Eutrophication Process Research Articles

Man-Made Lake of Taman Pertanian, Kuantan: The Valuation of Water Quality and Nutrient Removal by Using Hydrilla Verticillata Sp. and Myriophyllum Aquaticum Sp. as Submerged Plant Species

Polluted water caused by the impact of eutrophication process known as essential negative impacts by the impedance of cyanobacterial species towards the spread of biomass in a freshwater biological system. Phytoremediation is a built utilization of green plants in order the evacuate natural contaminants. The goal of study was to assess the chosen submerged plant species towards supplement expulsion coming from treated lake water in execution light and capacities. The types of submerged plant species used includes Hydrilla Verticillata Sp. (Esthwaite Waterweed) and Myriophyllum Aquaticum Sp. (Parrot’s Feathers) which is to evacuate contaminants in water utilizing phytoremediation process. The study was conducted seven times whereby time gap for every study was seven days. A total of 7 parameters includes Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Dissolved Oxygen (DO), Suspended Solid (SS), turbidity, pH, and Nitrite as for water quality evaluation. The comparison on the effectiveness of submerged plant species to evacuate and remediate contaminant substances shown Hydrilla Verticillata Sp. as the best plant in removing the contaminant based on the percentage of contaminant removal BOD = 66.72%; COD = 77.78%; TSS = 55.55% and Turbidity = 0.57%. In conclusion, there are significant changes before and after treatment from both plants.

Spatial heterogeneity of food web structure in a large shallow eutrophic lake (Lake Taihu, China): implications for eutrophication process and management

The knowledge of food web spatial heterogeneity is important for ecologists and lake managers to understand ecosystem complexity and lake management. Lake Taihu, a large shallow eutrophic lake in China, has two distinct zones: algae- and macrophyte-dominated. In this study, we assessed the spatial heterogeneity of food webs in the two lake zones using stable isotope analysis and isotope mixing model. The basal sources and consumers showed significant differences in δ13C and δ15N ratios between the two lake zones, except for the filter-feeding fishes. Overall, more δ13C-depleted and δ15N-enriched ratios were found in the algae- than the macrophyte-dominated zones for basal sources and consumers. Although the consumers in the algae-dominant zone had higher average δ15N values, the food web of the macrophyte-dominated zone had longer food chain length and more diverse trophic linkages. These spatial differences may have resulted from resource availability and environmental stress of Lake Taihu ecosystem. Factors associated with spatial trophic heterogeneity should be considered for the management and restoration of this shallow eutrophic lake.

Study on the Applicability of Landsat-8 Images as a Tool for Monitoring the Trophic State of Lake Guiers (Senegal)

In this study, an algorithm to transform LANDSAT 8 images of Lake Guiers into chlorophyll-a concentration maps was developed. The objective was to see the feasibility of this method as a mapping tool for monitoring the trophic state of the Lake. The available data are 15 in-situ measurements of the CHL-a content of Lake Guiers’ water using a Micro FLU device and images of the lake acquired in 2013 and 2016 by the LANSAT 8 OLI sensor. A series of correlation tests (simple linear functions, multi-variables, or containing two- order terms) were performed between the spectral sensor signal of June 19, 2016 LANSAT 8 image (“corrected” and converted into reflectance) and the CHL-a content of Lake waters measured on the same day of the satellite record. This was, to find the best regression equation that can be inferred to develop an algorithm to transform LANDSAT 8 image into CHL-a concentration maps. The best equation obtained by correlating the ground truths and the reflectance ratios of the visible and near infrared bands (B2, B3, B4 and B5), is as follows: where B2 = Blue band, B3 = Green band, B4 = Red band, B5 = NIR band. The obtained R2 is 0.703 (e.g., a correlation coefficientof 0.84), revealed that the measured concentrations are well reproduced by the regression model. Applying this model to the 2013 and 2016 image data revealed the monthly variations of the lake CHL-a contents and their seasonal evolution and interannual variations. The obtained results are quite consistent with those from similar studies and provide valuable information regarding Lake Guiers’ vulnerability to algal development. The calculation and analysis of the variability of the CHL-a contents over the study period made it possible to evaluate the trophic state of the Lake, which shows a general tendency for eutrophication process, leading to a progressive degradation of the quality of the water resource.

Eutrophication: a threat to freshwater reservoirs and human health

Eutrophication is an environmental problem that results from the increment of chemical nutrients (Phosphorous and Nitrogen) in a water body, transforming from oligotrophic into eutrophic, and in worst cases a hypertrophic stage. This process can occur naturally or due to human action. When the occurrence is natural, this phenomenon occurs slowly due to increase of organic matter by natural runoff from the soil and rock sediments. The anthropic actions generate punctual and diffuse pollution, this phenomenon favor aggravation of eutrophication process. The increment chemical induces a quickly increase of primary production of photosynthetic organisms in the aquatic systems, like phytoplankton and cyanobacteria, decreasing the light availability by increase of organic matter and consequently depletion of oxygen, resulting in loss of biodiversity. Eutrophication causes loss of water quality that is essential for human survival and development of social and economic activities. The eutrophic reservoirs usually present toxins, undesirable taste and odor, and DBPs formation in drinking water, the purification of the contaminated water might be complex and require long-term measures, turning the process quite costly. Therefore, actions to prevent the eutrophication of ecosystems are preferable. Sometimes the restoration of a disturbed environment is necessary, although expensive and complex, for which we present some methods of treatment of some chemical substances.

Recovery of Scenic Beauty of a Lake in Urban Park from Environmental Diagnosis and Implantation of Mitigating Measures

The city of Sao Paulo, state of Sao Paulo/Brazil, with about 12 million inhabitants is considered the largest city in Latin America. Just as in other large metropolises it is devoid of green areas, in this way it is of great socio-environmental importance of the preservation and maintenance of parks and green areas of the municipality. The Fernando Costa Park, known as the Parque da agua Branca, is an urban park located in the central region of the Municipality of S?o Paulo, and has more than 79 thousand m2 of green area, in a total area of 137 thousand m2. Two lakes, populated predominantly with carp, are inserted in the Park, and are important components of the urban landscape and the patrimony of the city, present landscape function (scenic beauty) and are used to contemplate the environment and leisure of the population. The lakes due to the intense eutrophication process with uncontrolled growth of the phytoplankton presented blue-green coloration, with formations of lumps and foams, low transparency, bad smell and unpleasant visual aspect impairing the visitation of this place. In the first stage of the present research, an environmental diagnosis was carried out and the second stage involved elaboration and implementation of mitigating measures aiming at its restoration. The recovery proposal included the implementation of Artificial Floating Islands (IFAs) aiming at pollution control. After 60 days, it was possible to observe the efficiency of the Eichhornia crassipes populated islands showing that the methodology of phytoremediation was efficient in controlling the eutrophication of urban lakes, guaranteeing the recovery and conservation of the scenic beauty of these places.

Оцінка процесів евтрофікації водних об’єктів річки Стрижень

According to the results of hydrological, hydrochemical and hydrobiological studies (May-October 2017) the estimation of eutrophication processes in water bodies of the Stryzhen River within the city of Chernihiv is presented. The seasonal dynamics of abiotic and biotic factors which form the water quality and trophic level of water bodies has been analyzed. It was found that the features of the hydrological regime of the Stryzhen River in 2016–2017 were low water content, the offset of the passage and a decrease in the duration of the spring flood. The volume of spring runoff was very low and reached 65% of the total annual runoff. Due to the moderate and heavy rains the water level rose slightly to 5-10 cm. It was established that at this time the movement of water in the channel sections of the reservoirs was absent. The important hydrodynamic characteristics of the ponds from an environmental point of view are mixing and wind-generated waves which cause horizontal and vertical migration of substances and enhance the self-purification capacity of water in the ponds. In the spring and summer, when forming a direct temperature stratification, the thickness of the surface layer of water which took part in the mixing processes in the first, second and third ponds was 0.5, 1-2 and 1 m, respectively. The thermocline divided the water column vertically into two parts, which differed from each other in temperature values, as well as in dissolved oxygen content and saturation, pH values, concentrations of ammonium nitrogen, nitrate ions and inorganic phosphorus. The surface layer of water was characterized by enough concentration of dissolved oxygen, whereas in the water column below the thermocline its deficiency was observed. In spring and summer there was alkalinization of the water in the surface layer of the ponds, which was caused by displacement of the hydrocarbon-calcium balance as a result of photosynthetic activity of algae. Under anaerobic conditions the concentration of ammonium nitrogen and inorganic phosphorus in the bottom water layer increased to 1.29–9.99 mgN/dm 3 and to 0.39–4.76 mgP/dm 3 respectively, the maximum values of which were observed in the first pond. During studies of the ponds of the Stryzhen River, it was found that phytoplankton was characterized by a rather rich species diversity of algae and high quantitative development rates that reached the level of water “blooming” due to the massive development of blue-green algae in July and October 2017. The species composition of macrozoobenthos in the studied ponds of the Stryzhen River was very poor, in total 35 species were found. The most favorable conditions for the development of benthic organisms were found in the river section above the third pond and below the first pond before the Stryzhen River flows into the Desna River. Bioindication analysis showed that the zoobenthos in the studied ponds was in a depressed state (TBI = 1-2), but in flowing river sites it was in the best conditions (TBI = 8). According to most of the studied indicators, water quality corresponded to categories 2-5, but content of dissolved oxygen and an inorganic phosphorus belonged to category 6-7 environmental water quality classification. According to the trophic index the studied ponds belonged to mesotrophic, but during “blooming” of water - to hypertrophic.

PREDICTION THE AVERAGE ANNUAL CONCENTRATION OF PHOSPHATE IN RIVERS USING ANN AND MLR MODELS

Clean and quality water is one of the main aims in achieving the seventeen adopted Sustainable Development Goals. That means taking legislative measures at national and international level for the preservation of water quality, prevention of pollution and continuous monitoring. According to global and regional cooperation which is stated by numerous legal regulations, all member countries have obligation to monitoring water quality and submit annual report. For that reason it is very important to obtain accurate and precise data of all monitored water pollutants. In developing countries, because of poor and underdeveloped environmental infrastructure, obtained data for pollutants could have a certain percentage of uncertainty. In order to avoid that problem it is very important the existence of a larger number of models to estimate concentration of water pollutants, including concentration of phosphate. Due to the increasing influence of anthropogenic sources on the content of phosphorus, first in the soil and then in water sources, and negative effects caused by the eutrophication process, it is crucial to monitor the state of water in terms of the presence of phosphate. In the present study, in order to obtain one optimal model to predict the average annual concentration of phosphate in rivers was used two different approaches. In the first approach, was used artificial neural network (ANN), two different ANN architecture: Multilayer Perceptron (MLP) and Radial Basis Function (RBF). In the second approach were used two type of Multiple Linear Regression (MLR) technique, simultaneous and stepwise MLR. Available data used in this study were obtained from Eurostat-the statistical office of the European Union, for 19 European countries for the period from 2004 to 2012. For all created models was used the same dataset. As input variables were used sustainable development indicators, in total 10. All selected inputs were chosen on the basis of their influence on phosphate concentration in rivers and also reviewing of adequate literature. As model performance indicators in this study was used Mean Absolute Error (MAE) and coefficient of determination (R2). Results of all created models first at all showed that comparing two ANN models, better performances on training and test dataset shows MLP model. On test dataset, MLP model gives satisfactory prediction with value of coefficient of determination 0,657. On the other side, developed MLR models show significantly poorer results. Taking into account performances of created models, it is clearly that MLP model shows the best predictive results. On the basis of results of MLP model, could be recognized that it can be an alternative model for prediction annual concentration of phosphate in rivers, and significant tool in water pollutant monitoring.

Spatial and seasonal variations in phosphorus speciation along a river in a lowland catchment (Warnow, Germany)

Losses of phosphorus (P) from arable land lead to P enrichment in surface waters and thus to eutrophication. To gain deeper insights into riverine P processing and transport, the temporal and spatial changes of P compounds along the lowland river Warnow and its tributaries were investigated. Surface water samples were taken monthly between August 2016 and August 2017 and analyzed for the four P fractions: dissolved reactive (DRP), dissolved nonreactive (DNP), particulate reactive (PRP) and particulate nonreactive (PNP) phosphorus. P-composition differed between the courses of the upper Warnow and the impounded middle Warnow due to differences in their hydrological conditions. In the catchment of the upper course, riverine lakes were the sources of PNP and DRP during the summer and autumn. From the catchment of the middle course, mainly PRP and DRP had been introduced into the river. The negative relationship between PRP and the chlorophyll (Chla) concentration (rho = −0.43, p < 0.001) indicated that this P fraction is potentially bioavailable. During the rainy summer of 2017, substantially higher amounts of DRP occurred in the whole Warnow river. The potentially bioavailable P fractions (DRP, PRP, DNP) supported phytoplankton growth in the middle course, and the PNP loads increased with increasing biomass. Total phosphorus (TP) loads increased along the Warnow flow path, due to increasing discharge volume. The annual TP load of 40 t to the estuary was dominated by DRP (32%) and PNP (31%), with smaller contributions by PRP and DNP (19% and 18%, respectively). Our results demonstrate that detailed information on P fractions are helpful to understand P-cycling in rivers and its influence on eutrophication processes. This knowledge should be included in the development of effective management strategies for the improvement of water quality.

Legacy of early anthropogenic effects on recent lake eutrophication (Lake Bénit, northern French Alps)

Abstract Mountain lakes are integrated sentinels of changes in the terrestrial environment, where these changes threaten the quality of the ecosystem services these lakes provide, including high biodiversity, economic and leisure activities. Few evidentiary records exist of the long-term relationships between human pressure and observed impacts. Multiproxy analyses of the Lake Benit sediment sequence, including dating, grain-size, geochemistry, pollen, non-pollen palynomorphs and chironomid assemblage reconstructions, allowed reconstruction of past environmental evolution and lake trophic changes. Combined with soil analyses of the catchment, these data provide a record of the relationships between human activities and the lake-catchment ecosystem, and show the effect of inundation of the shore previously used as pasture. From 2100 to 1100 yrs cal. BP, the catchment was forested. During the Middle Ages, grazing deforested the catchment, triggering an increase in erosion and a change in sediment sources. The lake remained oligotrophic over most of the last millennia. The trophic state changed abruptly in the 20th century with intensification and multiplication of tourist activities in the catchment, i.e., fishing, hiking, while pastoral activities decreased. The sudden eutrophication coincides with an artificial increase of the lake water level in AD 1964 to improve fishing activities. A release of phosphorus (P) from the flooded soils was observed, which may be responsible for the current eutrophication. One thousand years of grazing practices would have led to the observed P concentrations in the soils of the lake shore, transferred by the cattle to this area. Our study highlights the combined effects of past and recent activities on the current eutrophication process, and the legacy of both soils and early anthropogenic activities.

Receiving Water Quality Models for TMDL Development and Implementation

Water quality models are critical tools for the development of total maximum daily loads (TMDLs) and for the evaluation of water quality management alternatives by stakeholders and state environmental protection agencies. Currently there is a large availability of water quality models that can be used to support TMDL studies, and the selection of a particular model requires a good understanding of the model limitations, capabilities, and data requirements. The ASCE/Environmental and Water Resources Institute (EWRI) TMDL Analysis and Modeling Task Committee was established in part to produce guidance documentation to help modelers to identify and implement existing modeling approaches to address some of the most important causes of water quality impairment in the United States, including eutrophication, toxic chemicals, and metals. This paper presents a review of existing mathematical models to evaluate eutrophication processes, including carbon and nutrient cycling, phytoplankton dynamics, and dissolved oxygen availability, as well as a review of mathematical models to simulate the fate and transport of toxic chemicals and mercury. The paper also discusses the main capabilities and limitations of 11 widely used water quality models in the United States. Modelers can use this information to support more informed model selections and to facilitate an effective and successful application of models in TMDL studies.

Is it possible to evaluate the ecological status of a reservoir using the phytoplankton community?

Abstract Aim: The present study aims to evaluate the ecological status of the Broa reservoir through the application of the ecological index Evenness E2 on phytoplankton. Methods Phytoplankton samples from surface were obtained during the dry period (June/2015) in 9 points (P1 to P9), along a longitudinal transect in the reservoir. The qualitative analysis was performed using binocular optical microscope, and the quantitative analysis was performed using the sedimentation chamber method and inverted microscope analysis. The Uniformity Index was calculated on density and richness data. The reference values used in this study were set according to the literature covering 5 classifications (High, Good, Moderate, Low and Bad) for the water quality from Evenness E2 index for phytoplankton, being 1 the maximum value. Results The values observed ranged from 0.1142 in P1 to 0.1468 in P3, being both classified as “Bad”, since values were less than0.21. Conclusions The result reinforces the sanitary problem of the reservoir, the occurrence of consecutive algae blooms because the amount of nutrients in the region. A massive occurrence of Cyanobacteria was observed, with emphasis on the species Aphanizomenon gracile, which may be related to the adaptive advantages that this class presents on the community in eutrophic environments. Activities in the basin can contribute effectively to the eutrophication process of the reservoir, such as agriculture, sand mining and livestock. The water quality is compromised due to the dense presence of potentially toxic species, reflects of the eutrophication process, pointing commitments for the multiple uses of the reservoir, as well as human and ecosystem health. These processes could be corroborated by the application of the index and indication of poor water quality.

Wind-induced hydrodynamic changes impact on sediment resuspension for large, shallow Lake Taihu, China

The internal sediment release is a key factor controlling eutrophication processes in large, shallow lakes. Sediment resuspension is associated with the wave and current induced shear stress in large, shallow lakes. The current study investigated the wind field impacts on sediment resuspension from the bottom at Meiliang Bay of large, shallow Lake Taihu. The impacts of the wind field on the wave, current, and wave-current combined shear stresses were calculated. The critical wind speed range was 4–6 m/s after which wave and current shear stress started to increase abruptly, and onshore wind directions were found to be mainly responsible for greater shear stress at the bottom of Lake Taihu. A second order polynomial fitting correlation was found between wave (R2 0.4756) and current (R2 0.4466) shear stresses with wind speed. Wave shear stress accounted for 92.5% of the total shear stress at Meiliang Bay. The critical wave shear stress and critical total shear stress were 0.13 N/m2 for sediment resuspension whereas the current shear stress was 0.019 N/m2 after which suspended sediment concentrations (SSC) increased abruptly. A second order polynomial fitting correlation was found between wave (R2 0.739), current (R2 0.6264), and total shear stress (R2 0.7394) with SSC concentrations at Meiliang Bay of Lake Taihu. The sediment resuspension rate was 120 to 738 g/m2/d during 4–6 m/s onshore winds while offshore winds contributed ≥ 200 g/m2/d. The study results reveal the driving mechanism for understanding the role of the wind field in sediment resuspension while considering wind speed and direction as control parameters to define wave and current shear stresses.

The response of stocks of C, N, and P to plant invasion in the coastal wetlands of China.

The increasing success of invasive plant species in wetland areas can threaten their capacity to store carbon, nitrogen, and phosphorus (C, N, and P). Here, we have investigated the relationships between the different stocks of soil organic carbon (SOC), and total C, N, and P pools in the plant-soil system from eight different wetland areas across the South-East coast of China, where the invasive tallgrass Spartina alterniflora has replaced the native tall grasses Phragmites australis and the mangrove communities, originally dominated by the native species Kandelia obovata and Avicennia marina. The invasive success of Spartina alterniflora replacing Phragmites australis did not greatly influence soil traits, biomass accumulation or plant-soil C and N storing capacity. However, the resulting higher ability to store P in both soil and standing plant biomass (approximately more than 70 and 15kg P by ha, respectively) in the invasive than in the native tall grass communities suggesting the possibility of a decrease in the ecosystem N:P ratio with future consequences to below- and aboveground trophic chains. The results also showed that a future advance in the native mangrove replacement by Spartina alterniflora could constitute a serious environmental problem. This includes enrichment of sand in the soil, with the consequent loss of nutrient retention capacity, as well as a sharp decrease in the stocks of C (2.6 and 2.2 t C ha-1 in soil and stand biomass, respectively), N, and P in the plant-soil system. This should be associated with a worsening of the water quality by aggravating potential eutrophication processes. Moreover, the loss of carbon and nutrient decreases the potential overall fertility of the system, strongly hampering the reestablishment of woody mangrove communities in the future.

An Integrated Analysis of the Eutrophication Process in the Enxoé Reservoir within the DPSIR Framework

The Enxoé reservoir in southern Portugal has been exhibiting the highest trophic state in the country since its early years of operation. The problem has attracted water managers’ and researchers’ attention as the reservoir is the water supply for two municipalities. Extensive research was thus conducted over the last few years, including field monitoring and modelling at the plot, catchment, and reservoir scales. This study now frames all partial findings within the Driver-Pressure-State-Impact-Response (DPSIR) framework to better understand the eutrophication process in the Enxoé reservoir. Agriculture and grazing were found to have a reduced role in the eutrophication of the reservoir, with annual sediment and nutrient loads being comparably smaller or similar to those reported for other Mediterranean catchments. Flash floods were the main mechanism for transporting particle elements to the reservoir, being in some cases able to carry up three times the average annual load. However, the main eutrophication mechanisms in the reservoir were P release from deposited sediment under anoxic conditions and the process of internal recycling of organic matter and nutrients. Reducing the P load from the catchment and deposited sediment could lead to a mesotrophic state level in the reservoir. However, this level would only be sustainable by limiting the P internal load ability to reach the photic zone.

Phosphorus delivered to surface waters resulting from the use of powder detergents: environmental and public health aspects

This article addresses the social and environmental aspects related to the presence of phosphorus in surface water bodies, assessing the impacts caused by the utilization of powder detergents on the quality and availability of water resources, with particular respect to the occurrence of eutrophication. Based on data concerning the composition and consumption of the products currently sold in Brazil, the evolution of this phenomenon leading to the current situation is reported. Indications are that Brazilian detergents have a low phosphorus content, thus it is possible to infer that these products offer a small risk of impacting the trophic levels of surface waters. There is, however, a need to adjust the content of legislation to market practices, as well as improve public policies related to environmental education. By means of an intensive process of communication and education, awareness about the issue can be raised, keeping this major source of phosphorus in the environment under control and contributing to the increase in the availability of water, through the prevention of eutrophication processes.

Shellfish culture: a complex driver of planktonic communities

AbstractThis review features recent updates on planktonic community alteration attributed to shellfish farming across three major drivers: predation, nutrient availability and the hydrodynamic environment. The grazing pressure generated by filter‐feeder communities (shellfish and epibionts) constitutes a ‘top‐down’ control of planktonic communities in aquaculture areas, inducing a significant depletion of planktonic organism concentration. By selecting larger cells during the filtration process, shellfish also favour smaller organisms in the water column, leading to the dominance of the latter. Direct excretion and the benthic alteration process tend to fertilise the water column and significantly stimulate primary production. The associated epibiont community particularly contributes to this regeneration process. The expected consequence of increasing nutrient availability is generally a planktonic shift in favour of small planktonic species. However, investigation on the relationship between planktonic structure and nutrient conditions has revealed a wide complexity and variability. Finally, all structures used in shellfish farming activities interact with water currents and tend to significantly increase the residence time of planktonic organisms inside shellfish farming areas. In grazing‐dominated systems, an increase in residence time tends to increase the exposure time of planktonic populations to detrimental conditions, reducing biomass and production. The general consequences of shellfish farming are a decrease in primary production in farming ecosystems, and a possible alteration of structure and functioning of planktonic communities. The implications of shellfish farming also appear to be quite different from other aquaculture activities such as fish farming, which tend to promote primary production leading to eutrophication process.

STUDY OF THE TEMPERATURE CONDITION OF SURFACE WATERS OF NOVOTROITSKY RESERVOIR BASED ON REMOTE SENSING DATA AND EVALUATION OF ITS IMPACT ON FISH GROWTH AND DEVELOPMENT

Aim.The aim of the study is to analyze and reveal the features of the temperature regime of the Novotroitsky water reservoir surface based on remote sensing data; to determine the influence of the temperature regime of the surface waters of Novotroitsky reservoir on the ecological state of the reservoir, as well as to determine the areas of the surface water zones of the Novotroitsky reservoir with optimal and unfavorable temperature conditions for fish.Methods.The temperature values of the earth's surface (water area) were calculated according to the generally accepted methodology. Its essence lies in the fact that the calculation of the earth's surface temperature is performed after radiometric calibration of the images and compensation of the effect of the optical density of the atmosphere taking into account the emissivity of various objects on the earth's surface. The calculations were performed separately for the 10 and 11 channels of images from the Landsat 8 satellite, and then averaged.Results.Were established the quantitative characteristics of the inhomogeneity of the temperature fields of the water surface of Novotroitsky reservoir during the summer period due to discharges of the heated waters of the Stavropol GRES power plant. The peculiarities of the spatial variability of the temperature fields of the Novotroitsky water reservoir surface in summer season were revealed. It is shown that the use of the Novotroitsky water reservoir as a reservoir-cooler is potentially accompanied by the development of eutrophication processes and creation of risks for drinking purposes, as well as cultural, household and fishery use. The table shows the data demonstrating the temperature condition of the Novotroitsky reservoir water surface. The figure shows the temperature fields of the surface of the Novotroitsky water reservoir.Conclusions.In summer period, half of the water area of the Novotroitsky water reservoir can be attributed to the zones of optimum temperatures for the juvenile pikeperch. Were revealed the periods when the reservoir becomes practically unsuitable for growth and development of juveniles of oxyphilic fish. Excessive rise of water temperature in summer was established in accordance with SanPiN (Sanitary Rules and Regulations) 2.1.5.980-00.2.1.5. Such an increase in temperature is observed in 13-16% of the whole water area.

Influence of hydraulic retention time and amplitude of water level fluctuations on water quality in irrigation reservoirs of the Kala Oya river basin, Sri Lanka

Management of reservoir water quality is a global challenge due to the natural process of eutrophication and anthropogenic aggravation. In Sri Lanka, irrigation reservoirs support several secondary uses such as fish production, livestock farming, and many communal uses including drinking water supply. In the present study, basic limnological parameters of ten irrigation reservoirs of Sri Lanka were investigated from June 2013 to February 2016, with a view to identifying influence of hydrological regimes on reservoir water quality. Spatio-temporal similarities of water quality parameters were studied employing the self-organizing map (SOM) routine of the artificial neural network application. The sample vectors, classified on the SOM lattice, indicated 6 clusters at 50% similarity level. When reservoir that were categorized according to hydraulic retention time (HRT) and relative reservoir level fluctuation (RRWL; defined as the ratio of the mean reservoir level amplitude to mean depth), were compared with dominant water quality parameters in SOM lattice, it was evident that some productivity-related water quality parameters were influenced HRT and RRWL. The results of the study revealed that HRT and RRWL can essentially be controlled through management of hydrological regimes in irrigation reservoirs, thus, close dialogue between irrigation authorities and other users of reservoir water resources are needed to ensure desired water quality of the reservoirs.

Trophic state of an urban coastal lagoon (northern Brazil), seasonal variation of the phytoplankton community and environmental variables

Jansen Lagoon is an urban coastal area formed by damming the Ana Jansen Creek, which is located in the northwest of São Luis Island (northern Brazil) and is influenced by semidiurnal macro-tides. This study aimed to characterize the seasonal variation of the phytoplankton communities and its relationship with environmental variables to determine the trophic conditions in the Jansen Lagoon. Samples were collected bimonthly in five fixed sites in 2011 and 2012 to analyze biological and physicochemical data. A total of 55 taxa were identified including Bacillariophyta (25), Cyanobacteria (17), Chlorophyta (5), Charophyta (2), Euglenophyta (4) and Miozoa (2). The Closterium setaceum, Pleurosigma elongatum e Oscillatoria sp3 occurrence had a positive correlation with the higher rainfall period, increase in dissolved oxygen concentrations and nutrients (DIP and NO2−) and elevated trophic levels (TRIX). Cyclotella stelligera and Microcystis aeruginosa were strongly correlated with chlorophyll a concentration (microphytoplankton) under turbidity and wind speed influence. The trophic state of Jansen Lagoon ranged from eutrophic to hypereutrophic according to the TRIX index, and this poor water quality is explained by an intense eutrophication process in the rainy season due to elevated nutrient availability. Hence, to change the scenario presented in this study the reduction of point and non-point sources is necessary to slow down the eutrophication and growth of algal blooms in Jansen Lagoon.

Seasonal flux patterns of planktonic foraminifera in a deep, oligotrophic, marginal sea: Sediment trap time series from the Gulf of Aqaba, northern Red Sea

Annual and interannual planktonic foraminifera (PF) fluxes, species assemblage composition, vertical distribution (0–600 m) and shell-size-distribution (63–125, 125–500, 500–1000 µm) were characterized in the marginal oligotrophic Gulf of Aqaba (GOA), northern Red Sea, between January 2014 and February 2016 using a monthly resolved sediment trap time series.PF fluxes in the GOA demonstrate strong seasonality, with low values observed during summer months, gradually increasing during the autumn-winter. This increase is coeval with decreasing sea-surface temperatures and deepening of the mixed layer depth in the GOA that drives the admixing of nutrient-replete subsurface waters into the mixed layer. This in turn, triggers an increase in primary productivity, expressed by enhanced chlorophyll-a concentrations.Spinose species constitute the majority of the PF assemblage. The dominant shell size-fraction is between 63 and 125 µm (~86% of the total flux), which has generally been overlooked in previous studies, resulting in a significant knowledge gap related to the neanic stages and the small-adult-size PF. Indeed, the 63–125 µm size-fraction is dominated by the smallest species Turborotalita clarkei (36–92% of this size fraction). The 125–500 µm size-fraction (~13%) is dominated by the species Globigerinoides ruber, while less than 1% of the shells are in the range of 500–1000 µm, dominated by Orbulina universa.Over the last few decades, the already low number of PF species decreased in the GOA from 13 to 10, including the disappearance of Trilobatus sacculifer, the most common species in the GOA during the 1970s. This finding could reflect the sensitivity of the geographic location of the GOA, at the edge of a > 2000 km transect that begins in the productive Arabian Sea, and spans across the Red Sea, where a gradual decrease in nutrient availability and increase in surface salinity imposes a corresponding decrease in PF species richness, abundances and diversity. Thus, the northern GOA is an extreme case of an oligotrophic system whose ecosystem is already pre-screened by the Red Sea transect. Combined with previous episodes of Trilobatus sacculifer disappearance identified in downcore records in the Red Sea, we conclude that the change in the PF community over recent decades is probably not the result of local eutrophication processes, as has been suggested in recent studies, but rather, more likely reflects environmental changes on a larger regional to global scale.