Water Trophic Status Research Articles

The diversity and abundance of phytoplankton and benthic diatoms in varying environmental conditions in Kok River, Chiang Rai, Thailand as bio-indicators of water quality

Abstract. Prasertsin T, Suk-ueng K, Phinyo K, Yana E. 2021. The diversity and abundance of phytoplankton and benthic diatoms in varying environmental conditions in Kok River, Chiang Rai, Thailand as bio-indicators of water quality. Biodiversitas 22: 1853-1862. The study of living organisms was important information for bio-indicators which was utilized to assess the quality of the environment. In the river ecosystem, the algae with which one organism was interesting accordingly considered the relationship of 2 groups algae, including phytoplankton and benthic diatoms and the physical-chemical parameters of Kok River Chiang Rai, Thailand. Phytoplankton and benthic diatoms were collected from five sampling sites along the Kok River during January (cool dry), March (summer), and June (rainy season) 2018, and assessed as bio-indicators to monitor environmental factors that represent water quality across varying conditions and periods. Fifty-seven species of phytoplankton and thirty-nine species of benthic diatoms were found. The phytoplankton mainly belonged to the phylum Bacillariophyta (diatom group). Physical and chemical factors affecting the dominant phytoplankton and benthic diatom species were subjected to canonical correspondence analysis (CCA). Results showed that planktonic and benthic Gomphonema lagenula positively correlated with ammonium nitrogen, recording highest abundance during the rainy season. Abundance of Achnanthidium straubianum, a planktonic and benthic diatom, and Navicula cincta negatively correlated with river velocity and water conductivity, with lowest numbers during the rainy season. Water trophic status evaluated from the main parameters of the AARL-PC score indicated that during the cool dry and summer seasons all sampling sites were classified as mesotrophic, while during the rainy season they were classified as meso-eutrophic. The combination of phytoplankton and benthic diatom can be used as bio-indicators of water quality in the Kok River and other freshwater ecosystems.

Estimation of the Sizes of Suspended Organic Particles from Light-Scattering Phase Functions and Their Relationship to the Water Trophic State

Average sizes of organic particles suspended in water are calculated from measurements of light-scattering phase functions. Their correlation with the sizes of phytoplankton cells, visually determined with the use of a microscope, is derived. The relationship between the size of suspended organic particles and the water trophic state is studied. It is ascertained that the average size of suspended organic particles increases with a decrease in the water productivity (trophic state). Taking into account the correlation between the average size of organic particles suspended in water and the average size of phytoplankton cells, it was concluded that the size of phytoplankton cells increased in oligotrophic waters (low trophic state) as compared to eutrophic waters (high trophic state).

Trophic assessment in South American Atlantic coastal lagoons: Linking water, sediment and diatom indicators

Within two coastal shallow lagoons, trophic state was assessed by integrating water and sediment chemical indicators such as the TRIX and the benthic biopolymeric carbon (BPC) trophic indicator, altogether with biological environmental indicators (diatom species characterization). Spatial and temporal behavior of TRIX and BPC indices suggest that water column trophic indicators reflect rather short-term variations in water quality changes, while benthic trophic indicators rather reflect consistent long-term trends which make them useful as enduring indicators of eutrophication. Canonical Correspondence Analysis (CCA) showed that both sediment and transitional water trophic state indices increased eutrophic conditions with a decreasing salinity and increasing total nutrients. Diatom species associated with elevated eutrophic condition such as Staurosirella martyi, Staurosira breviestriata, Amphora copulata, Amphora veneta, Nitzschia sp., and Bacillaria paradoxa, showed a positive correlation with both trophic indices. We highlight the need for considering sediment eutrophication indicators towards in monitoring programmes within shallow coastal lagoons.

Status of water quality and level of trophic in Juanda Reservoir of Purwakarta Regency, West Java, Indonesia

Juanda reservoir is one of the reservoirs located in Purwakarta Regency, West Java Province, Indonesia, whose primary function is hydropower, water resources for irrigation, industrial and drinking water, and secondary function for fisheries and tourism activities. Currently, an increase in activities around the existing reservoir has affected its water quality. In order to determine the water quality and trophic level status of the Juanda reservoir, research has been conducted within five stations during the period of August-December 2020. The water quality status includes physical, chemical, and biological parameters that compared with Store standards on Class II and III. Meanwhile, the trophic status was determined by Trophic Level Index (TLI) based on the parameters of transparency, chlorophyll-a, total nitrogen, and total phosphorus. The results show that the water quality status of Juanda reservoir has been contaminated Class III and heavily polluted Class II. The parameters that exceed include ammonia, nitrate, and BOD5. The Juanda reservoir's tropic status was in the eutrophic category, with TLI values ranging from 4.6 to 5.2.

MODIS-based monitoring of spatial distribution of trophic status in 144 key lakes and reservoirs of China in summer of 2018

随着经济社会的快速发展和进步，我国湖库水体富营养化情况越来越严重.卫星遥感在水体营养状态监测方面具有重要潜力，但基于卫星遥感的全国范围内湖库水体营养状态监测和分析方面还鲜有研究.本文基于2018夏季的MODIS卫星遥感数据生产FUI指数产品，构建基于FUI水色指数的湖库营养状态评价方法，监测全国范围内144个重点湖库水体的营养状态等级.结果表明：贫营养、中营养、富营养的湖库比例分别为16%、24%、60%；营养状态在空间上分布不均匀，总体上呈现东高西低的现象；东北山地与平原和东部平原湖区以富营养状态水体为主；西部湖库水体以贫到中营养状态为主，尤其是青藏高原湖区贫营养比例比较高；海拔和地表温度等自然因素与工业点源和农业面源污染等人为因素是湖库营养状态的重要影响因素.;With the rapid development of the economy and society, the eutrophication of lakes and reservoirs in China is becoming increasingly serious. Satellite remote sensing has a great potential in the monitoring of water nutrient status, but little research exists on the monitoring and analysis of the water trophic status of lakes and reservoirs on a nationwide scale based on satellite remote sensing. In this study, MODIS data from summer 2018 was used to produce FUI index products, construction of evaluation method of lake and reservoir nutrition state based on FUI water color index and monitored the trophic status of 144 key lakes and reservoirs in China. The results show that the proportion of oligotrophic, mesotrophic, and eutrophic lakes and reservoirs is 16%, 24%, and 60%, respectively. The proportion of eutrophication is very high; the spatial distribution of trophic status is uneven, and the overall eutrophication is higher in the east than the west. Most reservoirs and lakes in the northeast and the east are eutrophic. The water bodies of western lakes are mostly oligotrophic to mesotrophic, an especially high percentage of oligotrophic in the Qinghai Tibet Plateau. Natural factors such as altitude and surface temperature, industrial point source, and agricultural non-point source pollution are important factors influencing the trophic state of lakes and reservoirs.

Nutrient concentrations and trophic state of three Andean lakes from Junín, Perú

The study assessed the trophic state of three lakes used as fish farms in the region of Junín-Peru, under different hydrological conditions. Surface water samples were collected from three points at each lake in 2018 during the rainy (March-April) and dry (June-July) seasons. Total phosphorus, turbidity, and chlorophyll-a (Chl-a) were measured. Trophic indexes (TSI Chl-a, and TSI TP) were also computed. The water trophic state categorization was performed by adapting and calculating the Trophic State Index (TSI). The TSI (TP) classified the three lakes in both seasons (rainy and dry) as mesotrophic (30 < TSI ≤ 60). Pomacocha and Tipicocha were classified as eutropic (60 < TSI ≤ 90) in the two seasons according to TSI (Chl a), while Tranca Grande was classified as mesotrophic (also two seasons). The results for TSI showed a predominance of eutrophic and mesotrophic conditions in all lakes used as fish farms.

Use of rotifer trophic state indices to show the effect of hydrobionts and nutrients on water trophic status in mesocosms

Abstract We have determined how Crustacea, zebra mussels (Dreissena polymorpha), fish and nutrients affect the trophic state in mesocosms filled with water collected from the pelagic zone of a eutrophic lake. We hypothesized that the pool of nutrients would increase both directly due to the input of phosphorus and nitrogen and/or indirectly due to the introduction of animal biomass. We used trophic state indices based on the abundance and species structure of rotifers to assess changes in the trophic state in mesocosms. The role of small detritophages in rotifer communities increased as a result of treatments. Our results clearly demonstrated that D. polymorpha was able to reduce the trophic status of mesocosm waters as indicated by reduced rotifer trophic state indices regardless of interactions with other treatment factors. Contrary to our expectations, neither the nutrients added at the beginning of the experiment nor the introduction of crustaceans or fish affected the rotifer trophic indices.

Linkage between water soluble organic matter and bacterial community in sediment from a shallow, eutrophic lake, Lake Chaohu, China

Lacustrine sediment played important roles in migration and transformation of its water soluble organic matter (WSOM), and the source and composition of WSOM would affect water trophic status and the fate of pollutants. However, we know little about the pathway of WSOM transformation and its driving bacterial communities in lacustrine sediment. In the present study, we investigated the spatial distribution patterns of sediment WSOM and its fluorescent fractions across Lake Chaohu using fluorescence spectroscopy, and explored WSOM compositional structure through our proposed calculated ratios. In addition, we also analyzed sediment bacterial community using Illumina sequencing technology, and probed the possible pathway of sediment WSOM transformation under the mediate of indigenous bacteria. Our results showed that the inflowing rivers affected the spatial distribution patterns of WSOM and its five fractions (including tyrosine-, tryptophan-, fulvic acid-, humic acid-like substances and soluble microbial productions), and sediment WSOM originated from fresh algae detritus or bacterial sources. In parallel, we also found that Proteobacteria (mainly γ-Proteobacteria and δ-Proteobacteria), Firmicutes (mainly Bacilli), Chloroflexi, Acidobacteria, Planctomycetes and Actinobacteria dominate sediment bacterial community. Furthermore, these dominant bacteria triggered sediment WSOM transformation, specifically, the humic acid-like substances could be converted into fulvic acid-like substances, and further degraded into aromatic protein-like and SMP substances. In addition, our proposed ratios (P-L:H-L, Ar-P:SMP and H-L ratio), as supplementary tool, were effective to reveal WSOM composition structure. These results figured out possible pathway of WSOM transformation, and revealed its microbial mechanism in lacustrine sediment.

Assessment of nutrient contamination in the waters of the El Fuerte River, southern Gulf of California, Mexico.

This study assessed the spatial and temporal nutrient variability in the El Fuerte River basin in northwestern Mexico, considering its effects on the water trophic status as well as the nutrient loading to the Gulf of California. Physicochemical parameters, inorganic species of nitrogen, phosphate, total nitrogen, total phosphorus, and chlorophyll-a (chl-a) were quantified at 16 selected sites along the river in April (dry season) and October (rainy season) 2017. Mean concentrations of nutrients during dry and rainy seasons were 36.3 ± 24.1 and 55.1 ± 74.6 μg L-1 of total ammonia nitrogen, 3.4 ± 3.6 and 4.5 ± 3.5 μg L-1 of NO2--N, 190.8 ± 256.0 and 163.6 ± 261.0 μg L-1 of NO3--N, 42.4 ± 44.2 and 104.9 ± 76.2 μg L-1 of PO43--P, 1.0 ± 1.3 and 691 ± 2242 mg L-1 of TN, 0.06 ± 0.06 and 0.08 ± 0.09 mg L-1 of TP, and 0.9 ± 0.6 and 2.0 ± 0.9 μg L-1 of chl-a with significant differences (p < 0.05) between sites and seasons. When waters are transported downstream, nutrient levels are enriched by 4 to 35 times compared to those upstream due to increased population and agriculture downstream, confirming the hypothesis of the study. The calculated TN and TP fluxes were 1.23 × 104 and 3.57 × 101 ton year-1, respectively. Factor analysis indicated that inorganic nitrogen species and phosphorus are the main factors affecting the river water quality. Despite N excess during the rainy season, the river reached mesotrophic waters due to phosphorus limitation. This suggests the need to establish a water quality monitoring program to understand the vulnerability of the river course to changes in its trophic state.

Inland water's trophic status classification based on machine learning and remote sensing data

In this work, we tested machine learning algorithms in classifying waters in a reservoir cascade with basis in trophic state. The classification was done through remote sensing reflectance (Rrs) measurements collected in situ. Chlorophyll-a (chla) content determined in the laboratory were used to define the trophic state in the sampling points distributed in four reservoirs (Barra Bonita, Bariri, Ibitinga and Nova Avanhandava), located at the Tietê River, Brazil. Those four impoundments exhibit widely differing optical properties from each other, which is rather evident in relation to chla concentration. From the dataset collected in the reservoir cascade, a trophic gradient is observed, decreasing from up-to downstream. To classify the trophic state, we tested three machine learning algorithms: Artificial Neural Network (ANN), Random Forest (RF) and Support Vector Machine (SVM). Results showed that ANN and RF algorithms exhibited the best performance in classifying the different trophic state in the cascade of reservoirs. Both approaches raised a global accuracy of 80.00% and average area under Receiver Operating Characteristics (ROC) curve (AUCROC) of 0.928 and 0.912, respectively. Comparing the machine learning approaches with a parametric algorithm, only SVM presented a slightly lower performance. The outcomes of this classification can be useful for trophic state mapping considering the large cascade of reservoirs or rivers. In addition, it can give a direction in bio-optical modeling studies, which have shown that a unique bio-optical algorithm is unable to accurately retrieving concentrations of optically active constituents in aquatic system with high optical variability. So that, it is possible to develop specific chla prediction models considering the optical characteristics of each stretch of river, since machine learning-based classifications (ANN and RF) indicate different optical regions.

Determination of the size of suspended organic particles from light scattering phase function and their relationship to the water trophic state

Determination of the size of suspended organic particles from light scattering phase function and their relationship to the water trophic state

Characteristics of organic phosphorus fractions in soil from water-level fluctuation zone by solution 31P-nuclear magnetic resonance and enzymatic hydrolysis

Phosphorus (P) is an essential nutrient element for biological growth that can contribute to eutrophication in aquatic ecosystems. Water trophic status and algae growth are primarily related to the content of bioavailable P, which is primarily related to enzymatically hydrolysable organic P(EHOP) and dissolved inorganic P(IP). In this study, soil samples from the water-level fluctuation zone (WLFZ) were collected from a tributary of the Three Gorges Reservoir (TGR) to characterize the properties of organic P(OP) fractions using solution 31P-nuclear magnetic resonance (NMR) and enzymatic hydrolysis. 31P-NMR showed that orthophosphate was the main part of the bioavailable P in the WLFZ soil and accounted for 80.4% of the NaOH-EDTA extractable total P (NaOH-EDTA TP), while phosphate monoester accounted for 60.5% of NaOH-EDTA extractable OP (NaOH-EDTA OP). The soil properties and replenishment from the mainstream of the Yangtze River to the Pengxi River have a certain effect on the content and distribution of P forms in the WLFZ soil of the tributary. The EHOP accounted for 28.1% of the NaOH-EDTA OP, and a significant positive correlation was observed between labile monoester P and EHOP and organic matter (OM). The water-soluble OP(H2O-OP), bicarbonate-extractable OP(NaHCO3-OP), and Fe- and Al-associated OP(Fe/Al-OP) were significantly hydrolyzed by phosphatase and thus exhibited great release potential. The ranking of the bioavailability of OP was Fe/Al-OP > H2O-OP > NaHCO3-OP. Phytate-like P were mainly found in H2O-OP and NaHCO3-OP, which indicated that periodic submersion–emersion cycles promoted the release of phytate-like P from Fe/Al-OP into the water column of the TGR. These observations suggest that when the external P input was effectively controlled, a huge risk of release of the internal OP from the WLFZ soil, and the biogeochemical cycling of the bioavailable P played an important role in maintaining the eutrophication of the reservoir.

Lagoon trophic state determination. Case of study Tecocomulco´s lagoon, Hidalgo, Mexico

Because of anthropogenic impacts on the trophic state of Tecocomulco´s lagoon in Hidalgo, Mexico, the quantities of nitrogen, phosphorus, and other biologically useful nutrients are being increased in spite of they are the primary determinants of a body of water's trophic state index. Nutrients such as nitrogen and phosphorus tend to be limiting resources in standing water bodies, so increased concentrations tend to result in increased plant growth, followed by corollary increases in subsequent trophic levels. Consequently, a body of water's trophicindex may sometimes be used to make a rough estimate of its biological condition. Actually, in order to protect the environment, a new level of planning and execution of development projects have been originated by life cycle assessment, environmental impact researchesand evaluating economic financial researches due to the understanding that, environment will be irreversible damaged by any kind ofproject.

Results of Bacterioplankton Studies in the Dnistrovskiy Estuary in 2003-2018

Purpose. Determination of long-term changes in bacterioplankton number in the Dnistrovskiy Estuary in 2003-2018 and data usage for aquatic environment quality assessment. Methods. Bacterioplankton number determination was done using direct microscopy method under microscope with magnification of 1200. Ecological classification of surface waters quality adopted in Ukraine was used for water trophic status assessment. Results. Changes of bacterioplankton quantitative characteristics in summer periods of 2003-2018 have been analyzed. Tendency of increase in bacteria quantity has been revealed in the past eight years, as well as the waters’ trophic status increase from polytrophic in summer periods of 2003-2005, 2007-2009 and 2015-2016 to hypertrophic in 2011-2014 and 2017-2018. Maximal out of all the years bacterial number was identified in July 2012 that exceeded the peak value in the end of past century. Existence of statistical connections between bacterioplankton and water conductivity, transparency, chlorophyll a, pheophytin and total phosphorus were shown. Conclusions. It has been established that microbiological regime forming in the Dnistrovskiy Estuary took place under the influence of natural processes of organic matter production and pollution factors that revealed themselves the most in the middle and southern parts of the estuary. Among the aquatic environment parameters controlled bacterioplankton number, like chlorophyll a, reflected the changes of the Dnistrovskiy Estuary trophic state the most realistic way. At that, index of bacterioplankton is indispensible for indication of water pollution with organic matter of anthropogenic origin.

Holocene climate vs. catchment forcing on a shallow, eutrophic lake in eastern Poland

This paper presents a sedimentary record from Lake Łukie located in the southeastern part of the Central European Plain, beyond the reach of the maximum extent of the last glaciation. The lake has thermokarstic origin and developed during the last glacial termination due to subsidence of the sub‐Quaternary carbonate basement triggered by permafrost thawing. A sediment core was investigated to reconstruct water trophic state and lake depth changes during the Holocene. We aimed at showing the relationship between ecological and geochemical changes in the lake and regional/supraregional climatic and hydrological trends throughout the Holocene. Results of subfossil Cladocera analysis were combined with data on the geochemistry and stable C and O isotopes in sedimentary carbonates. Isotopic and geochemical proxies helped to detect sources of sedimentary particles in the lake and thus to reconstruct changes in the intensity of atmospheric and catchment processes (e.g. precipitation and surface runoff). The Cladocera analysis results indicated endogenic processes in the lake such as trophic changes. Our data revealed that Lake Łukie has always been a rather eutrophic water body and the periods of particularly high productivity were in the lower Preboreal and upper Subatlantic. Periods of increased water depth were recorded in the lower Preboreal, lower Boreal and upper Subboreal, whereas low water stands were obtained during the late Preboreal, late Boreal, late Atlantic and Atlantic/Subboreal transition as well as during the lower Subboreal. The sediment succession from Lake Łukie provides the first full Holocene record of carbon and oxygen stable isotopes in lacustrine carbonates from the eastern part of the Central European Lowland. The record is characterized by uncommonly high δ13C and δ18O values of the carbonates resulting from a combination of within‐lake processes and dissolution of the carbonate bedrock of Cretaceous age. The impact of the old carbonates on isotope values was helpful in the reconstruction of the catchment forcing on the lake.

Is zooplankton an indicator of the water trophic level in dam reservoirs?

Abstract The trophic state of ten dam reservoirs was assessed using a zooplankton community. In order to determine the trophic state of dam reservoirs, we used indices calculated on the basis of density and species structure of Rotifera and Crustacea communities. Samples were collected once during summer 2012 in ten dam reservoirs. The largest numbers of zooplankton taxa were found in a lowland high meso-eutrophic dam reservoir (Koronowski) and the lowest ones in a submontane low eutrophic dam reservoir (Lubachowski). The trophic state was determined for the investigated dam reservoirs. In the case of the Rotifera community, the percentage of the tecta form in the Keratella cochlearis population and the proportion of high-trophic species in the total species density were the best indices to describe the water trophic status. In the case of the crustacean community, the best indices were the density of Crustacea and the biomass of Cyclopoida. The high value of all indices calculated on the basis of density and species structure of Rotifera and Crustacea was determined for Zygmunt August Lake, whose trophic status was defined as highly eutrophic to polytrophic. Our study has shown that zooplankton could be a good ecosystem indicator of the water trophic level in dam reservoirs.

Benthic Diatoms of the Ying River (Huaihe River Basin, China) and Their Application in Water Trophic Status Assessment

Benthic diatoms are an indispensable link of the water ecological system in terms of energy flow and material cycling, and they directly or indirectly reflect the status of the water environment. We sampled benthic diatoms and environmental factors from April to May of 2013 from 53 sites along the Ying River to study their application in local water trophic status assessment, with a focus on the dominant benthic diatom species, their composition and distribution pattern, and the relationship between benthic diatoms and environmental factors. A total of 370 species and varieties were identified, belonging to 56 genera and six orders. The dominant species were as follows: Nitzschia inconspicua Grunow, Achnanthidium minutissimum (Kützing) Czarnecki, Navicula aitchelbee L. L. Bahls, Nitzschia palea (Kützing) Smith, Cyclotella meneghiniana Kützing, Navicula submuralis Hustedt and Mayamaea atomus (Kützing) Lange-Bertalot. The Ying River was divided into five orders using the Strahler method and three regions according to total nitrogen, total phosphorus and ammonia nitrogen. In region Y-1, which had the lowest nutrient level, the dominant species was Achnanthidium minutissimum. In region Y-2, which had the highest nutrient level, Navicula aitchelbee, Nitzschia palea, and Cyclotella meneghiniana were dominant, while in region Y-3, which had moderate nutrient levels, Nitzschia inconspicua was dominant. Pearson’s correlation analysis and canonical correspondence analysis (CCA) revealed a significant correlation between the environmental factors with dominant species and diatom indices (especially the SPI). Our study indicates that dominant species and diatom indices can, to some extent, indicate the environment, especially nutrient distribution.

The development of the eutrophication process in Dobczyce reservoir

Eutrophication is currently a global threat to all types of aquatic ecosystems leading to a disturbance of their ecological balance and a deterioration of water quality. This problem is especially true for dam reservoirs, which play a key role in the economy of each country, being an important source of water supply. It is also a primary problem for all types of surface waters in Poland. Effective eutrophication abatement strategies should be based on reliable information about the actual trophic status of waters which in turn should be obtained with fast, accurate and low-cost monitoring. The aim of this paper is to investigate the possibility of the application of aggregated numerical indicators as an effective tool for the assessment of water trophic status and prove it using the example of the trophic state assessment of the Dobczyce dam reservoir. For this purpose, three numerical indicators elaborated by different authors were used.

Study of Changes of Trophic Status of the Kuchurganske Reservoir in 2006-2018

Purpose. Assessment of the trophic status of water in the Kuchurganske Reservoir in 2006-2018. Methods. Determination of hydrological, hydrochemical and hydrobiological characteristics of the water body's environment has been done using standard methodologies. Four indicators of water eutrophication have been used: chlorophyll a concentration, bacterioplankton number, trophic indices TSI and TRIX. Results. Features of physicochemical characteristics of water in the water-body have been analysed. Higher water temperature has been registered in the middle and lower parts of the water-body compared with its upper reaches. Mineral content increase in water has been found in the direction from lower to upper part; the critical for hydrobionts life decrease of oxygen concentration has been registered in the upper reaches the most often. Analysis of long-term changes in chlorophyll a and bacterioplankton has been carried out. Statistical interconnections have been established between trophic state indicators and physicochemical characteristics of the reservoir. A close positive correlation has been registered between chlorophyll а content and bacterioplankton number, which is caused by the functional dependence of bacteria on the organic matter produced by phytoplankton. It has been shown that with an increase of water volume in the reservoir the value of these indicators of trophic status went down, which was proved by close negative correlation dependence between those values and the depth of water-body. It was demonstrated for the first time that water transparency revealed close significant negative correlation with all the indices and indicators of water trophic status, which evidenced the possibility to use the transparency as a simple indicator of water trophic state as established that the Kuchurganske Reservoir’s trophic status assessment on chlorophyll a, bacterioplankton and the TSI trophic index practically coincided and evidenced the increase in trophic status of the water-body from eutrophic to hypertrophic in last 2016-2018. The reservoir’s upper reaches were characterized by higher water trophicity compared with the central and lower parts. The values of TRIX trophic index developed for marine water assessment had practically always been showing higher trophic status compared to other indicators.

Trophic Status of the Dniester Delta Lakes in 2006-2017

Purpose. Assessment of trophic status of the Dniester deltaic part lakes (Bile, Svine, Tudorovo and Putrino) in 2006-2017. Methods. Determination of hydrological, hydrochemical and hydrobiological characteristics of the lakes aquatic environment has been performed using standard methodologies. Three indicators of eutrophication have been used: chlorophyll a concentration, number of bacterioplankton, trophic indices TSI and TRIX. Results. Peculiarities of physicochemical characteristics of water in the Dniester deltaic lakes have been analysed. Increased nutrients concentration has been revealed in all the lakes during past 12 years. The lowest oxygen content and oxygen saturation was established in water of the Putrino Lake, where at the same time the highest concentrations of total nitrogen and phosphorus were observed. Analysis of long-term changes of chlorophyll a and bacterioplankton has been done. Based on the lakes integrated study in summer time of 2006-2017, assessment of water trophic state has been for the first time performed for each deltaic lake. Statistical interrelations between trophic state indicators and physicochemical characteristics of the lakes have been revealed. Conclusions. It was established that the assessment of four deltaic lakes trophic status based on chlorophyll a, bacterioplankton and TSI trophic index practically coincided and evidenced increased of the lakes’ trophic status and decrease of water quality in 2012-2017 compared with previous years. All the eutrophication indicators in water of the lakes Svine, Tudorovo and Putrino during six last years corresponded to hypertrophic status, while in the Bile Lake most of eutrophication indicators were lower and corresponded to eutrophic status. Trophic index TRIX, which was developed for seawater assessment, practically always showed somewhat higher trophic status of the lakes than other indicators.