<abstract>
<title style='display:none'>Abstract</title>
Periphyton communities were studied on several dominating macrophytes, Phragmites australis, Potamogeton lucens, and Nuphar lutea, in three different types of lakes. In soft-water mesotrophic Lake Mały Borek and in shallow, eutrophic Lake Gardno samples were collected about once every two months from April to November 2009. In eutrophic Szczecin Lagoon (the estuary of the Oder River), samples were only collected once in July. The aim of this paper was to determine the dry mass, the ash content, and the chlorophyll-a content of periphyton on a natural substratum, in order to determine the mass, the inorganicorganic status of periphyton, and the auto-heterotrophic character of this complex. The analyzed periphytic communities exhibited low dry mass at the beginning of the growth season, which increased with colonization period on the aquatic vegetation. The highest (but still low) values were achieved in autumn, which persisted, with small loss, until spring of the subsequent year. The differences in dry mass between each type of lake were small, but in the strongly eutrophic Szczecin Lagoon this index was slightly higher than in the other two water bodies. The highest dry mass was noted for periphyton dominated by Cordylophora caspia colonies overgrowing common reeds and for periphyton on Potamogeton lucens in Szczecin Lagoon. In shallow water bodies, such as Lake Gardno and Szczecin Lagoon, wind causes strong resuspension of sediments. This can explain the relatively high level of inorganic matter in dry mass of the periphyton in both water bodies. However, the small ash content in periphyton in Mały Borek may result from the soft-water character of this lake. The hetero-autotrophic status of the periphytic community prevailed throughout the study period in Gardno and Mały Borek lakes. The auto-heterotrophic status of periphyton was noted only in short periods of time in each lake.
</abstract>

Periphyton dry mass, ash content, and chlorophyll content on natural substrata in three water bodies of different trophy

<abstract>
<title style='display:none'>Abstract</title>
Frequency of occurrence and intensity of the raised water stage determine the structure of invertebrates in the wetland ecosystems of wetland river floodplains. In order to assess the relationships in a regulated, lowland river of moderate climate, samples of water and invertebrates inhabiting submerged shoots of reed Phragmites australis Trin Ex. Stued. were taken from the middle section of the Słupia River and five of its oxbow lakes.
The wetlands differed in hydrological activity (type of connection with the river). Redundancy Analysis (RDA) revealed that hydrological connectivity accounted for 37% of the total invertebrate variance, physico-chemical conditions — 21%, while the trophic state only — 7%. Linear regression showed that the highest species richness was observed in oxbow lakes connected to the river with one arm. Diversity and species evenness increased with the increasing hydrological connectivity. The study revealed that plant-associated invertebrates inhabiting wetlands can be the main source for the reconstruction of biodiversity after floods.
</abstract>

Composition and density of plant-associated invertebrates in relation to environmental gradients and hydrological connectivity of wetlands

<abstract>
<title style='display:none'>Abstract</title>
Eriocheir sinensis is a habitat for invertebrates living externally and internally. It may transport native and non-native species to new habitats. Present studies on the Chinese mitten crab from Lake Dąbie add four new taxonomic units to the number of pathogens: Ichthyophonus hoferi, Epistylis sp., Branchiobdella sp. and Digenea gen. sp., which until now have not been found in this host.
</abstract>

Four pathogens found associated with Eriocheir sinensis H. Milne-Edwards, 1853 (Crustacea: Brachyura: Grapsidae) from Lake Dąbie (Poland)

<abstract>
<title style='display:none'>Abstract</title>
An excess of nitrogen and phosphorus causes an increase in productivity, leading to degradation of a water reservoir. In order to reduce the eutrophication, protective and restoration methods are used. The objective of the paper was to determine the hourly and daily variability in nitrogen and phosphorus compounds in a lake restored by the hypolimnetic withdrawal method. In the epilimnion, the organic form dominates: 97% of Ptot and 75% of Ntot. Hourly variations in the concentration of the investigated compounds indicate that the highest values occurred at night and in the morning, whereas lower measurements were recorded at noon and in the evening. Such a distribution of the concentrations of nutrients during a day is strongly associated with photosynthesis. Along with depth, the proportion of this form decreased in favor of mineral forms. A high content of mineral phosphorus (70%) and ammonium ions (75%) in the hypolimnion results from their release from bottom sediments under anaerobic conditions. As a result of the generated thermocline, they are blocked and accumulated. At the experimental station, the concentration of mineral compounds was at a lower level than at the reference station since their amount was systematically reduced by the outflow of over-fertilized waters from the hypolimnion.
</abstract>

Hourly and daily variability in nitrogen and phosphorus in a lake restored by the hypolimnetic withdrawal method

<abstract>
<title style='display:none'>Abstract</title>
Studies on the fauna of water beetles inhabiting anthropogenic water bodies were conducted on 44 clay-pit and gravel-pit ponds. A total of 125 water beetle species were identified. The dominant species were <italic>Scarodytes halensis</italic> and <italic>Laccobius minutus</italic>, representing the argillophilous component. Eurytopic, lake and riverine, and peatland species were also identified. Among the environmental factors determining the diversity of the water beetle fauna in particular types of habitats, the most significant role was played by the substratum and succession stage.
</abstract>

The formation of water beetle fauna in anthropogenic water bodies

<abstract>
<title style='display:none'>Abstract</title>
Phytoplankton species composition, abundance and biomass were studied in samples taken from the epilimnion of Lake Strzeszyńskie in late August of each year from 2000-2005. The number of phytoplankton species was relatively low, with the greatest species diversity observed in the Chlorophyceae. Total phytoplankton abundance was high, with major contributions by picophytoplanktonic cyanobacteria, which formed aggregations. Total phytoplankton biomass was generally low, with the sum of the 2-5 biomass-dominant species always exceeding 50% of the total phytoplankton biomass. The taxonomic composition of the group of biomass dominants was relatively stable inter-annually. On the basis of phytoplankton biomass and chlorophyll <italic>a</italic> concentration, Lake Strzeszyńskie can be classified as oligo-mesotrophic and mesotrophic, respectively. Trophic index values calculated on the basis of abundance of phytoplankton indicator taxa were higher than the values based on their biomass, and mean values indicate that the lake is mesotrophic or intermediate between mesotrophic and eutrophic.
</abstract>

Trophic state assessment based on late summer phytoplankton community structure: a case study for epilimnetic lake water

<abstract>
<title style='display:none'>Abstract</title>
Morphological features of sagittal otoliths in <italic>Pagellus acarne</italic>, <italic>P. bogaraveo</italic>, and <italic>P. erythrinus</italic> samples collected from the Aegean Sea were used to assess the variability both between <italic>Pagellus</italic> species and between otolith pairs employing scanning electron microscopy (SEM) and contour shape analysis. Twenty-one otolith morphological characters were compared in detail using SEM analysis. Twelve of these characters differ between <italic>Pagellus</italic> species and are suitable for distinguishing between the three congeneric <italic>Pagellus</italic> species. Wavelet functions of otolith contour shape were compared for six <italic>Pagellus</italic> groups. The wavelet functions obtained from the contour shape analysis showed high variability in the antero-dorsal, postero-dorsal, and antero-ventral regions of otoliths among the six groups analyzed. The results of principal component analysis (PCA) of the wavelet data provided a clear distinction between the groups under study. Cluster analysis supported the PCA results and basically divided them into two main branches. One of these branches contained only <italic>P. erythrinus</italic>, while <italic>P. acarne</italic> and <italic>P. bogaraveo</italic> were present in the other branch. This is the first study to provide detailed morphological characters and wavelet analysis of left- and right-side otoliths in these three congeneric <italic>Pagellus</italic> species from the Aegean Sea.
</abstract>

Morphological variability of otolith organs in three congeneric <italic>Pagellus</italic> species

<abstract>
<title style='display:none'>Abstract</title>
The study investigated the inter-annual and seasonal population dynamics, as well as the feeding habits of the western tubenose goby <italic>Proterorhinus semilunaris</italic> in an invaded river close to its natural range (Dnieper River basin). Material was collected monthly in 2015–2016 and 2018 at one sampling site located in the Stugna River, at a distance of 1100 m from the point where it enters the Kaniv reservoir. Catch-per-unit-efforts (CPUE) of this species at the sampling site varied considerably, both between different months within a given year and between the analyzed years, from 1.1 to 127.1 fish 100 m-2. Peak abundances were observed in July in both 2015 and 2018, and then dropped sharply in the following months. The western tubenose goby is characterized by a protracted spawning season, lasting from April to July. A total of 50 prey taxa were recorded in the diet of the western tubenose goby at the sampling site, among which chironomids were the most abundant and most frequently encountered, followed by cladocerans. This gobiid at the sampling site preyed mainly among submerged vegetation, where phytophilous chironomids were the most important prey.
</abstract>

Population dynamics and feeding ecology of the western tubenose goby (<italic>Proterorhinus semilunaris</italic>) in the Stugna River, Dnieper River basin, Ukraine

<abstract>
<title style='display:none'>Abstract</title>
In this study, zebra mussels (<italic>Dreissena polymorpha</italic>) were exposed to advanced biological wastewater treatment plant effluent (ABWTPE) for 96 h. At the end of the 96th hour, antioxidant parameters such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione S-transferase (GST), malondialdehyde (MDA) and glutathione (GSH) were examined. The objective of the study was to identify biomarkers that are useful for assessing the potential toxic effects of ABWTPE in freshwater environments. We observed an increase in GPX, SOD activity and MDA levels, and a decrease in CAT, GST activity and GSH levels. The results obtained in our study showed that the measured biochemical parameters (GSH, MDA, SOD, CAT, GPX and GST) are useful biomarkers in determining the possible toxicity of ABWTPE in aquatic environments.
</abstract>

Toxicity assessment of advanced biological wastewater treatment plant effluent by integrated biomarker response in zebra mussels (<italic>Dreissena polymorpha</italic>)

<abstract>
<title style='display:none'>Abstract</title>
The main risks to the sustainability of Mediterranean mussel farming in Greece were assessed using a generic framework derived from the AS/NZS ISO 31000:2009 Risk Management Model. Risk management scenarios were reviewed after they were successfully tested in the field by semi-qualitative/quantitative data generation protocols. A critical synthesis of the results identifies key indicative aspects needed by stakeholders to formulate a valid operational risk management plan for the sector.
</abstract>

Risk management in the Greek mussel farming through ISO 31000

<abstract>
<title style='display:none'>Abstract</title>
Lake Nasser is a freshwater lake that supplies over 95% of Egypt’s freshwater budget. Therefore, the quality of water in the lake is critical for its conservation. In addition to assessing the metal pollution load, the quality of water and sediment in the lake was assessed by collecting water and sediment samples for metal content analysis. Lake Nasser is a warm monomictic water body with a single circulation cycle in the cold months. Dissolved oxygen content in bottom water samples often dropped significantly to levels below international guidelines, reflecting reduced rates of photosynthetic activity. Although 50% of the lake’s water samples contained Pb concentrations slightly above the World Health Organization’s (WHO) limit for drinking water, the metal pollution index did not exceed the critical level and was classified as low metal water pollution. Based on the geoaccumulation index (I-geo), the enrichment factor (EF) and the pollution load index, the sediments of Lake Nasser are practically uncontaminated with metals. Ni has the highest EF and I-geo values, while Ni and Cd contributed the most to the ecological risk and toxic risk index. The obtained results revealed that Cd and Ni in the sediments may pose a threat to organisms living in Lake Nasser.
</abstract>

Comprehensive assessment of water and sediment quality in Lake Nasser, Egypt, using various potential risk indices

<abstract>
<title style='display:none'>Abstract</title>
The present study investigated the reproductive biology of European anchovies obtained seasonally from fishermen in İzmir Bay (Aegean Sea). The total length range of the investigated individuals was 9.0 – 15.7 cm. Of the 750 samples in which sex was determined, 34% were males, and 66% were females, resulting in a female-to-male ratio of 1.91:1. The first maturation length was determined to be 10.47 cm for females and 9.95 cm for males. Based on the total values of the gonadosomatic index, it was concluded that the reproductive period of the species falls in the summer season. The batch fecundity of the species ranged from 2.123 to 6.951 oocytes, and the fecundity–length relationship was expressed as F = 1134.4TL – 10034 (R2 = 0.84). Histological examination of the female ovaries revealed the presence of oocytes at different stages of development, indicating multiple spawning during the reproductive season.
</abstract>

Reproductive biology of the European anchovy <italic>Engraulis encrasicolus</italic> (Linnaeus, 1758) in the Turkish Aegean Sea

<abstract>
<title style='display:none'>Abstract</title>
In this work, the authors examined the presence of cyanobacteria and cyanotoxins in 21 samples collected from fresh water bodies located in 5 provinces in Poland: Lublin (2), Podlasie (1), Pomerania (6), Warmia-Masuria (1) and Wielkopolska (11). In addition, to determine the general pattern of geographical distribution, frequency of cyanobacteria occurrence, and cyanotoxins production, the published data from 238 fresh water bodies in Poland were reviewed. On the basis of these collected results, we concluded that Planktothrix, Aphanizomenon, Microcystis and Dolichospermum were dominant. The general pattern in geographical distribution of the identified cyanobacterial genera was typical of other eutrophic waters in Europe. The production of cyanotoxins was revealed in 18 (86%) of the 21 samples analyzed in the present work and in 74 (75%) of the 98 total water bodies for which the presence of toxins had been examined. Among the 24 detected microcystin variants, [Asp3]MC-RR was most common. These results can be verified when more data from the less explored water bodies in the southern and eastern parts of Poland are available.
</abstract>

Cyanobacteria and cyanotoxins in Polish freshwater bodies

<abstract>
<title style='display:none'>Abstract</title>
In this study, the effect of multiple heavy metal stress on ascorbate (AsA), glutathione (GSH) and related enzymes was investigated in the leaves, stems and roots of <italic>Kandelia candel</italic> and <italic>Bruguiera gymnorrhiza</italic>. Mangrove seedlings were treated with five different concentrations of a heavy metal mixture (Cd2+, Pb2+ and Hg2+). Antioxidants in both the species were analyzed after one month. AsA, GSH, ascorbate peroxidase (APX, EC 1.11.1.11) and glutathione reductase (GR, EC 1.6.4.2) exhibited a similar trend with initial increase and subsequent decrease in response to heavy metal stress. At the highest metal concentration, a significant decrease of AsA and GR was observed in <italic>K. candel</italic> and <italic>B. gymnorrhiza</italic>. Glutathione peroxidase (GPX, EC 1.11.1.9) in the leaves, stems and roots of <italic>K. candel</italic> reached their respective maximal values at the highest metal concentration, whereas GPX activity in roots and stems of <italic>B. gymnorrhiza</italic> was similar to the controls at higher metal concentrations. Our results demonstrate that AsA, GSH, APX, GR and GPX in <italic>K. candel</italic> may play more important roles in defending against reactive oxygen species (ROS) than those in <italic>B. gymnorrhiza</italic>.
</abstract>

The effect of multiple heavy metals on ascorbate, glutathione and related enzymes in two mangrove plant seedlings (<italic>Kandelia candel</italic> and <italic>Bruguiera gymnorrhiza</italic>)

<abstract>
<title style='display:none'>Abstract</title>
This is the first comprehensive review to examine the role of the central European invasion corridor on fish introductions into Belarusian and Polish inland waters (Dnieper-Bug-Vistula-Oder-Elbe-Spree-Havel). Historical and recent data were assessed, including the results of a 2003–2008 survey along the Belarusian and Polish sections of the corridor. Since the eighteenth century, at least six fish species of Ponto-Caspian origin have spread via the corridor and migrated westwards to the Baltic basin, with five species found in recent surveys, namely the monkey goby Neogobius fluviatilis, round goby N. melanostomus, racer goby N. gymnotrachelus, tubenose goby Proterorhinus marmoratus and the white eye-bream Abramis sapa. Four other non-native species were also found within the corridor — the Amur sleeper Perccottus glenii, gibel carp Carassius gibelio, brown bullhead Ameiurus nebulosus and the topmouth gudgeon Pseudorasbora parva. Their presence is related to numerous accidental introductions to many localities in Belarus and Poland, rather than from using the corridor as an invasion route. One species, the ninespine stickleback, Pungitius pungitius, has migrated from the Baltic basin to the Black Sea drainage systems.
</abstract>

Non-native fish in Belarusian and Polish areas of the European central invasion corridor

<abstract>
<title style='display:none'>Abstract</title>
Nine lakes (Garda, Maggiore, Como, Iseo, Lugano, Idro, Pusiano, Ledro, and Levico) located in the Italian subalpine lacustrine district were chosen for a comparative study of the diversity and distribution of cyanobacterial toxins. All nine lakes are known to host different toxic cyanobacteria, mainly Planktothrix rubescens. An analytical protocol has been used, based on LC-MS technique, for determining 20 different toxins (14 microcystins, 2 nodularins, anatoxin-a and 3 cylindrospermopsins). In the investigation, microcystins were found in all lakes on all sampling dates. Anatoxin-a could be detected in 6 lakes, but it was only present in 4 lakes on all sampling dates (lakes Garda, Iseo, Como, and Maggiore). Nodularins and cylindrospermopsins were not detected at all. The number of microcystins detected in the survey was 9, but 4 were the most abundant (dmRR, YR, dmLR, and LR); they were differently distributed among the lakes, thus providing each lake a unique toxic potential. Statistical analysis showed positive correlations between total microcystin concentrations and eutrophication indicators and also between anatoxin-a concentrations and water temperature, suggesting that anthropic and climate-related stressors can have different impacts on the presence of different cyanotoxins.
</abstract>

Diversity and distribution of cyanobacterial toxins in the Italian subalpine lacustrine district

<abstract>
<title style='display:none'>Abstract</title>
A four-year study carried out in a lake with perennial water blooms caused by toxigenic Planktothrix agardhii (Oscillatoriales) and Anabaena lemmermanii, Anabaena flos-aquae, Anabaena spp. and Aphanizomenon issatchenkoi (Nostocales) revealed that the lake-dwelling fish were threatened by simultaneous exposure to intracellular and extracellular microcystins (MCs) as well as anatoxin-a (ANTX). Higher contents of anatoxin-a and microcystins were found in livers than in fish muscles. This is the first report on ANTX accumulation in the common fish, indigenous to European freshwaters during perennial cyanobacterial blooms. Generally, the omnivorous roach (Rutilus rutilus) and Prussian carp (Carassius gibelio) accumulated higher amounts of MCs in their tissues compared to mostly predacious perch (Perca fluviatilis), and similar amounts of ANTX. The long-lasting presence of MCs exceeding the safe levels for consumption was found in fish muscles. ANTX accumulation in fish muscles (up to 30 ng g−1 FW) suggests the probability of its transfer in a food chain.
</abstract>

Simultaneous accumulation of anatoxin-a and microcystins in three fish species indigenous to lakes affected by cyanobacterial blooms

<abstract>
<title style='display:none'>Abstract</title>
Two rivers situated in Central Poland, the Bzura and the Pilica, were selected for analysis of their water quality using benthic diatom species as indicators. The Bzura River has previously been strongly contaminated with organic pollutants, while the Pilica River has been classified as having good water quality. Samples were collected from nine sites along the Bzura in April 2003 and seven sites along the Pilica in April 2006. The main aims of the study were to determine the dominant diatom species present in the rivers and to assess their usefulness as biological indicators. Water quality of the rivers was estimated on the basis of the SPI - Specific Pollution sensitivity Index (CEMAGREF 1982) and the GDI - Generic Diatom Index (Coste, Ayphassorho 1991) while trophic status was estimated using TDI - Trophic Diatom Index (Kelly, Whitton 1995).Indices determining saprobic water pollution (SPI, GDI) indicated water quality of class III and IV for the Bzura River and class II and III for the Pilica River. The trophic status determined on the basis of the TDI index revealed the Bzura water to be classified in the eutrophic-to-hypertrophic zone and that of the Pilica River to the oligo-mesotrophic-to-eutrophic zone.The diatom taxa that dominated in the Bzura River were species that are generally considered to be tolerant and resistant with respect to organic water pollution, including: <italic>Cyclotella meneghiniana</italic> Kützing, <italic>Gomphonema parvulum</italic> (Kützing) Kützing, <italic>Nitzschia palea</italic> (Kützing) W. Smith, <italic>Nitzschia paleacea</italic> Grunow, <italic>Sellaphora pupula</italic> (Kützing) Mereschkovsky, <italic>Stephanodiscus hantzschii</italic> Grunow, <italic>Ulnaria ulna</italic> (Nitzsch) Compere. In the Pilica River diatoms from groups that are sensitive and tolerant to organic pollution were seen to dominate, such as: <italic>Achnanthidium minutissimum</italic> (Kützing) Czarnecki, <italic>Aulacoseira granulata</italic> (Ehrenberg) Simonsen, <italic>Cocconeis neodiminuta</italic> Krammer, <italic>Cocconeis placentula</italic> Ehrenberg, <italic>Cocconeis placuntula</italic> var. <italic>lineata</italic> (Ehrenberg) Grunow, <italic>Cyclotella radiosa</italic> (Grunow) Lemmermann, <italic>Fragilaria crotonensis</italic> Kitton, <italic>Geissleria decussis</italic> (Øestrup) Lange-Bertalot et Metzeltin, <italic>Melosira varians</italic> Agardh, <italic>Navicula reichardtiana</italic> Lange-Bertalot, <italic>Planothidium frequentissimum</italic> (Lange-Bertalot) Lange-Bertalot, <italic>Pseudostaurosira brevistriata</italic> (Grunow) Williams &amp; Round, <italic>Rhoicosphenia abbreviata</italic> (Agardh) Lange-Bertalot and <italic>Staurosira pinnata</italic> Ehrenberg.
</abstract>

The use of benthic diatoms in estimating water quality of variously polluted rivers

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