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Abstract

Trait-based approaches may give insights into underlying mechanisms of relationships between biological communities and environmental stressors, and are increasingly used in ecological studies, but are only very recently considered for freshwater riverine microalgae. Here, we i) review the research trend in riverine microalgae during the past 26 years in order to conduct a quantitative and qualitative analysis for global trends in the research field, ii) summarize the use of algae traits in riverine biomonitoring and iii) propose future research perspectives. The bibliometric analysis showed that the annual number of publications on microalgae increased significantly from 1991 to 2016, although their proportions to total numbers of scientific articles remained steady. The studies have become increasingly concerned on issues arisen from global environmental changes such as “eutrophication”, “pollution”, “land use”, “biomonitoring”, “biodiversity”, “functional group”, etc. The use of algae traits in biomonitoring has become popular and includes e.g. functional diversity, cell size, guild, life form, eco-morphology, spore formation as well as algal quality. Here we collate all relevant algal traits, their different categories and propose their responses to resource supply and disturbance frequency in a conceptual model, which should be validated in future studies. In order to expand the knowledge and future use of microalgae in biomonitoring research efforts should also include: i) description of relationships between algal traits and ecosystem functions (e.g., nutrient uptake, metabolism, energy transfer across the food web) and underlying mechanisms; ii) selection of robust traits reflecting and disentangling the effects of multiple stressors; iii) water resource management in an interdisciplinary manner linking risk assessment and management scenarios by an integrated modelling system using microalgae.

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... Algae are important primary producers in aquatic environments, and their presence is closely related to factors such as land use (Leland and Porter, 2001), nutrients (Leventer and Dunbar, 1996), and topography (Ciutti, 2005). Diatoms have been used as indicator taxa in environmental assessments because they have short life cycles, high reproductive capacity, and large population base (Wu et al., 2017;Ciutti, 2005). While studies on algal diversity provide theoretical evidence that dam construction interferes with ecosystems, there was no research about changes in algae functional diversity around the dam (Paquette and Messier, 2015;Virta et al., 2021;Vogt et al., 2010). ...
... We hypothesize that specific traits will respond differently to conditions generated by small dams (hypothesis 3)-for example, low profile diatom taxa predominantly attach to the substratum, high profile taxa are larger and/ or tend to form long stalks or colonies, and motile and planktonic taxa are faster moving and better suited to gather resources in low-flow depositional environments (Passy, 2007). Smaller-celled diatom taxa have higher nutrient uptake and growth rates than larger-celled taxa, and are more common in nutrient-limited and highly disturbed conditions (Berthon et al., 2011;Rimet and Bouchez, 2012;Wu et al., 2017). Diatoms with stronger attachment to a substratum are better adapted to high disturbance conditions, but filamentous diatoms, while better adapted at gathering resources, are more susceptible to disturbance (Lange et al., 2016;Passy, 2007;Rimet and Bouchez, 2012;Wu et al., 2017). ...
... Smaller-celled diatom taxa have higher nutrient uptake and growth rates than larger-celled taxa, and are more common in nutrient-limited and highly disturbed conditions (Berthon et al., 2011;Rimet and Bouchez, 2012;Wu et al., 2017). Diatoms with stronger attachment to a substratum are better adapted to high disturbance conditions, but filamentous diatoms, while better adapted at gathering resources, are more susceptible to disturbance (Lange et al., 2016;Passy, 2007;Rimet and Bouchez, 2012;Wu et al., 2017). Accordingly, we expect impacted sites with lower flow velocity and greater stability (e.g., below dams) to favor high profile, motile, planktonic and larger taxa, and weakly attached and filamentous taxa. ...
Article
Knowledge of benthic diatom traits can help understand ecosystem function and guide biodiversity conservation. This is particularly important in rivers on which there are small run-of-river dams, which currently receive less attention. These dams generate power by drawing water from upstream and discharging it downstream after a large drop in penstock. We examine 15 functional diatom traits in habitats upstream, surrounding, and downstream of 23 small run-of-river dams in Xiangxi River, China. We compare the effects of these small dams on benthic diatom species traits, and taxonomic and functional diversity, from 90 sites. Dams change local environmental (e.g., channel width, flow velocity, depth) and physicochemical (e.g., dissolved oxygen, water temperature) variables, and a shift in diatom life forms and guilds is apparent, from taxa with strong attachment and low profile in high velocity waters (i.e., H1, H2 and H4) to those with weak attachment or that are planktonic below dams and outlets (i.e., H3 and H5), and towards high profile taxa below dams. Significant differences in biodiversity, particularly in functional richness, redundancy, and evenness, are apparent. Species and functional diversity indices are influenced by physical and chemical environmental factors (especially flow velocity and water depth). We found that diatom functional traits reflect longitudinal changes in flow and ecological condition, and suggest that monitoring such traits could be useful in adjusting flows to minimize ecosystem impacts. To maintain ecological flow and reasonable water depth within rivers we advocate for improved connectivity, carrying capacity and resilience of water ecosystems via a long-term, trait-based understanding of the impacts of small run-of-river dams.
... In particular, a significant decrease of the relative proportion of Bacillariophyta has affected chlorophyll values in July, August and September. In particular, diatoms proved again to be the photosynthetic group most negatively influenced by drought and chlorophyll content was influenced diatoms, was also observed in previous studies [58,59]. The results indicated that SRP (0.222 µgL -1 ) and NO3-N (0.010 mgL -1 ) was the limiting factor for algal abundance in July. ...
... Especially epilithic algae, as adaptations to the habitats, have been used by many researchers [12,57,59,62,63]. Through the river flow, the quality variations arising from environmental factors have caused the change in the population dynamics and abundance of the algae. ...
... Considering that many interrelated factors affect algal community structure, these analyses and indices applied for future monitoring are a precious contribution. The evaluated ecological variables (indices of community and multivariate analyses) were found to be helpful in differentiating of microhabitats affected from environmental factors in the study area on and the efficiency use of algal monitoring tools [59,66,67]. Villar-Argaiz et al. [50] stated that in rapid industrialization of the world, there should be an interdisciplinary priority to obtain a better understanding about how multiple environmental stressors interact as well as the predictive modelling of their complex results. ...
Research
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The Tohma Stream is among the most important tributaries of the transboundary Euphrates River. The aim of this work is to evaluate which are the most important environmental variables that might affect epilithic communities in Tohma Streams and species composition in microhabitats. A total of 89 taxa belonging to 4 phyla were identified in the study area (Bacillariophyta, Chlorophyta, Cy-anobacteria and Charophyta). According to temporal and spatial heterogeneity of Tohma Stream, ecological indices of epilithic algal composition demonstrated significant differences at the 95% confidence level. Mean DIN: SRP< 10 ratio was recorded at sts 4, 5, 8 and 9 in dry and wet seasons. Mean DIN: SRP was detected 80.028 ratio due to excessive pollution runoff. There was a correlation between community diversity and Bacillariophyta which is the most abundance group. According to changes in the species level of community composition, stations have been separated into 2 main groups in UPGMA cluster analysis. St11 was placed 2 nd main group and this situation has also been confirmed in the RDA analysis due to Tohma Stream derived mainly from agricultural , domestic and organic runoffs from industrial zone were mostly higher than the other stations.
... Among the groups of phytoplankton, diatoms are the most widely spread in the world. Furthermore, based on the fast response to changes in water quality, diatoms have been widely used as bio-indicators to assess the ecological status of aquatic ecosystems (B-Béres et al., 2016;Hill et al., 2000Hill et al., , 2003Stevenson et al., 1999;Wu et al., 2009Wu et al., , 2017Zalack et al., 2010). Diatom abundance and diversity are the basic and traditional features to represent the variation of diatom communities. ...
... However, the Shannon index and NMDS showed higher autocorrelation, which indicates that the similarity of Shannon index and NMDS remain higher than the similarity of diatom abundance and species richness in a few consecutive days. This could be because the indices consider more of the biological and ecological characteristics of the species or so-called functional features (Mouchet et al., 2010;Passy, 2007;Weithoff and Beisner, 2019;Wu et al., 2017), which generally can be shared by several species or even genera. This higher 'stability' also demonstrates better performance in the modeling prediction. ...
... In comparison with lakes, reservoirs and the other lentic aquatic habitats, a lowland river system is relatively more dynamic. That explains why hydrological conditions of lowland rivers play important roles in structuring biotic communities (Wu et al., 2017;Sun et al., 2018), higher wetness condition (higher API) increases diatom richness and diversity. This finding is in agreement with other research which reveals that drought is a strong negative stressor for diatom richness in lowland streams (B-Béres et al., 2019). ...
Article
With the growing demand of assessing the ecological status, there is the need to fully understand the relationship between the planktic diversity and the environmental factors. Species richness and Shannon index have been widely used to describe the biodiversity of a community. Besides, we introduced the first ordination value from non-metric multidimensional scaling (NMDS) as a new index to represent the community similarity variance. In this study, we hypothesized that the variation of diatom community in rivers in an agricultural area were influenced by hydro-chemical variables. We collected daily mixed water samples using ISCO auto water samplers for diatoms and for water-chemistry analysis at the outlet of a lowland river for a consecutive year. An integrated modeling was adopted including random forest (RF) to decide the importance of the environmental factors influencing diatoms, generalized linear models (GLMs) combined with 10-folder cross validation to analyze and predict the diatom variation. The hierarchical analysis highlighted antecedent precipitation index (API) as the controlling hydrological variable and water temperature, Si²⁺ and PO4-P as the main chemical controlling factors in our study area. The generalized linear models performed better prediction for Shannon index (R² = 0.44) and NMDS (R² = 0.51) than diatom abundance (R² = 0.25) and species richness (R² = 0.25). Our findings confirmed that Shannon index and the NMDS as an index showed good performance in explaining the relationship between stream biota and its environmental factors and in predicting the diatom community development based on the hydro-chemical predictors. Our study shows and highlights the important hydro-chemical factors in the agricultural rivers, which could contribute to the further understanding of predicting diatom community development and could be implemented in the future water management protocol.
... As an important primary producer in aquatic ecosystems, diatoms were increasingly involved as environmental indicators in freshwater ecosystems due to their well-known distinct features (Wijewardene et al., 2021;Wu et al., 2017). Consequently, diatombased biodiversity studies have been widely carried out around the world (Benito et al., 2018;Branco et al., 2020;Leboucher et al., 2019;Wu et al., 2021). ...
... Trait-based studies have been widely considered in stream macroinvertebrates (Menezes et al., 2010), aquatic plants (Baattrup-Pedersen et al., 2016) and fish communities (López-Delgado et al., 2020), but only recently were implemented for riverine diatoms (Guo et al., 2020;Wu et al., 2017Wu et al., , 2019. Several studies have shown their advantage in freshwater biomonitoring and biodiversity conservation (Perez Rocha et al., 2018;Wang et al., 2022;White et al., 2017;Wijewardene et al., 2021). ...
... To obtain trait-based temporal beta diversity and its decomposition, we assigned diatom species into three categories (i.e. biovolume, ecological guild and life-form) including 15 traits based on trait information from literature (Biggs et al., 1998;Lange et al., 2016;Passy, 2007;Wagenhoff et al., 2013;Witteveen et al., 2020;Wu et al., 2017) (Table 1). ...
Article
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1. A sound understanding of the community changes over time and its driving forces is at the centre of biodiversity conservation and ecology research. In this study, we examined: (i) the relative roles of turnover and nestedness components to trait-and taxonomy-based temporal beta diversity of riverine diatoms; (ii) whether trait-based temporal beta diversity provides complementary information to taxonomy-based temporal beta diversity; (iii) the relative roles of hy-drology (e.g. discharge, antecedent precipitation index), metal ions (e.g. Mg 2+ , Si 2+) and nutrients (e.g. nitrogen, orthophosphate) to the both facets of temporal beta diversity and their components (i.e. total beta diversity, turnover and nestedness); and (iv) whether inclusion of environment regimes increase their explained variations. 2. A total of 338 daily samples of riverine diatom communities were collected. We employed Mantel tests to evaluate the complementarities between trait-and taxonomy-based temporal beta diversity. Using distance-based redundancy analysis (db-RDA) and variation partitioning, we investigated the relative roles of hydrology, metal ions and nutrients to each facet of temporal beta diversity and its components. 3. Correlations between trait-and taxonomy-based temporal beta diversity and their components were weak, which showed their complementary ecological information. Taxonomy-based total beta diversity had a high contribution by turnover component, whereas trait-based total beta diversity was largely driven by nestedness component. Results of variation partitioning demonstrated that the pure and shared fractions of hydrology, metal ions and nutrient differed among the components of trait-and taxonomy-based temporal beta diversity. Furthermore, addition of environment regimes could dramatically increase the explained variation of temporal beta diversity and its components.
... Benthic algae are important primary producers in freshwater ecosystems, and these organisms have been globally used as environmental indicators in streams (Stevenson et al., 2010) because of some of their distinct features, such as being cosmopolitan with well-known autecology, having a short-term life cycle, and being easy to sample (Wu et al., 2017). As a result, algae-based assessments in freshwater ecosystems have been developed worldwide (Siddig et al., 2016). ...
... Furthermore, trait-based studies provide insights into the mechanisms driving community and ecosystem processes (Litchman & Klausmeier, 2008), and this approach may help disentangle the impacts of multiple interacting stressors (e.g., nutrients, flow and temperature; Baattrup-Pedersen et al., 2016;Lange et al., 2014). Therefore, trait-based approaches have been widely implemented in terrestrial plants (Grime, 1979;Tilman, 1980), macroinvertebrates (Menezes et al., 2010;Usseglio-Polatera et al., 2000) and fish (López-Delgado et al., 2020;Villéger et al., 2013) but only recently have also been considered for freshwater algae (Guo et al., 2019;Lange et al., 2016;Wu et al., 2017). ...
... Recent studies demonstrated the advantages of applying trait-based approaches for biodiversity conservation and biomonitoring in freshwater ecosystems (McGill et al., 2006;Perez Rocha et al., 2018;White et al., 2017). A growing number of studies on benthic algae have adopted trait-based approaches (Wu et al., 2017). For example, the most universally accepted biological traits of diatoms are their guilds, which are distinguished according to their potential to tolerate physical disturbance and nutrient limitations (i.e. ...
Article
Aim Understanding the variation in biodiversity and its underlying drivers and mechanisms is a core task in biogeography and ecology. We examined (a) the relative contributions of species replacement (i.e., turnover) and richness difference (i.e., nestedness) to taxonomically and trait-based β-diversity of stream benthic algae; (b) whether these two facets of β-diversity are correlated with each other; and (c) the relative contributions of local environmental, geo-climatic and spatial factors to the two facets of β-diversity and their components. Location Hun-Tai River Basin, northeastern China. Taxon Stream benthic algae. Methods A total of 157 sites were sampled. Mantel tests were used to examine the complementarities between the two facets of β-diversity and their components. Distance-based redundancy analysis and variation partitioning were utilized to investigate the relative contributions of local environmental, geo-climatic and spatial factors to each facet of β-diversity and their components. Results Weak correlations between taxonomically and trait-based β-diversity and their components were detected, which indicated complementarity of ecological information. Taxonomically based total β-diversity was largely driven by turnover, whereas trait-based total β-diversity was more driven by nestedness. Variation partitioning results indicated that local environmental and spatial factors contributed more than geo-climatic variables to the total explained variation in taxonomically and trait-based β-diversity. Main conclusions Different facets of β-diversity and their decomposition are important for understanding diversity patterns of benthic algae relative to abiotic factors. A high level of trait-based convergence among benthic algae communities, despite high taxonomic divergence, demonstrated turnover of species with similar biological traits across our study region. Our study provides a trait-based insight into stream benthic algae communities, which was less documented by previous freshwater studies that focused on regions undergoing recovery following human disturbances.
... Thus, riparian canopies can reduce the incident photosynthetically active radiation (PAR) by more than 95% (Steinman, 1992) and riparian forests will, as a consequence, reduce the light availability for autochthonous production (Allan and Castillo, 2007;Azim et al., 2005). These stressors related to global change have direct effects on periphyton biomass and composition (Allan et al., 2013;Biggs et al., 1998;Lowe and Pan, 1996;Wu et al., 2017). ...
... Periphyton production depends on resource availability (light and nutrients), its tolerance to disturbances (e.g. current velocity and grazing), and its biomass typically increases with increasing nutrient availability and decreases under high discharge as a result of higher scouring (Biggs et al., 1998;Passy and Larson, 2011;Pérez-Calpe et al., 2021;Wu et al., 2017). Periphyton may exhibit different life strategies under different current velocities, nutrient and light availabilities. ...
... Periphyton may exhibit different life strategies under different current velocities, nutrient and light availabilities. High current velocity conditions promote communities dominated by low profile, adnate or prostrate adherent organisms, typically firmly attached to the substrate to tolerate the higher scouring (Neif et al., 2017;Passy, 2007;Schneck and Melo, 2012;Wu et al., 2017). These low profile organisms are typically stress-tolerant (Baattrup-Pedersen et al., 2020;Wu et al., 2019) and they are less abundant under low current velocity conditions, where high profile groups, large-sized and loosely attached organisms, with better access to nutrients, become dominant (Biggs et al., 1998;Larson and Passy, 2012;Piggott et al., 2015;Schneck and Melo, 2012;Wu et al., 2019). ...
Article
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Climate-induced changes in precipitation and land-use intensification affect the discharge of streams worldwide, which, together with eutrophication and loss of riparian canopy, can affect periphyton biomass and composition, and therefore, ultimately the stream functioning. We investigated the responses of periphyton biomass and life-forms (i.e., high profile, low profile and motile) to these changes applying an experimental approach by modulating nutrients (nutrient diffusion substrates enriched with 0.5 M NH4NO3 + 0.031 M KH2PO4 and without nutrient enrichment) and light availability (50% shade and full light) along a gradient in discharge ranging from 0.46 to 3.89 L/s (0.7 to 6.5 cm/s) in twelve large-sized (12- m long) outdoor flumes resembling lowland streams. We also analysed the potential effects of other environmental variables including macroinvertebrates on the responses of periphyton to discharge, nutrients, and light. Light and nutrient availability drastically affected periphyton biomass and composition responses to discharge. Periphyton biomass decreased with increasing discharge when shaded but this did not happen when exposed to full light. Under full light conditions, nutrient enrichment mediated an increase in the periphyton biomass with increasing discharge, possibly reflecting an increased metabolism, but this did not happen under non-enriched conditions. Enrichment further affected the compositional responses of periphyton to discharge, with an increase in the biomass of motile, fast-growing, small-sized flagellated at low discharge conditions, and mitigating a loss of high profile periphyton under higher discharges. Light did not affect periphyton composition, and the abundance or feeding-group composition of the macroinvertebrates did not affect biomass or composition of the periphyton either. Our results suggest that nutrient enrichment and light play an important synergistic role in the responses of the periphyton biomass and composition to discharge and emphasize the relevance of riparian canopy conservation and eutrophication control to avoid periphyton growth under increased discharge scenarios in small lowland streams.
... Therefore, we propose a framework ( Fig. 1) that aim to (1) determine the most influencing factors from spatial parameters, land use pattern, indices of hydrological alteration and local physiochemical variables when observing multidimensional biological descriptors, and (2) simulate the response of phytoplankton to combined key determinants, of phytoplankton as manifested in term of changes in community biological characterization, including abundance, species richness (SR) and functional richness (FR). In this study, we focused on phytoplankton community because it is pronounced primary producer to support the aquatic ecosystem (Wu et al., 2011;Jackson et al., 2016), and they are highly sensitive responder to environmental changes (Wu et al., 2017;Shoener et al., 2019;Charles et al., 2021). The riverine phytoplankton has been discussed their critical contributions in promoting the river ecosystem have been addressed from food web and metabolism aspects from recent studies (Kim et al., 2021;Pathak et al., 2022). ...
... SR is a fundamental biodiversity indicator and a convenient tool for applied ecologist, as the irreplaceable metric to measure and further interpret. FR groups the species with similar functioning in the ecosystem by the species' morphological, physiological, and phenological traits which affect their growth, reproduction and survival abilities can best present the response of phytoplankton community to environment changes (Wu et al., 2017;Wijewardene et al., 2021). All of them are valuable and comparable tools for broader stakeholders and environmental managers to receive intelligible and straightforward information to support further diagnosis based on the primary producer phytoplankton in the streams. ...
Article
Given the many threats to freshwater biodiversity, we need to be able to resolve which of the multiple stressors present in rivers are most important in driving change. Phytoplankton are a key component of the aquatic ecosystem, their abundance, species richness and functional richness are important indicators of ecosystem health. In this study, spatial variables, physiochemical conditions, water flow alterations and land use patterns were considered as the joint stressors from a lowland rural catchment. A modeling approach combining an ecohydrological model with machine learning was applied. The results implied that land use and flow regime, rather than nutrients, were most important in explaining differences in the phytoplankton community. In particular, the percentage of water body area and medium level residential urban area were key to driving the rising phytoplankton abundance in this rural catchment. The proportion of forest and pasture area were the leading factors controlling the variations of species richness. In this case deciduous forest cover affected the species richness in a positive way, while, pasture share had a negative effect. Indicators of hydrological alteration were found to be the best predictors for the differences in functional richness. This integrated model framework was found to be suitable for analysis of complex environmental conditions in river basin management. A key message would be the significance of forest area preservation and ecohydrological restoration in maintaining both phytoplankton richness and their functional role in river ecosystems.
... Diatom pigments have more yellow colour than green pigments make, which also known as golden brown algae [12]. Microalgae are divided into two categories, namely pelagic and benthic microalgae [13,14]. Pelagic microalgae are microalgae suspended in water bodies. ...
... River water allows for dissolved nutrients such as nitrogen. The slow and slightly calmer river flow is an additional point for the growth of microalgae [14,15]. ...
Article
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Microalgae are protists with eukaryotic cell structures which can be found in aquatic ecosystems such as rivers, lakes, reservoirs, ponds, and oceans. The protist culture method can be considered as a technique to allow protists to grow in a certain controlled environment. The objective of this study was to determine the growth of microalgae in the different water sources A modified closed photo-bioreactor (bottle) was used in this research. The number of experiments was 130, each experiment comparing 5 different natural water resources which are well, pond, pool, paddle, river, tap water, and mineral water and tap water as control, all with 25 replications. Those bottles were put under the sun for 2 weeks. Every day, the colour changes were documented. The result showed that within 2 weeks, no colour changes for mineral and tap waters. On the fourth and fifth days, the watercolour of rivers, ponds, paddle, pools turn the greenish or murky brownish. This indicated the growth of microalgae in the bottle. The different colour indicates the different species or a group of species. This simple experiment able to be developed for practical work during pandemic Covid-19, when students have to study at home, but are still able to get their competence by small project-based learning.
... Algae at the first step of the food web in the aquatic ecosystem are used as bioindicators for the determination of water pollution (Wu et al., 2017). Studies dealing with the biogeochemical cycle of algae species and their resistance levels to environmental factors have important ecological roles. ...
... Assessing healthy sustainability of wastewater treatment using indicators of algal species may be used as a way to alleviate these worries. This is because algae are one of the good indicators to show the quality of the treated waters (Wu et al., 2017). For this aim, the relationships between stressors of wastewaters and algal assemblages should be well documented. ...
Article
Water scarcity and water pollution are important issues in the world. Therefore, reusing treated wastewater for irrigation can be a crucial approach in arid and semi-arid regions. There are still some concerns about the sustainability of wastewater irrigated agriculture. Thereby, the present study is aimed to evaluate responses of algal species to stressors in the central wastewater treatment plant using the modified algae pollution index and multivariate approaches to assess healthy sustainability of wastewater effluent quality and to give the suggestion for reusing such kind of waters, especially for irrigation. Samplings of water and algae were carried out twice a month between October 2019 and August 2020. Canonical correspondence analysis (CCA) explained 94.1% of the relationships between environmental factors and species. Water and air temperatures, precipitation, chemical oxygen demand (COD), electrical conductivity (EC), pH, and NO3 played important roles in the temporal occurrence/succession of algae composition in the wastewater treatment plant. Ordination of commonly encountered algae species relatively near the center of the CCA indicates their wide range of tolerance levels to the changes in environmental conditions in the system. Of the species, Navicula aitchelbee, Nitzschia fonticola, and Euglena oxyuris preferred high EC levels; Brachysira exilis, Chlorella vulgaris, G. parvulum, and C. ovata associated with high COD levels, and Navicula tripunctata, Nitzschia umbonata and C. vulgaris related to high NO3 levels (>75% of the percentile). The modified pollution index developed in the present study indicated that the wastewater treatment plant had mainly high organic pollution (>3.00) in the summer and fall seasons, when it had moderate organic pollution (>2.50) in the winter and spring seasons. Results of the study suggest that crucial algae-stressors relationships can be used as an assessment tool to ensure sustainable water supply for the irrigation purpose in arid and semi-arid regions.
... Benthic algae in rivers have the advantages of short life cycle, easy access, sensitive to physical and chemical changes in water bodies. As a consequence, they are increasingly used as indicators for water quality assessment (Lepisto et al., 2004;Wu et al., 2017). However, the current research on the impact of small run-of-river dam construction is mainly focusing on taxonomybased α-diversity. ...
... The benthic diatoms collected at 90 sampling points were classified by trait. The trait information of all observed species comes from the literature (Passy, 2007;Wagenhoff et al., 2013;Wu et al., 2017;Witteveen et al., 2020). We divided it into three categories: cell size, guild, and life form, which included 15 different traits: cell size (large, macro, meso, micro, or nano), guild (high profile, low profile, motile, or planktonic guild), and life form (filamentous, unicellular, or colonial life form; high, medium, or low attachment) ( Table 1). ...
Article
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Being increasingly constructed worldwide, dams are a main driver of flow regime change and biodiversity decline. Although small run-of-river dams have exceeded the number of large dams, their impacts on taxonomic and functional β-diversity as well as community assembly process of aquatic organisms have been largely neglected. Ninety sites within twenty three small run-of-river dams in the Xiangxi River were selected, and the hydrological and physicochemical variables for each site were measured. We analyzed the traits and β-diversity of benthic diatoms, and explored the key driving mechanism of benthic diatom community assembly. Our results indicated that the construction of small run-of-river dams could affect the β-diversity of benthic diatoms and the mechanism of community assembly. Specifically, we found that small run-of-river dams could change the relative contribution of nestedness components to the trait-based β-diversity of benthic diatoms, but generally the taxonomy-based β-diversity was relatively higher than the trait-based β-diversity. Furthermore, the community assembly process of benthic diatoms was also affected. In areas affected directly by small run-of-river dams, dispersal assembly was the key mechanism for community assembly. Compared to unregulated habitats, the dispersal assembly process between the impacted and the unregulated habitats has been enhanced. We advocate that this study can be expanded to other organisms (such as macroinvertebrates, phytoplankton, fish) in future to fully understand impacts of small run-of-river dams on biodiversity from a multi-trophic level aspect. Based on our results, we suggest that maintaining genetic and ecological connectivity based on an effective impact assessment in dry seasons is a potential solution to mitigate the impacts of such dams, as key to adaptive management and sustainability.
... During the hydrobiological monitoring, as a priority of biocenoses, we have identified periphyton and zoobenthos. The high informative capacity of the periphyton (fouling organisms) together with its high indicator capacity is primarily due to the complex species composition of organisms represented by numerous ecologically diverse species (Vis et al. 1998;Shcherbak and Semenyuk 2011;Barinova et al. 2015;Wu et al. 2017;Schneider and Petrin 2017;Kuchkarov 2018). Phytoplankton is a key indicator of ecosystem state in shallow lakes (Scheffer et al. 1993). ...
... The periphyton, as an integral part of aquatic ecosystems, undergoes changes due to various natural and anthropogenic factors, which is expressed in spatial and temporal successions of periphyton communities. These are the examples of very dynamic biological systems (Talskikh 1990;Vis et al. 1998;Wu et al. 2017;Schneider and Petrin 2017). In functional terms, zoobenthos is an important part of the heterotrophic component of ecosystems, and the animal organisms that represent it belong to the consumers. ...
Chapter
In the general system of hydrobiological monitoring, information on the biodiversity of aquatic biocenoses is the only necessary and final link that allows us to move from the statement of the fact of pollution to the assessment of the biological consequences of this pollution. This allows a direct assessment of the ecological status of water bodies. In lotic ecosystems, periphyton and zoobenthos are the most significant indicator biocenoses. This article is based on the results of background hydrobiological monitoring of water ecosystems in the Aral Sea basin. It includes Uzbekistan and sections of the catchment basins from adjacent countries with a total area of more than 300,000 km2. The chapter includes studies carried out by Uzhydromet within the national network of observation points, their background, and impact levels, confined to the zone of flow formation (ZFF) and the zone of flow intensive consumption (ZFC). Hydrobiological data also covers data from several international projects. To assess the environmental situation, we have developed a scale of invariant ecological statuses of indicator aquatic biocenoses of periphyton and zoobenthos by allocating five main statuses: 1. Background (reference) state is evaluated as AE(B). 2. Background (good) status condition – also rated as AE(B). 3. Satisfactory status is rated as AE. 4. Transitional, unsatisfactory, and poor status is rated as AE-Ar or Ar. 5. Unallowable status – rated as ar (A, metabolic and E, ecological progress; B, background; r, ecological regress; a, metabolic regress). An analysis of the taxonomic composition and bioindication of the summer and autumn phases (intra-annual temporal patterns of biocenoses) has revealed the emerging threat of the transition of the water quality class “clean” water to intermediate class “clean-moderately polluted” waters in the small rivers of mountain and foothill areas where the border ZFC and gradually expanding urban areas are shifting toward ZFF. In ZFC, in comparison with background watercourses in the ZFF, where the change in periphyton biocenoses occur in the direction of their natural evolution, the moderate pollution of the midstream of rivers maintains their eutrophic state throughout the year by activating the metabolism of periphyton, which in this case is caused first by increasing the diversity (total number of species) of the autotrophic component, and then, with increasing pollution load. The developed complex ecological statuses scale of lotic ecosystems makes it possible to trace the main directions in changing the taxonomic and trophic structure of indicator biocenoses under the influence of complex abiotic factors and to organize control over the ecological status in the regional hydrographic network. In the future, their regular implementation is extremely important from the point of view of studying biosphere processes, inventory, and assessment of the status of the gene pool of large landscape complexes (nature reserves).KeywordsAquatic ecosystemsEcological statusFlow formationIntensive consumption zonesPeriphytonWater pollutionZoobenthos
... Water quality assessment is the overall process of evaluation of the physical, chemical and biological nature of water and, nowadays, it is one of the most challenging tasks tackled by research scientists worldwide [1,2]. Among all monitoring techniques, microscopy imaging of microorganisms in knowledge, any previous study concerning diatom species classification required expert diatomists for the dataset labelling and a large amount of training data for each class. ...
... Mapping the composition of microplankton in seawater is important in the field of environmental monitoring to assess the status of marine habitats [1]. Unicellular algae, namely diatoms, are biomarkers of water quality, since the species populating a certain portion of marine water and the morphometry of each element within a species are affected by the presence of pollutants [2]. Thus, automatic diatoms taxonomy is a highly desirable goal [4,6]. ...
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Diatoms are among the dominant phytoplankters in marine and freshwater habitats, and important biomarkers of water quality, making their identification and classification one of the current challenges for environmental monitoring. To date, taxonomy of the species populating a water column is still conducted by marine biologists on the basis of their own experience. On the other hand, deep learning is recognized as the elective technique for solving image classification problems. However, a large amount of training data is usually needed, thus requiring the synthetic enlargement of the dataset through data augmentation. In the case of microalgae, the large variety of species that populate the marine environments makes it arduous to perform an exhaustive training that considers all the possible classes. However, commercial test slides containing one diatom element per class fixed in between two glasses are available on the market. These are usually prepared by expert diatomists for taxonomy purposes, thus constituting libraries of the populations that can be found in oceans. Here we show that such test slides are very useful for training accurate deep Convolutional Neural Networks (CNNs). We demonstrate the successful classification of diatoms based on a proper CNNs ensemble and a fully augmented dataset, i.e., creation starting from one single image per class available from a commercial glass slide containing 50 fixed species in a dry setting. This approach avoids the time-consuming steps of water sampling and labeling by skilled marine biologists. To accomplish this goal, we exploit the holographic imaging modality, which permits the accessing of a quantitative phase-contrast maps and a posteriori flexible refocusing due to its intrinsic 3D imaging capability. The network model is then validated by using holographic recordings of live diatoms imaged in water samples i.e., in their natural wet environmental condition.
... Numerous studies have shown that benthic diatoms are more sensitive to the trophic status change of lotic systems during water quality assessments (Atazadeh et al., 2021;Charles et al., 2021;Oleksy et al., 2021;Plante et al., 2021). Similarly, planktonic diatoms are commonly used as nutrient indicators in lentic systems (Wu et al., 2017). Nevertheless, it remains unclear whether significant differences exist between planktonic and benthic diatom compositions, biotic indices, and environmental correlates for assessing water quality. ...
... CODcr has previously been shown as a key factor affecting benthic diatom community composition (Yin et al., 2011). Increased CODcr concentrations negatively affect the growth and development of individual benthic diatom species, leading to lower biomass and production (Wu et al., 2017). CODcr-tolerant diatoms are also tolerant to other environmental stressors (Arnan et al., 2015). ...
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Diatoms are useful indicators of lotic ecosystem environmental conditions, but little is known of differences between benthic and planktonic diatom assemblages as it relates to water quality changes in large lotic systems. Heavy rainfall event in Songhua River Basin is infrequent. The water quality of Songhua River Basin is closely implication for regional ecological health and food safety. The aim of this study was to compare the effectiveness of benthic and planktonic diatom assemblages for indicating water quality during a rainstorm event, which has been little studied. Spatial variation of benthic and planktonic diatom assemblages were investigated in Songhua River Basin during a rainstorm event. Firstly, we found that richness and abundances of benthic and planktonic diatom communities were low. Secondly, results of two-way cluster analysis (TWCA) and principal component analysis (PCA) revealed that diatom assemblage still had the potential to indicate water quality despite the strong flow caused by rainstorm event. Thirdly, alpha diversity indices (Shannon-weaver, Margalef, and Pielou indices) had a weak ability in indicating water quality during rainstorm event. Conversely, trophic diatom index (TDI) was observed closely associate with water quality change. Fourthly, Redundancy analysis (RDA) indicating that planktonic diatoms assemblages were more sensitive to changes in turbidity. RDA also revealed that benthic diatom assemblages was closely related to chemical oxygen demand (CODcr), total phosphorus (TP), and dissolved oxygen (DO) concentrations. These results demonstrate the effectiveness of water quality assessment between planktonic and benthic diatoms had a significant different. The results of the study provide a key information about diatom-based biomonitoring in the extreme condition at lotic ecosystem. Our study highlights that rational choices of appropriate diatom metrics for biological monitoring of water quality in large lotic ecosystems are critical for assessments during a rainstorm event. More studies during rainstorm period at different precipitation are required to fully understand how natural disturbance shape diatom assemblage in lotic ecosystem with aims to improve biomonitoring efforts.
... Nutritional characteristics of microalgae examined through exposing to metals and metallic NPs, and pigments, biological macromolecules, and phenolic compounds reduced in the presence of these deleterious materials [26]. For this, microalgae have been always considered as ideal candidates and indicators in biological and ecological monitoring of the aquatic biota [27]. Moreover, phytoplanktons are being consumed as functional foods and reliable supplementary ingredients in human diet [26,27,29]. ...
... For this, microalgae have been always considered as ideal candidates and indicators in biological and ecological monitoring of the aquatic biota [27]. Moreover, phytoplanktons are being consumed as functional foods and reliable supplementary ingredients in human diet [26,27,29]. Having the richest source of unsaturated fatty acids, antioxidants, proteins, and pigments, microalgae have played a pivotal role in supplying aquatic-based bioactive compounds for consumers [30]. ...
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This study investigated the effects of Fe 3 O 4 nanoparticles released from synthesized Thiourea catalyst to Chlorella vulgaris as an essential primary producer in aquatic systems. A range of Fe 3 O 4 concentrations (0, 10, 100, 250, 500, 750, and 1000 mg L ⁻¹ ) was applied for the exposure test. Biological parameters of C. vulgaris , including cell density, cell viability, and pigment content were assessed. Bioconcentration factor and bioaccumulation were evaluated for contaminated microalgae. Non-carcinogenic risks were then assessed using target hazard quotient (THQ) for potential human consumptions. Findings showed that C. vulgaris cell numbers increased from 0 to 500 mg L ⁻¹ of Fe 3 O 4 . Chlorophyll a represented a time-dependent response, and greatest values were detected in 250 and 500 mg L ⁻¹ Fe 3 O 4 at 4.2 and 4 mg/g, respectively. Chlorophyll b content showed a time-related manner in exposure to Fe 3 O 4 with the highest values recorded at 250 mg L ⁻¹ after 96 h. Moreover, bioaccumulation displayed a dose-dependent response as bioaccumulated iron was in the largest amount at 15000 µg/g dw in 1000 mg L ⁻¹ , whereas the lowest one was in the control group at 1700 µg/g dw. The bioconcentration factor showed a concentration-relevant decrease in all iron treatments and 10 mg L ⁻¹ of Fe 3 O 4 represented the greatest BCF at 327.3611. Non-carcinogenic risks illustrated negligible hazard (THQ < 1) in a dose-response pattern and the largest EDI and THQ were calculated in 1000 mg L ⁻¹ at 7.4332E-07 (mg kg ⁻¹ day ⁻¹ ) and 1.06189E-09, respectively. In essence, iron is an essential trace element for biological aspects in aquatic systems, but in exceeding concentrations could impose toxicity effects in C. vulgaris populations.
... Water quality assessment is the overall process of evaluation of the physical, chemical and biological nature of water and, nowadays, it is one of the most challenging tasks tackled by research scientists worldwide [1,2]. Among all monitoring techniques, microscopy imaging of microorganisms in knowledge, any previous study concerning diatom species classification required expert diatomists for the dataset labelling and a large amount of training data for each class. ...
... Mapping the composition of microplankton in seawater is important in the field of environmental monitoring to assess the status of marine habitats [1]. Unicellular algae, namely diatoms, are biomarkers of water quality, since the species populating a certain portion of marine water and the morphometry of each element within a species are affected by the presence of pollutants [2]. Thus, automatic diatoms taxonomy is a highly desirable goal [4,6]. ...
... In rivers, microbes play an important role in both providing ecosystem services and influencing ecosystem functions (Zhang et al., 2019a). Given that aquatic macrophytes and invertebrates have extremely low biomass in polluted rivers Wu et al., 2017), benthic microorganisms are probably the first to recover from environmental stress due to their extreme sensitivity to environmental conditions, their high diversity, and their growth rate (Wu et al., 2019). It should be noted that benthic communities contribute largely to the overall bacterial diversity in river ecosystems (Liu et al., 2018;Wang et al., 2021). ...
Article
Catastrophic shifts in river ecosystems can abruptly degrade their structures and functions, often reducing the efficacy of traditional remediation targeting physicochemical properties. Alternative stable states theory can not only explain this phenomenon but also provide a new insight into river restoration; however, little is known about the existence and implications of alternative stable states in a river. Considering the important role of benthic microbiota in sustaining river ecosystem structures and functions, ecological theory and DNA sequencing were combined to firstly investigate multi-stability in microbial communities and its relationship with environmental factors in river sediments. The Nanjing reach of the Yangtze River was selected as the study area because of its huge spatial heterogeneity and varying degrees of pollution. Bimodal distributions combined with temporal variations of microbiota status provided direct evidence of bistability by showing the instability at the intermediate. In addition, environmental stress, particularly concentrations of NH4+−N and NO3−−N, was identified as an important driver of alternative microbiota states from the perspectives of the behavior of bistable ecosystems. Comparison of α-diversity indices and network properties between two alternative microbiota states revealed that the diversity and co-occurrence pattern of microbial communities will be high if they are settled in favorable environments (i.e., comprehensive sediment quality identification index > 3.7). Key taxa, including Clostridiales, Nitrospirales and Myxococcales, were discerned by combining LEfSe and network analysis, and their strong interspecies interactions were believed to be an important factor in triggering alternative microbiota states. This study suggests alternative stable states theory should be considered in river remediation to better understand the response of river ecosystems to environmental stress and the effect of hysteresis, benefiting the implementation of effective monitoring and restoration strategies in a river of urban area.
... Several bibliometric analyses of relevant research on freshwater biodiversity have been conducted either at the global or regional scale. For example, the bibliography of biodiversity of aquatic organisms in urban ponds (Oertli and Parris, 2019), insects in streams and rivers (Brasil et al., 2020), microalgae in rivers (Wu et al., 2017) and macroinvertebrates in streams (Luiza-Andrade, Montag & Juen, 2017) at the global scale and freshwater Rhodophyta (red algae) (Ganesan et al., 2018), phytoplankton (Roshith et al., 2018) at the regional scale have been previously addressed. However, the existing bibliometric analyses are mainly focused on one or two aquatic environments (Ho and Goethals, 2020), and lacks the research on different types of freshwater habitats. ...
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The immense value of ecosystem services provided by freshwater bodies is incomputable. However, the productivity and biodiversity of freshwater bodies are undergoing dramatic degradation as a result of climate-and anthropogenic-induced changes worldwide. Despite a well-documented literature on freshwater biodiversity, we still lack a comprehensive and objective overview of biodiversity research conducted in different types of freshwater bodies. Here, we conducted a comparative study of freshwater biodiversity in different ecosystem types at the global scale to describe the current state of knowledge, map the scientific geographical distribution and international collaboration network and identify persistent and emerging themes. Thus, metadata of biodiversity studies carried out in six freshwater ecosystem types-river, lake, wetland, stream, reservoir and pond-were extracted from SCI-E and SSCI databases of the Web of Science and then visualized for science mapping using bibliometric analysis. Our findings showed that in the field of freshwater biodiversity (i) the number of publications in various freshwater habitats has risen considerably over the last two decades with the highest average annual growth rate in river-and lake-related studies, (ii) there was a clear bias in the geographical distribution of the research with fewer scientific production and international collaboration in less developed parts of the world. The USA (20%) and China (19%) are the main leading countries and Europe (30%), Asia (26%, mainly China and India) and North America (24%) are major continents contributing to this field, (iii) taxonomic groups have been investigated disproportionally among different freshwater habitats, (iv) habitat heterogeneity and fragmentation, land use change, climate change, eutrophication and invasive species are the most frequent driving factors, (v) the persistent and emerging themes differ among water ecosystems, e.g. disproportionate assessment of biodiversity measures. Furthermore, functional and phylogenetic facets in this area are poorly understood. Overall, clear obtained distinctions in the hotspots and thematic areas of different freshwater environments can contribute to identify the missing pieces in current research, and put an effort to investigate the non-explored or under-explored areas of research.
... When seeking variations in diatomic taxonomic assemblages in situ, our results have shown that the heterogeneity of communities is such that the data is not suitable to serve as a contamination indicator. The length of time and the difficulties necessary to acquire taxonomic information from tropical countries actually favours other metrics, such as life forms, cell sizes (or biovolumes) and ecological guilds which are all possibilities for purposes of ecological studies and bioassessments [57][58][59] . We thus prospect for alternative indicators. ...
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Abstract Chlordecone (CLD) levels measured in the rivers of the French West Indies were among the highest values detected worldwide in freshwater ecosystems, and its contamination is recognised as a severe health, environmental, agricultural, economic, and social issue. In these tropical volcanic islands, rivers show strong originalities as simplified food webs, or numerous amphidromous migrating species, making the bioindication of contaminations a difficult issue. The objective of this study was to search for biological responses to CLD pollution in a spatially fixed and long-lasting component of the rivers in the West Indies: the epilithic biofilm. Physical properties were investigated through complementary analyses: friction, viscosity as well as surface adhesion were analyzed and coupled with measures of biofilm carbon content and exopolymeric substance (EPS) production. Our results have pointed out a mesoscale chemical and physical reactivity of the biofilm that can be correlated with CLD contamination. We were able to demonstrate that epilithic biofilm physical properties can effectively be used to infer freshwater environmental quality of French Antilles rivers. The friction coefficient is reactive to contamination and well correlated to carbon content and EPS production. Monitoring biofilm physical properties could offer many advantages to potential users in terms of effectiveness and ease of use, rather than more complex or time-consuming analyses.
... Due to their diversity, ubiquity, rapid turnover, and their sensitivity to environmental alterations (e.g., pH, salinity, inorganic nutrients, organic, and heavy metal pollution), diatoms have been used as bioindicators of water quality assessment especially in freshwater ecosystems (Fernandez et al., 2018;Hall & Smol, 2010;Kwandrans et al., 1998;Lobo et al., 2016;Salmaso & Quadroni, 2019). Diatoms have specific response and degrees of tolerance to environmental conditions and most aquatic species have well-known autoecological indicator values for several environmental variables (Carayon et al., 2019;Van Dam et al., 1994;Wu et al., 2017). This has led many authors to develop several diatom indices on the basis of autoecological values and species pollutionsensitivities according to the formula of Zelinka and Marvan (1961). ...
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Diatoms, unicellular siliceous microalgae, are one of the most known groups of eukaryotic algae, commonly used as bioindicators for assessing water quality in aquatic ecosystems. Conversely, studies on terrestrial diatoms as potential bioindicators of soil quality are rather scarce. This study aims to assess the arid suburban soils quality of Marrakesh disturbed by various anthropogenic activities using diatom communities as bioindicators. The sampling of soil and physicochemical measurements were carried out at six sites with different land use. A total of 26 diatom taxa has been identified with 13 genera. The highest species richness and algal biomass were recorded in agricultural irrigated soils with treated wastewater dominated by pollution-tolerant species of Nitzschia (71.43%). In canonical correspondence analysis, suburban soils were subdivided into three groups depending on the chemical properties and diatom composition. The diatom diversity was significantly correlated with the total organic carbon (TOC), P-PO4, and N-NH4+ contents. While diversity and biomass were significantly lower in the soils affected by municipal and mining solid wastes, the input of organic matter and nutrients from treated wastewater appears to have a positive impact on the soil microflora and its richness. This first exploratory survey showed that diatom communities were more sensitive to the anthropic disturbances on urban soil and could be used as bioindicators of the quality and soils conditions.
... Greater algal biodiversity with nutrient addition (Hillebrand et al. 2007, Passy andLarson 2019) should translate into overall larger co-occurrence networks with more nodes and edges. Eutrophic conditions promote speciose overstory guilds (high profile and motile) that are sensitive to nutrient limitation, whereas understory low profile species dominate under nutrient limitation (Passy 2007, Marcel et al. 2017, Wu et al. 2017. Eutrophication is, therefore, likely to produce networks with greater local clustering, modularity and path lengths due to coexistence of different functional groups, while oligotrophic conditions may lead to greater network connectivity and global clustering among fewer and comparatively functionally uniform species. ...
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The amounts and ratios of nutrients (nitrogen and phosphorus) are important determinants of producer community biodiversity and composition and their responses to climate and dispersal. However, the nutrient effects on co-occurrence network topology, particularly in freshwaters, are understudied. Here, we investigate 1) whether nutrient supply and ratio constrain topological properties of algal co-occurrence networks in streams and 2) to what extent climate and space (a surrogate for dispersal) affect co-occurrence network topology versus metacommunity composition across nutrient supply and ratio contexts. We used a subcontinental dataset of benthic algae from 840 stream localities in the conterminous US. We constructed co-occurrence networks representing nutrient supply contexts (oligotrophic versus eutrophic) and nutrient ratio contexts (N-limited versus P-limited) and statistically assessed topological variability within each pair via randomization. We then used a null model framework and direct gradient analysis to ascertain the importance of climate and space in driving, respectively , network topology and metacommunity composition. Nutrient supply was only positively related to network size (species node counts), which was driven by motile species, while other topological differences were non-significant. Climatic and spatial variables had pronounced and for the most part comparable effects on network topol-ogy that further depended on nutrient context. A comparative assessment of topo-logical versus compositional responses to climate and space across nutrient contexts identified both similarities and differences. While climate and space contributed to both network topology and metacommunity composition, space was a stronger pre-dictor of compositional variability than climate, regardless of nutrient context. Our findings highlight the need for developing integrative multi-level approaches (from metacommunities to co-occurrence networks) to fully understand biological responses to complex and interactive abiotic forces.
... Last decades, the researchers immensely focused on applying informatics, chemometrics, machine learning, policy-driven and trait-based techniques to assess the ecological status of RWQ. These tools increase the accuracy and ability of the WQI tool for RWQ monitoring and management (Ahmed et al., 2019;Soininen et al., 2016;Tapolczai et al., 2017;Wang et al., 2014;Waylen et al., 2019;Wu et al., 2017). However, it wasn't easy to restrict the exact possible reason for the popularity of different WQI tools. ...
Article
Water quality is a substantial measure in coordinating water demand and supply. An adequate level of freshwater is eminent for biological needs and a vital side of integrated sustainable environmental development. There has been a disrupting ascend in the water pollution due to the natural and anthropogenic events. Past few years, research has enormously engrossed on the development of water quality index (WQI), as a prevalent tool for water quality assessment. This review article presented an in-depth literature-based look up of WQI's potentials concerning their use as a scientific tool for river water quality monitoring and management. This study also highlighted the importance, limitations and future directions of WQI tool to afford additional information about its usage. The review indicated the influence of the environmental features, like geographic locations and sampling periods, on the estimation of WQI. Also, WQI was projected as a single value which decreased the immense amount of water quality parameters and epitomized the data in a simple way. The incessant use of WQI tool provided long-term information for helping the water resource managers, environmental engineers and scientists in decision making and management.
... Globally, these environments already face major challenges owing to new climatic regimes caused by global warming and the increasing water demands for agriculture, domestic and industrial purposes (Larkin et al. 2020). In addition to the economic and social impact, all these processes strongly influence the trophic interactions of aquatic communities, leading to the loss of biotic integrity (Wu et al. 2017). Among biotic communities, microalgae play a crucial role in the functioning and maintenance of aquatic ecosystems. ...
Article
Natural and human pressures increasingly threatening the biodiversity and water resources of dryland rivers. Fluvial environments of Patagonia harbour high diatom diversity, but their management value is overlooked. The aim of this study is to explore the diatom distribution in surface sediments of the Chubut River and evaluate their relationship with environmental variables. In total, 243 diatom taxa were identified in 16 littoral zone sites. The physical and chemical variables independently explained the variance in diatom data, whereas sediment texture had a low influence. Conductivity, major ions (HCO3–, Cl–, SO42–, Na+, K+, Ca2+ and Mg2+) and pH were the main environmental drivers explaining the diatom composition. As the highlighted variables increased near the mouth, so did the relative abundances of marine–brackish taxa such as Amphora copulatoides, Sarcophagodes alfred-wegeneri, Nitzschia fonticola and Tryblionella apiculata. Meanwhile, the presence of high pollution-tolerant diatoms can be put forward to explain the river health deterioration towards downstream areas. The marine–brackish taxa found at freshwater sites reflect a weak tidal influence in the estuary compared with other coastal systems of Patagonia. This study provides valuable information to test the hypothesis on the ecological status of aquatic resources and the potential effects of climatic and hydrological changes in the area.
... Phytoplankton are important primary producers in freshwater ecosystems and play a vital role in nutrient cycling and energy flow (Brierley, 2017). Further, phytoplankton are ideal for stress-response studies due to their high sensitivity to environmental gradients, short generation time and well-known autecology (Qu et al., 2018b;Wu et al., 2017). Pesticides are the synthetic products using for crop management in agriculture and mainly consist of herbicides, insecticides and fungicides (Schäfer et al., 2011). ...
Article
Agrochemicals such as pesticides and nutrients are concurrent chemical stressors in freshwater aquatic ecosystems surrounded by agricultural areas. Lentic small water bodies (LSWB) are ecologically significant habitats especially for maintaining biodiversity but highly understudied. Phytoplankton are ideal indicator species for stress responses. Functional features of the phytoplankton are important in revealing the processes that determine the structure of the communities. In this study, we investigated the effects of pesticides, nutrients, and local environmental variables on the species composition and functional features of phytoplankton communities in LSWB. We studied pesticide toxicity of ninety-four pesticides, three nutrients (NH4-N, NO3-N and PO4-P) and local environment variables (precipitation, water level change, temperature, dissolved oxygen concentration, electrical conductivity, pH) in five LSWB over twelve weeks during the spring pesticide application period. We explored respective changes in species composition of phytoplankton community and functional features. Redundancy analysis and variance partitioning analysis were applied to correlate phytoplankton community compositions with the pesticide toxicity (as maximum toxicity in toxic units), nutrients and local environment variables. We used multiple linear regression models to identify the main environmental variables driving the functional features of phytoplankton communities. Pesticide toxicity, nutrients and local environmental variables significantly (p < 0.001) contributed to shaping phytoplankton community composition individually. Local environment variables showed the highest pure contribution for driving phytoplankton composition (12%), followed by nutrients (8%) and pesticide toxicity (2%). Functional features (represent by functional diversity and functional redundancy) of the phytoplankton community were significantly affected by pesticide toxicity and nutrients concentrations. The functional richness and functional evenness were negatively affected by PO4-P concentrations. Pesticide toxicity was positively correlated with functional redundancy indices. Our findings emphasized the relative importance of concurrent multiple stressors (e.g., pesticides and nutrients) on phytoplankton community structure, directing potential effects on metacommunity structures in aquatic ecosystems subjected to agricultural runoff.
... Literature shows that eutrophication has become a common phenomenon and geographic distribution of HABs is uniformly rising year after year (Paul et al. 2020). Despite the fact that upstream ow management may lessen the quantity and toxicity of sewage and e uents, it is not fully possible to prevent entry of pollutants into water bodies (Wu 2017). In the new era of scienti c development and technological upgradation of existing water treatment methods, ecohydrology has been observed as an interdisciplinary approach to address all hydrochemical and geochemical aspects of water bodies. ...
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Eutrophication of water bodies and deterioration of water quality is an emerging environmental crisis. The root causes, pathways and consequences of eutrophication are multidirectional and provide a huge scope of risk-analysis and risk-assessment in the domain of remediation studies. However, a deep insight on restoration studies shows a global transitional trend of evolution of traditional restoration methods to advanced innovative techniques with pioneering development in the field of science and technology. This study introduces a novel approach of considering ecohydrological assessment of eutrophication emphasizing classical biomanipulation practices and their evolution into innovative methods coined as ‘eco-bioengineering’ method. The main objective of this study is to critically analyse and recognize the research gaps in classical biomanipulations and appreciate the reproducibility and efficacy of eco-bioengineering methods at micro- and macrolevel aquatic ecosystems. Comprehensive literature review was conducted in offline and online planforms, and our survey revealed continuation of a historical trend in classical biomanipulation practices (75.36%) and an ascending drift in eco-bioengineering research (24.64%) in the immediate decade (2010–2020). At a global scale, recent biomanipulation research is skewedly distributed in Europe (43.48%), East Asia (34.78%), North America (8.70%), South America (2.90%), South Africa (4.35%), Oceania (1.45%), Middle East (1.45%) and non-specific regions (2.90%). Finally, this study revealed the comprehensiveness of eco-bioengineering methods and their strong ecological resilience to recurrence of eutrophication and fluctuating environmental flows in the future. Therefore, this study reinforces eco-bioengineering methods a cost-effective green technologies that will sustainable solutions for restoration of eutrophic waters at a global scale.
... Traits are defined as "any morphological, physiological or phenological measurable feature at the individual level" [98] and are more tightly linked to ecosystem functioning than species; thus, their study provides a more integrative ecological assessment potential at the ecosystem level [88]. Traits described in benthic diatoms are cell size, ecological guilds and life forms, and have been successfully related to environmental stressors (i.e., pesticides-herbicides, heavy metals, nutrients and organic pollution) [99][100][101][102][103][104][105]. ...
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The European Water Framework Directive 2000/60/EC (WFD) has been implemented over the past 20 years, using physicochemical, biological and hydromorphological elements to assess the ecological status of surface waters. Benthic diatoms (i.e., phytobenthos) are one of the most common biological quality elements (BQEs) used in surface water monitoring and are particularly successful in detecting eutrophication, organic pollution and acidification. Herein, we reviewed their implementation in river biomonitoring for the purposes of the WFD, highlighting their advantages and disadvantages over other BQEs, and we discuss recent advances that could be applied in future biomonitoring. Until now, phytobenthos have been intercalibrated by the vast majority (26 out of 28) of EU Member States (MS) in 54% of the total water bodies assessed and was the most commonly used BQE after benthic invertebrates (85% of water bodies), followed by fish (53%), macrophytes (27%) and phytoplankton (4%). To meet the WFD demands, numerous taxonomy-based quality indices have been developed among MS, presenting, however, uncertainties possibly related to species biogeography. Recent development of different types of quality indices (trait-based, DNA sequencing and predictive modeling) could provide more accurate results in biomonitoring, but should be validated and intercalibrated among MS before their wide application in water quality assessments.
... Biomonitoring is reliable and economical means of water quality monitoring (Kohlmann et al., 2018;Pham, 2020). Phytoplankton due to their small size and ability to provide strong response to environmental changes are being routinely used for biomonitoring especially for trophic state of the water (Allende et al., 2019;Wu et al.,2017).Multiple algal indices have been developed to assess the water quality. For reliable results indices are required to be tested for ability to provide linear response for the water quality parameter to be monitor (Arab et al., 2019;Cupertino et al., 2019;Tang et al., 2013). ...
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Eutrophication of the urban water bodies is one the biggest challenge causing severe ecological and economic loss. Urban ponds are more prone to eutrophication due to their small size and polluted catchment areas. Biomonitoring using phytoplankton provides cost-effective estimation of the level of eutrophication. Ten urban ponds in different areas of the Mumbai city were chosen to investigate the phytoplankton community structure, and level of eutrophication. We assessed the 3 algal indices viz. Shannon-Wiener indices, Palmer and Nygard's (Myxophycean and diatom) indices. Linear relationship of these indices was tested against Carlson trophic state indices in order to assess the effectiveness of these indices to measure the degree of eutrophication in urban lakes. All ten lakes were found to be eutrophic, of which two were very low eutrophic (TSI-53.74-53.95), four were low-mid eutrophic (TSI-55.18-57.5), and four lakes were mid eutrophic (TSI 61.4-62.2). Shannon-Wiener indices (r=-0.73) and Myxophycean indices (r= 0.77) showed strong correlation with TSI whereas Diatom indices (r=-0.12) and Palmer's Algal Pollution Indices (r=-0.47) showed weak correlation with TSI. Thus study found that Shannon-Wiener indices and Myxophycean indices are reliable and cost effective means to assess the eutrophication of urban ponds in Mumbai.
... Among the plant models that may be exploited in ecotoxicological investigations in freshwater ecosystems, there is a wide variety of aquatic plant organisms ranging from algae, bryophytes, pteridophytes, and flowering plants. These usually are utilized as bioindicators of water quality status (e.g., Ceschin et al. 2010Ceschin et al. , 2012Søndergaard et al. 2010;Wu et al. 2017), and of hydro-morphological alterations of river and lake ecosystems (e.g., Daniel et al. 2006;Benítez-Mora and Camargo 2014;Tombolini et al. 2014;Abati et al. 2016), as well as phytoremediation agents for the removal of toxicants from civil, agricultural, and industrial wastewater (e.g., Tripathi and Shukla 1991;Mkandawire et al. 2014;Li et al. 2018;Ceschin et al. 2019Ceschin et al. , 2020. In the first case, the sensitivity of some plant species to certain contaminants or alteration conditions is exploited, while in the second case, the focus is on the capability of other species to tolerate the presence of contaminants and bioaccumulate them in their tissues. ...
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This paper reviews the current state-of-the-art, limitations, critical issues, and new directions in freshwater plant ecotoxicology. We selected peer-reviewed studies using relevant databases and for each (1) publication year, (2) test plant species, (3) reference plant group (microalgae, macroalgae, bryophytes, pteridophytes, flowering plants), (4) toxicant tested (heavy metal, pharmaceutical product, hydrocarbon, pesticide, surfactant, plastic), (5) experiment site (laboratory, field), and (6) toxicant exposure duration. Although aquatic plant organisms play a key role in the functioning of freshwater ecosystems, mainly linked to their primary productivity, their use as biological models in ecotoxicological tests was limited if compared to animals. Also, toxicant effects on freshwater plants were scarcely investigated and limited to studies on microalgae (80%), or only to a certain number of recurrent species (Pseudokirchneriella subcapitata, Chlorella vulgaris, Lemna minor, Myriophyllum spicatum). The most widely tested toxicants on plants were heavy metals (74%), followed by pharmaceutical products and hydrocarbons (7%), while the most commonly utilized endpoints in tests were plant growth inhibition, variations in dry or fresh weight, morpho-structural alterations, chlorosis, and/or necrosis. The main critical issues emerged from plant-based ecotoxicological tests were the narrow range of species and endpoints considered, the lack of environmental relevance, the excessively short exposure times, and the culture media potentially reacting with toxicants. Proposals to overcome these issues are discussed.
... To fulfill the goals of this study, three objectives have been proposed and various research articles, e-reports, books, and book chapters were retrieved matching to the requirements stated in the objectives. An online literature survey was conducted using search engines like Google Scholar, Scopus, Web of Science, PubMed, ScienceDirect, EBESCO and Research Gate following Wu et al. (2017) and Das et al. (2019). Online literature survey revealed extensive information on commonly practiced methods of eutrophication treatment including physical, chemical, biological, and modified engineering methods. ...
Article
Eutrophication of freshwater bodies causes loss of earth’s biological resources and aggravates climate change, thus assuming major environmental concern. Both endogenous and exogenous nutrient enrichment are responsible for eutrophication. Numerous monitoring and management studies conducted worldwide have resulted high-level technological innovations. These studies cumulatively uphold the significance of ecohydrological and ecological engineering approaches. However, holistic and insightful reviews with feasible recommendations of such huge academic outputs are rather scanty. Therefore, our main objective was to introduce a new perspective of eutrophication as an ecohydrological component; to discover all possibilities of monitoring and restoration of eutrophic water bodies. Furthermore, the present study critically analyzes various methods of treatment of eutrophication (physical, biological, chemical, and eco-engineering). Comprehensive volume of literature has been surveyed using search engines like Scopus, Google Scholar, PubMed, ScienceDirect etc. Meaningful keywords were used to obtain reliable information on methods of ecohydrological assessment in relation to eutrophication of freshwater bodies. According to our survey, ecohydrological research is diversified into conceptual knowledge (37.2%), assessment (32.6%), climate change (9.3%), algae/cyanotoxins (7%), engineering and restoration (7%), modelling (4.6%) and biodiversity (2.3%), in the instant decade (2010–2020). We have identified a clear trend of transition of restoration methods from traditional towards modern techniques over time. Moreover, this review recognizes a pool of biophysicochemical and ecological engineering techniques, which are very effective in regard to time, cost, and labor and have immense scopes of modification for improved results. This work focuses on the importance of ecohydrology and eco-engineering tools for restoration of eutrophic water bodies for the first time. We have highlighted how these approaches have emerged as one of the best suitable and sustainable water resource conservation routes in the present era.
... This observation might be an artefact of the artificial substrate that we provided for phytobenthos sampling. Also unexpectedly according to literature (Wu et al., 2017), largest size class was significantly more frequent in lotic stations, and smallest size class in lentic ones (Fig. 4C, supplementary doc 4). However Sun et al. (2018) found in a German river that smallest diatoms' size class better correlated to low water conditions occurring in summer, whilst the largest size class occurred more frequently in high flow conditions occurring in winter and spring. ...
Article
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We studied three commonly used bioindicator groups: phytoplankton, phytobenthos and benthic invertebrate communities’ structure patterns in transitions between lotic and lentic habitats as consequences of two consecutive large dams constructed in the early twentieth century on the intermediate reach of a lowland river in Normandy (NW, France), the Selune. According to sampling station position along the river, including two in the two reservoir lakes, we defined three sorts of transitions, from upstream to downstream: lentic to lotic transition (hereafter len-lot), lentic to lentic transition (hereafter len-len), within the two reservoir lakes, and lentic to lotic transition (hereafter len-lot). Lot-len transition, imposed by damming, and the recovery of lotic character of the river afterward dams, promoted different diversity patterns for the studied organisms’ groups. Phytobenthos’ α diversity significantly incresed in the len-lot transition, and the highest β diversity score was observed in the lot-len. Both, habitat conditions and spatial controls drove phytobenthos community structure. Benthic invertebrate community was mainly shaped by habitat conditions. Invertebrate’s α diversity significantly changed in the lot-len and len-lot transitions, with the β diversity score being the highest in the lot-len transition. Community’s traits composition of invertebrates best fitted predictions on lotic- and lentic- type communities. Phytoplankton’s α diversity remained unchanged in the transitions and subsequently β diversity scores were low. According to the results, we proposed three classes of organisms based on their response to river damming: i) organisms indifferent or tolerant to dams effect, like phytoplankton communities in this study, that were neither hampered by changes in water flow velocity, and did not display dispersal limitation neither; ii) organisms sensitive to habitat conditions shift but not limited in their dispersal capacity by the dam, like benthic invertebrates and phytobenthos in this study. Benthic invertebrate community and phytobenthos communities differed in their response likely due to their differential dispersal capabilities and niche breadth; iii) organisms limited in their dispersal by the dam, not represented in this study. Riverine organisms best tracked transitions, while β diversity assessment revealed as the most useful metric to disentangle the relative contribution of dispersal limitation or habitat modification provoked by multiple dams.
... The U.S. National Sanitation Foundation Water Quality Index (NSFWQI), Canadian Council of Ministers of the Environment WQI (CCMEWQI), British Columbia WQI (BCWQI), and Oregon WQI (OWQI) are the most common indices utilizing physical and chemical parameters for the evaluation of water body qualities (Burigato Costa et al. 2019;Şener et al. 2017). Recently, microalgae have been utilized as reliable bioindicators for the evaluation of water quality of wetlands and rivers, since the biodiversity and biodistribution of microalgal communities are highly sensitive to the physical, chemical and biological modifications that existed in the water resources (Atazadeh et al. 2007;Chun et al. 2018;Wu et al. 2017). More specifically, microbial community (microalgae and Cyanophyta) structure (MCS) could directly and sensitively respond to changes in conductivity, pH, organic pollutions, and nutrient availability. ...
Article
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The Kani Barazan and Yadegarlou wetlands in the southern part of Lake Urmia (Iran) have been substantially modified due to human activities and anthropogenic use. In recent years, freshwater-based eco-biological studies to recognize the quality of water resources have been greatly expanded. Microalgae and Cyanophyta are considered important bioindicators for the evaluation of water quality and wetland health worldwide. Herein, 22 microalgae and 5 Cyanophyta genera were identified in both wetlands, in which Cyanophyta has mainly caused blooms. Principal components analysis (PCA) was carried out based on links between the distribution of microalgae and Cyanophyta with physical and chemical parameters. The data showed that depth, turbidity, and the temperature had a significant influence on the microalga and Cyanophyta communities in both wetlands. Based on the biological properties, it seems that the Kani Barazan and Yadegarlou international wetlands experience meso-eutrophic conditions. The integration of the physical, chemical and biological parameters with the water quality index (WQI) revealed that both wetlands were polluted as a consequence of human activities. Moreover, a close relationship between WQI and the biological parameters was documented. Thus, we concluded that microalgae and Cyanophyta communities, their abundance patterns, and water quality changes could provide valuable data for the conservation of the Kani Barazan and Yadegarlou international wetlands.
... Microalgae are a highly diverse group of photosynthetic micro-organisms ubiquitous to every aquatic ecosystem, which can also be found in terrestrial environments (Hoffmann, 1989) and even on human made structures (Rifón-Lastra & Noguerol-Seoane, 2001). Due to their role as first trophic level in the ecosystems they occupy, they are directly impacted by environmental changes (anthropogenic or natural), though not all microalgae species are affected in the same way, as they are not equally sensitive (Wu et al., 2017). The diversity of phytoplankton in water systems is highly dependent on nutrients availability, temperature, light, grazing pressure, with parameters such as water quality, N:P and C:N ratios, pH and silica concentration playing a significant role in the species composition and the lineages present, as well as in their productivity and physiology (El-Sheekh et al., 2000;Granéli et al., 2008). ...
Article
Aims: Microalgae are ubiquitous in aquatic environments, including aquaculture farms, but few studies have delved into their phytoplankton diversity and bioremediation potential. In this study, the cultivable phytoplankton of a rainbow trout freshwater aquaculture farm was isolated, phylogenetically analysed and used to assemble a consortium to polish an aquaculture derived effluent, with low concentrations of ammonium, nitrite, and nitrate. Methods and results: Through standard plating in different selective media, a total of 15 microalgae strains were isolated from sludge from a rotary drum filtering system which removes suspended solids from the water exiting the facility. Based on 18S rRNA gene sequences, isolates were assigned to nine different genera of the Chlorophyta phylum: Asterarcys, Chlorella, Chloroccocum, Chlorosarcinopsis, Coelastrella, Desmodesmus, Micractinium, Parachlorella, and Scenedesmus. Species from most of these genera are known to inhabit freshwater systems in Galicia and continental Spain, but the Coelastrella, Asterarcys or Parachlorella genera are not usually present in freshwater streams. In an on-site integrative approach, the capacity of a consortium of native microalgae isolates to grow on aquaculture derived effluents, and its nutrient removal capacity were assessed using a raceway pond. After 7 days, removal efficiencies of approximately 99, 92 and 49% for ammonium, nitrite and nitrate were achieved concomitantly with a microalgae biomass increase of ca. 17%. Conclusions: Sludge from the aquaculture filtering system presents a high diversity of microalgae species from the Chlorophyta phylum, which application in a consortial approach revealed to be efficient to polish aquaculture derived effluents with low nutrient content. Significance and impact of study: The use of native microalgae consortia from aquaculture systems can contribute to the development of efficient treatment systems for low-nutrient wastewater, avoiding nutrients release to the environment and promoting water recirculation. This may further strengthen the use of phycoremediation at the industrial scale, as an environment-friendly strategy.
... More recently, freshwater riverine microalgae, also referred to as diatoms, are also being used as bioindicators of rivers and streams, because of their strong response to environmental changes (Chonova et al., 2019;Vasselon et al., 2017;Wu et al., 2017). Although microscopic morphological identification is currently the method of choice for diatom biomonitoring, high-throughput DNA metabarcoding of environmental samples has facilitated scaling up, primarily because of the ability of this method to bypass time-consuming morphology-based identifications (Kermarrec et al., 2014;Maitland et al., 2020;Rivera et al., 2018;Tapolczai et al., 2019). ...
Article
Freshwater systems are experiencing rapid biodiversity losses resulting from high rates of habitat degradation. Ecological condition is typically determined through identifying either macroinvertebrate or diatom bioindicator assemblages and comparing them to their known tolerance to stressors. These comparisons are typically conducted at family or genus levels depending on the availability of taxonomic keys and expertise for focal groups. The objective of this study was to test whether a more taxonomically comprehensive assessment of communities in benthic samples can provide a different perspective of ecological conditions. DNA metabarcoding was used to identify macroinvertebrates and diatoms from kick-net samples collected from sites with different habitat status. Sites with ‘good’ condition were associated with higher beta diversity as well as slightly higher directed connectance and modularity indicating higher resilience compared with ‘fair’ condition sites. Indicator value and correlation analyses used DNA metabarcoding data to detect 29 site condition indicator species consistent with known bioindicators and expected relative tolerances. DNA metabarcoding and trophic network analysis also recovered 11 keystone taxa. This study demonstrates the importance of taxonomic breadth across trophic levels for generating biotic data to study ecosystem status, with the potential to scale-up ecological assessments of freshwater condition, trophic stability, and resilience.
... They are the most abundant and diverse group of benthic algae, primary producers and therefore a crucial component in the nutrient cycle and energy flow in water ecosystems (Wang et al. 2018). Diatoms represent excellent, widely used bioindicators, because of their short generation time and fast response to environmental changes (Wu et al. 2017). Both biotic and abiotic factors, as well as chemical variables control diatom community composition. ...
Article
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The aim of this study was determining and comparing diatom diversity and dominant taxa in 4 seasons from the Crnica River. A total of 170 diatom taxa, 24 among them as dominant ones were recorded. The highest diversity expressed in number of taxa was observed in the spring (139) and the lowest in the autumn season (94). The most of 45 the best fitted taxa on the CCA ordination diagram are recorded in more than two seasons, often in all four seasons. One group of taxa (e.g. Hanaea arcus, Meridion constrictum, Navicula gregaria, N. lanceolata) was characteristic only for spring and other for winter season (e.g. Gomphonema innocens, G. lagenula, Stauroneis phoenicenteron, Nitzschia oligotraphenta). There were no taxa exclusively recorded only in summer and autumn.
... Diatoms have been used to monitor the unprecedented intensive anthropogenic disturbances altering the environmental conditions, resulting to water quality degradation and human-induced climate change that are a great concern to environmentalists and ecologists as revealed by the journals'publications in this study. The use of diatoms as bioindicators in water quality assessment started as early as twentieth century (Wu et al. 2017), triggered by degraded water quality in streams, rivers, reservoirs and lakes among others, caused by human activities such as agriculture and urbanization. Additionally, human-induced climated change caused by global warming has had an enormous impact on these aquatic ecosystems (Peeters et al. 2007), thereby altering the timings of algal blooms and consequently enhancing the proliferation of harmful algal blooms (Kosten et al. 2012), hence leading to a remarkable increase in diatoms research related to climate change over the last decade. ...
Article
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Living organisms are used in water quality evaluation, thus reflecting the constantly changing physical and chemical characteristics of aquatic ecosystems. Diatoms are among the aquatic organisms used in water quality monitoring of both lentic and lotic ecosystems. The objectives of our present study were to summarize the topics in diatoms for water quality evaluation, and identify the past trends as well as the future directions through the analyses of trends in diatoms bioassessment topics in Africa. We retrieved diatoms distribution data from Web of Science (WoS) database using the following keywords “Diatoms for water quality monitoring in Africa”, and “Diatoms for bioassessment in Africa”. We used VOS viewer software (version 1.16.15) in the construction of knowledge map of application diatoms in monitoring and bioassessment. A total of 481 documents on diatom in water quality monitoring and bioassessment were found. A subsequent thresholding of keywords centered on 15 times occurrence yielded 37 keywords. Diatom indicators were related to diversity, benthic diatoms, communities, community structure, assemblages, land-use, and water quality as clustered by VOS viewer software. Regionally, South Africa is one of the top most developed country in Africa, and this has been attributted to greater infrastructural, human resource, and financial capacity to carry out research that led to substantial collaborations both locally and globally. Institutionally, the connection between University of Cape Town and Bayworld Centre for Research and Education in South Africa was strongest probably due to their better infrastructural capacity in diatoms research. Therefore, the study provided insights that are likely to contribute to the future development of water quality monitoring framework using diatoms in Africa, thereby enhancing global environmental sustainability.
... Diatoms have been used to monitor the unprecedented intensive anthropogenic disturbances altering the environmental conditions, resulting to water quality degradation and human-induced climate change that are a great concern to environmentalists and ecologists as revealed by the journals'publications in this study. The use of diatoms as bioindicators in water quality assessment started as early as twentieth century (Wu et al. 2017), triggered by degraded water quality in streams, rivers, reservoirs and lakes among others, caused by human activities such as agriculture and urbanization. Additionally, human-induced climated change caused by global warming has had an enormous impact on these aquatic ecosystems (Peeters et al. 2007), thereby altering the timings of algal blooms and consequently enhancing the proliferation of harmful algal blooms (Kosten et al. 2012), hence leading to a remarkable increase in diatoms research related to climate change over the last decade. ...
Article
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The recognition of nature-based solutions (NbS) is on a growing trend worldwide in an era of climate change, and intensified demand for improved human health, better preparedness for disasters, food and water security. The solutions seek to restore, protect and sustainably manage natural and modified ecosystems to optimize biodiversity and human wellbeing benefits. In this study, a scientometric analysis of works indexed in Web of Science database until April 2022 was carried out to analyze 123 studies on NbS in Africa. The most active institutions, authors, and countries involved in publication on the topic and their evolution with time was assayed. African countries with exception of South Africa conducted limited research on the topic. About 38.2% of total searched outputs were affiliated to South African institutions. Most research output on the search query was in the environmental sciences and ecology subjects. A sluggish growth in research on the topic was established from the bibliographic coupling of authors and countries as well as keyword analysis. The study recommended for institution and policy overhaul, creation of NbS awareness and better financing of related projects to enhance the documentation and research on the topic in Africa by African researchers to supplement research already conducted by developed countries.
... The effectiveness of taxonomic diversity indices in discriminating disturbances has been confirmed by many studies, and they have been used in various biomonitoring and bioassessment programms throughout the world ☆ This paper has been recommended for acceptance by Dr. Sarah Harmon. (Morse et al., 2007;Beck et al., 2013;Wu et al., 2017). However, during recent decades, an increasing number of researchers have recognized the shortcomings of taxonomic diversity metrics on the grounds that they ignore organisms' traits and evolutionary relationships. ...
Article
The accelerated eutrophication of freshwater lakes has become an environmental problem worldwide. Increasing numbers of studies highlight the need to incorporate functional and phylogenetic information of species into bioassessment programms, but it is still poorly understood how eutrophication affects multiple diversity facets of freshwater communities. Here, we assessed the responses of taxonomic, phylogenetic and functional diversity of benthic macroinvertebrates to water eutrophication in 33 lakes in the Yangtze River floodplain in China. Our results showed that macroinvertebrate assemblage structure was significantly different among four lake groups (river-connected, macrophyte-dominated, macrophyte-algae transition, and algae-dominated). Three taxonomic, two phylogenetic and two functional diversity indices were significantly different among the lake groups. Except for the increasing trend of Lambda⁺, these metrics showed a clear decreasing trend with increasing levels of eutrophication, with highest values detected in river-connected and macrophyte-dominated lakes, followed by macrophyte-algae transition lakes and algal-dominated lakes. Although differing in the number and identity of key environmental and spatial variables among the explanatory models of different diversity indices, environmental factors (eutrophication-related water quality variables) played more important role than spatial factors in structuring all three facets of alpha diversity. The predominant role of environmental filtering can be attributed to the strong eutrophication gradient across the studied lakes. Among the three diversity facets, functional diversity indices performed best in portraying anthropogenic disturbances, with variations in these indices being solely explained by environmental factors. Spatial factors were mostly weak or negligible in accounting for the variation in functional diversity indices, implying that trait-based indices are robust in portraying anthropogenic eutrophication in floodplain lakes. However, variation in some taxonomic and phylogenetic diversity indices were also affected by spatial factors, indicating that conservation practitioners and environmental managers should use these metrics with caution when providing solutions for addressing eutrophication in floodplain lakes.
... Monitoring the dynamics of microbial communities in different niches could identify the microbial indicators and provide insights to assess environmental variations and the status of ecosystem health [64][65][66][67]. For example, previous studies reported that several taxa (such as Alphaproteobacteria, Rhodospirillales, Caulobacterales and Rhizobiales) were the dominant indicators in river or lake sediments located at a distance from human activities and indicated a minimally polluted environment [68][69][70]. The natural prokaryotic community and microbiota serve as indicators of the health of coral reefs and soil [23,25]. ...
Article
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Rhizoplane microbes are considered proxies for evaluating the assemblage stability of the rhizosphere in wetland ecosystems due to their roles in plant growth and ecosystem health. However , our knowledge of how microbial assemblage stability is promoted in the reed rhizosphere of wetlands undergoing recovery is limited. We investigated the assemblage stability, diversity, abundance , co-occurrence patterns, and functional characteristics of reed rhizosphere microbes in restored wetlands. The results indicated that assemblage stability significantly increased with recovery time and that the microbial assemblages were capable of resisting seasonal fluctuations after more than 20 years of restoration. The number of bacterial indicators was greater in the restoration groups with longer restoration periods. Most bacterial indicators appeared in the 30-year restoration group. However, the core taxa and keystone species of module 2 exhibited greater abundance within longer recovery periods and were well organized, with rich and diverse functions that enhanced microbial assemblage stability. Our study provides insight into the connection between the rhizosphere microbiome and recovery period and presents a useful theoretical basis for the empirical management of wetland ecosystems.
... Algal and bacterial assemblages are especially useful indicators because they are directly affected by nutrients and have important roles in primary production, food webs, and nutrient and carbon cycling (Bunn et al., 1999;Peterson et al., 2001;Bernot et al., 2010;Woodward et al., 2012). Benthic diatoms, in particular, are very diverse, unicellular algae that are frequently used in stream monitoring and assessment programs around the world because of their responsiveness to changes in environmental conditions (Smol and Stoermer, 2010;Rimet, 2012;Stevenson, 2014;Wu et al., 2017;Pérez-Burillo et al., 2020;Charles et al., 2021), including nutrients (Potapova and Charles, 2007;Lavoie et al., 2008;Stevenson et al., 2008;Smucker et al., 2013). Likewise, bacteria, which coexist with diatoms in benthic periphyton, are highly diverse and are affected by nutrients. ...
Article
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Interest in developing periphytic diatom and bacterial indicators of nutrient effects continues to grow in support of the assessment and management of stream ecosystems and their watersheds. However, temporal variability could confound relationships between indicators and nutrients, subsequently affecting assessment outcomes. To document how temporal variability affects measures of diatom and bacterial assemblages obtained from DNA metabarcoding, we conducted weekly periphyton and nutrient sampling from July to October 2016 in 25 streams in a 1293 km² mixed land use watershed. Measures of both diatom and bacterial assemblages were strongly associated with the percent agriculture in upstream watersheds and total phosphorus (TP) and total nitrogen (TN) concentrations. Temporal variability in TP and TN concentrations increased with greater amounts of agriculture in watersheds, but overall diatom and bacterial assemblage variability within sites—measured as mean distance among samples to corresponding site centroids in ordination space—remained consistent. This consistency was due in part to offsets between decreasing variability in relative abundances of taxa typical of low nutrient conditions and increasing variability in those typical of high nutrient conditions as mean concentrations of TP and TN increased within sites. Weekly low and high nutrient diatom and bacterial metrics were more strongly correlated with site mean nutrient concentrations over the sampling period than with same day measurements and more strongly correlated with TP than with TN. Correlations with TP concentrations were consistently strong throughout the study except briefly following two major precipitation events. Following these events, biotic relationships with TP reestablished within one to three weeks. Collectively, these results can strengthen interpretations of survey results and inform monitoring strategies and decision making. These findings have direct applications for improving the use of diatoms and bacteria, and the use of DNA metabarcoding, in monitoring programs and stream site assessments.
... The effectiveness of taxonomic diversity indices in discriminating disturbances has been confirmed by many studies, and they have been used in various biomonitoring and bioassessment programms throughout the world ☆ This paper has been recommended for acceptance by Dr. Sarah Harmon. (Morse et al., 2007;Beck et al., 2013;Wu et al., 2017). However, during recent decades, an increasing number of researchers have recognized the shortcomings of taxonomic diversity metrics on the grounds that they ignore organisms' traits and evolutionary relationships. ...
... Algae (benthic and pelagic) serve as the reliable bioindicators of aquatic environment globally (Lange et al., 2016; because of their strong sensitivity to environmental perturbations Stevenson, 2014). Algae are extensively used as indicators to monitor the biotic conditions of water due to the following reasons: (1) they are highly sensitive to ecosystem situations, (2) easier to detect and sample, and (3) algal communities are sessile, species-rich and cosmopolitan in distribution (Gökçe, 2016;Wu et al., 2017). Algae are the unicellular as well as multicellular photosyntnetic organisms which comprises of two groups: Macroalgae and microalgae. ...
... Algae (benthic and pelagic) serve as the reliable bioindicators of aquatic environment globally (Lange et al., 2016; because of their strong sensitivity to environmental perturbations Stevenson, 2014). Algae are extensively used as indicators to monitor the biotic conditions of water due to the following reasons: (1) they are highly sensitive to ecosystem situations, (2) easier to detect and sample, and (3) algal communities are sessile, species-rich and cosmopolitan in distribution (Gökçe, 2016;Wu et al., 2017). Algae are the unicellular as well as multicellular photosyntnetic organisms which comprises of two groups: Macroalgae and microalgae. ...
Chapter
Over the last few decades, the studies on the factors of climate change viz. temperature, carbon dioxide etc. and their impact on different ecosystems have been gaining importance, as they are threatening the ecological balance. The most immediate effect of change in climate is expected to be seen in water bodies with change in temperature affecting their pH, salinity, solubility, diffusion rate and viscosity. Water acidification due to rise in CO2 concentration, and nutrient load (eutrophication) as a result of anthropogenic activities are the major forces which are expected to have negative impact on water quality. They modify the structure, function and algal diversity (toxic or nontoxic- harmful algal blooms), having detrimental effects on the aquatic ecosystems. Algae (Latin- alga, seaweed), the diverse group of photosynthetic eukaryotic, unicellular or multicellular organisms (kingdom Protista), can be found in vast habitats including rivers, streams, lakes, oceans and other exclusive habitats like ice or snow, thermal vents, and also in terrestrial ecosystems. Besides being used as a food and a substrate for biofuel production, they possess characteristics like rapid reproduction rates, short life cycle, sensitivity and ability to accumulate pollutants, and responsiveness to natural or environmental disturbances at spatio-temporal scales, which qualify them as one of the biological indicators for changing climate. There are several species of algae which respond to the change in environmental factors, and some of them are used as indicators of change. Besides being the indicators, the large-scale production of algal foods and biofuels also have a significant impact on global energy requirements and greenhouse gas emissions. Algae as indicators of climate change have been studied only in few locations and started very recently, so without the past knowledge, the present and the future effects are very difficult to quantify.
... Algae (benthic and pelagic) serve as the reliable bioindicators of aquatic environment globally (Lange et al., 2016; because of their strong sensitivity to environmental perturbations Stevenson, 2014). Algae are extensively used as indicators to monitor the biotic conditions of water due to the following reasons: (1) they are highly sensitive to ecosystem situations, (2) easier to detect and sample, and (3) algal communities are sessile, species-rich and cosmopolitan in distribution (Gökçe, 2016;Wu et al., 2017). Algae are the unicellular as well as multicellular photosyntnetic organisms which comprises of two groups: Macroalgae and microalgae. ...
Preprint
Over the last few decades, the studies on the factors of climate change viz. temperature, carbon dioxide- CO2 etc. and their impact on different ecosystems have been gaining importance, as they are threatening to the ecological balance. The most immediate effect of change in climate is expected to be seen in water bodies with change in temperature affecting their pH, salinity, solubility, diffusion rate and viscosity. Water acidification due to rise in CO2 concentration, and nutrient load (eutrophication) as a result of anthropogenic activities are the major forces which are expected to have negative impact on water quality. They modify modify the structure, function and algal diversity (toxic or nontoxic- harmful algal blooms), having detrimental effects on the aquatic ecosystems. Algae (Latin- alga, seaweed), the diverse group of photosynthetic eukaryotic, unicellular or multicellular organisms (kingdom Protista), can be found in vast habitats including rivers, streams, lakes, oceans and other exclusive habitats like ice or snow, thermal vents, symbiotic, as epiphytes and also in terrestrial ecosystems. Besides being used as a food and for biofuel production, they possess characteristics viz. rapid reproduction rates, very short life cycle, sensitivity and ability to accumulate pollutants, and responsiveness to natural or environmental disturbances at spatial and temporal levels, which qualify them as one of the biological indicators for changing climate. There are several species of algae which respond to the change in environmental factors, and some of the species which are used as the indicators of change. Besides being the indicators, the large scale production of algal foods and bio-fuels also have significant impact on global energy requirements and greenhouse gas emissions. Algae as the indicators of climate change have been studied only in few locations, and started very recently, so without the past knowledge, the present and future effects are very difficult to quantify.
... They are susceptible to herbicides and changes in phytoplankton communities lead to many consequences on other aquatic biota as they are the basis of the food chains and food webs (Lozano et al., 2018(Lozano et al., , 2019Pérez et al., 2007). Furthermore, phytoplankton are one of the best ecological indicators for aquatic stress responses (Wu et al., 2017). Despite the importance of phytoplankton in aquatic ecosystems, studies focusing on effects of herbicides on phytoplankton are lacking as only a few studies have focused on metazachlor and none on flufenacet. ...
Article
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Agrochemicals are the main pollutants in freshwater ecosystems. Metazachlor and flufenacet are two common herbicides applied in fall (i.e., August-October) to agricultural fields in Northern Germany. High concentrations of these herbicides are often found in adjacent aquatic ecosystems. Phytoplankton are one of the highly susceptible non-targeted aquatic organismal groups for herbicides and effects on phytoplankton may initiate a chain of consequences in meta communities through trophic interactions. Few studies have focused on responses of the phytoplankton community for metazachlor and, no studies have focused on flufenacet. We studied the effects of metazachlor and flufenacet on the phytoplankton community by conducting a microcosm experiment exposing natural fall phytoplankton communities to environmentally realistic concentrations as 0 (control), 0.5, 5 and 50 µg L − 1 of metazachlor and flufenacet treatments over a 4-week period. We measured changes in density, composition (i.e., in phyla and species level), taxonomic diversity indices, and functional features of phyto-plankton communities as a response to herbicides. A reduction in the density of Chlorophyta species (e.g., Koliella longiseta, Selenastrum bibraianum) and Cyanobacteria species (e.g., Merismopedia tenuissima and Aphanocapsa elegans) was observed in herbicide treatments compared to controls. The phytoplankton community shifted towards a high density of species from Bacillariophyta (e.g., Nitzschia fonticola and Cyclotella meneghiniana), Miozoa (i.e., Peridinium willei), and Euglenozoa (i.e., Trachelomonas volvocina) in herbicide treatments compared to controls. Metazachlor and flufenacet showed significant negative effects on taxonomic diversity indices (e.g., species richness, the Shannon-Wiener index) and functional features (e.g., functional dispersion and redundancy) of the phytoplankton communities, with increasing herbicide concentrations. Our study provides insights into direct, selective, and irrecoverable effects of metazachlor and flufenacet on phytoplankton communities in the short-term. The comprehensive understanding of these effects of environmentally realistic herbicide concentrations on aquatic biota is essential for a sustainable management of aquatic ecosystems in agricultural areas.
... The U.S. National Sanitation Foundation Water Quality Index (NSFWQI), Canadian Council of Ministers of the Environment WQI (CCMEWQI), British Columbia WQI (BCWQI), and Oregon WQI (OWQI) are the most common indices utilizing physical and chemical parameters for the evaluation of water body qualities (Burigato Costa et al. 2019;Şener et al. 2017). Recently, microalgae have been utilized as reliable bioindicators for the evaluation of water quality of wetlands and rivers, since the biodiversity and biodistribution of microalgal communities are highly sensitive to the physical, chemical and biological modifications that existed in the water resources (Atazadeh et al. 2007;Chun et al. 2018;Wu et al. 2017). More specifically, microbial community (microalgae and Cyanophyta) structure (MCS) could directly and sensitively respond to changes in conductivity, pH, organic pollutions, and nutrient availability. ...
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