Estuary Water Research Articles

River plume and sediment transport seasonality in a non-tidal semi-enclosed brackish water estuary of the Baltic Sea

Our study aims to determine the development of sediment-rich freshwater plumes in a non-tidal brackish water-dominated (salinity < 6) estuary in the Halikonlahti Bay, Northern Baltic Sea. We studied three seasons with different wind conditions and discharges: two open water periods, one with low (~0.2 m³/s) and one with high (31–40 m³/s) river discharges, and one ice-covered period with high (28–40 m³/s) river discharge. To conduct our analyses, we measured suspended sediment concentration (SSC), turbidity, salinity and temperature of bottom and surface waters together with current measurements along the estuary. Water samples were collected with LIMNOS water sampler and current measurements were done with acoustic Doppler current profiler. The results indicate that river plume develops under high river discharge, while during low river discharge the plume is very limited in extent. In open water conditions, SSC increased approximately ten-fold in the estuary head, with increased discharge from 0.2 m³/s to 31 m³/s. Buoyant plumes developed in both open channel and ice-cover conditions during high river discharge periods even in a weakly stratified environment, where the salinity difference was less than five over the entire water column. Unlike salinity, small temperature differences between river and seawater did not contribute the development of buoyant sediment plume. Weak stratification together with reduced wind-induced mixing was found to limit the sediment mixing between fresh surface and saline (~5) bottom layers in both ice-covered and open water conditions. For example, even 2–5 times higher SSCs were found at surface waters compared to bottom waters over a shallow (~4 m) water column. Wind and river discharge induced estuarine currents were found. Inverse estuary circulation developed under the conditions of low river discharge and inshore directed wind. High river discharge together with salinity stratification formed a positive estuarine circulation pattern, with surface outflow and bottom inflow.

Testing thermodynamics method for salt intrusion during infrequent astronomical event

Knowledge of the processes governing salt intrusion in estuaries is important since it influences the eco-environment of estuaries as well as its water resource potential in many ways. The aim of this paper is to test the effectiveness of the new 1-D thermodynamic salt intrusion equation proposed by Zhang and Savenije (i.e., is an extreme power theory for the mixing of saline sea water and fresh river water in estuaries); and existing salt intrusion model (i.e., Van der Burgh method) at two previously unsurveyed estuaries in India and Morocco. To successfully perform the analysis using the 1-D models, real time data is required. Field measurements during infrequent astronomical event were recorded along the estuaries (31/01/2018 for Ashtamudi estuary (India); and during 31/01/2018 for Bouregreg estuary (Morocco)). Shape (geometry) and salinity analyses were performed on each of the estuaries. The results obtained show good agreement between the simulated and observed salinity distribution in the estuaries with high R 2 values. Finally, by utilizing the new predictive equation, we can estimate the minimum amount of river discharge needed, and the maximum allowable depth for dredging, to prevent saline water intruding further into the areas studied. Thus, the simple and effective approach presented in this study can describe the current state of salt intrusion in India and Morocco estuaries, and be used for future development.

Heavy metals (Pb, Cd, Cu and Cr) accumulation on different shell size of Polymesoda sp from Estuary Waters of Parepare Bay

This study revealed the differences in the concentration of heavy metals Pb, Cd Cu, and Cr accumulated in a different-sized group of Polymesoda sp shells originating from the waters of Parepare City. Shellfish were divided into three size groups, namely Small (23-41 mm); medium (42-59 mm), and large (59-77 mm). Heavy metal concentrations in shell, water and sediment samples were analyzed using atomic absorption spectrophotometers (AAS). The results showed that the concentration of heavy metals in waters and sediments had the same pattern, Cu> Pb> Cd> Cr. Heavy metals, Pb and Cu, had the highest accumulation in the large-sized shells, while Cd was in the medium-sized shells. Cr, however, showed the lowest accumulation in all size groups. This situation shows that Polymesoda sp shells originating from the waters of Parepare Bay are still suitable for consumption.

Human-driven spatiotemporal distribution of phosphorus flux in the environment of a mega river basin

Large river basins transport considerable nutrients to the ocean every year. However, phosphorus (P) generated by human activities not only threatens aquatic ecosystem health in the river basin, but also has a negative effect on the estuary water environment. To better understand the environmental effects of anthropogenic P in a mega basin, we examined its inputs and distribution characteristics, and analyzed the factors driving it in the Yangtze River Basin (YRB) and sub-catchments. Anthropogenic P flux in the sub-catchments gradually increased from upper to lower reaches, and hotspots were primarily concentrated in traditional agricultural areas such as the Sichuan Basin and the Middle-Lower Yangtze plains. Agricultural sources were the main anthropogenic P inputs, of which fertilizer P was the leading contributor and driver of P changes, but livestock manure also accounted for a high proportion. Presently, anthropogenic P inputs in the YRB are considerably higher than in other parts of the world. Although long-distance transportation allows some P from the entire basin to be deposited in freshwater, a large amount of P still reaches the estuary and has a negative effect on water quality, outweighing the influence of local coastal inputs. To maintain the ecological health of the river basin and estuary, it will be necessary to further improve P utilization efficiency and encourage greater cooperation between different regions in the river basin.

Features of dynamics of the Ingul river aquatic environment parameters during the summer low-water period

Global climate change causes changes in the humidification regime and, as a result, makes adjustments to economic activities and features of water use. In the context of Ukraine, against the background of climate change, the runoff of most ukrainian rivers is declining, which especially in the low-water period exacerbates the issue of balanced use of ecosystem services of aquatic ecosystems and prioritization of needs during resource allocation, control of rivers and establishment of their functioning. Therefore, recognizing the strategic importance of freshwater ecosystems in ensuring sustainable regional and national development, the Ingul River study focused on assessing its ecological status in order to identify sources of negative anthropogenic impacts and general ecosystem distortions that may affect the functional integrity of the aquatic ecosystem. Thus, on the basis of field research, the assessment of the ecological condition of the Ingul River in the lower course was carried out in the work. Regularities of pH dynamics and mineralization of the water environment are established. The limits of the spatial influence of the sea waters of the Bug estuary on the Ingul River have been clarified, the continental advance of which (upstream) can be largely attributed to the regulation of runoff. The same processes, as a consequence, affect not only biodiversity, but also the features of industrial and domestic water use. Using the stenobiont approach, the level of ecological safety of the Ingul ecosystem in the lower reaches was assessed. Based on the obtained results of stenobioindication, the zoning of the lower reaches of the Ingul River is proposed, which compares quite well with the results of pH and mineralization measurements. Natural factors that may affect the intensity and quality of self-healing properties of the aquatic ecosystem upstream have also been identified.

Distributions of volatile halocarbons and impacts of ocean acidification on their production in coastal waters of China

The volatile halocarbons (VHCs) CH3I, C2HCl3, C2Cl4, and CH2Br2 were measured in the Changjiang Estuary and adjacent waters during autumn 2018. Results revealed that their concentrations in coastal waters were influenced by anthropogenic activities, biological release, and complex hydrographic features. The vertical distributions of VHCs were determined mostly by the mixing of water masses. By investigating the impacts of temperature, salinity, chlorophyll a, nutrients, and pH on the distributions of these trace gases we revealed that C2HCl3 and C2Cl4 were positively correlated with salinity and nutrient availability. The sea-to-air fluxes of CH3I, C2HCl3, C2Cl4, and CH2Br2 were estimated to be 27.62, 280.3, 221.73, and 142.41 nmol m−2 day−1, respectively, suggesting that the study area was a net source of these trace gases. The impact of elevated fCO2 on the production of the four volatile halocarbons was studied using mesocosms in Wu Yuan Bay, Xiamen. The results showed that elevated fCO2 had little impact on the VHCs. Positive relationships were observed between CH2Br2 and phytoplankton biomass when fCO2 was low, and between CH3I and phytoplankton biomass when fCO2 was high, suggesting that algal release was a significant source of both compounds.

Effect of Seasonal Changes on Steroid Hormones Concentrations in the Golden Horn Estuary (Sea of Marmara, Turkey)

In this study, the presence, distribution and concentration of steroidal hormones (Estrone, 17β-estradiol and 17α-ethynylestradiol) were examined in the Golden Horn Estuary (Marmara Sea, Turkey) for one year. The bottom and surface water samples were collected from nine stations in the Golden Horn Estuary four seasons a year. In order to determine the hormone amounts, solid phase extraction was applied to the water samples and then these samples were analyzed on the HPLC with DAD detector. Recoveries of these hormones were range from 92–100% for estuary water. The highest concentrations of estrone, 17β- estradiol, 17α- ethynylestradiol were measured as 1.069 µg/L, 5.25 µg/L, 1.65 µg/L in Golden Horn, respectively. The concentrations of these three hormones are found higher in bottom water than the surface water and the highest concentrations of all hormones were determined in winter season.

Methods for predicting berm height at Temporarily Open/Closed Estuaries

This study investigates the berm crest elevation at 20 Temporarily Open/Closed Estuaries (TOCEs) along the wave-dominated, microtidal coastline of South Africa and provides suitable methods of prediction. Several years of berm survey and estuary water level data were analysed for the selected estuaries, resulting in a relatively large record of historical berm crest elevations compared to previous regional datasets. The new dataset was utilised to test and develop multiple methods for the prediction of berm height and consequently flood levels within TOCEs. Long-term wave runup elevations (R2%) were simulated at the estuary berms using existing runup parameterisations to establish the exceedance probability threshold of R2% associated with the maximum berm height (BMAX). It was found that the 5% exceedance probability of runup provided consistent predictions of BMAX at the selected TOCEs with a mean absolute error (MAE) of 0.28 m. A Berm Height Criteria was developed to predict BMAX based on the wave height, beach face slope, sediment grain size and tidal range at the estuary. The criteria-based approach ensures ease of use and is intended as a first estimate of BMAX (with MAE of 0.23 m). Lastly, a stepwise berm growth model was tested according to its potential to track short-term berm growth during inlet closure to breach cycles. The model provides a simplified approach to predict berm accretion based on the overwash potential depth, which is defined as the elevation difference between R2% and the berm height. The use of a site-specific scaling parameter for berm accretion provided predictions of the berm height at breach with MAEs varying between 0.03 m and 0.17 m among estuaries for the short-term scenarios tested. The hydrodynamic and morphological variability displayed by the selected South Africa TOCEs increased the robustness of the results, potentially making the findings relevant to TOCEs in other parts of the world.

Stunted Mangrove Trees in the Oligotrophic Central Red Sea Relate to Nitrogen Limitation

Mangroves are important coastal ecosystems of warm climatic regions that often grow in shallow saline or brackish waters of estuaries and river mouths affected by wide tidal intervals and receive abundant nutrient supply. However, mangroves also occur in areas of little tidal influence and devoid of riverine inputs, where they can develop a stunted plant form. Here we report that Avicennia marina trees in the fringe of the Red Sea have maximum heights toward the lower range of that reported elsewhere (average maximum canopy height of 4.95 m), especially in the central region, where mangroves are stunted with an average tree height of 2.7 m. Maximum tree height and chlorophyll a concentration correlated positively with nitrogen concentration in the leaves of A. marina. We conclude that the stunted nature of mangrove trees in the central Red Sea is likely driven by nitrogen limitation.

Targeted and non-targeted analysis of organic compounds of moderate polarity in water using liquid chromatography-time of flight mass spectrometry in all ion mode with particular reference to analysis of pesticides

We have developed a novel yet efficient method for the multi residue analysis of organic compounds of diverse polarities in water using Liquid Chromatography-Time of Flight mass spectrometry (LC-MS-TOF) equipped with a jet stream Electrospray ionization (ESI) source. Use of three different fragmentor voltages (low, medium and high) enabled the qualitative and quantitative analysis of a diverse range of targeted organic compounds in environmental waters. No prior optimization of compounds being quantified was required, the limiting factors were ionization behaviour of compounds under conditions of ESI and good chromatography. Same data file could be subjected to repeated post-run data analysis to figure out the presence of non-targeted compounds, including designer drugs if any. The technique has been illustrated with reference to a group of pesticides having diverse chromatographic and ionization behaviours. The optimized Solid Phase Extraction (SPE) followed by method validation yielded a robust yet simple quantitative method for a group of fourteen pesticides. We were able to achieve quantitation at 10 ng/L or lower depending upon ionization behaviour of substrates against the usual regulatory requirement of 1000 ng/L. The method was used for targeted and non-targeted detection of pesticides in Nueces estuary waters, TX, USA, and several untargeted pesticides, pharmaceuticals and personal care products were identified.

СЕЗОННАЯ ДИНАМИКА ХИМИЧЕСКОГО СОСТАВА ВОД ОВРАЖНО-БАЛОЧНЫХ СИСТЕМ ГОРОДСКИХ ТЕРРИТОРИЙ (НА ПРИМЕРЕ САРАТОВА)

Актуальность исследования определяется необходимостью обеспечения экологического благополучия водных объектов в зоне воздействия крупных городов. В соответствии с современными природоохранными, экологическими и градостроительными требованиями водный сток с урбанизированных территорий не должен оказывать негативного воздействия на качество водных ресурсов. Цель: определение сезонной динамики (весенний максимум и летне-осенний минимум стока) поступления загрязняющих веществ с водным стоком оврагов и балок с территории города Саратова в Волгоградское водохранилище. Методы: морфометрический анализ водосборных бассейнов овражно-балочных комплексов; картографирование притоков естественного и техногенного происхождения; опробование вод в устьевых створах перед впадением в Волгоградское водохранилище; химический анализ состава поверхностных вод по приоритетным показателям по общепринятыми методикам (суммарно 140 определений); оценка и анализ качества вод относительно нормативов для водных объектов рыбохозяйственного значения. Результаты. Выполнена характеристика функционирования городских оврагов и балок; определены особенности формирования химического состава и транспорта вод по эрозионной сети урбанизированной территории; установлен состав вод десяти крупнейших овражно-балочных комплексов по приоритетным загрязняющим веществам для Волгоградского водохранилища (нитриты, железо общее, медь, цинк, сульфаты, азот аммония, нефтепродукты); в водном стоке обнаружены концентрации загрязняющих веществ, многократно превышающие установленные нормативы для водоемов рыбохозяйственного назначения. Качество водного стока не соответствует нормативам, установленным для водных объектов рыбохозяйственного значения, к которым относится Волгоградское водохранилище как часть волжского бассейна. В сезонной динамике химического состава вод не обнаруживается однонаправленных тенденций. Из 70 сравнительных пар проб весеннего и летне-осеннего стока снижение концентраций летом выявлено в 41 случае (58,6 %), повышение – в 21 (30 %), отсутствие изменений – в 8 (11,4 %). Контроль качества стока следует вести исходя из анализа конкретных водосборных бассейнов. Учитывая, что водохранилище служит источником централизованного хозяйственно-питьевого водоснабжения и объектом рекреационной деятельности, необходима организация систем очистки поверхностного водного стока.

Aqueous Mercury Removal with Carbonaceous and Iron Sulfide Sorbents and Their Applicability as Thin-Layer Caps in Mercury-Contaminated Estuary Sediment

This study aimed to investigate the Hg removal efficiency of iron sulfide (FeS), sulfurized activated carbon (SAC), and raw activated carbon (AC) sorbents influenced by salinity and dissolved organic matter (DOM), and the effectiveness of these sorbents as thin layer caps on Hg-contaminated sediment remediation via microcosm experiments to decrease the risk of release. In the batch adsorption experiments, FeS showed the greatest Hg2+ removal efficiencies, followed by SAC and AC. The effect of salinity levels on FeS was insignificant. In contrast, the Hg2+ removal efficiency of AC and SAC increased as increasing the salinity levels. The presence of DOM tended to decrease Hg removal efficiency of sorbents. Microcosm studies also showed that FeS had the greatest Hg sorption in both freshwater and estuary water; furthermore, the methylmercury (MeHg) removal ability of sorbents was greater in the freshwater than that in the estuary water. Notably, for the microcosms without capping, the overlying water MeHg in the estuary microcosm (0.14−1.01 ng/L) was far lesser than that in the freshwater microcosms (2.26−11.35 ng/L). Therefore, Hg compounds in the freshwater may be more bioavailable to microorganisms in methylated phase as compared to those in the estuary water. Overall, FeS showed the best Hg removal efficiency, resistance to salinity, and only slightly affected by DOM in aqueous adsorption experiments. Additionally, in the microcosms, AC showed as the best MeHg adsorber that help inhibiting the release of MeHg into overlying and decreasing the risk to the aqueous system.

Anti-inflammatory drugs in the Vistula River following the failure of the Warsaw sewage collection system in 2019

At the end of August 2019, in Warsaw, the sewage collection system of the Wastewater Treatment Plant malfunctioned. During the subsequent 12 days, over 3.6 million m3 of untreated sewage was introduced from the damaged collector directly into the Vistula River. It is one of the biggest known failures of its kind in the world so far. In this study we investigated to what extent the incident contributed to the increased discharge of anti-inflammatory drugs into the environment. The study covered the section from the point of discharge to the city of Toruń (ca. 170 km downstream). It was found that in the river waters downstream of the damaged collector, the concentrations of selected pharmaceuticals increased considerably in comparison with the waters upstream of the collector. The highest concentrations were observed for paracetamol (102.9 μg/L), ibuprofen (5.3 μg/L) and diclofenac (4.8 μg/L). We also measured to what extent and at what rate these pollutants were distributed along the river. The effects of the incident were observed in further parts of the river after 16 days. In the study we also detected elevated concentrations of ibuprofen and diclofenac in the bottom sediments collected 6 weeks after the failure. Measurements of the levels of pharmaceuticals in estuarial and marine waters in the vicinity of the mouth of the Vistula River indicate that the incident did not significantly increase the load of these pollutants in the waters of the southern Baltic Sea.

Exchange Dynamics of Typical Emerging and Legacy Persistent Organic Pollutants at the Air‐Water Interface Over a Strongly Human‐Influenced Large River Estuary

AbstractTo explore the riverine or atmospheric influence on the source‐sink fates of typical persistent organic pollutants (POPs): polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in the large river estuary, atmospheric and seawater samples were collected simultaneously over a whole year at a remote small island in the Yangtze River Estuary (YRE), the East China Sea. A comparable net input of BDE‐209 from the atmosphere to the sea for both air‐water gas exchange and dry/wet deposition was observed. The gas deposition of BDE‐209 had a strong dependence on the gaseous concentration, which was in turn governed by atmospheric transport. For Br&lt;10‐BDEs, which have been prohibited in recent years, the gas exchange almost reached equilibrium at the air‐water interface during the whole observation period. However, a strong net gas volatilization was observed for legacy ΣICESPCBs especially in the flood season, and the volatilization was significantly associated with ambient parameter‐wind speed. These remarkably different exchange dynamics of PBDEs and PCBs at the air‐water interface over the YRE could be attributed to their primary emission intensity and inconsistent environmental transport pathways. The reversal of the source‐sink fates of BDE‐209 and legacy PCBs suggest that the strongly human‐influenced large river estuary water could act as a source‐sink buffer for POPs during the switch from approved to prohibited usage.

Determination of estrogens by solid-phase quadruplex stable isotope dansylation coupled with liquid chromatography-high resolution mass spectrometry in environmental samples

Estrogens distribute widely in the environment as endocrine-disrupting chemicals (EDCs), which have to be monitored to evaluate their environmental impact. Aim to improve the analytical throughput of liquid chromatography-high resolution mass spectrometry (LC-HRMS), a quadruplex stable isotope dansylation method was developed, with which three real samples could be quantitatively analyzed in one injection. As the estrogens were at trace level in complex matrices, magnetic solid-phase extraction (MSPE) was applied to enrich these analytes and remove the interfaces. By integrating MSPE and quadruplex stable isotope dansylation, a solid-phase quadruplex labeling method was developed for the LC-HRMS analysis of estrogen analogues. For the tested seven estrogens, the developed method showed low detection limits (0.1–0.5 ng/L for pond water and 0.01–0.05 μg/kg for poultry manure), good precision (RSD < 5.5%) and accuracy (96.8–108.3%). The method was applied in the determination of estrogens in environmental samples, and the results revealed that all the tested estrogens were present in the estuary water (unquantifiable to 71.2 ng/L) and chicken manure (undetectable to 25.43 μg/kg).

Assessment of the efficiency of controls to prevent biologic invasions at the San Lorenzo Port, Argentina.

The problem created by invasive non-native species through ships' ballast water has caused the International Maritime Organization (IMO), through the Ballast Water Management (BWM) Convention and many countries to develop their own laws to prevent their introduction. One of the most important non-native species in Argentina, the golden mussel (Limnoperna fortunei), causes a significant economic impact on the Plata Basin. Argentina has a great amount of maritime and fluvial ports that receive ships from different regions of the world. Particularly, the San Lorenzo-San Martín Port Complex (here termed SLOR), placed in the terminal portion of the Paraná Basin, receives ocean ships with great loading capacity, which increases the possibility of invasions and the need of an adequate environmental management. This work proposes to estimate the potential vulnerability of SLOR port, in relation with the origin of the ballast water and its volume. For this purpose, an adaptation of the risk assessment model of the GloBallast Program was used. The results suggest that SLOR has important similarities with different fluvial ports of the world, especially in Brazil and China. However the amount of ships coming from the nearest estuary waters, where the diversity of invasive species has major effects, is also important. This article provides the necessary information to conduct the efforts through surveys and enforcement regulations, and could be the foundation for future research using global data that could provide basic information for other fluvial ports with similar features.

Komposisi Jenis Plankton Pada Musim Penangkapan Ikan Penja (Gobioidea sp) Di Muara Sungai Mandar

Penja is an endemic fish in the Mandar river and is one of the small pelagic fish species that has been used by fishermen in Polewali Mandar for a long time. Penja fish is one of the water organisms that utilize plankton as its food. This study aims to determine the composition of the plankton species the fishing season in Mandar waters of Polewali Mandar Regency, West Sulawesi Province. This research was conducted in November-December 2017. The sampling location was conducted in two different water locations which are at estuary and body of Mandar River, Polewali Mandar Regency, West Sulawesi Province. And the identification of samples was done at the Biology Laboratory of Plankton and Natural Feed at the Research Center for Brackishwater Aquaculture Development and Fisheries Extension (BRPBAP3) of Maros Regency. The results of this study indicate that the highest abundance of plankton during the fishing season in the estuary waters and the month of December. Bacillariophyceae class is the most plankton class found during the study and there is 37 genus plankton consisting of 28 genus of phytoplankton and 9 genus of zooplankton. The range of diversity index value during fishing time, sampling location, research month and sampling time are 1 &lt;H '&lt;3 which means medium diversity, uniformity index value is 0.7-0.9 so that the plankton uniformity index is relatively the same or equal, and the Domination index value indicates that no domain genus in the community.

Spatial distribution, control factors and sources of heavy metal in the surface sediments of Fudu Estuary waters, East Liaodong Bay, China

To investigate the sediment quality of Fudu Estuary waters in East Liaodong Bay, the grain size, concentrations of total organic carbon (TOC) and heavy metal (Cr, Cu, Zn, As, Cd, Pb) of 25 surface sediments were tested. The concentration of heavy metals was found to be higher in the Southwest of Yingkou Port and outside the Fudu Estuary. Cd is the principal contaminant with mild pollutant and moderate ecological risk. Cr may cause negative biological effects. The abnormal enrichment of Cu and TOC may respectively be caused by riverside industrial activities and mariculture. The abnormal enrichment of Pb in Moon Bay Beach and the Lagoon was suggested to be caused by the mooring of boats or excessive tourist activities. Grain size dominates the concentrations of heavy metals in the study area. The impact of coastal engineering on sediment quality through changing sedimentary dynamics should also be given particular attention.

Prevalence of the nematodes Eustrongylides exisus Jägerskiöld, 1909, – larvae (Nematoda: Dioctophymatidae) infection in the Rutilis rutilis, linnaeus 1758 and the seasonal dynamics of the infection in the waters of the Dnipro-Buh estuari in southern Ukrai

In this study, we determined the prevalence and seasonal dynamic of the infection of the Rutilis rutilis, Lіnnaeus 1758 with the nematode Eustrongylides excisus. The fish was caught in the waters of the Dnipro-Buh estuary in seven sample collection sites between 2016 and 2019. They all underwent ichthyopathological examination. Parasites, found during examination, undergone microscopy to determine their taxonomy. Overall 595 specimens were obtained. The mean prevalence of infection over entire study period (2016–2019) was 17.4 %. Ichthyopathological examination of the roach caught in the waters of the Dnipro-Buh estuary revealed the infection with larvae E. excises nematode. The parasitic larvae were found in the muscles of the ventral abdominal wall of the roach. There was more than two-fold difference in the prevalence of infection between sample collection sites – from 12 % in site 5 near Sofiivka to 28 % in site 3 near the village Oleksandrivka over the study period in 2016–2019. The total prevalence of infection in roaches in the Dnipro-Buh estuary was 17.4 %. Seasonal changes were not statistically significant and ranged from 12.8 % in summer to 20.1 % in spring. Annual changes suggested a possible upward trend, but more observations are needed to confirm it. Аnnual changes were not statistically significant. The prevalence of infection changed throughout the year: there were two peaks in spring (20.1 %) and autumn (18.3 %). In summer (12.8 %) and winter (15.1 %) the prevalence of infection was lower. Morphologically, the E. excisus larvae found in roaches were different compared to those found in predatory fishes: they had more pale color and were smaller in length. E. excisus is a prevalent infection of roach in Dnipro-Buh estuary. Considering seemingly increasing prevalence of E.excisus infection, further studies are required to understand a pathophysiology of E.excisus infection in mammals and humans, since data remain limited.

Nitrate inversion based on remote sensing in the Pearl River Estuary, China

Against a background of ongoing economic and industrial development, the impact of human activities on the offshore environment has become increasingly significant in recent years. In many regions, contamination of the marine environment necessitates the need for dynamic, real-time and wide-coverage water quality monitoring and satellite remote sensing, such that multi-temporal and spatial scale observation of various oceanic parameters are realized. In this paper, using salinity, in situ spectral data, nitrate and other water quality data from five sampling campaigns in the Pearl River Estuary and adjacent waters, studies on the inversion of nitrate concentrations using an artificial neural network were performed. Two inversion models, based on input of the measured salinity and field spectral data and just the field spectral data, were investigated. After comparing the accuracy of the two models, it was considered that the nitrate model with salinity and field spectral data as input performed best. Finally, the selected model was applied to MODIS data to achieve inversion of the nitrate concentrations in the estuary waters and obtain the temporal distribution of nitrate concentrations as a means to monitor and evaluate water quality in the estuary.