Search Results (14)

To address the denitrification challenges in the high-dissolved-oxygen (DO) aquatic environment system caused by the secondary effluent of wastewater treatment plants, this study innovatively developed a sulfur–polycaprolactone (S⁰-PCL) dual-electron donor composite carrier embedded in polyurethane sponge to mitigate high DO stress. The system demonstrated remarkable resilience, with a denitrification efficiency decline of only 11.3% under a DO gradient (0–6.5 mg/L), significantly outperforming previously reported efficiency losses exceeding 90%. Metatranscriptomic analysis revealed that the millimeter-scale pores in the sponge created potential anoxic microzones, providing a microenvironment conducive to maintaining key denitrification gene expression. The anoxic stage was dominated by the sulfur-autotrophic denitrification (SAD) microorganism Sulfurovum (abundance 68.1%, expression 55.1%). In high-DO conditions, Alicycliphilus (55.3, 41.1%) and Paracoccus (31.6%, 31.8%) synergistically drove denitrification, while Hyphomonas (8.7%, 24.1%) assisted in DO and organics consumption. Gene expression data further revealed that Alicycliphilus hydrolyzed PCL to enter the tricarboxylic acid cycle, while Paracoccus simultaneously utilized S⁰ for SAD, establishing a dual-electron donor transfer pathway to sustain denitrification activity. The S⁰-PCL–polyurethane sponge provided resilience via oxygen isolation, sustained carbon release, and metabolic diversification, enabling microbial and functional gene reconfiguration. This study provides a novel technological pathway for deep nitrogen removal in oxygen-rich environments. Full article

The significant interest in the islands in the Russian Arctic has been in terms of available oil reserves, which determine the direction of economic development and associated environmental risks for this sector of the Arctic in the near future. Kotelny Island is the largest island of the New Siberian Islands Archipelago included in the protected zone of the Lena Delta Nature Reserve, which is located at 76° N, washed from the west by the Laptev Sea, washed from the east by the East Siberian Sea in a permafrost zone, and characterized by harsh climatic conditions defined by the northeast winds that prevail in vegetative season. January sees temperatures ranging from −32 to −35 °C, and July from +6 to +8 °C, which causes a short growing season. Samples were taken between August 3 and 8, 2018 in 12 freshwater bodies where 210 taxa were revealed. Aquatic communities were dominated by zygnematophycean and diatom algae, grouped in the basins of two rivers and associated with the position on the island’s landscape, which suggests the influence of cold north-east winds, leading to the avoidance of habitats in open and high places, which was revealed by statistical methods and also confirms the high individuality of taxa composition. Bioindication methods showed that water bodies are slightly alkaline, with low ion concentrations, with the presence of sulfides in low-lying habitats, and average saturation with organic matter. The mesotrophic status of the studied water bodies was evaluated through an assessment and the type of nutrition in the communities of algae and cyanobacteria indicates they formed there as true autotrophs, which corresponds to the status of a protected area and can serve as a reference level for monitoring anthropogenic impact. Full article

Microplastics (MPs) represent small plastic particles with sizes between 1 μm and 5 mm, are insoluble in water, andclassified as primary (these are originally produced in small sizes) or secondary (the result of the degradation of plastic) types. MPs accumulate in all ecosystems, including freshwater environments, where they are subjected to degradation processes. Due to their ubiquitous nature, freshwater ecosystems, which have a vital importance in human life, are permanently subjected to these small plastic particles. In this context, MPs pollution is considered to be a global issue, and it is associated with toxic effects on all the elements of the freshwater environment. In this review, we present, in detail, the main physical (density, size, color, shape, and crystallinity) and chemical (chemical composition and modification of the MPs’ surface) properties of MPs, the mechanism of biodegradation, and the consequences of autotrophic organisms and fauna exposure by focusing on the freshwater environment. The toxicity mechanisms triggered by MPs are related to the critical parameters of the particles: size, concentration, type, and form, but they are also dependent on species exposed to MPs and the exposure route. Full article

Land use disrupts the ecosystem functioning of freshwater systems and significantly affects trophic state. Consequently, biodiversity is severely affected by changes to the ecosystem. Microbial eukaryotes (i.e., protists) play an essential role in ecosystem functioning, contributing to biogeochemical processes, nutrient cycling, and food webs. Protist composition is a useful biological quality parameter for monitoring aquatic ecosystems and determining aquatic system health. In this study, we investigated the effects of land usage and trophic state on the communities of microbial eukaryotes in the New River (Belize, C.A.). Land use and trophic state both significantly affected protist community compositions, with impacted and mesotrophic sampled sites having higher biodiversity when compared to other sites. Autotrophic organisms dominated indirectly impacted and eutrophic sites, while impacted and mesotrophic sites had proportional ratios of autotrophic and heterotrophic organisms. Our study highlights the significant effects of trophic gradients on protistan community composition, even at the local scales. Full article

The article presents a list of algal species and cyanobacteria found in the continental waters of Israel in 1898–2022. Research progressed in 2000–2022 by increasing the list from 1261 to 1628 species belonging to fourteen phyla. Taxonomic analysis shows that diatoms, cyanobacteria, and green algae predominated. The first-time data has been synthesized to identify the indicator properties of Israel’s aquatic flora carried out on algae and cyanobacteria, which can be used to monitor water quality. The species’ ecological preferences are given for ten environmental variables: substrate preference, temperature, oxygen saturation with water mobility, water pH preferences, water salinity, organic pollution according to Watanabe and Sládeček with species-specific index of saprobity S, trophic state, and type of nutrition (autotrophic or heterotrophic). This list of species with indicator values for each species is used to characterize the water properties in Israel. In addition, it can be applied to assess the state of aquatic ecosystems and monitor water quality based on bioindication methods. Full article

Who’s cooking, who’s cleaning, and who’s got the remote control within the waters blanketing Earth? Anatomically tiny, numerically dominant microbes are the crucial “homemakers” of the watery household. Phytoplankton’s culinary abilities enable them to create food by absorbing sunlight to fix carbon and release oxygen, making microbial autotrophs top-chefs in the aquatic kitchen. However, they are not the only bioengineers that balance this complex household. Ubiquitous heterotrophic microbes including prokaryotic bacteria and archaea (both “bacteria” henceforth), eukaryotic protists, and viruses, recycle organic matter and make inorganic nutrients available to primary producers. Grazing protists compete with viruses for bacterial biomass, whereas mixotrophic protists produce new organic matter as well as consume microbial biomass. When viruses press remote-control buttons, by modifying host genomes or lysing them, the outcome can reverberate throughout the microbial community and beyond. Despite recognition of the vital role of microbes in biosphere housekeeping, impacts of anthropogenic stressors and climate change on their biodiversity, evolution, and ecological function remain poorly understood. How trillions of the smallest organisms in Earth’s largest ecosystem respond will be hugely consequential. By making the study of ecology personal, the “housekeeping” perspective can provide better insights into changing ecosystem structure and function at all scales. Full article

Bicarbonate ions are the primary source of inorganic carbon for autotrophic organisms living in aquatic environments. In the present study, we evaluated the short-term (hours) effects of sodium bicarbonate (NaHCO₃) addition on the growth and photosynthetic efficiency of the green algae Chlorella sorokiniana (211/8k). Bicarbonate was added to nonaxenic cultures at concentrations of 1, 2, and 3 g L⁻¹ leading to a significant increase in biomass especially at the highest salt concentration (3 g L⁻¹) and also showing a bactericidal and bacteriostatic effect that helped to keep a reduced microbial load in the algal culture. Furthermore, bicarbonate stimulated the increase in cellular content of chlorophyll a, improving the photosynthetic performance of cells. Since microalgae of genus Chlorella spp. show great industrial potential for the production of biofuels, nutraceuticals, cosmetics, health, and dietary supplements and the use of bicarbonate as a source of inorganic carbon led to short-term responses in Chlorella sorokiniana, this method represents a valid alternative not only to the insufflation of carbon dioxide for the intensive cultures but also for the production of potentially bioactive compounds in a short period. Full article

The presence of pharmaceutical and personal care product (PPCP) residues in the aquatic environment is an emerging issue due to their uncontrolled release through gray water, and accumulation in the environment that may affect living organisms, ecosystems and public health. The aim of this study is to assess the toxicity of benzophenone-3 (BP-3), bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT), butyl methoxydibenzoylmethane (BM), methylene bis-benzotriazolyl tetramethylbutylphenol (MBBT), 2-ethylhexyl salicylate (ES), diethylaminohydroxybenzoyl hexyl benzoate (DHHB), diethylhexyl butamido triazone (DBT), ethylhexyl triazone (ET), homosalate (HS) and octocrylene (OC) on marine organisms from two major trophic levels, including autotrophs (Tetraselmis sp.) and heterotrophs (Artemia salina). In general, results showed that both HS and OC were the most toxic UV filters for our tested species, followed by a significant effect of BM on Artemia salina due to BM—but only at high concentrations (1 mg/L). ES, BP3 and DHHB affected the metabolic activity of the microalgae at 100 µg/L. BEMT, DBT, ET, MBBT had no effect on the tested organisms, even at high concentrations (2 mg/L). OC toxicity represents a risk for those species, since concentrations used in this study are 15–90 times greater than those reported in occurrence studies for aquatic environments. For the first time in the literature, we report HS toxicity on a microalgae species at concentrations complementing those found in aquatic environments. These preliminary results could represent a risk in the future if concentrations of OC and HS continue to increase. Full article

Chromophoric dissolved organic matter (CDOM) is a key component with a critical role in the littoral zones of eutrophic shallow lakes; yet the characteristics of CDOM in these zones remain seldom systematically reported. In this study, the differences in sources, biogeochemical characteristics, and fates of CDOM between the littoral zones of eutrophic lakes Taihu (LLT; frequently occurring algal blooms and longer lake residence time) and Hongze (LLH; no obvious algal blooms and shorter residence time) were compared during the algal bloom season using ultraviolet-visible spectra and excitation and emission matrix spectroscopy combined with parallel factor analysis. Three humic-like fluorescent dissolved organic matter (FDOM) components (C1, C3, and C4) and one protein-like component (C2) were identified. Results showed that FDOM components were dominated by protein-like fluorescent substances in LLT, and humic-like materials in LLH, respectively. The CDOM in LLT had a lower relative aromaticity and molecular weight, humification degree and a higher autotrophic productivity because of algal blooms. Furthermore, CDOM depletion rates in LLT were higher than those in LLH due to a longer lake residence time in LLT. In addition, CDOM shifted from high molecular weight to low molecular weight as the humification degree decreased during the CDOM depletion process. This comparative study showed that algal blooms and lake residence time were the significant factors for distinguishing characteristics of CDOM between littoral zones of shallow lakes on a similar trophic level. This study provides field-based knowledge for remote sensing CDOM measurement and serves as a reference for lakeshore aquatic environmental management. Full article

Bicarbonate plays a fundamental role in the cell pH status in all organisms. In autotrophs, HCO₃⁻ may further contribute to carbon concentration mechanisms (CCM). This is especially relevant in the CO₂-poor habitats of cyanobacteria, aquatic microalgae, and macrophytes. Photosynthesis of terrestrial plants can also benefit from CCM as evidenced by the evolution of C₄ and Crassulacean Acid Metabolism (CAM). The presence of HCO₃⁻ in all organisms leads to more questions regarding the mechanisms of uptake and membrane transport in these different biological systems. This review aims to provide an overview of the transport and metabolic processes related to HCO₃⁻ in microalgae, macroalgae, seagrasses, and terrestrial plants. HCO₃⁻ transport in cyanobacteria and human cells is much better documented and is included for comparison. We further comment on the metabolic roles of HCO₃⁻ in plants by focusing on the diversity and functions of carbonic anhydrases and PEP carboxylases as well as on the signaling role of CO₂/HCO₃⁻ in stomatal guard cells. Plant responses to excess soil HCO₃⁻ is briefly addressed. In conclusion, there are still considerable gaps in our knowledge of HCO₃⁻ uptake and transport in plants that hamper the development of breeding strategies for both more efficient CCM and better HCO₃⁻ tolerance in crop plants. Full article

Temporary Mediterranean ponds are complex ecosystems which support a high diversity of organisms that include heterotrophic microorganisms, algae, crustaceans, amphibians and higher plants, and have the potential to supply food and a resting place to migratory birds. The role of heterotrophs at the base of the food web in providing energy to the higher trophic levels was studied in temporary ponds in Central and Southern Portugal. The relative quantification of the hetero and autotrophic biomass at the base of the food web in each pond was derived from the polar fatty acid (PLFA) composition of seston through the application of the matrix factorization program CHEMTAX that used specific PLFA and their relative proportion as markers for e.g., classes of bacteria, algae and fungi. The species composition of the culturable microbial communities was identified through their fatty acid profiles. The biomass in the lower trophic level of some ponds presented an even proportion of auto to heterotrophic organisms whilst either bacteria or algae dominated in others. In a selected subset of ponds, the incorporation of bacterial fatty acids was observed to occur in potentially herbivorous zooplankton crustacean. Zooplankton consumed and incorporated bacterial fatty acids into their body tissues, including into their phospholipids, which indicates that energy of heterotrophic origin contributes to the aquatic food webs of temporary ponds. Full article

Lake Vostok is the largest of the nearly 400 subglacial Antarctic lakes and has been continuously buried by glacial ice for 15 million years. Extreme cold, heat (from possible hydrothermal activity), pressure (from the overriding glacier) and dissolved oxygen (delivered by melting meteoric ice), in addition to limited nutrients and complete darkness, combine to produce one of the most extreme environments on Earth. Metagenomic/metatranscriptomic analyses of ice that accreted over a shallow embayment and over the southern main lake basin indicate the presence of thousands of species of organisms (94% Bacteria, 6% Eukarya, and two Archaea). The predominant bacterial sequences were closest to those from species of Firmicutes, Proteobacteria and Actinobacteria, while the predominant eukaryotic sequences were most similar to those from species of ascomycetous and basidiomycetous Fungi. Based on the sequence data, the lake appears to contain a mixture of autotrophs and heterotrophs capable of performing nitrogen fixation, nitrogen cycling, carbon fixation and nutrient recycling. Sequences closest to those of psychrophiles and thermophiles indicate a cold lake with possible hydrothermal activity. Sequences most similar to those from marine and aquatic species suggest the presence of marine and freshwater regions. Full article

In particular niches of the marine environment, such as abyssal trenches, icy waters and hot vents, the base of the food web is composed of bacteria and archaea that have developed strategies to survive and thrive under the most extreme conditions. Some of these organisms are considered “extremophiles” and modulate the fatty acid composition of their phospholipids to maintain the adequate fluidity of the cellular membrane under cold/hot temperatures, elevated pressure, high/low salinity and pH. Bacterial cells are even able to produce polyunsaturated fatty acids, contrarily to what was considered until the 1990s, helping the regulation of the membrane fluidity triggered by temperature and pressure and providing protection from oxidative stress. In marine ecosystems, bacteria may either act as a sink of carbon, contribute to nutrient recycling to photo-autotrophs or bacterial organic matter may be transferred to other trophic links in aquatic food webs. The present work aims to provide a comprehensive review on lipid production in bacteria and archaea and to discuss how their lipids, of both heterotrophic and chemoautotrophic origin, contribute to marine food webs. Full article