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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)
... Taxonomic diversity is one of the most studied metrics in community ecological surveys . However, co-occurring species can exhibit different extents of "shared" habitat preference, functional features, or life history (Grigoropoulou et al., 2022;Richter et al., 2021;Wu et al., 2017). Considering species richness or taxonomic diversity could not capture or reflect sufficiently their ecological functions in the ecosystems, functional diversity (the value and the range of variability of functional traits) has been increasingly recommended although they showed some positive correlations with taxonomic diversity (Du et al., 2021;Meynard et al., 2011). ...
... The collected samples were preserved with 99.7% alcohol. In the laboratory, permanent diatom slides were made by hydrogen peroxide (30% H 2 O 2 solution) method (Wu et al., 2017) and a minimum of 300 valves were counted for each slide. Following the identifications of Hu et al. (1980) and Zhu and Chen (2000), benthic diatoms were identified to the lowest possible taxonomic level (mostly to species level). ...
... To investigate the relationships between species traits and the surrounding environment and calculate functional alpha and beta diversity, we collected data on three widely used diatom species trait categories (i.e., cell size, guild, and life forms) resulting in 15 traits using 0-1 for presence and absence (for details see Table S1 and previous studies: Passy, 2007;Rimet & Bouchez, 2012;Wu et al., 2017). ...
Understanding the processes and mechanisms that shape the distribution patterns and variations of biodiversity along spatial gradients continues to be a priority for ecological research. We focused on the biodiversity of benthic diatom communities within a large near‐natural watershed. The objectives are: (1) to explore the overall spatial patterns of benthic diatom biodiversity; (2) to investigate the effects associated with watercourse position and environmental variables, as well as both common and rare species on two facets (i.e., taxonomic and functional) of alpha and beta diversity; and (3) to unveil the mechanisms underlying their spatial variations. Alpha diversity indices along the stream watercourse showed a clear increasing trend from upstream to downstream sites. Results of random forest regression identified conductivity as the primary factor influencing functional alpha diversity, while elevation emerged as the predominant factor for taxonomic alpha diversity. Beta diversity partitioning revealed that taxonomic beta diversity generally exceeded functional beta diversity. These diversity measures exhibited different patterns along the watercourse position: taxonomic beta diversity remained relatively consistent along the watercourse, whereas functional total beta diversity and its two components of middle stream sites were lower than those of upstream and downstream sites. Functional beta diversity was sustained by dominant and common species, while rare species made significant contributions to taxonomic beta diversity. Both taxonomic and functional beta diversity and its components displayed a stronger influence from spatial factors than from local environmental, geo‐climatic, and nutrient variables. Collectively, taxonomic and functional alpha and beta diversity demonstrated distinct responses to the main environmental gradients and spatial factors within our catchment, highlighting their different insights into diatom diversity. Furthermore, research is required to assess the generalizability of our findings to similar ecosystems. In addition, this study presents opportunities for expansion to include other taxa (e.g., macroinvertebrates and fish) to gain a comprehensive understanding of the driving mechanisms behind stream biodiversity.
... 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). ...
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 hydrology (e.g. discharge, antecedent precipitation index), metal ions (e.g. Mg²⁺, Si²⁺) 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.
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.
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.
Synthesis. Our results highlighted the importance of the two facets of temporal beta diversity as well as their decomposition for exploring diversity patterns of riverine diatoms in relation to abiotic factors, particularly the environment regimes. Although a high temporal taxonomic divergence was detected, the high level of temporal trait convergence indicated that species turnover with similar biological traits occurred during our study period. Our study, for the first time, provides a new perspective into temporal beta diversity of daily riverine diatom communities, which has not yet been documented by previous freshwater studies.
... Thus, traits describing morphology, motility and life form are broadly used to infer diatom community functioning as they reflect not only the difference of dispersal ability but also the environmental adaptability (Passy et al. 2007;Rimet and Bouchez 2012;Wu et al. 2019). Most traits are co-regulated by disturbance intensity and resource supply (Wu et al. 2017). For example, studies show that large cell size, high profile and functional diversity decrease with increasing disturbance frequency and decreasing resource supply (Wu et al. 2017). ...
... Most traits are co-regulated by disturbance intensity and resource supply (Wu et al. 2017). For example, studies show that large cell size, high profile and functional diversity decrease with increasing disturbance frequency and decreasing resource supply (Wu et al. 2017). Thus, traitbased approaches allow for the assessment of important components of ecosystem structure and functioning such as high or low resource supply or disturbance (Hooper et al. 2005). ...
Arctic streams are highly sensitive to climate change and their biological communities are subjected to considerable changes. Benthic diatom communities are an important basal resource for higher trophic levels in these oligotrophic streams. However, our knowledge on how they respond to stream physicochemical characteristics in the Arctic is limited. The objective of this study was to describe diatom communities’ characteristics and assess how they are related to physicochemical parameters in 15 stream reaches in Northeast Greenland. Overall, we found 36 species across the streams from which Planothidium frequentissimum was the most abundant followed by Nitzschia palea. Based on physicochemical variables, including water nitrogen concentration, dissolved organic carbon concentrations and conductivity, the sampling sites were separated into three stream types: headwater, valley and glacial and snowpack runoff streams. Trait analyses showed that the majority of the species belonged to the ‘macro’ cell size category, strongly correlated with higher concentration of nitrogen. Diatom diversity was negatively affected by water velocity with glacial and snowpack runoff streams to be characterized by the lower number of species. Very small variation was explained solely by the physicochemical variables indicating that the distribution of diatom communities is influenced significantly by catchment characteristics. Overall, our study underlines the need for more comprehensive assessments in order to understand how diatom community composition is controlled by larger scale environmental variables in Arctic streams.
... The autoecology of particular species may be linked to its spatial structure, because of individual species' traits that affect their ability to colonize new habitats or their likelihood of extinction (Mcabendroth et al., 2005). In general, diatoms are usually categorized as low attachment, medium attachment and high attachment, and those with higher attachment ability are better adapted to highly disturbed environments compared to others (Passy, 2007;Rimet and Bouchez, 2012;Lange et al., 2015;Wu et al., 2017). Rich and widespread species with large niches and the ability to attach the substrates can support sustained populations in diverse stream habitats (Virtanen et al., 2011). ...
... taxonomic level (Wang et al., 2022a, Wang et al., 2022b. The attachment ability of diatom species described in Supplementary Table S1, which was judged on the basis of previous studies (Passy, 2007;Rimet and Bouchez, 2012;Lange et al., 2015;Wu et al., 2017). ...
Insight into the non-random distribution patterns of species in different regions is a foundational aim of research in community ecology and biogeography. The nestedness pattern, which investigates changes in species composition and abundance, has been widely used in numerous studies. However, studies on the nestedness of benthic diatoms are extremely rare, and consequently little has been mentioned of their assemblage mechanisms. To fill this gap, based on 168 benthic diatom species from 147 sampling sites in the Thousand Island Lake (TIL) catchment, we calculated their nestedness and niche width with the aim of i) analyzing the nestedness of benthic diatoms communities with different attachment abilities in TIL; ii) calculating niche width differences between nested and idiosyncratic species with different attachment abilities; iii) investigating the differences in alpha and beta diversity between nested and idiosyncratic sites; iv) examining whether environmental variables influencing the nestedness of benthic diatom communities are dependent on attachment ability. The results demonstrated a significant nestedness pattern in the benthic diatom metacommunity, and the sampling sites of low attachment species not only exhibited a nestedness pattern, but also with a lower nestedness value compared to the sampling sites of all species. Nested and idiosyncratic species differed in niche width, whereas differences between nested and idiosyncratic species of low attachment species were smaller. Additionally, significant differences in alpha and beta diversity were observed between nested and idiosyncratic sites. Furthermore, it was revealed that the nestedness of benthic diatom metacommunity in our study area were mostly influenced by local environmental variables. Our study contributes to the understanding of the significant nestedness observed in benthic diatom metacommunity in TIL, highlighting its relevance to biodiversity conservation efforts.
... 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
... Functional indicators have been used to assess various disturbances, including land use change (Verberk et al., 2013;Masese et al., 2014a;Fierro et al., 2017;Sitati et al., 2021a,b), increased fine sediment deposition (Wagenhoff et al., 2012;Ntloko et al., 2021;Odume, 2022), and ecological condition assessments (Merritt et al., 2017). Although most of these studies are based on macroinvertebrates, several studies have also investigated functional structure in fishes (trophic groups or environmental guilds; Welcomme et al., 2006;Hoeinghaus et al., 2007), algae or periphyton (Wu et al., 2017;Graco-Roza et al., 2021) and macrophytes (Ali et al., 2021a,b;Feio et al., 2017). The functional approach presents several advantages. ...
Multiple stressors are increasingly recognized as major concerns in the sustainability of aquatic ecosystems in Africa and the myriad of ecosystem services deriving to millions of people on the continent. Stressors commonly interact to affect environmental conditions (e.g., habitat and water quality), individual species, communities, and ecological functions. Because of the complex ecological responses (that is, additive, antagonistic, and synergistic effects) they elicit, it is often challenging to develop a biomonitoring program that is effective and accurate at identifying and measuring their effects. However, with economic development in Africa, multiple stressors, such as chemical, nutrient, and organic pollution, as well as hydromorphological alterations, are growing accordingly. Thus, there is a need for evidence-based and effective natural resource management and ecosystem protection to face emerging challenges. However, despite the advancement in knowledge, progressive laws and regulations for the protection of the environment, many African countries and regions lack biomonitoring programs for assessing and monitoring ecological conditions in rivers. This chapter reviews advances made in the biomonitoring of multiple stressors in river ecosystems. Many regions of the world developed regional or national biomonitoring programs, but in Africa, most countries, except South Africa, rely on physicochemical parameters to guide water resources management and conservation. The chapter explores the range of biological communities used in bioassessment programs and the stressors against which they are best suited. The chapter further presents case studies on developing regional indices for use at the national level (e.g., Tanzanian River Scoring System, TARISS). The chapter also discusses the level of adoption of biomonitoring for the management and conservation of aquatic ecosystems in Africa and the challenges (e.g., capacity, legal and institutional frameworks) faced in developing and adopting such indices. We also discuss approaches for promoting biomonitoring and overcoming the challenges that bioindication as a tool for environmental management and conservation face. Additionally, we vouch for advancing biomonitoring in Africa to address challenges and enhance environmental management and conservation efforts. By adopting bioindication and implementing appropriate strategies, we can deepen our understanding of ecosystem health and make informed decisions for the sustainable management of aquatic ecosystems across the continent.
... These studies have revealed easily discernible variation in aquatic assemblages, including fishes, benthic macroinvertebrates, macrophytes and algae, in relation to multiple anthropogenic disturbances. Previous studies have also shown significant advancements in taxonomy-based approach in certain areas, such as improving the efficacy of biomonitoring and biological evaluation (Beck et al. 2013;Hitt and Angermeier 2011;Morse et al. 2007;Wu et al. 2017). However, during recent decades, increasing numbers of studies pointed out some shortcomings of taxonomic approach, including regional independence (Göthe et al. 2017;Heino 2013) and highlighted the need of incorporating functional trait information into biological monitoring and assessment programs (Dolédec et al. 2006;Menezes et al. 2010). ...
Measures based on functional traits are often capable of indicating local environmental conditions and are thus considered promising tools for environmental monitoring and assessment programs. Benthic macroinvertebrates exhibit a diverse array of functional traits that can be used for assessing ecological quality of freshwater ecosystems. However, the associations between functional structure of macroinvertebrates and anthropogenic disturbances remain inadequately understood, especially for floodplain lakes. In our study, we compared the response of taxonomic and functional trait composition of macroinvertebrates to anthropogenic eutrophication in lake ecosystems of the Yangtze River floodplain. We found that the relative abundance of Mollusca, Gastropods, Bithyniidae, Bivalvia and Ephemeroptera showed significant differences among four lake groups (river-connected, macrophyte-dominated, macrophyte-algal transitional and algal-dominated lakes) subjected to different disturbance levels from mesotrophic to highly eutrophic. Using a trait-based approach, we found 13 categories, belonging to seven traits, showed significant differences observed among lake groups. Regarding influence of environmental factors on macroinvertebrate assemblages, both taxonomic measures and functional traits were mainly affected by water quality factors associated with eutrophication. However, the number and specific key environmental factors varied between measures of functional traits and taxonomic composition. The taxonomic composition responded to more environmental factors (seven factors: Chl a, CODmn, TN, area, water depth, NH4⁺-N and conductivity), but showed lower explained variation (24.4%) compared with functional structure (three factors: aquatic vegetation coverage, conductivity and Chl a, 36.4% explained variation). Furthermore, spatial factors only affected taxonomic composition, but they were not correlated with functional composition. In general, our study showed that functional trait structure of macroinvertebrate assemblages responded more sensitively and reliably to eutrophication than measures based on taxonomic composition in floodplain lakes. Thus, we recommend the incorporation of macroinvertebrate functional trait information into biomonitoring programs for floodplain lakes and other aquatic ecosystems, as it can be considered as a more promising approach than taxonomy-based approaches in biomonitoring programs.
... Investigations on the toxicity of nanomaterials, aimed at evaluating the potential impacts of copper oxide nanoparticles, revealed that a potential hazard is posed to a long list of nontarget aquatic flora and fauna ranging from photosynthetic organisms to, aquatic invertebrates, that include bacteria [29,[50][51][52], algae [12,53,54], aquatic plants [55][56][57][58], cnidarians [59], oligochaetes [39,60,61], bivalves [62][63][64], and gastropods [65][66][67]. They are considered useful indicators in toxicology and monitoring of aquatic atmosphere [68,69]. They share many close metabolic, physiological, and close evolutionary relation with more complex lifeforms, such as our own species [70][71][72]. ...
Purpose of Review
Nanotechnology has transformed various aspects of contemporary life, technology, and research. This is evident in the rising global demand for and use of nanoparticles, leading to a corresponding increase in their discharge into the environment through diverse human activities. In the last few years, the rampant use of copper oxide nanoparticles (CuO-NPs) has piqued interest.
Recent Findings
CuO-NPs are widespread and tend to remain in the environment, enabling them to increase in concentration through the food chain and ultimately impact human health. When aquatic organisms are exposed to CuO-NPs, it may cause oxidative stress. This can change proteins, cause lipid peroxidation, and damage DNA. This can ultimately cause cytotoxicity, genotoxicity, and epigenetic changes.
Summary
CuO-NPs produce reactive oxygen species (ROS), which can have various consequences for organisms and the environment. The objective of the review was to introduce a refreshed audit on the ecotoxicity, a comparison of systems related to CuO-NPs, and an assessment of the safe limit to prevent chronic toxicity across different taxa: aquatic invertebrates, plants, and algae. Additionally, the article briefly discusses the existing knowledge gaps in this area and makes recommendations for future research.
... The topics in the most influential articles (Table 2) were centered in cyanobacterial blooms, climate change, nutrients and control (Paerl & Paul, 2012;Xu et al., 2015;Huisman et al., 2018), eutrophication (Smith & Schindler, 2009), sediments, phosphorus, nitrogen, and phytoplankton (Sondergaard et al., 2003;Xu et al., 2010;Wu et al., 2017;Ho et al., 2019). ...
Aim This study aims to analyze the scientific literature on phytoplankton in assessing lake water quality, based on bibliometric and network techniques. Methods PRISMA criteria were adopted to produce reliable results. The Scopus and Web of Science databases were consulted to retrieve the documents to be studied. The number of publications, citations and bibliographic coupling were techniques used to identify relevant journals, countries, authors, and articles. The conceptual evolution was analyzed by keywords co-occurrence and thematic mapping. Results Based on 2429 documents selected from the 1973-2023 annual period, the main results indicated 519 journals, 6450 authors, 54907 references, and 4844 keyword authors, among others. The annual growth index was 10.27%, reflecting the upward trend at the time. Erick Jeppesen resulted as the top influential author, China leaded in publications and collaborations with The United States of America. Hydrobiologia was the top journal. Top influential articles content theme related to cyanobacterial blooms. According to the results of the analysis of the conceptual framework, phytoplankton, water quality, eutrophication, and cyanobacteria were the most relevant themes. Furthermore, the trending topics were mainly climate change and degradation. Conclusions This comprehensive analysis allowed us to interpret the development of research related to the subject of assessing lake water quality.
... Cell size c1 < 100 μm 3 Berthon et al. (2011), Rimet and Bouchez (2012) and Wu et al. (2017) Yes or no Soininen et al. (2016) where M jk is MacArthur and Levins' niche overlap of Species k on Species j; p ij is proportion that Resource i constitutes of the total resources used by species j; p ik is proportion that Resource i constitutes of the total resources used by Species k; n is total number of resource states. Niche width and niche overlap were calculated by the niche.width ...
Context Freshwater primary productivity is threatened by the decline in biodiversity associated with nutrient enrichment, but there is still uncertainty about how the biodiversity and productivity relationship (BPR) varies with the trophic states. Aims We aimed to examine the variation of benthic diatom BPRs in three plateau lakes with different trophic states and their underlying driving mechanisms. Methods We examined the relationship between diatom taxonomic and functional diversity, niche width, and niche overlap with productivity. Key results The taxonomic and functional diversity, niche width and productivity of benthic diatoms were highest in the mesotrophic lake. The benthic diatom BPRs were linear and positive, with the slope of BPRs being the lowest in eutrophic lake. Motile, non-attached and small-sized diatoms were dominant in eutrophic lake. Nutrient concentrations indirectly affected primary productivity by influencing algal community structure, niche width and biodiversity change. Conclusions Diatom productivity and diversity showed a positive relationship, but nutrient enrichment weakened this relationship. By combining taxonomic and functional diversity indices, supplemented by niche analysis, we can further understand the variation of diatom productivity. Implications The results provide a basis for predicting the changes in BPRs of benthic diatoms in the littoral zone with different trophic states.
... This occurs as different species can display similar functional traits over broad temporal or spatial scales (Peláez & Pavanelli, 2019). Consequently, some reports have recommended that traits-based rather than taxa-based diatom indicators are more suitable for river biomonitoring (B-Béres et al., 2016;Wu et al., 2017). ...
Unraveling biodiversity patterns and their driving processes is paramount in ecology and biogeography. However, there remains a limited understanding regarding the underlying mechanisms of community assembly, particularly in alpine streams where significant elevation gradients and habitat heterogeneity exist. We investigated the patterns and drivers of beta diversity, explicitly focusing on taxonomic and functional diversity, in the three parallel rivers region in China. We employed a beta diversity partitioning approach to examine the turnover and nestedness components of beta diversity and further deconstructed the diatom community into attached and unattached groups. Our results revealed distinct diversity patterns and drivers for taxonomic and functional beta diversity. Specifically, taxonomic beta diversity was mainly driven by the turnover component affected by spatial processes, whereas functional beta diversity was dominated by the nestedness component affected by environmental processes. Furthermore, our analysis of the division of the whole communities demonstrated that the varying responses of benthic diatoms with different attached abilities to environmental filtering, dispersal limitation, and directional flow were the essential reasons for shaping the biodiversity patterns of species turnover and functional nestedness in the alpine stream. Our findings suggested that partitioning beta diversity and dividing the entire community can more deeply infer underlying community assembly processes, thereby providing valuable insights into understanding biodiversity patterns, drivers, and conservation strategies.
... Second, from the biotechnologist perspective, they offer means to help society shift from its fossil-based, doomed, paradigm to a bio-based, sustainable, one [7]. Third, from the ecologist's standpoint, their pivotal place in the environment makes them valuable advanced bio-sensors to document the tremendous anthropic pressure humanity is exerting on the planet [8,9]. ...
... The determination of the effects of herbicides used for chemical plant protection on algal species is crucial for the toxicological assessment of herbicide formulations. Various algal species are widely used for environmental biological monitoring [62] and bioremediation activities [63]. The different effects of glyphosate, its metabolite, coformulants, and/or commercial herbicide formulations on green algae and cyanobacterial species are summarized in Table 1 partially based on our previous review about aquatic ecotoxicity of glyphosate, its formulations, and co-formulants [20]. ...
The occurrence of the market-leading glyphosate active ingredient in surface waters is a globally observed phenomenon. Although co-formulants in pesticide formulations were considered inactive components from the aspects of the required main biological effect of the pesticide, several studies have proven the high individual toxicity of formulating agents, as well as the enhanced combined toxicity of the active ingredients and other components. Since the majority of active ingredients are present in the form of chemical mixtures in our environment, the possible combined toxicity between active ingredients and co-formulants is particularly important. To assess the individual and combined phytotoxicity of the components, glyphosate was tested in the form of pure active ingredient (glyphosate isopropylammonium salt) and herbicide formulations (Roundup Classic and Medallon Premium) formulated with a mixture of polyethoxylated tallow amines (POEA) or alkyl polyglucosides (APG), respectively. The order of acute toxicity was as follows for Roundup Classic: glyphosate < herbicide formulation < POEA. However, the following order was demonstrated for Medallon Premium: herbicide formulation < glyphosate < APG. Increased photosynthetic activity was detected after the exposure to the formulation (1.5–5.8 mg glyphosate/L and 0.5–2.2 mg POEA/L) and its components individually (glyphosate: 13–27.2 mg/L, POEA: 0.6–4.8 mg/L), which indicates hormetic effects. However, decreased photosynthetic activity was detected at higher concentrations of POEA (19.2 mg/L) and Roundup Classic (11.6–50.6 mg glyphosate/L). Differences were demonstrated in the sensitivity of the selected algae species and, in addition to the individual and combined toxicity of the components presented in the glyphosate-based herbicides. Both of the observed inhibitory and stimulating effects can adversely affect the aquatic ecosystems and water quality of surface waters.
... While recognizing advances in understanding diatom biology and ecology, this article points out remaining gaps in knowledge about diatom responses to environmental stressors and their roles in nutrient cycling. It advocates for expanded research efforts to address these gaps, aiming to enhance our understanding of aquatic ecosystems and refine assessment methodologies [1,76,77]. ...
This paper reviews the evolution and integration of diatom-based water quality assessments with environmental DNA (eDNA) techniques for advancing river ecosystem health evaluations. Traditional methods, relying on microscopy and diatom indices, have significantly contributed to our understanding of aquatic ecosystems but face challenges such as the need for taxonomic expertise and the labor-intensive nature of sample collection. Recent advancements in molecular biology, particularly eDNA analysis, offer opportunities to overcome these limitations, providing more accurate and comprehensive assessments. This study highlights the benefits of combining traditional microscopy with modern molecular techniques, enhancing the precision and efficiency of water quality evaluations. By addressing the challenges of standardizing methods and improving species identification through comprehensive reference libraries and advanced bioinformatics tools, this integrated approach aims to refine and advance the effectiveness of diatom-based strategies in monitoring and managing river health amidst environmental changes.
... Microalgae of phytoplankton and periphyton are key primary producers in shallow lakes (Wetzel, 1964;Robinson et al., 1997) and provide helpful information on the general ecology and water quality in aquatic ecosystems (Kireta et al., 2012;Lemley et al., 2016;Wu et al., 2017). Both communities compete for nutrients and light resources (Vadeboncoeur et al., 2001;Sánchez et al., 2016;Kazanjian et al., 2018). ...
Eutrophication is a global environmental problem in aquatic ecosystems, mainly caused by increased nutrient loads (nitrogen and phosphorus). Phytoplankton and periphyton responses to the nutrients increase and temporal variation may be related to mutual seeding and/or variable environmental constraints. Each of these communities may be useful for characterizing and monitoring eutrophication processes. However, little information exists about the simultaneous responses or interactions between such communities during eutrophication, even less in high-altitude tropical lakes such as Lake Titicaca. Here, we first established a eutrophication gradient with stable isotopes (δ15N and δ13C) and physicochemical variables in a shallow bay of Lake Titicaca. Later, we analyzed the shifts in taxonomic and morphological forms of phytoplankton and periphyton colonizing the underwater stems of totora (Schoenoplectus californicus ssp. tatora), an emergent aquatic macrophyte, along the eutrophication gradient. There is a clear turnover (groups, genera, and morphological forms) in phytoplankton and periphyton and decreased biodiversity along the eutrophication gradient. Gomphonema genus relative abundance increase with eutrophication in both communities, while Achnanthidium abundance decreases. However, other genera behave differently in each community, allowing for the identification of specific bioindicators of eutrophication for phytoplankton (Oscillatoria, Spirogyra, and Euglena) and periphyton (Oedogonium, Stigeoclonium, and Characium). They share genus composition with some taxa showing similar behaviors, thus interactions between phytoplankton and periphyton may exist. We also believe that each compartment can act as a seeding reservoir for the other, though remaining independent to some extent.
... 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.
... High sensitivity to environmental changes, the ease of collecting and the wellknown autecology (Van Dam et al. 1994;Wu et al. 2017) of freshwater diatom communities, can be easily transferred to soil diatoms as well. Moreover, ecological studies of diatom communities on soils are also quite responsive as well as sensitive to several environmental variables such as soil moisture and pH (Lund 1945;Hayek and Hulbary 1956;Van De Vijver and Beyens 1998;Van Kerckvoorde et al. 2000;Van de Vijver et al. 2002;Souffreau et al. 2010;Antonelli et al. 2017). ...
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
... 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.
Small hydropower plants (SHPs) play a crucial role in clean energy production, yet they also disrupted river ecosystems. To achieve a balance between energy production, biodiversity conservation, and ecosystem integ-rity, it is essential to study how aquatic organisms respond to SHP operations. Prior researches had shown that SHP operations have the most significant impact in dewatering sections, but studies often overlook the influence of ecological flows. Therefore, our study focused on the Oujiang river basin, where SHPs are prevalent, to investigate the effects of SHP operations on riverine algae under ecological flow and conditions of intensive exploitation. We compared species composition, traits composition, and diversity indices across different river sections and used multiple linear regression models to identify the main drivers influencing algal communities. The results showed: 1) SHP operations significantly altered hydrological and physicochemical conditions in reservoir sections, leading to distinct differences in algal community composition and traits; 2) physicochemical factors had the greatest influence on diversity indices, driving the observed patterns; and 3) SHP operations indirectly affected algal communities through interspecific interactions, particularly with macroinvertebrates like Scrapers. These findings emphasize the need for stronger governance and enforcement to ensure adequate ecological flow releases by SHPs, especially under growing environmental and climate challenges.
Exploring extremotolerant and extremophilic microalgae opens new frontiers in sustainable biotechnological applications. These microorganisms thrive in extreme environments and exhibit specialized metabolic pathways, making them valuable for various industries. The study focuses on the ecological adaptation and biotechnological potential of these microalgae, highlighting their ability to produce bioactive compounds under stress conditions. The literature reveals that extremophilic microalgae can significantly enhance biomass production, reduce contamination risks in large-scale systems, and produce valuable biomolecules such as carotenoids, lipids, and proteins. These insights suggest that extremophilic microalgae have promising applications in food, pharmaceutical, cosmetic, and biofuel industries, offering sustainable and efficient alternatives to traditional resources. The review concludes that further exploration and utilization of these unique microorganisms can lead to innovative and environmentally friendly solutions in biotechnology.
Chlorella vulgaris is of great importance in numerous exploratory or industrial applications (e.g., medicals, food, and feed additives). Rapid quantification of algal biomass is crucial in photobioreactors for the optimization of nutrient management and the estimation of production. The main goal of this study is to provide a simple, rapid, and not-resource-intensive estimation method for determining the algal density of C. vulgaris according to the measured parameters using UV–Vis spectrophotometry. Comparative assessment measurements were conducted with seven different methods (e.g., filtration, evaporation, chlorophyll a extraction, and detection of optical density and fluorescence) to determine algal biomass. By analyzing the entire spectra of diluted algae samples, optimal wavelengths were determined through a stepwise series of linear regression analyses by a novel correlation scanning method, facilitating accurate parameter estimation. Nonlinear formulas for spectrometry-based estimation processes were derived for each parameter. As a result, a general formula for biomass concentration estimation was developed, with recommendations for suitable measuring devices based on algae concentration levels. New values for magnesium content and the average single-cell weight of C. vulgaris were established, in addition to the development of a rapid, semiautomated cell counting method, improving efficiency and accuracy in algae quantification for cultivation and biotechnology applications.
Benthic diatoms are the dominant part of phytobenthos and key primary producers in rivers. Apart from being one of the most common and important BQEs for the purposes of Water Framework Directive (WFD), their distribution patterns across Greek rivers have not been studied so far. The scope of this study was to describe taxonomic and functional patterns of benthic diatoms in Greek rivers and to identify the relationships between environmental parameters and diatom functional traits. To achieve this goal, we compiled benthic diatom and environmental data from three years of the National Monitoring Programme (2018-2020) and we formulated both a taxonomy-based and a functional trait-based dataset. We tested spatial patterns based on biogeographical areas formerly suggested for freshwater fish. Taxonomic data suggested a strong geographical pattern, where diatom assemblages from islands were distinct from assemblages in the mainland. On the other hand, functional patterns could be better explained based on environmental variables' variation. The results discussed herein could have implications for biomonitoring, as taxonomic quality indices applied so far could be biased of biogeographical patterns.
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.
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.
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.
Introduction Assessments of environmental conditions in rivers and streams using diatoms have a long history in which two basic conceptual approaches emerged. First, based on the work of Kolkwitz and Marsson (1908), autecological indices were developed to infer levels of pollution based on the species composition of assemblages and the ecological preferences and tolerances of taxa (e.g. Butcher, 1947; Fjerdingstad, 1950; Zelinka and Marvan, 1961; Lowe 1974; Lange-Bertalot, 1979). Second, Patrick’s early monitoring studies (Patrick, 1949; Patrick et al., 1954; Patrick and Strawbridge, 1963) relied primarily on diatom diversity as a general indicator of river health (i.e. ecological integrity), because species composition of assemblages varied seasonally and species diversity varied less. The conceptual differences in these two approaches really address two different goals for environmental assessments, one inferring pollution levels and the other determining biodiversity, a more valued ecological attribute (Stevenson, 2006). Thus, the concepts and tools for assessing ecosystem health and diagnosing causes of impairment in aquatic habitats, particularly rivers and streams, were established and developed between ∼50 and 100 years ago. Today, diatoms are being used to assess ecological conditions in streams and rivers around the world (Asai, 1996; Kelly et al., 1998; Wu, 1999; Lobo et al., 2004; Wang et al., 2005; Chessman et al., 2007; Taylor et al., 2007; Porter et al., 2008). They have become valuable elements in large-scale national and international assessment programs of the United States and Europe (e.g. Kelly et al. 2009a).
The value of algae as bio-indicators has already been recognized in the
mid of 19th century, however, little attention has been paid to the application
of phytoplankton in ecological evaluation of rivers. In this review, we found
that studies of phytoplankton showed a long-term increasing trend from 1961
to 2014. However, most of these studies were carried out in oceans, coastal
areas, gulfs, lakes and reservoirs, while very few of them (14%) focused on
riverine phytoplankton. As well as modeling studies, the utilizations of riverine
phytoplankton as bio-indicator are still poorly investigated and the available
few studies were those mainly published after the year of 2000. Therefore,
we describe 28 algal indices of riverine phytoplankton potentially used for bioassessment,
which belong to community index, growth form, diversity index and
biotic index. We also elucidate the calculation and classification methods of 5
common indices proposed in 1950s (Shannon’s diversity index, saprobity index)
and nowadays (trophic diatom index, Q index and phytoplankton index). Finally,
four future directions and applications of riverine phytoplankton research were
discussed and proposed: 1) standardization of sampling methods, 2) relations
with environmental factors, 3) bio-indication and 4) modeling and predicting
dynamics of riverine phytoplankton
