mg·L−1 and 1.34 mg·L−1, respectively in 2017. Single factor index, Nemerow's pollution index, and Trophic level index revealed that the heavily polluted areas were Tashi and Sanjiang town.

An Improved Eutrophication Assessment Algorithm of Estuaries and Coastal Waters in Liaodong Bay

Eutrophication is considered to be a significant threat to estuaries and coastal waters. Various localized studies on the world’s oceans have recognized and confirmed that the Forel-Ule Color Index (FUI) or optical measurements are proportional to several water quality variables based on the relatively clear Chl-a-based waters. However, the application potential of FUI in the turbid estuary with complex optics has not been explored. In this study, we selected the coastal waters in the northern Liaodong Bay as the study area, using the field hyperspectral reflectances (Rrs) collected in 2018 to correct the hue angle and verify the Sentinel-2 images algorithm of FUI by in situ FUI in 2019–2020. The results show that there is a good agreement (R2 = 0.81, RMSE = 1.32, MAPE = 1.25%). Trophic Level Index (TLI) was used to evaluate the eutrophication status. The relationship between the in situ FUI and TLI collected in 2018 was discussed based on the difference in the dominant components of waters, while a number of non-algae suspended solids in the estuaries and coastal waters led to the overestimation of eutrophication based on FUI. The R(560)–R(704) (when FUI is between 11 and 15) and R(665)/R(704) (when FUI is between 19 and 21) was employed to distinguish total suspended matter (TSM)-dominated systems in the FUI-based eutrophication assessment. Based on the analysis, a new approach to assessing the eutrophication of coastal waters in Liaodong Bay was developed, which proved to have good accuracy by the field data in 2019 and 2020 (accuracy is 79%). Finally, we used Sentinel-2 images from Google Earth from 2019 to 2020 and locally processed data from 2018 to analyze the FUI spatial distribution and spatial and temporal statistics of the trophic status in the northern Liaodong Bay. The results show that the northern Liaodong Bay always presented the distribution characteristics of high inshore and low outside, high in the southeast and low in the northwest. The nutrient status is the worst in spring and summer.

Biological indicators in the environmental monitoring of gray forest soil of agrosystems

The objective was to monitor the biological indicators to assess the ecological sustainability of gray forest soil, due to the different level of agrotechnical burden on agricultural landscapes. During 10 years of research (2011-2020) the number of bacteria using various forms of nitrogen was continuously decreasing on the background of mineral intensification. The total average pool of active microflora on organomineral and mineral backgrounds in moulboard plowing was 20.1 and 16.1 million CFU g-1 of soil, respectively, during the period of observations. In non-moldboard plowing, the same average pool was 18.8 and 15.9 million CFU g-1. The minimum pool was maintained on a high-intensity mineral background in moldboard plowing, amounting to 14.5 million CFU g-1 of soil. The decrease in the total bacterial number in the soil of mineral backgrounds indicates a deterioration in their ecological stability. The calculated ecological and trophic indices indicate less ecologically stable low-intensity mineral background in moldboard plowing. This variant showed relatively low values of humus accumulation coefficients (Ch = 0.39) and transformation of organic residues into soil organic matter (Ct = 5.4) established at the highest mineralization coefficient (Cm = 1.57). In this soil, mineralization of organic matter prevails, which reduces its fertility and environmental sustainability. On this background, the activity of the studied enzymes was lower than in other variants and in the soil deposits. A set of micromycetes has shown to grow on mineral intensification backgrounds, especially on a high-intensity mineral background, where moldboard plowing was used as the main treatment. The lowest phytotoxicity was noted on a high-intensity organic-mineral intensification background –21.4%. Both microbiological and biochemical parameters represents an informative diagnostic feature of the ecological state of agrolandscapes. They ensure an objective assessment of the efficiency and degree of agrotechnical burden, predicting a decrease in environmental sustainability on mineral intensification backgrounds.

Variaciones limnológicas espaciotemporales de un lago altoandino tropical al norte de Perú

Lake Pomacochas is located in the montane forest region of northern Perú, in an area of great agricultural and fish farming importance, activities that represent the basis of the local economy. The population settled on its margins discharges part of its wastewater into the lake without treatment. The main aim of this study was to determine the spatio-temporal dynamics of this lentic ecosystem, evaluating the limnological and trophic conditions during the dry and rainy periods, and their relationship with each other. The following limnological variables were analyzed at 15 sampling sites: transparency, chlorophyll ‘a’, temperature, pH, conductivity, oxygen saturation, turbidity, nitrates, nitrites, ammonium and soluble reactive phosphorus. Besides, the following trophic indices were calculated: Carlson’s trophic status index (TSIC), trophic status index modified by Aizaki et al. (TSIA), trophic status index modified by Toledo et al. (TSIT) and trophic status index by Vollenweider et al. (TRIX). The lake showed temporal, but not spatial, variation for both limnological variables and trophic indices. The dynamics of the limnological variables in the different climatic periods was also analyzed. The TSIC and TSIA indexes indicated that the lake can be characterized as α-mesotrophic to β-eutrophic, and according to TSIT index as α-mesotrophic to α-eutrophic. The TRIX showed the system has a poor water quality, highly productive, and a very high trophic level. The results reveal that the TSIA best described the trophic state of the lake, while the TSIC was the worst. All these results were statistically significant (P&lt;0.05). The trophic indices evidenced that lake Pomacochas shows a strong tendency to the eutrophication due to agricultural activities. The study also showed that the system is conditioned by climatic seasonality.

Phytoplankton dynamics and renewable energy potential induced by the environmental conditions of Lake Burullus, Egypt.

The research evaluates the spatio-temporal phytoplankton community structure and abundance along with the pollution sources and the lake bioenergy potential, primarily in order to better understand the interplay of the environmental factors affecting them in inland coastal waters. Burullus Lake, located in the north of the Nile Delta of Egypt, is selected as a case study area. Field investigations along with sampling of lake water from 55 sites in the period 20-25 September 2020 are performed. The physicochemical analysis is carried out for the lake water bathymetry, temperature (T°C), pH, salinities (total dissolved solids (TDS) and electric conductivity), and nutrient contents (nitrate, nitrite, ammonia, and phosphate). Phytoplankton identification and biological analysis are used to document the taxa and abundance along with their contents of chlorophyll-a, protein, carbohydrates, and lipids. Then, the trophic index (TRIX), along with the total phytoplankton biomass and the energy potentials, is estimated. Statistical analyses were appraised for the univariate summary statistics, correlation analysis, regression analysis, multivariate statistical analysis including principal component analysis (PCA), and clustering techniques (both geographic position and the k-means clustering) which were conducted using the PAST 4.03 package. The geostatistical modeling of the ordinary kriging implemented in the ArcGIS 9.3 package was appraised for mapping the studied parameters. Results clarified ranges with wide variations for the water depth of 0.90-2 m (av. 130.5 cm), T°C of 26.6-30.20°C (av. 28.3 °C), alkaline pH of 7.78-8.92 (av. 8.6), and TDS of 0.3-17.09 (av. 4.33) gm/l. Ranges of nutrients (mg/l) are also widely varied with nitrates of 0.44-8.36 (av. 3.5), nitrites of 0.004-7.45 (av. 0.4), ammonia range of 0.03-8.54 (av. 1.4), and phosphate of 0.1-4.9 (av. 0.9). A much-diversified phytoplankton community showed maximum counts of 1005 × 103 units.l-1 to a minimum of 340 × 103 units.l-1 for a total of 145 taxa from 61 genera and six classes typically of freshwater forms. The largest biomass (3.06 × 10-3 kg/m3) and energy potential (19.87 × 10-3 kWh/kg) marked the downstream area of the Brimbal Canal, followed by the area located in front of the eastern Burullus and El-Gharbiya drains, which exhibited 2.76 × 10-3 kg/m3 and 17.96 × 10-3 kWh/kg, for the biomass and the energy potential, respectively. Geographic position and k-means clustering techniques distinguished three homogenous classes of marked intra-class variations. PCA analysis distinguished three principal components summed for about 95% of the variations. Intense environmental pollution at the drain downstream areas is indicated by many fish mortality occurrences that were related to the blooms of the toxic Microcystis aeruginosa among the cyanophyte species, and also due to the dominance of the Euglena spp. and Phacus spp. of the Euglenophyceae, which assimilate lots of organic matters in these areas. Lake water movement in the form of turbulent flows and mixing regimes is affected by wind direction and the amount of flows from the sea drains. The estuarine Nile canal has a great effect on the water's physicochemical properties, particularly the nutrient loads, inducing the phytoplankton composition and abundance, total biomass, and the biological contents hence the energy potential. Nutrient load from discharged water from drains was a major contributor to raising the total algae counts and their corresponding contents of the carbohydrates, lipids, proteins, and the chlorophyll-a, which arranged in decreasing order of influence. Phytoplankton dynamics are mostly linked to climatic, hydrologic fluctuation of the drain water flows, and hence, the associated nutrient load discharged from land use changes to fish farms and the related agricultural practices south of the lake. The adopted integrated analyses proved promising, which confirmed the combined effects of environmental factors on lake pollution and the bioenergy potentials.

Application of Machine Learning for eutrophication analysis and algal bloom prediction in an urban river: A 10-year study of the Han River, South Korea

The increasing release of nutrients to aquatic environments has led to great concern regarding eutrophication and the risk of unwanted algal blooms. Based on observational data of 20 water quality parameters measured on a monthly basis at 40 stations from 2011 to 2020, this study applied different Machine Learning (ML) algorithms to suggest the best option for algal bloom prediction in the Han River, a large river in South Korea. Eight different ML algorithms were categorized into several groups of statistical learning, regression family, and deep learning, and were then compared for their suitability to predict the chlorophyll-derived trophic index (TSI-Chla). ML algorithms helped identify the most important water quality parameters contributing to algal bloom prediction. The ML results confirmed that eutrophication and algal proliferation were governed by the complex interplay between nutrients (nitrogen and phosphorus), organic contaminants, and environmental factors. Of the models tested, the adaptive neuro-fuzzy inference system (ANFIS) exhibited the best performance owing to its consistent and outperforming prediction both quantitatively (i.e., via regression) and qualitatively (i.e., via classification), which was evidenced by the lowest value of mean absolute error (MAE) of 0.09, and the highest F1-score, Recall and Precision of 0.97, 0.98 and 0.96, respectively. In a further step, a representative web application was constructed to assist common users to predict the trophic status of the Han River. This study demonstrated that ML techniques are not only promising for highly accurate water quality modeling of urban rivers, but also reduce time and labor intensity for experiments, which decreases the number of monitored water quality parameters, providing further insights into the driving factors of water quality deterioration. They ultimately help devise proactive strategies for sustainable water management.