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Using river microalgae as indicators for freshwater biomonitoring: Review of published research and future directions
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.
Supplementary resource (1)
... 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). ...
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.
... 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. ...
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. ...
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.
... 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). ...
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.
... 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). ...
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.
... 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. ...
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.
... 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). ...
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.
... 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. ...
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.
... 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). ...
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. ...
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
... 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]. ...
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.
... 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]. ...
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.
... Considerable metrics exist for quantifying riverscape condition and testing hypotheses about structure and function (Table 1). Scientists working with multiple interacting stressors focus on developing assessment tools such as biological indices that should correlate with reference expectations (Statzner and Beche, 2010;Noges et al., 2016;Wu et al., 2017;Lemm et al., 2019). ...
Rivers and their flooded alluvial plains integrate physical, biological, and human processes at the scale of continents. Despite their ecological and economic values, these complex ecosystems are poorly understood and highly modified by humans. A primary problem is that most research in fluvial ecosystems has been conducted in small streams and then scaled up to rivers. Furthermore, the point where a stream transitions into a river is not well understood. Although many conceptual models exist, the role that large river–floodplain complexes play within these frameworks is lacking. These models focus on flooding as a temporary reset to river ecosystems, but floodplains and rivers may continue to interact long after floodwaters recede. We revisit the concept of the riverscape, a unique mosaic of perennially interacting wetland and channel habitats that have unique ecological properties during both non-flood and flooding periods relative to the small tributary streams within the riverscape network. This strong bidirectional interaction within low-lying alluvial plains may define large rivers. To determine whether a riverscape is indeed a useful unit of study for river ecology, conservation, and restoration, baseline conditions with measurable, comparable metrics, such as primary and secondary production need to be established. Responses of these metrics to multiple stressors and restoration such as levee setbacks, wetland mitigation, and dam removals will inform both basic models of riverscape function and future management actions. Because humans currently affect nearly all aspects of the environmental structure and function of riverscapes, human perceptions of riverscape value and threat need to be considered as a fundamental component of riverscape ecology.
... Diatom taxonomy mainly followed the work by Krammer and Lange-Bertalot [38]. The diatom habitat, either planktonic or non-planktonic (epiphytic/benthic), was identified following previously published papers [6,14]. Given the encounter of high numbers of some non-planktonic species (i.e., genus Fragilaria, Navicula, Gomphonema and Nitzschia, and also infrequent occurrences of individual species) and their similar ecological preferences, we grouped these species into genera and calculated the relative abundance (%) for further statistical analysis. ...
As one of the world’s four Greater Bay Areas, the Guangdong–Hong Kong–Macao Greater Bay Area (GBA) faces many environmental challenges along with rapid economic development, causing significant degradation of aquatic ecosystems. However, there is limited knowledge on long-term environmental changes (i.e., >50 years), and restoration of the degraded aquatic ecosystems in the GBA has become increasingly difficult. This study selects a typical inland water body, the Miaotan Reservoir, from Huizhou City in the GBA, to explore long-term changes in water and the eco-environment over the past 70 years and to provide some restoration and management strategies for degrading aquatic ecosystems in the region. We collected a sediment core from the reservoir center and established an age–depth profile by integrating 210Pb and 137Cs dating. We then set up high-resolution diatom community succession stratigraphy and multiple indicators (grain size, element, geochemical and social indicators) as responses to environmental changes in the reservoir. Our results show that significant changes have occurred in the ecosystem and environment of the Miaotan Reservoir and its catchment over the past 70 years. The diatom community underwent a gradual transition from absolute dominance of the mesotrophic species Aulacoseira granulata to dominance of the eutrophic species Nicizschia gracilis, Nicizschia palea and Achanathes sp., indicating the onset of water quality degradation and ecosystem changes in the 1990s due to eutrophication. The RDA (Redundancy analysis) results demonstrate that exogenous pollutant inputs into the Miaotan Reservoir resulting from agricultural activities over the period led to serious environmental changes, e.g., toxic algal bloom and heavy metal pollution. This study enriches our understanding of long-term environmental changes in inland lakes and reservoirs in South China and provides insights into the restoration and management of aquatic ecosystems in the GBA.
... Algae can act as an indicator of degree of alterations in water quality resulted from anthropogenic stress because of having specific ecological requirements (Omar 2010, Dell et al. 2017). Many algal indicators are increasingly been used in bio-monitoring and conservation of water bodies around the world (Wu et al. 2017, Komal et al. 2021. Therefore, availability of information on the distribution and diversity of algae is very important as they represent an ecologically important group of organisms. ...
This checklist of algae has been compiled by critical reviewing all available literature and provides a consolidated, up-to-date account of the diversity of algae in Himachal Pradesh state of India. According to the compiled data the algal flora of the state is represented by a total of 629 algal species of 158 genera belonging to 53 families of 31 orders of the 8 algal classes. The maximum number reported species are belongs to class Cyanophyceae (320 species) followed by Chlorophyceae (139 species), Bacillariophyceae (117 species), Euglenophyceae (25 species), Xanthophyceae (6 species), Dinophyceae (3 species), Coscinodisophyceae (3 species) and Chrysophyceae (2 species) from different habitats of the state. This checklist with taxonomically updated/accepted name of genera/species of algal species reported so far will be helpful for future floristic studies from the region.
... The discharge of untreated sewage contributes to eutrophication [11,64,65] and the density of phytoplankton is considered to be an important indicator of eutrophic environments [66]. In the study area, the discharge of sewage into the Cereja River appears to have contributed to an increase in the chlorophyll-a concentrations in the most urbanized sector through the proliferation of microalgae, which was reflected in a longitudinal gradient, with the lowest chlorophyll-a values being recorded in sector P1 and the highest in P6 (15% higher than P1, on average). ...
The database on water quality in Amazonian rivers located in unplanned urbanized regions along the Brazilian Amazon Coast is still quite limited. This study addresses these concerns, and the tested hypothesis was that the water quality of the Cereja River has deteriorated in recent years, despite the efforts of government authorities to mitigate anthropogenic impacts. To assess changes in water quality, seven campaigns were conducted, collecting data at six fixed points during two different periods. High-resolution satellite images were used to document unplanned occupation. Unfortunately, the number of houses along the Cereja River has increased, in violation of the law. This has contributed to the river’s intense trophic condition, lower dissolved oxygen concentrations, higher concentrations of pathogenic bacteria, and loss of vegetation cover. According to national water quality standards, the Cereja is unsuitable for any human use. This is in stark contrast to the scenario a few decades ago when the river was used for leisure, fishing, and other activities. The results obtained confirm the initial hypothesis and can support potential management strategies and decision-making by authorities. The observed scenario can be extrapolated to other rivers located in urban areas in the Amazon region that have similarly regrettably experienced relatively uncontrolled growth.
... Taxonomic α-diversity metrics, such as species richness and Shannon-Wiener diversity index, are commonly used to unravel the impact of human activities or environmental changes on ecological communities (Magurran, 2021;Wu et al., 2017). Despite wide application in biomonitoring and bioassessment programs globally, many researchers have acknowledged the limitations of taxonomic α-diversity that disregards organismal traits and evolutionary relationships. ...
Rivers play a vital role in the maintenance of the biosphere and human society, since they participate in the global water cycle and provide varied habitats to support biodiversity. Microhabitat heterogeneity is regarded as a key factor driving biodiversity and it plays an active ecological role in different types of mountain rivers. Whether river microhabitat heterogeneity exhibits the same ecological patterns across hydrological periods remains unclear. Here, we analyzed the changes in macroinvertebrate community composition, functional traits, and multi-faceted α-diversity in five debris flow gullies in the Xiaojiang River Basin (southwestern China) between two different hydrological periods. We explored the responses of biodiversity to river microhabitat heterogeneity and its driving factors before and after hydrological disturbance. The results indicated that river microhabitat heterogeneity and three facets of macroinvertebrate α-diversity decreased after hydrological disturbance, with macroinvertebrate state traits becoming more unbalanced. Macroinvertebrate taxonomic diversity increased with increasing river microhabitat heterogeneity across hydrological periods, and this pattern was more prominent before hydrological disturbance. A high J o u r n a l P r e-p r o o f Journal Pre-proof 2 correlation emerged between macroinvertebrate phylogenetic diversity and river microhabitat heterogeneity only before hydrological disturbance. Hydrogeomorphic parameters prominently affected macroinvertebrate communities before hydrological disturbance. Water environmental parameters worked together with hydrogeomorphic parameters to shape macroinvertebrate communities in hydrologically disturbed debris flow gullies, indicating a reduced ecological role of river microhabitat heterogeneity. The ecological health of debris flow gullies can be improved by increasing vegetation coverage on river bank slopes to increase slope stability and mitigate hydrological disturbances, as well as placing large rocks into river channels to enhance riverbed stability and create habitats for more biological groups.
... The discharge of untreated sewage contributes to eutrophication (Dodds 2006;Wu et al. 2017;Tang et al. 2020) and the density of phytoplankton is considered to be an important indicator of eutrophic environments (Yusuf 2020). In the study area, the discharge of sewage into the Cereja River appears to have contributed to an increase in the chlorophyll-a concentrations in the most urbanized sector through the proliferation of microalgae, which is reflected in a longitudinal gradient, with the lowest chlorophyll-a values being recorded in sector P1 and the highest in P6 (15% higher than P1, on average). ...
This study focuses on the Cereja River, a Permanent Preservation Area located in Amazon coast. The hypothesis tested was that the water quality of the Cereja River has worsened over recent years due to unplanned urban growth. To assess changes in the water quality, seven campaigns were undertaken with data being collected at six fixed points, during two distinct periods (2013–2014 and 2018–2019). High-resolution satellite images from GoogleEarth (2012 and 2019) were used to register unplanned occupation. The DPSWR (Driver-Pressure-State-Welfare-Response) socioecological framework was used to identify potential measures for the management of environmental and anthropogenic problems. The increase in the number of households found on the Cereja margins between 2012-2019 has contributed to the river’s intense trophic condition, low concentrations of dissolved oxygen, high concentrations of pathogenic bacteria, and loss of vegetation cover. The water of the Cereja River is inadequate for any human use, and its contamination is one of the principal factors determining the reduction of the water quality of the Caeté estuary. According to the obtained results, the DPSWR model proved to be an excellent analytical tool for the evaluation of specific local scenarios, through the integrated analysis of socio-environmental issues. The scenario observed can be extrapolated to other rivers located within urban areas in the Amazon region that have relatively unplanned growth.
... Habitat destruction, loss, or homogenization caused by human activities can also result in changes in aquatic communities, which in turn can affect freshwater ecosystem functions and services (Dudgeon et al., 2006;Grill et al., 2019). Diatoms are increasingly used as bioindicators for environmental monitoring due to their short lifespan and sensitivity to environmental changes (Stevenson et al., 1996;Wu et al., 2010;Liu et al., 2014;Wu et al., 2017;Wang et al., 2022). Hence, we chose diatoms to develop an index of biotic integrity in this study. ...
Incorporating functional metrics into the development of a diatom-based index of biotic integrity (D-IBI) is conducive to a more comprehensive assessment of water quality and the degree of external impact on ecosystem function. A D-IBI was developed by incorporating functional metrics to candidate metrics. Four metrics were selected and divided into five levels to evaluate 147 sampling sites. By comparing the D-IBI scores in Thousand Islands Lake (TIL) catchment, we found that the total D-IBI score ranged from 20 to 100 (median was 45). Compared with reference sites, the resource competition of impaired sites was weaker, and the community was more stable. In response to basin damage, we recommend source protection, long-term monitoring, increased hydrological connectivity, and ecological management of small watersheds. For the assessment of water environmental health, we suggest that the functional metrics should be included in the biological assessment, and the candidate metrics that are greatly affected by the dispersal process should be excluded. Moreover, the assessment should be conducted at the multi-dimension level and watershed scale.
... 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. ...
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.
... La biología y taxonomía de este grupo son propicias para respaldar su uso exitoso en el biomonitoreo basado en sus respuestas específicas a los cambios ambientales, especialmente la contaminación orgánica. Presentan un amplio espectro de tolerancia, desde condiciones oligotróficas hasta eutróficas, estas microalgas han sido ampliamente utilizadas como bioindicadores de la calidad del agua (Bellinger & Sigee, 2010;Wu et al., 2017;Ballesteros et al., 2020). ...
La cuenca Salí-Dulce es una de las principales del Noroeste de Argentina y en su recorrido se ve afectada debido a la incorporación de sustancias contaminantes. En los ecosistemas acuáticos continentales las diatomeas constituyen un grupo destacado. Su biología y taxonomía son adecuadas para su uso en el biomonitoreo. El objetivo fue caracterizar la dinámica y la composición de las taxocenosis de diatomeas y su relación con variables ambientales en los arroyos Mista y Calimayo, pertenecientes a la cuenca del río Salí-Dulce (Tucumán-Argentina). Para esto se seleccionaron tres sitios en cada arroyo y se tomaron datos de variables ambientales y biológicas según metodologías convencionales. La calidad del agua fue variable según el aporte de contaminantes y la estacionalidad climática. El ensamble de diatomeas resultó ser una taxocenosis bioindicadora sensible a las características ambientales de los arroyos. En este trabajo se registraron 61 especies de las cuales 11 serían buenas indicadoras del estado de contaminación. El uso de dos índices bióticos permitió afirmar que el Índice de Diatomeas Pampeano modificado según datos propios, resultó más sensible y eficaz en la determinación de la calidad del agua, por lo que se podría considerar como una herramienta diagnóstica, de seguimiento de la calidad del agua y de planificación que serviría para brindar información válida y de fácil aplicación en cuencas del Noroeste de Argentina.
... 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). ...
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. ...
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. ...
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. ...
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]. ...
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. ...
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. ...
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. ...
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. ...
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. ...
... 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. ...
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). ...
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.
... 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. ...
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.
... 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). ...
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.
https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119857839.ch8
This study addresses the gap in understanding the diversity, species, and functional trait distribution of different algal groups that occur in the Okavango Delta (a near-pristine subtropical wetland in northwestern Botswana) across hydrological and habitat gradients. We systematically characterize the delta’s algal flora, addressing the gap left by previous research that was limited to single algal groups (e.g., diatoms) and/or only looking at upstream areas in the Okavango River basin. We analyzed 130 algal samples from 49 upstream and downstream sites with higher and lower flooding frequency, respectively, across a river-to-floodplain habitat gradient. Chlorophyta and Bacillariophyta dominated both abundance and taxon richness (>80%) of the total 494 taxa found from 49,158 algal units counted (cells, colonies, coenobia, and filaments). Smaller algae were more abundant in downstream floodplains than in upstream channels and lagoons. Motile and siliceous algae were much more abundant than non-motile, nitrogen fixing, and phagotrophic algae. The frequency of these traits was associated more with flooding frequency than habitat type. The highest algal richness and diversity were found downstream, where shallow floodplain ecosystems with seasonally fluctuating water depths offer greater habitat heterogeneity, and macronutrients are resuspended. The increasing threats from upstream water abstraction plans, fracking, and climate change require enhanced protection and monitoring of the Okavango Delta’s natural annual flood-pulse to maintain the high species and functional diversity of this unique wetland’s microalgae.
In recent years, there has been a growing interest in the impacts caused by the presence of microplastics (MP) in aquatic environments. The impacts of microalgae exposure to microplastics are still insufficiently investigated and further studies are needed to understand the possible outcomes. In addition, much of the literature has focused on the study of concentrations above those found naturally in the environment and in less toxic polymer matrices. Acrylonitrile-butadiene-styrene (ABS) plastics have a composition rich in additives and, so far, have been studied superficially. In the present study, two of the most commonly used green microalgae species in toxicity assays, Chlorella vulgaris and Raphidocelis subcapitata, were exposed to different concentrations of primary ABS-MP for a period of 6 days. Here, we observed physiological changes in cell growth and chlorophyll a content induced by the concentration and time of exposure to ABS-MP. The lowest concentration did not prove to be potentially toxic to cells, while the highest concentration was the most toxic. Primary consumers, such as microalgae, are essential for the proper functioning of entire ecosystems. Changes in these communities can lead to permanent damage to the communities of organisms at higher levels, so it is essential that their study be done carefully in the face of threats such as MP.
The biological integrity of global freshwater ecosystems is threatened by ever-increasing environmental stressors due to increased human activities, such as land-use change, eutrophication, toxic pollutants, overfishing, and exploitation. Traditional ecological assessments of lake or riverine ecosystems often require human supervision of a pre-selected reference area, using the current state of the reference area as the expected state. However, selecting an appropriate reference area has become increasingly difficult with the expansion of human activities. Here, an unsupervised biological integrity assessment framework based on environmental DNA metabarcoding without a prior reference area is proposed. Taxon richness, species dominance, co-occurrence network density, and phylogenetic distance were used to assess the aquatic communities in the Taihu Lake basin. Multi-gene metabarcoding revealed comprehensive biodiversity at multiple trophic levels including algae, protists, zooplankton, and fish. Fish sequences were mainly derived from 12S, zooplankton mainly from mitochondrial cytochrome C oxidase subunit I, and algae and protists mainly from 18S. There were significant differences in community composition among lakes, rivers, and reservoirs but no significant differences in the four fundamental biological indicators. The algal and zooplankton integrities were positively correlated with protist and fish integrities, respectively. Additionally, the algal integrity of lakes was found to be significantly lower than that of rivers. The unsupervised assessment framework proposed in this study allows different ecosystems, including the same ecosystem in different seasons, to adopt the same indicators and assessment methods, which is more convenient for environmental management and decision-making.
Diatoms have long been utilized as robust ecological indicators for aquatic ecosystems. Ecological data of aquatic diatoms have been well documented. Autecological and biotic indices have extensively used for ecoassessment of water bodies throughout the world. In spite of the fact that diatoms are quite abundant in terrestrial environments and respond quickly to soil environment fluctuations, ecological studies on these entities are substantially lacking as compared to their aquatic counterparts. Of late researchers have investigated certain aspects of soil diatom ecology from some parts of the world. Terrestrial diatoms have been found to be quite responsive to soil environmental conditions, anthropogenic disturbances and agricultural practices. This review attempts to assemble the diverse findings associated with the terrestrial diatoms and their response towards various stressors and explores the future prospects of soil diatom ecology.KeywordsTerrestrial diatomsSoil microbiomeAgricultural practices
Herbicide pollution poses a worldwide threat to plants and freshwater ecosystems. However, the understanding of how organisms develop tolerance to these chemicals and the associated trade-off expenses are largely unknown. This study aims to investigate the physiological and transcriptional mechanisms underlying the acclimation of the green microalgal model species Raphidocelis subcapitata (Selenastraceae) towards the herbicide diflufenican, and the fitness costs associated with tolerance development. Algae were exposed for 12 weeks (corresponding to 100 generations) to diflufenican at the two environmental concentrations 10 and 310 ng/L. The monitoring of growth, pigment composition, and photosynthetic performance throughout the experiment revealed an initial dose-dependent stress phase (week 1) with an EC50 of 397 ng/L, followed by a time-dependent recovery phase during weeks 2 to 4. After week 4, R. subcapitata was acclimated to diflufenican exposure with a similar growth rate, content of carotenoids, and photosynthetic performance as the unexposed control algae. This acclimation state of the algae was explored in terms of tolerance acquisition, changes in the fatty acids composition, diflufenican removal rate, cell size, and changes in mRNA gene expression profile, revealing potential fitness costs associated with acclimation, such as up-regulation of genes related to cell division, structure, morphology, and reduction of cell size. Overall, this study demonstrates that R. subcapitata can quickly acclimate to environmental but toxic levels of diflufenican; however, the acclimation is associated with trade-off that result in smaller cell size.
Periphyton can contribute to maintaining oligotrophic conditions in restored shallow lakes and reservoirs. In two mesocosm experiments, we evaluated the periphyton responses to enrichment and nutrient dilution in a hypereutrophic reservoir. Effects of the isolated and combined N and P enrichment and dilution levels on periphyton biomass and structure on artificial substrate were investigated. For colonization of periphyton, glass slides were exposed for 14 days (enrichment experiment) and 21 days (dilution experiment) at 20 cm deep. We monitored the effects of N and P enrichment and dilution on the algal biomass, density, and species composition in the periphyton. P was a primary limiting factor for periphyton development. Periphyton algal density and biomass increased in response to combined and isolated P enrichment. Only the 75 % dilution had a positive and significant effect on biomass and algal density in the periphyton. In both mesocosm experiments, the periphyton structure changed, with Nitzschia palea (Kutz.) Smith responding positively to P enrichment and negatively to dilution. Achnanthidium minutissimum Complex becoming dominant following 50 % and 75 % eutrophic water dilution. Our results suggest that major environmental changes are necessary for a heterogeneous algal community structure in the periphyton in hypereutrophic con¬ditions. We conclude that, after a restoration process that reduces P-competition with phytoplankton and shading, periphyton can become an important primary producer in a hypereutrophic reservoir.
The timeliness of monitoring is essential to algal bloom management. However, acquiring algal bio-indicators can be time-consuming and laborious, and bloom biomass data often contain a large proportion of extreme values limiting the predictive models. Therefore, to predict algal blooms from readily water quality parameters (i.e., DO, pH, etc.), and to provide a novel solution to the modeling challenges raised by the extremely distributed biomass data, a Bayesian scale-mixture of skew-normal (SMSN) model was proposed. In this study, our SMSN model accurately predicted over-dispersed biomass variations with skewed distributions in both rivers and lakes (in-sample and out-of-sample prediction R2 ranged from 0.533 to 0.706 and 0.412 to 0.742, respectively). Moreover, we successfully achieve a probabilistic assessment of algal blooms with the Bayesian framework (Accuracy > 0.77 and Macro-F1 score > 0.72), which robustly decreased the classic point-prediction-based inaccuracy by up to 34%. This work presented a promising Bayesian SMSN modeling technique, allowing for real-time prediction of algal biomass variations and in-situ probabilistic assessment of algal bloom.
It has been well documented that periphyton communities play a key role in primary productivity, nutrient cycling, and food web interactions. However, a worldwide overview of research on the key themes, current situation, and major trends within the field is lacking. In this study, we applied the machine learning technique (latent Dirichlet allocation, LDA) to analyze the abstracts of 6690 publications related to periphyton from 1991 to 2020 based on the Web of Science database. The relative frequency of classical and basic research on periphyton related to colonization, biomass, growth rate, and habitats has been clearly decreasing. The increasing trends of research on periphyton are embodied in the periphyton function in freshwater ecosystems (e.g., application as ecological indicators, function in the removal of nutrients, and application in paleolimnology), the research at macroscales (e.g., spatial–temporal variation, and functional and taxonomic diversity), and the anthropogenic themes (e.g., climate warming, response to multiple stressors, and land use type). The keyword and title analysis showed that the periphyton studies are concentrated mainly on diatom aspects, especially with respect to streams relative to lakes. The thematic space based on non-metric multidimensional scaling (NMDS) showed that the classical themes such as growth rate, colonization, and environmental factors (e.g., multiple stressors and climate warming) were most linked to other research themes. We proposed that future trends in the periphyton should focus on the function of periphyton in lakes and their response to multiple environmental pressures with the increasingly extensive eutrophication in lakes and the increasingly significant change in the climate.
Increasing anthropogenic pressure and the effects of climatic change on aquatic ecosystem tolerances and functions require an understanding of ecological processes. It is important to control environmental limiting factors to maintain the ecosystem balance. Therefore, positive and negative feedback mechanisms at the habitats are critical control systems. Biomonitoring is a necessary step to observe the ecological effects caused by environmental change. It is essential to consider that the primary producer community changes quickly as a response to changes in water quality. Phytoplankton and algae components (e.g., pigment, population dynamics, and community composition) provide more evidence concerning alterations in water quality. Long-term, standardized measurement and observation are evaluated to define the ecosystem state and studies can be grouped as chemical monitoring, toxicity monitoring, and ecosystem monitoring processes. Holistic biological monitoring studies for water quality and ecosystem sustainability provide valuable information for environmental deterioration, and balance based on temporal variation.
Periphyton is a key primary producer in shallow lakes, sensitive to global warming and changes in nutrient balances. Reduced nitrogen availability due to accelerated denitrification at higher temperatures or in response to reduced N loadings aimed to reduce the eutrophication may affect periphyton biomass and composition, to compensate for the low N availability (e.g. promoting N2-fixing). We analysed periphyton responses to N decline in 12 eutrophic shallow lake mesocosms during one year of low N compared to high N, under three temperature scenarios: ambient, A2 IPCC scenario and A2 increased by 50%. We used two submerged macrophytes (Potamogeton crispus and Elodea canadensis) and artificial imitations of these as substrates for periphyton growth. Nitrogen decline increased periphyton biomass and induced compositional changes irrespective of season, plant type, and temperature. Periphyton biomass was negatively associated to phytoplankton and positively to plant complexity. Warmer scenarios negatively affected periphyton exclusively at high N loadings. Low N conditions were associated with lower periphyton taxonomic richness, lower N2-fixing cyanobacteria biovolume and increased biovolume of large-sized chlorophytes and non-N2-fixing cyanobacteria. Our results suggest that low N conditions promoted periphyton due to a more efficient use of nutrients and improved light conditions resulting from lower phytoplankton biomass and contrasting effects of temperature.
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.
Man's activities have had profound, and usually negative, influences on freshwater fishes from the smallest streams to the largest rivers. Some negative effects are due to contaminants, while others are associated with changes in watershed hydrology, habitat modifications, and alteration of energy sources upon which the aquatic biota depends. Regrettably, past efforts to evaluate effects of man's activities on fishes have attempted to use water quality as a surrogate for more comprehensive biotic assessment. A more refined biotic assessment program is required for effective protection of freshwater fish resources. An assessment system proposed here uses a series of fish community attributes related to species composition and ecological structure to evaluate the quality of an aquatic biota. In preliminary trials this system accurately reflected the status of fish communities and the environment supporting them.
Stream metacommunities are structured by a combination of local (environmental filtering) and regional (dispersal) processes. The unique characters of high mountain streams could potentially determine metacommunity structuring, which is currently poorly understood. Aiming at understanding how these characters influenced metacommunity structuring, we explored the relative importance of local environmental conditions and various dispersal processes, including through geographical (overland), topographical (across mountain barriers) and network (along flow direction) pathways in shaping benthic diatom communities. From a trait perspective, diatoms were categorized into high-profile, low-profile and motile guild to examine the roles of functional traits. Our results indicated that both environmental filtering and dispersal processes influenced metacommunity structuring, with dispersal contributing more than environmental processes. Among the three pathways, stream corridors were primary pathway. Deconstructive analysis suggested different responses to environmental and spatial factors for each of three ecological guilds. However, regardless of traits, dispersal among streams was limited by mountain barriers, while dispersal along stream was promoted by rushing flow in high mountain stream. Our results highlighted that directional processes had prevailing effects on metacommunity structuring in high mountain streams. Flow directionality, mountain barriers and ecological guilds contributed to a better understanding of the roles that mountains played in structuring metacommunity.
A high number of species often represents a relevant redundancy in terms of ecological adaptation strategies. Collecting species to groups based on their functional adaptations can handle this redundancy and obtain the “real” functional complexity of ecosystems. Functional traits are proxies of adaptation strategies under particular environmental conditions, and a set of functional traits are interpreted as life-strategies. Organisms with life-strategies occupying a similar niche can be collected in ecological groups (functional group/guild). In this study, we review the latest trait-based approaches and existing attempts at functional classifications in phytobenthos studies. Advantages and shortcomings of these classifications are discussed with perspectives of their utility in ecological status assessment.
1. While many streams and rivers are dominated by terrestrial inputs of organic carbon, algae are important trophic base for stream food webs. However, the nutritional importance of algae for stream invertebrates has only recently been highlighted. Algae are acknowledged as higher quality food than terrestrial organic matter for the growth and reproduction of invertebrates. In part, this is because of algal higher polyunsaturated fatty acid (PUFA) content. Here we review the important influence of algal food quality, as assessed by PUFA, in stream food webs.
2. Current field investigations have mainly focused on the fatty acid dynamics of macroinvertebrates, and indicate that algal eicosapentaenoic acid (EPA), α-linolenic acid (ALA), and linoleic acids (LIN) are present in all macroinvertebrates. However, fungal and bacterial tracers have also been observed in a range of macroinvertebrates. The ω3/ω6 ratio >1 in most macroinvertebrates strongly indicates that algae as dietary energy are highly retained in stream food webs. Interspecific differences in PUFA composition seem to be affected by dietary PUFA and consumer physiology.
3. Some studies have suggested that besides dietary EPA, LIN and ALA can also improve growth and reproduction of stream invertebrate consumers. Some macroinvertebrates may preferentially retain or synthesize long-chain PUFA from C18 PUFA when experiencing low quality food. However, this process is controversial since other species have shown very limited ability to synthesis long-chain PUFA.
4. Algal PUFA composition is strongly influenced by abiotic factors, particularly light, nutrients, and temperature. Human disturbance (i.e., riparian vegetation removal and nutrient inputs) on algal PUFA content and their consequent effects on macroinvertebrates and fish clearly warrant further scientific attention. Controlled feeding trials and manipulative studies are required to measure PUFA conversion capacities and reproductive investment of stream macroinvertebrates under different food quality conditions, which will provide insights into how freshwater species can cope with different nutritional food conditions due to human disturbance and climate change.
Understanding and predicting ecosystem responses to multiple environmental pressures is a long‐standing interest in ecology and environmental management. However, few studies have examined how the functional features of freshwater biological communities vary along multiple gradients of environmental stress. Furthermore, modelling these functional features for a whole river network constitutes a strong potential basis to improve ecosystem management.
We explored how functional redundancy of biological communities ( FR , a functional feature related to the stability, resistance and resilience of ecosystems) responds to single and multiple environmental filters. We compared these responses with those of functional richness, evenness and divergence. We used riparian vegetation of a Mediterranean basin, and three of the main environmental filters affecting freshwater communities in such regions, that is drought, flow regulation and agricultural intensity, thus considering the potential effect of natural environmental variability. We also assessed the predictability of FR and estimated it for the entire river network.
We found that all functional measures decreased with increasing environmental filter intensity. However, FR was more sensitive to single and multiple environmental filters compared to other functional measures. The best‐fitting model explained 59% of the FR variability and included agriculture, drought and flow regulation and the pairwise interactions of agriculture with drought and flow regulation. The parameters of the FR models differed from null model expectations reflecting a non‐random decline along stress gradients.
Synthesis and applications . We found non‐random detrimental effects along environmental filters' gradients for riparian functional redundancy (the most sensitive functional index), meaning that increased stress could jeopardize stability, resistance and resilience of these systems. In general, agriculture caused the greatest impact on functional redundancy and functional diversity measures, being the most important stressor for riparian functionality in the study area. Temporary streams flowing through an agricultural, regulated basin had reduced values of functional redundancy, whereas the free‐flowing medium‐sized, perennial water courses flowing through unaltered sub‐basins displayed higher values of functional redundancy and potentially greater stability against human impacts. All these findings along with the predicted basin‐wide variation of functional redundancy can assist environmental managers in improving monitoring and ecosystem management.
Acid mine drainage (AMID) characterized by low pH, high concentrations of dissolved metals and metal oxide deposits affects aquatic ecosystems severely. However, the quantitative impacts of AMID on lotic ecosystem, especially the seasonal variation of impacts, are still unclear. We developed a diatom-based index of biotic integrity (AMD-DIBI) to evaluate AMID impairment on Gaolan River. Pollution Tolerance Index (PTI), % No. of Cocconeis species, % No. of Pinnularia species, No. of Cymbella species, relative abundance of prostrate diatoms, and relative abundance of Achnanthes were selected to build AMID-DIBI. AMD-DIBI scores between reference and impaired sites displayed significant differences. On the basis of AMID-DEBI scores, the ecological conditions of most reference sites were "excellent" or "good", while the impaired sites were "Poor" or "Moderate". AMID impairments were more severe in dry season than that in wet season: about 20km lower reach were impaired in wet season, while 50km at least in dry season. AMD-DIBI is meaningful to assess the ecological conditions, quantify impairment of AMID and measure the effectiveness of restoration.
Algal polyunsaturated fatty acids (PUFA), essential for somatic growth and reproduction of aquatic animals, are influenced by ambient environmental conditions, including light and nutrients. Few studies have addressed the extent to which changes in dietary PUFA can influence stream herbivore PUFA profiles and the implications for stream food webs. We manipulated subtropical stream periphyton by applying two light levels (open and shaded canopy) and two nutrient regimes (ambient and enriched) to investigate the response of PUFA and somatic growth in stream herbivores. After six weeks, the relative content of periphyton PUFA (%) changed distinctly and differed among treatments. Periphyton in the control treatment with open canopy showed a decline in eicosapentaenoic acid (EPA) relative to initial conditions, whereas shading increased EPA and total highly unsaturated fatty acids (HUFA), but decreased α-linolenic acid (ALA), linoleic acid (LIN) and total C18 PUFA. The interaction of open canopy and added nutrients increased periphyton ALA compared with initial conditions, while the combined effects of shading and added nutrients had greater total HUFA. Fatty acid similarity between stream grazers (the mayfly Austrophlebioides and caddisfly Helicopsyche) and periphyton increased with periphyton HUFA content. In addition, the growth of large instars of both grazers also increased in response to increased periphyton HUFA%. Our findings show that environmental changes, associated with riparian canopy and nutrients, can lead to changes in periphyton PUFA composition that in turn affect growth and PUFA composition in stream grazers and are likely to have implications for higher order consumers.
The use of trait-based approaches to detect effects of land use and climate change on terrestrial plant and aquatic phytoplankton communities is increasing, but such a framework is still needed for benthic stream algae. Here we present a conceptual framework of morphological, physiological, behavioural and life-history traits relating to resource acquisition and resistance to disturbance. We tested this approach by assessing the relationships between multiple anthropogenic stressors and algal traits at 43 stream sites. Our "natural experiment" was conducted along gradients of agricultural land-use intensity (0-95% of the catchment in high-producing pasture) and hydrological alteration (0-92% streamflow reduction resulting from water abstraction for irrigation) as well as related physicochemical variables (total nitrogen concentration and deposited fine sediment). Strategic choice of study sites meant that agricultural intensity and hydrological alteration were uncorrelated. We studied the relationships of seven traits (with 23 trait categories) to our environmental predictor variables using general linear models and an information-theoretic model-selection approach. Life form, nitrogen fixation and spore formation were key traits that showed the strongest relationships with environmental stressors. Overall, FI (farming intensity) exerted stronger effects on algal communities than hydrological alteration. The large-bodied, non-attached, filamentous algae that dominated under high farming intensities have limited dispersal abilities but may cope with unfavourable conditions through the formation of spores. Antagonistic interactions between FI and flow reduction were observed for some trait variables, whereas no interactions occurred for nitrogen concentration and fine sediment. Our conceptual framework was well supported by tests of ten specific hypotheses predicting effects of resource supply and disturbance on algal traits. Our study also shows that investigating a fairly comprehensive set of traits can help shed light on the drivers of algal community composition in situations where multiple stressors are operating. Further, to understand non-linear and non-additive effects of such drivers, communities need to be studied along multiple gradients of natural variation or anthropogenic stressors.
Based on the phytoplankton associations described for lakes (REYNOLDS, 2002), an assessment method has been elaborated for rivers. All phytoplankton associations were evaluated and scored by a number between 0-5. As many rivers can be defined as shallow, turbid, mesotrophic ecosystems of short residence time, those associations that prefer this type of environment were given high factor numbers, and those that are typical of stable hypertrophic lakes have got the lowest values. Highest values were given to those assemblages that contain mainly periphytic diatoms. To achieve an index, each species in the sample must be assigned to the appropriate functional group. Then the relative share of each functional groups are calculated. Relative shares are then multiplied by the factor number. The sum of these scores is the index. The reference values of the upper river sections are close to 5, while those of the lower river stretches are approximately 4. The method has been tested with hundreds of phytoplankton samples, it is simple, and after applying to a phytoplankton database can be computerised easily. Another advantage of the method that it is not restricted to a specific geographic region.
Historically, close attention has been paid to negative impacts associated with nutrient loads to streams and rivers, but today hydromorphological alterations are considered increasingly implicated when lowland streams do not achieve good ecological status. Here, we explore if trait-abundance patterns of aquatic plants change along gradients in hydromorphological degradation and eutrophication in lowland stream sites located in Denmark. Specifically, we hypothesised that: i) changes in trait-abundance patterns occur along gradients in hydromorphological degradation and ii) trait-abundance patterns can serve to disentangle effects of eutrophication and hydromorphological degradation in lowland streams reflecting that the mechanisms behind changes differ. We used monitoring data from a total of 147 stream reaches with combined data on aquatic plant species abundance, catchment land use, hydromorphological alterations (i.e. planform, cross section, weed cutting) and water chemistry parameters. Traits related to life form, dispersal, reproduction and survival together with ecological preference values for nutrients and light (Ellenberg N and L) were allocated to 41 species representing 79% of the total species pool. We found clear evidence that habitat degradation (hydromorphological alterations and eutrophication) mediated selective changes in the trait-abundance patterns of the plant community. Specific traits could distinguish hydromorphological degradation (free-floating, surface; anchored floating leaves; anchored heterophylly) from eutrophication (free-floating, submerged; leaf area). We provide a conceptual framework for interpretation of how eutrophication and hydromorphological degradation interact and how this is reflected in trait-abundance patterns in aquatic plant communities in lowland streams. Our findings support the merit of trait-based approaches in biomonitoring as they shed light on mechanisms controlling structural changes under environmental stress. The ability to disentangle several stressors is particularly important in lowland stream environments where several stressors act in concert since the impact of the most important stressor can be targeted first, which is essential to improve the ecological status.
Agricultural land use practices were found to have a great impact on river water quality. Highly variable boundary conditions such as seasonal weather influence or market impacts lead to dynamic changes in the use of agricultural crops. In rural areas with a huge share of agricultural land use, these dynamics are accompanied with changes of river water quality. To quantify these impacts for the future, it is common practice to apply scenario simulations with eco-hydrological catchment models. For this, it is essential to represent spatially and temporal variations in agricultural crops. In this study, we present a dynamic modelling approach of spatial agricultural crops distribution and its impacts on nitrate loads in rivers at the catchment scale. Area proportions of crops are reproduced in a data-based approach according to the current land use situation in the catchment. Using this spatial crop distribution, the eco-hydrological model SWAT is calibrated for discharge and nitrate time series. Within scenario simulations, the spatial crop distribution is updated dynamically for each year, while non-agricultural land use areas remain constant. The dynamic approach is compared with a static land use scenario, in which the land use information is changed only once immediately at the beginning of the scenario period. Good model results were realised for discharge and nitrate loads in the calibration and validation period. The evaluation of the land use change scenarios for the period from 2021 to 2030 revealed changes in nitrate loads. The analysis of the dynamic land use update illustrates an increase in the changes between the scenarios within the modelling period. Consequently, the presented approach allows the quantification of nutrient dynamics that are related to dynamic changes of land use during the simulation period. We conclude that this study shows how the dynamic modelling leads to a more realistic temporal development of land use change and its impacts on nitrate.
Aim:
Ecological and evolutionary forces shape the functional traits of species within and across environments, generating biogeographical patterns in traits. We aimed to: (1) determine the extent to which temperature traits of phytoplankton are adapted to their local environment, and (2) detect and explain differences in patterns of adaptation between functional groups (reflecting evolutionary history) and across ecosystems (freshwater versus marine).
Location:
We used laboratory-measured data on phytoplankton strains isolated from marine (76° N to 75° S) and freshwater ecosystems (80° N to 78° S).
Methods
We studied variation in five temperature traits: optimum temperature for growth (Topt), maximum and minimum persistence temperature (Tmax, Tmin), temperature niche width and maximum growth rate, estimated in 439 strains from over 200 species. We tested whether these traits change along environmental temperature gradients (across latitude and ecosystems) and also investigated differences in trait–environment relationships related to evolutionary history (functional group identity). We used mixed models to evaluate our hypotheses while accounting for intraspecific variation.
Results:
We identified three patterns caused by adaptation and community assembly: (1) Topt, Tmax and Tmin decline sharply with latitude; (2) Topt, Tmax and Tmin are similar across all functional groups at the equator, where temperature variation is low; and (3) Topt and Tmax are higher in freshwater locations than marine locations at similar latitudes. Additionally, evolutionary history explained substantial variation in all traits: functional groups differ strongly in their niche widths and maximum growth rates, as well as their Topt, Tmax, and Tmin relationships with latitude.
Main conclusions:
Globally, phytoplankton temperature traits are well adapted to local conditions, changing across ecosystems and latitude. Functional groups differ strongly in their patterns of adaptation: traits are similar in hot tropical environments, but diverge at temperate latitudes. These differences reflect two possible evolutionary constraints: cyanobacterial inability to adapt to low temperatures and differences in nutrient requirements between groups.
Abstract Indicator species (IS) are used to monitor environmental changes, assess the efficacy of management, and provide warning signals for impending ecological shifts. Though widely adopted in recent years by ecologists, conservation biologists, and environmental practitioners, the use of IS has been criticized for several reasons, notably the lack of justification behind the choice of any given indicator. In this review, we assess how ecologists have selected, used, and evaluated the performance of the indicator species. We reviewed all articles published in Ecological Indicators (EI) between January 2001 and December 2014, focusing on the number of indicators used (one or more); common taxa employed; terminology, application, and rationale behind selection criteria; and performance assessment methods. Over the last 14 years, 1914 scientific papers were published in EI, describing studies conducted in 53 countries on six continents; of these, 817 (43%) used biological organisms as indicators. Terms used to describe organisms in IS research included "ecological index", "environmental index", "indicator species", "bioindicator", and "biomonitor," but these and other terms often were not clearly defined. Twenty percent of IS publications used only a single species as an indicator; the remainder used groups of species as indicators. Nearly 50% of the taxa used as indicators were animals, 70% of which were invertebrates. The most common applications behind the use of IS were to: monitor ecosystem or environmental health and integrity (42%); assess habitat restoration (18%); and assess effects of pollution and contamination (18%). Indicators were chosen most frequently based on previously cited research (40%), local abundance (5%), ecological significance and/or conservation status (13%), or a combination of two or more of these reasons (25%). Surprisingly, 17% of the reviewed papers cited no clear justification for their choice of indicator. The vast majority (99%) of publications used statistical methods to assess the performance of the selected indicators. This review not only improves our understanding of the current uses and applications of IS, but will also inform practitioners about how to better select and evaluate ecological indicators when conducting future IS research.
We summarize the scientific trends in phytoplankton studies between 1991 and 2013 based on bibliometric analysis. The annual publication output on phytoplankton demonstrated a rapid linear increasing tendency during the past two decades, and its contribution to total scientific articles remained below 10%. Under the context of fast scientific research development, the yearly numbers of dependent publications (in terms of multi-aquatic ecosystems and international collaborations) indicate a linear increasing trend. The variations of keywords associated with research regions are mainly contributed by geographic adjacent countries, which are also generally the top contributors. Various trends of all the keywords relating to research methods, research contents and environmental factors indicate that phytoplankton studies carried out on large scale and long term are showing a significantly ascending trend, while traditional and local scale studies are showing a descending trend.
Assessing zooplankton grazing on phytoplankton is crucial to understand, model, and predict the structure and dynamics of pelagic communities. Our hypothesis is that phytoplankton consumption by zooplankton in freshwater lakes can be well represented by clustering phytoplankton species into morphology-based functional groups (MBFG) and zooplankton species into broad taxonomic units: cladocerans, calanoid copepods, and rotifers. We characterized zooplankton potential grazing on MBFG based on an extensive literature review of experimental data including clearance and ingestion rates. Rotifers show greater potential grazing upon small- and medium-sized species (MBFG I and IV) and presented a Type III trait-based functional response. Cladocerans also show greater potential impact upon MBFG IV but a Type II response. Both groups maintained their respective feeding response regardless of the type of food available, indicating poor food selectivity. Copepods consumed different MBFGs, but a clear Type II pattern was observed when feeding on MBFGs V and VI. Prediction intervals indicated a greater variability in cladocerans’ and copepods’ response. This approach is a step to summarize and characterize grazing to the future quantification of ecosystem models. Further efforts should be done to include information about different larval stages and phytoplankton traits not directly related to morphology.
Nutrient transformation processes such as assimilation, dissimilatory transformation, and sorption to sediments are prevalent in benthic zones of headwater streams, but may also occur in the water column. The river continuum concept (RCC) predicts that water column processes become increasingly important with increasing stream size. We predicted that water column nutrient uptake increases with stream size, mirroring carbon/energy dynamics predicted by the RCC. We measured water column uptake of ammonium (NH4+), nitrate (NO3-), and soluble reactive phosphorus (SRP) in 1st through 5th order stream and river reaches (discharge: 50–68,000 L s−1) in three watersheds ranging from <1 to >70 % developed lands. We found that water column volumetric uptake (Uvol) of (NH4+), (NO3-), and SRP did not significantly differ among watersheds and we did not find any longitudinal patterns for Uvol. Uptake velocity (vf) of (NH4+) increased with stream size, whereas NO3- and SRP vf did not differ with stream size or among watersheds. Both Uvol and vf were related to water column metabolism and material suspended in the water column, but specific relationships differed among solutes and uptake metrics. Median water column vf across 15 sites was 4, 9, and 19 % of median whole-stream NH4+, NH4+, and SRP vf based upon a previous meta-analysis. Thus, although we could not demonstrate a generalized longitudinal pattern in water column nutrient uptake, water column processes can be important. An improved mechanistic understanding of the controls on uptake and the ultimate fate of nutrients will facilitate effective management and restoration for mitigating downstream nutrient export.
Global environmental change entails not only climatic alterations, but also changes in land use. Freshwater ecosystems are particularly sensitive to both of these changes, and their sustainable management requires better information on likely responses.
To examine the effects of climate and land use on the freshwater community, the distributions of stream macroinvertebrates of the Changjiang catchment in south‐east China were modelled. The present distributions of 72 taxa were predicted using environmental variables generated by regional climate, land‐use and hydrological models.
Hydrological predictors, sensitive to both climate and land use, were the most relevant predictors in the species distribution models ( SDM s), followed by land use.
The stream macroinvertebrates’ distributions were then projected for the period 2021 to 2050 using three different future scenarios: (i) climate change, (ii) land‐use change and (iii) climate and land‐use change combined.
Land‐use change was predicted to have the strongest negative impact on the community, with reductions in local richness (−20%), predicted diversity (−0.3%) and range size (−25%) and a general shift towards higher altitudes (+12%). The climate‐change scenario had a negative effect on predicted diversity (−0.1%) and resulted in a moderate altitudinal shift (+3%) along with increased richness (+15%) and range size (+19%). In the combined scenario, climate and land‐use changes counterbalanced each other to a certain degree, but had an overall detrimental effect.
The results underscore the high relevance of land‐use change in future distribution predictions, exemplify the possible effect of interactions between land use and climate on hydrology and indicate how such responses can vary among freshwater taxa. The model also allows the detection of key environmental variables, the identification of vulnerable species and the definition of their potential distributions. This information is essential to establishing effective management and conservation strategies and gives a more comprehensive insight into the possible effects of global environmental change on freshwater ecosystems.