•Coexisting ions affect electrochemical reduction of nitrate.•Ions responsible for water hardness inhibit electrochemical reduction of nitrate.•Scaling formation limits access to active sites on the ...cathode surface.•Softening increases nitrate conversion and decreases energy consumption.•The pH control does not influence NO3− conversion nor N2 selectivity.
Water matrix composition impacts water treatment performance. However, matrix composition impacts have rarely been studied for electrochemical water treatment processes, and the correlation between the composition and the treatment efficiency is lacking. This work evaluated the electrochemical reduction of nitrate (ERN) using different complex water matrices: groundwater, brackish water, and reverse osmosis (RO) concentrate/brine. The ERN was conducted using a tin (Sn) cathode because of the high selectivity towards nitrogen evolution reported for Sn electrocatalysts. The co-existence of calcium (Ca2+), magnesium (Mg2+), and carbonate (CO32−) ions in water caused a 4-fold decrease in the nitrate conversion into innocuous nitrogen gas due to inorganic scaling formation on the cathode surface. XRF and XRD analysis of fouled catalyst surfaces detected brucite (Mg(OH)2), calcite (CaCO3), and dolomite (CaMg(CO3)2) mineral scales formed on the cathode surface. Surface scaling created a physical barrier on the electrode that decreased the ERN efficiency. Identifying these main sources of ERN inhibition was key to devising potential fouling mitigation strategies. For this reason, the chemical softening pre-treatment of a real brackish water was conducted and this significantly increased nitrate conversion and faradaic efficiency during subsequent ERN treatment, leading to a lower electric energy consumption per order. Understanding the ionic foulant composition responsible for influencing electrochemically-driven technologies are the first steps that must be taken to move towards niche applications such as decentralized ERN. Thus, we propose either direct ERN implementation in regions facing high nitrate levels in soft waters, or a hybrid softening/nitrate removal system for those regions where high nitrate and high-water hardness appear simultaneously.
Salinity is a significant factor for structuring microbial communities, but little is known for aquatic fungi, particularly in the pelagic zone of brackish ecosystems. In this study, we explored the ...diversity and composition of fungal communities following a progressive salinity decline (from 34 to 3 PSU) along three transects of ca. 2000 km in the Baltic Sea, the world's largest estuary. Based on 18S rRNA gene sequence analysis, we detected clear changes in fungal community composition along the salinity gradient and found significant differences in composition of fungal communities established above and below a critical value of 8 PSU. At salinities below this threshold, fungal communities resembled those from freshwater environments, with a greater abundance of Chytridiomycota, particularly of the orders Rhizophydiales, Lobulomycetales, and Gromochytriales. At salinities above 8 PSU, communities were more similar to those from marine environments and, depending on the season, were dominated by a strain of the LKM11 group (Cryptomycota) or by members of Ascomycota and Basidiomycota. Our results highlight salinity as an important environmental driver also for pelagic fungi, and thus should be taken into account to better understand fungal diversity and ecological function in the aquatic realm.
This paper is the second part of the “Ichthyofauna of the Fresh and Brackish Waters of Russia and Adjacent Areas: Annotated List with Taxonomic Comments”, which we started in 2022 based on a critical ...analysis of scientific publications of the last 200 years, and on the data of the author’s research. The current paper includes all currently known fishes of the order Cypriniformes of Russia and adjacent waters, represented by three suborders Catostomoidei, Cobitoidei and Cyprinoidei, comprising ten families, 64 genera and 177 species. The most specious families were the Leuciscidae (59 species/33.3% of all species), Gobionidae (35/19.8%) and Xenocyprididae (23/13.0%), which together represent just over 66% the total cypriniform species. Fourteen of the studied species (24.7% of all cyprinids in Russia) are introduced species, 21 species (11.9%) are endemic; 32 species (18.1%) are recorded from Russia for the first time. In relation to the habitat, 131 species live and breed exclusively in fresh waters, 31 species are of freshwater origin, but can also tolerate slightly brackish waters, ten species are represented by anadromous forms (all with residential populations), and three species are amphidromic, capable of live and reproduce both in brackish water and in freshwater. According to the IUCN criteria, the majority of fish are classified as Least Concern (135 species/76.3%), but two species,
Cobitis taurica
and
Gobio tauricus,
are Critically Endangered.
Great attention has been given to freshwater ecosystems worldwide due to the increased exploitation of water resources and the degradation of water quality. This study was aimed to demonstrate the ...phytoplankton-stressor interactions using multivariate approaches and assess the ecological conditions of 28 sampling stations of 12 lentic ecosystems (five lakes and seven reservoirs) in the western Mediterranean basin using phytoplankton indices in dry and rainy seasons 2018. Freshwater and brackish water systems were separately ordinated by canonical correspondence analysis. The brackish ecosystems were under pressures of Ar (arsenic), N-N
O
2
−
(nitrite), Ca (calcium), EC (electrical conductivity), Cl (chloride), B (boron), etc., whereas shallow freshwater ecosystems were associated with total organic carbon. These factors had significant effects on phytoplankton distribution among lentic ecosystems on the basin. Ecological associations of phytoplankton assemblages varied in the western Mediterranean basin during the study.
Pseudanabaena catenata
and
Palatinus apiculatus
, considered tolerant taxa, are associated with higher Ar, EC, and V (vanadium) while
Desmodesmus abundans
and
Microcystis flos-aquae
are related to total organic carbon. The modified PTI (phytoplankton trophic index) had the highest correlation coefficient value. Scores of the PTI varied from 2.02 in Çavdır Reservoir to 2.59 in Lake Kocagöl. Results of phytoplankton indices indicated that two (Gölhisar and Yazır) lakes and two (Yapraklı and Çavdır) reservoirs were classified as Good, and three lakes and five reservoirs were classified as Moderate condition. Other predicted classifications (high, poor, and bad) by phytoplankton metrics were not represented. The modified PTI could be a suitable phytoplankton metric for assessing the ecological status of lentic ecosystems in the Mediterranean system according to its highest correlation coefficient value. Overall, the results of this limno-ecological study demonstrated that responses of phytoplankton taxa to explanatory factors provide crucial ecological information about their ecology and to estimate the ecological status of lentic ecosystems.
—
A complete annotated list of fresh and brackish waters ichthyofauna of the Russian Federation and adjacent areas, based on a critical analysis of scientific publications of the last 200 years, and ...on the data of the authors’ research, is the aim of this study. The taxonomic composition of the freshwater and brackish water fish fauna of Russia remains insufficiently studied. This may result incorrect data on the true number of fish species of this category, not only for the waters of Russia, but also in the modern system of the world ichthyofauna as a whole, and also does not give a complete idea of the range, degree of endemism, abundance, conservation status, commercial value, and others important aspects. Until the present study, according to various sources, the Russian freshwater and brackish water ichthyofauna was estimated to amount from 351 to 486 species, respectively. However, based on our ongoing research, these numbers are too low and need to be revised. The total species number in all categories should include at least 800 species also including the introduced non-native species, as well as species not yet recorded from Russian waters, but suggested to be found in the future. In this first part of our updated checklist, we provide a basic historical review of ichthyological research in Russia, together with the first 77 species belonging to three classes (Petromyzonti, Elasmobranchii and Actinopteri), ten orders (Petromyzontiformes, Lamniformes, Carcharhiniformes, Squaliformes, Rajiformes, Myliobatiformes, Acipenseriformes, Elopiformes, Anguilliformes and Clupeiformes), nineteen families (Petromyzontidae, Alopiidae, Lamnidae, Triakidae, Carcharhinidae, Sphyrnidae, Somniosidae, Squalidae, Rajidae, Arhynchobatidae, Dasyatidae, Acipenseridae, Polyodontidae, Megalopidae, Anguillidae, Muraenesocidae, Clupeidae, Engraulidae and Pristigasteridae) and 38 genera. For each species, the following details are presented: scientific and English common names, taxonomic position with comments and synonyms (if necessary), conservation status, world distribution, zoogeographic characteristics, distribution in Russian waters and adjacent areas, abundance, and commercial value.
This paper analyzes whether physicochemical properties significantly influence the occurrence of zooplankton in a brackish reservoir. The studies were carried out on the Vistula Lagoon in August and ...September from 2006 to 2009 at 32 research sites. The environmental conditions in the Vistula Lagoon varied widely. At the time of the investigation, 17 species of rotifers, six species of Cladocera, and ten species of Copepoda were noted, and the total density of plankton fauna ranged from 145 to 765ind.dm−3. Statistical analysis demonstrated a significant correlation between the occurrence of some zooplankton species and certain environmental parameters, whereas the sampling sites were grouped according to study years. The zooplankton systems recorded at the research sites in 2006 constitute the most disparate group. Thus, it can be concluded that physicochemical properties might significantly impact both individual species (depending on their environmental demands) and entire zooplankton clusters.
In this review we highlight the relevance of biodiversity that inhabit coastal lagoons, emphasizing how species functions foster processes and services associated with this ecosystem. We identified ...26 ecosystem services underpinned by ecological functions performed by bacteria and other microbial organisms, zooplankton, polychaetae worms, mollusks, macro-crustaceans, fishes, birds, and aquatic mammals. These groups present high functional redundancy but perform complementary functions that result in distinct ecosystem processes. Because coastal lagoons are located in the interface between freshwater, marine and terrestrial ecosystems, the ecosystem services provided by the biodiversity surpass the lagoon itself and benefit society in a wider spatial and historical context. The species loss in coastal lagoons due to multiple human-driven impacts affects the ecosystem functioning, influencing negatively the provision of all categories of services (i.e., supporting, regulating, provisioning and cultural). Because animals’ assemblages have unequal spatial and temporal distribution in coastal lagoons, it is necessary to adopt ecosystem-level management plans to protect habitat heterogeneity and its biodiversity, ensuring the provision of services for human well-being to multi-actors in the coastal zone.
Over the past few decades, the number of available spawning grounds for anadromous pikes,
Esox lucius,
on the Baltic Sea coast has been significantly reduced resulting in a drastic pike population ...decline in those areas. It is therefore a question if saline Baltic waters may support the spawning of anadromous pike. In the present experimental study, salinity had a harmful impact on the development of eggs from pikes of freshwater origin. The hatching success rates were 0% at 7PSU and only 16.7% at 4PSU, while hatching success at 0PSU was 89.7%. However, when the eggs were fertilized in fresh water and transferred to the tested salinities after 1 h, salinity had a positive effect on egg development and hatching success (0PSU: 80%; 4PSU: 83.3%; and 7PSU: 93.7%). We concluded that the spawning of the freshwater pike population in the saline water of the Baltic Sea is most likely not successful. Simultaneously, inflows of coastal marine waters into near-shore spawning grounds do not have a harmful effect on egg development if the eggs are already fertilized. The main management measures that can be suggested are to rebuild the anadromous population by spawning ground reconstruction. Sea-spawning population introduction can also be considered.
This study aimed to statistically prove the influence of salinity on growth kinetics and intracellular lipid accumulation in microalgae. The species Chlorella sp., Scenedesmus acuminatus, ...Nannochloropsis sp., Monoraphidium contortum and Pediastrum tetras were studied, which were isolated in the Brazilian semi-arid region and cultivated in synthetic media with the addition of NaCl. From the crops, growth kinetics, dry biomass production and lipid content were analyzed, using the experimental planning for one factor as a tool, with the NaCl concentration as an independent variable. The kinetic parameters maximum growth speed (µmax) and generation time (tg), as well as lipid concentration were the response variables studied. The results showed that, in the species Scenedesmus acuminatus, Nannochloropsis sp. and Pediastrum tetras, salt stress contributed to the increase in µmax and the consequent decrease in tg. The highest levels of lipid accumulation were obtained in Nannochloropsis sp. (62.04%), in the medium with the highest salinity and Pediastrum tetras (54.04%) in the lowest. Dry biomass production was higher in Scenedesmus acuminatus (1,941.37 mg.L-1) and Nannochloropsis sp. (1237.05 mg.L-1), both at a concentration of 4.0 g.L-1. Therefore, saline stress acted directly on the cell growth and lipid content of the species, which can be used as a device to enhance lipid production for the purpose of producing biofuels.
With the burst of silver nanoparticles (AgNPs) applications, their potential entry into the environment has attracted increasing concern. To date, researches about the impacts of AgNPs on microbial ...communities have been scarcely conducted in the brackish waters. Here, the effects of interactions of AgNPs and Ag+ (as a positive control) with dissolved oxygen on natural brackish water microbial communities were investigated for 30 d. The introduction of AgNPs and Ag+ in natural brackish waters resulted in distinct bacterial community composition and structure as well as reduction of the richness and diversity, effects that were not eliminated completely during the tested periods. Anoxic conditions could attenuate the effects of AgNPs and Ag+ on the community, and dissolved oxygen made more contributions to community compositions for short-term exposure. High doses of AgNPs had more pronounced long-term impacts than Ag+ amendment. Compared with the controls, two general AgNP and Ag+ responses, namely, sensitivity and resistance, were observed. Sensitive species mainly included those of the genera Synechococcus and unclassified_f_Rhodobacteraceae, while resistant species mostly belonged to the phylum Bacteroidetes and participated in carbon metabolic processes. Our results indicated that the microbial communities that were involved in nutrient cycles (such as carbon, nitrogen, and sulfide) and photoautotrophic bacteria that contained bacteriochlorophyll were adversely affected by AgNPs and Ag+. In addition, dissolved oxygen could further change the microbial communities. These results implied that under different oxygen conditions AgNPs possibly resulted in varying microbial survival strategies and affected the biogeochemical cycling of nutrients in natural brackish waters.
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•Photoautotrophic bacteria containing bacteriochlorophyll were sensitivity to AgNPs.•Most AgNP-tolerant bacteria participated in carbon metabolic processes.•Bacterial communities related to nutrient cycling were obviously affected by AgNPs.•Anoxic conditions could attenuate the effects of AgNPs and Ag+ on the community.•High doses of AgNPs had pronounced long-term impacts on bacterial communities.
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