Aquatic fungi in relation to the physical and chemical parameters of water quality in the Augustów Canal

Dry and wet seasonal variations of the sediment fungal community composition in the semi-arid region of the Dali River, Northwest China

Microbial communities play an important role in water quality regulation and biogeochemical cycling in freshwater ecosystems. However, there has been a lack of research on the seasonal variation of sediment microorganisms in the sediments of small river basins in typical semi-arid region. In this study, high-throughput DNA sequencing was used to investigate the fungal community and its influencing factors in the sediment of the Dali River in the dry and wet seasons. The results showed that there were obvious seasonal differences in fungal alpha diversity. The diversity and richness of fungi in the dry season were greater than that in the wet season, but the evenness of fungi in the dry season was lower than that in the wet season. In addition, Ascomycota and Basidiomycota were the most important phyla in the Dali River fungal community, but their distributions showed clear seasonal differences. In the dry season, the relative abundance of Ascomycota and Basidiomycota were 12.34-46.42% and 17.59-27.20%, respectively. In the wet season, the relative abundances of these two phyla were 24.33-36.56% and 5.75-12.26%, respectively. PICRUSt2 was used to predict the metabolic function of fungal community in the sediment, and it was found that at the first level, the proportion of biosynthesis in the dry season was higher than that in the wet season. The ecological network structure showed that the fungal community in the wet season was more complex and stable than that in the dry season. The characteristic fungi in the dry season sediment were chytrid fungi in the family Rhizophydiaceae and the order Rhizophydiales, whereas those in the wet season sediment were in the orders Eurotiales and Saccharomycetales. Canonical correspondence analysis (CCA) showed that the physicochemical properties of water and sediment together explained a greater proportion of the dry-season fungal community changes than of the wet-season changes. In the dry season, temperature and ammonia nitrogen in the water were the main factors affecting the change of fungal community, whereas in the wet season, total nitrogen concentration of the water, electrical conductivity, total organic carbon and available phosphorus of the sediment, pH, and temperature were the main factors affecting the changes in fungal community composition. The results of this study enhanced our understanding of microbial communities in semi-arid river ecosystems, and highlight the importance of the management and protection in river ecosystems.

Traditional and new proposals for environmental microbial indicators-a review

The continuous increment in world population coupled with the greatest natural resource consumption and waste generation has an enormous impact on the environment. To date, using biological indicators (bioindicators) to evaluate the biological quality of natural environments is very common. Nonetheless, selecting those suitable for each ecosystem or contaminant is one of the most important issues for environmental sciences. Bacteria and helminths are mainly related to fecal contamination, while antibiotic-resistant bacteria, fungi, viruses, and microalgae are organisms used to determine deteriorated ecosystems by diverse contaminants. Nowadays, each bioindicator is used as a specific agent of different contaminant types, but detecting and quantifying these bioindicator microorganisms can be performed from simple microscopy and culture methods up to a complex procedure based on omic sciences. Developing new techniques based on the metabolism and physiological responses of traditional bioindicators is shown in a fast environmental sensitivity analysis. Therefore, the present review focuses on analyzing different bioindicators to facilitate developing suitable monitoring environmental systems according to different pollutant agents. The traditional and new methods proposed to detect and quantify different bioindicators are also discussed. Their vital role is considered in implementing efficient ecosystem bioprospection, restoration, and conservation strategies directed to natural resource management.

Seasonal fluctuations and diversity of Ingoldian mycobiota in two water bodies receiving different effluents at Assiut Governorate (Upper Egypt)

In the current study, fifty-eight Ingoldain fungal species assignable to forty-one genera were recovered from two water bodies receiving the treated sewage and the effluents of oils and soaps factory at Assiut Governorate (Upper Egypt), of which Anguillospora, Amniculicola, Flagellospora, and Mycocentrospora were the most prevalent genera. The most widespread identified species were Anguillospora furtive, Amniculicola longissima and Flagellospora fusarioides. Forty-three species were identified for the first time in Egypt. The most Ingoldain taxa were estimated for El-Zinnar canal, with the highest recorded taxa in winter. Whereas, the highest dominance of Ingoldian fungi was estimated for the El-Ibrahimia canal. The highest Simpson and Shannon diversity indexes were estimated for El-Zinnar canal samples recording 0.9683 and 3.741, respectively. The poorest water sites with Ingoldian fungi were those exposed directly to either treated sewage or industrial effluents, with which relatively higher values of water conductivity, cations and anions. Water temperature was the main abiotic factor driving the seasonal occurrence of Ingoldian fungi. It is interesting to isolate some Ingoldian fungal species from the stressful water sites receiving the effluents which provide valuable insights regarding their adaptation, predictive and putative role as bioindicators and their potentiality in pollutants degradation, organic decomposition, and transformation of xenobiotic compounds.

Environmental factors and stochasticity affect the fungal community structures in the water and sediments of Hulun Lake, China

Aquatic fungi form both morphologically and ecologically diverse communities. However, lake ecosystems are frequently overlooked as fungal habitats, despite the potentially important role of fungi in matter cycling and energy flow. Hulun Lake is a typical example of a seasonal glacial lake; however, previous studies have only focused on bacteria in this ecosystem. Therefore, in the current study, internal transcribed spacer ribosomal RNA (ITS rRNA) gene high-throughput sequencing was used to investigate the fungal communities in paired water and sediment samples from the Hulun Lake Basin in China. A significant difference was found between the fungal communities of the two sample types. Across all samples, we identified nine phyla, 30 classes, 78 orders, 177 families, and 307 genera. The dominant phyla in the lake were Ascomycota, Basidiomycota and Chytridiomycota. Our results show that both water and sediments have very high connectivity, are dominated by positive interactions, and have similar interaction patterns. The fungal community structures were found to be significantly affected by environmental factors (temperature, chemical oxygen demand, electrical conductivity, total phosphorus, and pH). In addition, the dispersal limitations of the fungi affected the structure of the fungal communities, and it was revealed that stochasticity is more important than deterministic mechanisms in influencing the structure and function of fungal communities. This study provides unique theoretical support for the study of seasonally frozen lake fungal communities and a scientific basis for the future management and protection of Hulun Lake.

Species Diversity of Mycoplankton on the Background of Selected Indicators of Water Quality in Stratified Mesotrophic Lakes

The aim of the study was to determine mycoplankton species diversity in relation to the physico-chemical parameters of lake waters. The research was carried out in the summer months in 15 mesotrophic lakes and showed a high ecological significance index for Rhodotorula glutinis, Epicoccum nigrum, Fusarium sporotrichioides, and Trichophyton violaceum. Mycoplankton abundance and species diversity decreased with the depth of water, which coincided with a decrease in oxygen content and organic matter concentration. A high concentration of nitrogen compounds (total nitrogen-TN and dissolved nitrogen-DN) limited the development of mycobiota in the hypolimnion. In the metalimnion, the intensive development of organisms, especially bacteria, limited mycoplankton abundance despite perfect physical and chemical conditions for its development. Finally, mycoplankton functioned the best in slightly alkaline waters.

Effect of Humic Acid on the Growth and Metabolism of Candida albicans Isolated from Surface Waters in North-Eastern Poland

The aim of this study was to determine the effect of humic acid on the growth and metabolism of Candida albicans, a common waterborne pathogenic yeast. At 10–20 mg/L, humic acid caused the greatest increase in biomass and compactness of proteins and monosaccharides, both in cells and in extracellular secretion of the yeast. At higher humic acid concentrations (40–80 mg/L), C. albicans cells still had higher protein levels compared to control, but showed reduced levels of metabolites and inhibited growth, and a significant increase in the activity of antioxidant enzymes, indicating a toxic effect of the humic acid. The increase in protein content in the cells of C. albicans combined with an increase in the activity of antioxidant enzymes may indicate that the studied yeast excels in conditions of high water enrichment with low availability of organic matter. This indicates that Candida albicans is capable of breaking down organic matter that other microorganisms cannot cope with, and for this reason, this yeast uses carbon sources that are not available to other microorganisms. This indicates that this fungus plays an important role in the organic carbon sphere to higher trophic levels, and is common in water polluted with organic matter.

Distinct fungal plastisphere across different river functional zones: A watershed scale study

Fungi not only play important roles in biogeochemical processes but also can form biofilm on plastic debris. However, knowledge of structure composition and spatiotemporal pattern of fungal plastisphere on different kinds of plastic debris in river with specific usages, known as river functional zones, is still missing. In this study, we investigated the spatial distribution of the fungal plastisphere across a complete urban river with different functional zones (drinking, farm irrigation, aquaculture, and tail lake). Our research was performed based on both field residual plastic debris collection and a 30-day field in situ incubation experiments. Our study revealed that plastic debris enriched distinct fungal communities (including pathogenic fungi) significantly different from the surrounding water. Tracking the source of the fungi colonized on plastic debris suggested that the fungal taxa colonized on the different kinds of plastic debris were not from the surrounding water. Human activities had considerable effects on the fungal community structure on plastic debris, and the plastisphere fungal community structure strikingly varied across different river functional zones. Plastisphere may be used as an indicator for fungi biogeography and pathogenic fungi pollution in river with different functional zones. These findings are essential for ecological risk assessment and management decisions for pollution control of plastic debris and maintaining ecological health.

Structural Characteristics and Driving Factors of the Planktonic Eukaryotic Community in the Danjiangkou Reservoir, China

Planktonic eukaryotes are widespread in aquatic ecosystems, and the study of their community composition and driving factors is of great significance to protecting and maintaining the balance of these ecosystems. This study evaluates five typical ecological sites in the Danjiangkou Reservoir—the water source for the project. This was done to comprehensively understand the composition of Danjiangkou Reservoir planktonic eukaryotes, and ensure the ecological balance of the water source for the South-to-North Water Diversion Project. The diversity of the planktonic eukaryotes in surface water and the factors driving changes in their abundance are analyzed with an 18S ribosomal DNA sequencing approach. Monitoring shows that the Danjiangkou Reservoir has good water quality. The Danjiangkou Reservoir planktonic eukaryote community is mainly composed of 11 phyla, of which Cryptomonadales is dominant, accounting for an average percentage of 65.19% of the community (47.2–84.90%). LEFSe analysis shows significant differences among samples in the abundances of 13 phyla, 20 classes, 23 orders, 26 families, and 27 genera, and there are also significant differences in the diversity of planktonic eukaryotes at different temporal and spatial scales. Redundancy analysis (RDA) show that water temperature, DO, SD, TN, and Chla are significant factors that affect the composition of the planktonic eukaryote community. Spearman rank correlation analysis combined with taxonomic difference analysis shows that Kathablepharidae and Choanoflagellida are not sensitive to environmental or physicochemical factors and that the interannual variations in their abundance are not significant. Network analysis shows that Protalveolata, Basidiomycota, P1-31, Bicosoecida, and Ochrophyta represent important nodes in the single-factor network, while Chytridiomycota, P1-31, Cryptomycota, Ochrophyta, Ichthyosporea, Bicosoecida, Protalveolata, and physicochemical factors (ORP, TN, WT, DO, SD, NH3-N, and NO3-N) represent important nodes in the two-factor network.

Anthropogenic impact on the historical phytoplankton community of Lake Constance reconstructed by multimarker analysis of sediment-core environmental DNA

During the 20th century, many lakes in the Northern Hemisphere were affected by increasing human population and urbanization along their shorelines and catchment, resulting in aquatic eutrophication. Ecosystem monitoring commenced only after the changes became apparent, precluding any examination of timing and dynamics of initial community change in the past and comparison of pre- and postimpact communities. Peri-Alpine Lake Constance (Germany) underwent a mid-century period of eutrophication followed by re-oligotrophication since the 1980s and is now experiencing warm temperatures. We extended the period for which monitoring data of indicator organisms exist by analysing historical environmental DNA (eDNA) from a sediment core dating back some 110 years. Using three metabarcoding markers-for microbial eukaryotes, diatoms and cyanobacteria-we revealed two major breakpoints of community change, in the 1930s and the mid-1990s. In our core, the latest response was exhibited by diatoms, which are classically used as palaeo-bioindicators for the trophic state of lakes. Following re-oligotrophication, overall diversity values reverted to similar ones of the early 20th century, but multivariate analysis indicated that the present community is substantially dissimilar. Community changes of all three groups were strongly correlated to phosphorus concentration changes, whereas significant relationships to temperature were only observed when we did not account for temporal autocorrelation. Our results indicate that each microbial group analysed exhibited a unique response, highlighting the particular strength of multimarker analysis of eDNA, which is not limited to organisms with visible remains and can therefore discover yet unknown responses and abiotic-biotic relationships.

The occurrence of potentially pathogenic filamentous fungi in recreational surface water as a public health risk

Microfungi occurring in surface water may represent an important health risk. Recreational water reservoirs are a potential reservoir of pathogenic fungi. The aim of the study was to assess the diversity of mycobiota in selected artificial bathing reservoirs with regard to its biosafety for the human population. The studies were conducted during the summer of 2016 in three research seasons (June (I), July and August (II), and September (III)), taking into account the various periods of recreational activities. Filamentous fungi were isolated from water samples collected at five different ponds utilized for recreation. From 162 water samples, 149 fungal taxa of filamentous fungi were identified: 140 were classified to species level and only nine to genus level. Aspergillus fumigatus was the dominant species. The highest species richness (S) was noted in June, with 93 fungal taxa (Menhinick's index from 2.65 to 4.49). Additionally, in season I, the highest diversity of fungal species was revealed (Simpson's diversity index from 0.83 to 0.99). The average number of CFU/1 mL sample ranged between 0.4 and 4.6 depending on the time of sampling and ponds. Of all the isolated species, 128 were clinically relevant (11 from RG-2 and 117 from RG-1), highlighting the need to introduce seasonal mycological monitoring of such reservoirs.

Fungal Community as a Bioindicator to Reflect Anthropogenic Activities in a River Ecosystem

The fungal community interacts with the ambient environment and can be used as a bioindicator to reflect anthropogenic activities in aquatic ecosystems. Several studies have investigated the impact of anthropogenic activities on the fungal community and found that community diversity and composition are influenced by such activities. Here we combined chemical analysis of water properties and sequencing of fungal internal transcribed spacer regions to explore the relationship between water quality indices and fungal community diversity and composition in three river ecosystem areas along a gradient of anthropogenic disturbance (i.e., less-disturbed mountainous area, wastewater-discharge urban area, and pesticide and fertilizer used agricultural area). Results revealed that the level of anthropogenic activity was strongly correlated to water quality and mycoplankton community. The increase in organic carbon and nitrogen concentrations in water improved the relative abundance of Schizosaccharomyces, which could be used as a potential biomarker to reflect pollutant and nutrient discharge. We further applied a biofilm reactor using water from the three areas as influent to investigate the differences in fungal communities in the formed biofilms. Different community compositions were observed among the three areas, with the dominant fungal phyla in the biofilms found to be more sensitive to seasonal effects than those found in water. Finally, we determined whether the fungal community could recover following water quality restoration. Our biofilm reactor assay revealed that the recovery of fungal community would occur but need a long period of time. Thus, this study highlights the importance of preserving the original natural aquatic ecosystem.

Influence of water quality on diversity and composition of fungal communities in a tropical river

Freshwater fungi are key decomposers of organic material and play important roles in nutrient cycling, bio-remediation and ecosystem functioning. Although aquatic fungal communities respond to pollution, few studies have quantitatively assessed the effect of freshwater contamination on fungal diversity and composition; and knowledge is scarcer for tropical systems. Here we help fill this knowledge gap by studying a heavily-contaminated South American river spanning a biodiversity hotspot. We collected 30 water samples scattered across a quality gradient over two seasons and analyzed them using Terminal Restriction Fragment Length Polymorphisms (T-RFLP) coupled with 454 Pyrosequencing. Using T-RFLP we identified 451 and 442 Operational Taxonomy Units (OTUs) in the dry and rainy seasons respectively, whereas Pyrosequencing revealed 48,553 OTUs from which 11% were shared between seasons. Although 68% of all identified OTUs and 51% of all identified phyla remained unidentified, dominant fungal phyla included the Ascomycota, Basidiomycota, Chytridiomycota, Glomeromycota, Zygomycota and Neocallimastigomycota, while Calcarisporiella, Didymosphaeria, Mycosphaerella (Ascomycota) and Rhodotorula (Basidiomycota) were the most abundant genera. Fungal diversity was affected by pH and dissolved iron, while community composition was influenced by dissolved oxygen, pH, nitrate, biological oxygen demand, total aluminum, total organic carbon, total iron and seasonality. The presence of potentially pathogenic species was associated with high pH. Furthermore, geographic distance was positively associated with community dissimilarity, suggesting that local conditions allowed divergence among fungal communities. Overall, our findings raise potential concerns for human health and the functioning of tropical river ecosystems and they call for improved water sanitation systems.

Planktonic fungal community structures and their relationship to water quality in the Danjiangkou Reservoir, China

Planktonic fungi are important components of aquatic ecosystems, and analyses of their community composition and function have far-reaching significance for the ecological management and maintenance of reservoir environments. However, few studies have investigated the composition, distribution, and function of planktonic fungi in reservoir ecosystems and their relationship with water quality. Here, the composition of the planktonic fungal community in the surface water layer of the Danjiangkou Reservoir is investigated using Illumina MiSeq sequencing. According to the results, the reservoir community is primarily composed of 7 phyla, including Ascomycota, Rozellomycota, Basidiomycota, Chytridiomycota, and Zygomycota, comprising 294 genera, demonstrating the rich diversity of this community. Redundancy analysis (RDA) of the planktonic fungal community and environmental factors showed dissolved oxygen (DO), chemical oxygen demand (COD), total nitrogen (TN), chlorophyll a (Chl a), and permanganate (CODMn) to be important factors influencing the distribution of planktonic fungi. Spearman correlation analysis of the planktonic fungal community composition and diversity indices with physical and chemical water quality parameters showed that the impacts of TN, COD and DO were the most significant. The results of this study on the planktonic fungal community in the Danjiangkou Reservoir area using high-throughput sequencing revealed that the community is sensitive to water quality parameters. This result provides a reference for studying the composition and distribution of the planktonic fungal community in Danjiangkou Reservoir and its role in the biogeochemical cycle.

Tannery mixed liquors from an ecotoxicological and mycological point of view: Risks vs potential biodegradation application

Fungi are known to be present in the activated sludge of wastewater treatment plants (WWTP). Their study should be at the base of an overall vision of the plant effectiveness and of effluents sanitary impact. Moreover, it could be fundamental for the implementation of successful bioaugmentation strategies aimed at the removal of recalcitrant or toxic compounds. This is one of the first studies on the cultivable autochthonous mycoflora present in the mixed liquors of two WWTP treating either vegetable or chromium tannery effluents. All samples showed a risk associated with potential pathogens or toxigenic species and high ecotoxicity (Lepidium sativum and Raphidocelis subcapitata were the most sensitive organisms). Diverse fungal populations developed, depending on the origin of the samples (63% of the 102 identified taxa were sample-specific). The use of a fungistatic was determinant for the isolation and, thus, for the identification of sample-specific species with a lower growth rate. The incubation temperature also affected the mycoflora composition, even though at lower extent. A selective medium, consisting of agarised wastewater, allowed isolating fungi with a biodegradation potential. Pseudallescheria boydii/Scedosporium apiospermum species complex was ubiquitously dominant, indicating a possible role in the degradation of pollutants in both WWTP. Other species, i.e. Trichoderma spp., Trematosphaeria grisea, Geotrichum candidum, Lichtheimia corymbifera, Acremonium furcatum, Penicillium simplicissimum, Penicillium dangeardii, Fusarium solani, Scopulariopsis brevicaulis potentially could be involved in the degradation of specific pollutants of vegetable or chromium tannery wastewaters. However, several of these fungi are potential pathogens and their application, for an in situ treatment, must be carefully evaluated.

Application of the microbial community coalescence concept to riverine networks

Flows of water, soil, litter, and anthropogenic materials in and around rivers lead to the mixing of their resident microbial communities and subsequently to a resultant community distinct from its precursors. Consideration of these events through a new conceptual lens, namely, community coalescence, could provide a means of integrating physical, environmental, and ecological mechanisms to predict microbial community assembly patterns better in these habitats. Here, we review field studies of microbial communities in riverine habitats where environmental mixing regularly occurs, interpret some of these studies within the community coalescence framework and posit novel hypotheses and insights that may be gained in riverine microbial ecology through the application of this concept. Particularly in the face of a changing climate and rivers under increasing anthropogenic pressures, knowledge about the factors governing microbial community assembly is essential to forecast and/or respond to changes in ecosystem function. Additionally, there is the potential for microbial ecology studies in rivers to become a driver of theory development: riverine systems are ideal for coalescence studies because regular and predictable environmental mixing occurs. Data appropriate for testing community coalescence theory could be collected with minimal alteration to existing study designs.

Abundance and Species Diversity of Fungi in Rivers with Various Contaminations

The main objective of this work was to determine the abundance and species diversity of fungi in the waters of selected rivers of Central Europe, NE Poland (Augustów Lakeland), differing in size, physical and chemical properties, and streamflow rate. The minimum abundance of fungi in the analysed rivers was recorded for a river with low concentration of organic matter (8200 CFU/mL, Czarna Hańcza River), and maximum for a strongly anthropogenically polluted river (24,800 CFU/mL, Kamienny Bród River). A total of 49 fungal species were identified based on PCR ITS-RFLP and DNA sequencing methods. However, RFLP-PCR method has proved to be sufficient to determine the species of 34 fungi. The highest taxonomic diversity was determined for the waters abundant in organic matter (Piecówka and Rospuda Rivers), and the lowest for rivers poor in organic matter (Netta and Czarna Hańcza Rivers). From the 49 identified species, 47% were aquatic hyphomycetes, and 18% were potentially pathogenic fungi mainly occurring in the waters of polluted rivers with increased organic matter concentrations. Moreover, a higher number of fungal taxa were recorded in fluvial waters distinguished by higher streamflow rate, and therefore, stronger water turbulence. The study results suggest that the most important factors influencing the structure of mycoplankton in rivers include pH of water, content of organic matter, degree of anthropogenic pollution, and streamflow rate.

Effect of metalimnetic gradient on phytoplankton and zooplankton (Rotifera, Crustacea) communities in different trophic conditions

Theory predicts and recent study revealed that depth of the thermocline can strongly influence the nutrient availability and composition of plankton communities. We are focused on the effect of metalimnetic gradients on water chemistry and plankton communities in three stratified lakes with different trophic conditions. Vertical changes in water chemistry revealed significant increase of macroelement concentrations in the metalimnion of all studied lakes. However, there was no significant increase of nutrient concentrations in the thermocline of lakes with smoother metalimnetic gradient, whereas sharp and deep thermocline zone caused higher concentration of orthophosphates and dissolved inorganic nitrogen in the metalimnion. The maximum concentrations of phytoplankton were observed just below the thermocline and were caused mostly by the abundance of diatoms and cryptophytes. Vertical distribution of the crustacean zooplankton was similar to the distribution of phytoplankton. Especially, Daphnia cucullata was strongly related with the phytoplankton distribution and reached maximum densities in deep layers with high chlorophyll concentrations, and, conversely, smaller crustacean species and rotifers were not affected by the vertical distribution of phytoplankton.