Algal Community Structure Research Articles

Application of Environmental DNA Metabarcoding to Differentiate Algal Communities by Littoral Zonation and Detect Unreported Algal Species

Coastal areas are the most biologically productive and undoubtedly among the most complex ecosystems. Algae are responsible for most of the gross primary production in these coastal regions. However, despite the critical importance of algae for the global ecosystem, the biodiversity of many algal groups is understudied, partially due to the high complexity of morphologically identifying algal species. The current study aimed to take advantage of the recently developed technology for biotic community assessment through the high-throughput sequencing (HTS) of environmental DNA (eDNA), known as the “eDNA metabarcoding”, to characterize littoral algal communities in the Northern Gulf of Mexico (NGoM). This study demonstrated that eDNA metabarcoding, based on the universal plastid amplicon (UPA) and part of the large nuclear ribosomal subunit (LSU) molecular markers, could successfully differentiate coastal biotic communities among littoral zones and geographical locations along the shoreline of the NGoM. The statistical significance of separation between biotic communities was partially dependent on the dissimilarity calculation metric; thus, the differentiation of algal community structure according to littoral zones was more distinct when phylogenetic distances were incorporated into the diversity analysis. Current work demonstrated that the relative abundance of algal species obtained with eDNA metabarcoding matches previously established zonation patterns for these species. In addition, the present study detected molecular signals of 44 algal species without previous reports for the Gulf of Mexico, thus providing an important, molecular-validated baseline of species richness for this region.

Differences in seasonal dynamics, ecological driving factors and assembly mechanisms of planktonic and periphytic algae in the highly urban Fenhe River

BackgroundAlgae play important roles in urban river ecosystems and are the cornerstones of most water quality monitoring programs. Thus, a better understanding of algal community dynamics is needed to support sustainable management of water resources in urban rivers.ResultsIn this study, we quantified the seasonal variations in planktonic and periphytic algal community structure in the highly urban Fenhe River and identified environmental factors affecting algal community structure and diversity. We monitored planktonic (drifting) and periphytic (attached) algal communities in the Taiyuan section of the Fenhe River over one year. The results indicated that Cyanophyta was the dominant phylum in both communities, followed by Bacillariophyta and Chlorophyta. Significant differences were observed in the composition of the planktonic and periphytic algal communities. In particular, the periphytic algal community was more diverse than the planktonic community. Water temperature and pH were the main environmental factors affecting planktonic and periphytic algal community structure, respectively, while nutrients were the most significant factor affecting planktonic and periphytic algal diversity. Ecological modeling indicated that the variations in the algal communities of the Fenhe River are mainly driven by stochastic processes. A co-occurrence network developed for the communities displayed positive interactions between the planktonic and periphytic algae.ConclusionsThese findings deepen our understanding of the seasonal interaction between planktonic and periphytic algae and the driving factors affecting community structure in the Fenhe River. They also provide a theoretical basis for the managing and protecting water resources in urban river ecosystems.

Eutrophication weakens the positive biodiversity–productivity relationship of benthic diatoms in plateau lakes

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.

Inter-algal associations and nutrients linked by Scenedesmus and Desmodesmus structure eukaryotic algal communities.

Eutrophication reduces the variability of the community composition of plankton. However, the mechanisms underlying the diversity and restructuring of eukaryotic algal communities remain unknown. This study analysed the diversity and compositional patterns of algal communities in shallow eutrophic lakes. It investigated how these communities were modified by key genera through mediating inter-algal associations under the influence of abiotic factors. Inter-algal associations explained more variance in algal communities than environmental variables, and variation in composition and diversity was primarily derived from Scenedesmus, Desmodesmus and Cryptomonas, rather than nutrients. Scenedesmus and Desmodesmus were positively correlated with the genera of Chlorophyta and formed the hub of the algal association network. When the relative abundance of Scenedesmus and Desmodesmus increased from 0.41% to 13.74%, communities enriched in biomarkers of Bacillariophyta, Chrysophyceae and Cryptophyta transitioned to communities enriched in biomarkers of Chlorophyta. Moreover, negative associations between the Chlorophyta hub genera and other non-Chlorophyta genera increased. High concentrations of total phosphorus altered the composition of algal communities by increasing the abundance of Scenedesmus and Desmodesmus, which in turn had cascading effects through inter-algal associations. Additionally, algal communities with higher abundances of Scenedesmus and Desmodesmus were more susceptible to the effects of total phosphorus. Our study suggested that inter-algal associations, centred on Scenedesmus and Desmodesmus, had a greater influence on algal diversity and community structure than other factors. Nutrient levels were not a direct driver of algal diversity and community structure adjustments, but acted indirectly by enhancing the influence of Scenedesmus and Desmodesmus.

Response of the algal-bacterial community to thermal stratification succession in a deep-water reservoir: Community structure, co-assembly patterns, and functional groups

Thermal stratification in lakes and reservoirs may intensify and become more persistent with global warming. Periodic thermal stratification is a naturally occurring phenomenon that indicates a transition in aquatic ecosystem homeostasis, which could lead to the deterioration of water quality and impaired aquatic communities. However, the responses of communities and associated nutrient cycling processes to periodic thermal stratification are still poorly understood. This study delved into the changes in water quality, algal-bacterial communities, and functional diversity influenced by thermal stratification succession, and their relationship with nutrient cycling. The results indicated that the apparent community dynamics were driven by environmental factors, with ammonium (NH4+) and nitrate (NO3−-N) being the most important factors that influenced the algal and bacterial community structure, respectively. Ecological niche widths were narrower during thermal stratification, exacerbating the antagonism of the communities, and stochastic processes dominated community assembly. Then, the complexities of the co-occurrence network decreased with succession. Algal community assembly became more deterministic, while bacterial assembly became more stochastic. Moreover, the roles of algal-bacterial multidiversity in nutrient cycling differed: bacterial diversity enhanced nutrient cycling, whereas algal diversity had the opposite effect. These findings broadened our understanding of microbial ecological mechanisms to environmental change and provided valuable ecological knowledge for securing water supplies in drinking water reservoirs.

Optimizing performance efficiency of algal-bacterial-based wastewater treatment system using response surface methodology

Developing wastewater treatment technologies is crucial for enhancing treatment efficiency and promoting the reuse of treated water. In this article, the Algal-Bacterial integrated system (ABIS) is employed to treat municipal wastewater collected from the Zenin wastewater treatment plant in Giza governorate, Egypt. This system relies on the synergy between heterotrophic bacteria and microalgae to form a biofilm capable of absorbing contaminants from the wastewater. The main objective of this study is to optimize the factors influencing the treatment efficiency using response surface methodology derived from the experimental design software of Design Expert 6.0.8. The optimal results revealed that using an absorber amount of 0.18 g/L for a hydraulic retention time of 1.4 d provides removal efficiency of BOD, COD, TSS, and turbidity are 88.57%, 82.7 %, 94.90%, and 95.91%, respectively. These findings were experimentally and statistically verified with an accuracy exceeding a 95% confidence interval and 95% prediction interval. The physicochemical characteristics, algal community structure, as well as the density of total coliform, fecal coliform, and Escherichia coli (E. coli), were determined for the treated wastewater and compared to the Egyptian code of practice for the use of treated municipal wastewater for agricultural purposes to assess its suitability for unrestricted irrigation.

Bioaccumulation, transfer, and impacts of microplastics in aquatic food chains

Plastics have become a pervasive global contaminant since the mid-20th century, causing harm to organisms at all levels. Preventative measures to reduce plastic pollution and awareness-raising campaigns about the damaging effects of plastic debris on the environment and its inhabitants are crucial; however, most plastic assessments focus on singular trophic levels. Microplastics, tiny plastic particles ranging from 25 μm to 5 mm, have emerged as a widespread form of pollution found in ecosystems worldwide. They can enter the environment directly or through the breakdown of larger plastic debris and are thought to be mistaken for food by foraging animals. This leads to microplastics circulating through ecosystems via direct and indirect consumption, ultimately impacting even higher-order predators. Here, we assess the impacts of microplastics on Chlorophyll a concentrations, algal community structure, copepod survivorship, and fish behavior in experimental trials, in addition to simulated top-predator foraging success on plastic-exposed fish. Our results indicate that microplastics have detrimental effects on algal growth and copepod survival. We also observed the trophic transmission of small plastic spheres from copepods to fish predators, highlighting a concerning pathway for microplastic pollution within aquatic ecosystems, where fish consumed plastics through direct and indirect means. Primary consumers, like copepods, face dual pressures from top-down forcing, as they are preferred over plastic particles as food sources, and bottom-up resource depletion, as algal food supplies can be limited by microplastic exposure. Our findings demonstrate the system-wide impacts that can occur when microplastics are included in food chains and underscore the urgent need for comprehensive strategies to mitigate the entry of plastic debris into aquatic ecosystems.

Salamander loss alters montane stream ecosystem functioning and structure through top‐down effects

AbstractAmphibians are among the most endangered taxa worldwide, but little is known about how their disappearance can alter the functioning and structure of freshwater ecosystems, where they live as larval stages. This is particularly true for urodeles, which often are key predators in these ecosystems. The fire salamander (Salamandra salamandra) is a common predator in European fresh waters, but the species is declining due to habitat loss and the infection by fungal pathogens. We studied the consequences of fire salamander loss from three montane streams, by comparing two key ecosystem processes (periphyton accrual and leaf litter decomposition) and the structure of three communities (periphytic algae, aquatic hyphomycetes and invertebrates) using stream enclosures with and without salamander larvae. Salamander loss did not cause changes in invertebrate abundance or community structure, except for one stream where abundance increased in the absence of salamander larvae. However, salamander loss led to lower periphyton accrual, changes in algal community structure and slower leaf litter decomposition, with no associated changes in fungal communities or microbial decomposition. The changes observed may have been caused by release of salamander predatory pressure on invertebrates, which could have promoted their grazing on periphyton, in contrast to their preference for leaf shredding in the presence of salamander. Our study demonstrates an important role of salamander larvae in montane streams through top‐down control of lower trophic levels and thus in regulating key stream ecosystem processes. Our results highlight the need for improving protection measures for amphibians to prevent these alterations on ecosystem structure and function.

Distribution patterns and co-occurrence network of eukaryotic algae in different salinity waters of Yuncheng Salt Lake, China

The community structure and co-occurrence pattern of eukaryotic algae in Yuncheng Salt Lake were analyzed based on marker gene analysis of the 18S rRNA V4 region to understand the species composition and their synergistic adaptations to the environmental factors in different salinity waters. The results showed indicated that the overall algal composition of Yuncheng Salt Lake showed a Chlorophyta-Pyrrophyta-Bacillariophyta type structure. Chlorophyta showed an absolute advantage in all salinity waters. In addition, Cryptophyta dominated in the least saline waters; Pyrrophyta and Bacillariophyta were the dominant phyla in the waters with salinity ranging from 13.2 to 18%. Picochlorum, Nannochloris, Ulva, and Tetraselmis of Chlorophyta, Biecheleria and Oxyrrhis of Pyrrophyta, Halamphora, Psammothidium, and Navicula of Bacillariophyta, Guillardia and Rhodomonas of Cryptophyta were not observed in previous surveys of the Yuncheng Salt Lake, suggesting that the algae are undergoing a constant turnover as the water environment of the Salt Lake continues to change. The network diagram demonstrated that the algae were strongly influenced by salinity, NO3−, and pH, changes in these environmental factors would lead to changes in the algal community structure, thus affecting the stability of the network structure.

Different seasonal dynamics, ecological drivers, and assembly mechanisms of algae in southern and northern drinking water reservoirs

The role of environmental factors on the community structure of algae has been intensively studied, but there are few analyses on the assembly mechanism of the algal community structure. Here, changes in the community structure of algae in different seasons, the effects of environmental variables on the algal community structure, and the assembly mechanism of the algal community structure in northern and southern reservoirs were investigated in this study. The study revealed that Bacillariophyta, Cyanophyta, and Chlorophyta were the predominant algal species in the reservoirs, with Bacillariophyta and Cyanophyta exhibiting seasonal outbreaks. Compared to the northern reservoirs, the algal diversity in the southern reservoirs was greater. The diversity and algal community structure could be significantly impacted by variations in water temperature and nitrogen level. According to the ecological model, the interaction among algal communities in reservoirs was primarily cooperation. The key taxa in the northern reservoirs was Aphanizomenon sp., while the outbreak in the southern reservoirs was Coelosphaerium sp. The community formation pattern of reservoirs was stochastic, with a higher degree of explanation observed in the southern reservoirs compared to the northern reservoirs. This study preliminarily explored the assembly mechanism of the algal community, providing a theoretical basis for the control of eutrophication in drinking water reservoirs.

Algal symbiont genera but not coral host genotypes correlate to stony coral tissue loss disease susceptibility among Orbicella faveolata colonies in South Florida

Stony coral tissue loss disease (SCTLD) has spread throughout the entirety of Florida’s Coral Reef (FCR) and across the Caribbean, impacting at least 30 coral species. The threatened hermatypic coral, Orbicella faveolata, demonstrates intraspecific variation in SCTLD affectedness with some colonies experiencing chronic disease lesions, while other nearby O. faveolata colonies appear unaffected with no disease signs over long monitoring periods. This study evaluated potential genotypic underpinnings of variable disease responses to SCTLD by monitoring and sampling 90 O. faveolata colonies from southeast Florida and the lower Florida Keys. High resolution analyses of >11,000 single nucleotide polymorphisms (SNPs) generated from 2bRAD sequencing indicated there were no SNP loci or genetic lineages significantly associated with O. faveolata SCTLD affectedness. Genotypic differences may still contribute to SCTLD susceptibility; however, these differences were not captured using this reduced representation sequencing approach. Algal symbiont community structure characterized from 2bRAD data revealed that the presence of Durusdinium spp. corresponded with SCTLD-affected colonies as compared to unaffected colonies, suggesting that algal symbiont community make-up may play some role in SCTLD resistance. Data generated by this study will be combined with complementary molecular and physiological approaches to further investigate the complex drivers of intraspecific SCTLD susceptibility and resilience.

A method for quantifying the contribution of algal sources to CODMn in water bodies based on ecological chemometrics and its potential applications

In natural water bodies, especially in eutrophic or waterbloom water bodies, algal sources are an important source of the permanganate index (CODMn), and their contribution ratio and analytical methods for rapid and quantitative require more research. In this study, continuous monitoring sampling was conducted in the Jiuqu River Basin of the Tuojiang River, and the response relationship between the algal community structure and the CODMn of the overlying water was analysed by detecting and analysing algal biomass, river water quality indicators, algal source organic matter characteristics and the component characteristics of river CODMn. A rapid quantitative analysis model of algal-source CODMn contribution was established based on ecological chemometrics with coupled chlorophyll indicators. Studies have shown that algal abundance is closely related to the dynamic changes in CODMn in water bodies, especially Cyanobacteria, which have a significant advantage in water bodies with high concentrations of CODMn and can be indicating oxygen-depleted polluted water bodies. The contribution of nascent humic substances in algal source material to the CODMn of the overlying water was greater than that of protein substances. The contribution of chlorophyll-a to the estimate of CODMn from algal sources in this study watershed was modeled as CODMn%=[(0.1077Chla−0.1483)/Overlying waterCODMn]×24.50%, and the components and the methods for establishing of an automatic algal sources CODMn monitoring and analysis system were proposed. This study provides technical support for the research and quantitative control of oxygen depletion pollution in rivers, lakes and reservoirs during the waterbloom period.

Ecological evolution of algae in connected reservoirs under the influence of water transfer: Algal density, community structure, and assembly processes

Reservoir connectivity provides a solution for regional water shortages. Understanding the water quality of reservoirs and the response of algal communities to water transfer could provide the basis for a long-term evolutionary model of reservoirs. In this study, a water-algal community model was established to study the effects of water transfer on water quality and algal communities in reservoirs. The results showed that water transfer significantly decreased total nitrogen and nitrate concentrations. However, the water transfer resulted in an increase in the CODMn concentration and conductivity in the receiving reservoir. Additionally, the algal density and chlorophyll-a (chl-a) concentration showed an increase with water transfer. Bacillariophyta, Cyanophyta, and Chlorophyta were the dominant algal phyllum in all three reservoirs. Water transfer induced the evolution of the algal community by driving changes in the chemical parameters of the receiving reservoir and led to more complex relationships within the algal community. The effects of stochastic processes on algal communities were also enhanced in the receiving reservoirs. These results provide specific information for water quality safety management and eutrophication prevention in connected reservoirs.

Efeitos das mudanças na estequiometria de N e P sobre a clorofila-a do epipélon e do fitoplâncton em condição eutrófica

ABSTRACT Nitrogen and phosphorus are essential elements for the growth and performance of organisms, and the environmental N:P ratio can determine the biomass and structure of algal communities. We investigated the effects in the N:P molar ratio changes on epipelon and phytoplankton chlorophyll-a under eutrophic conditions. An enrichment experiment was performed in open-bottom mesocosms to simulate P limitation, N limitation, and good N and P availability. Under eutrophic conditions, the combined availability of N and P enhanced phytoplankton bloom, while an increase in P limitation resulted in the loss of phytoplankton biomass. Under conditions of high P limitation, there was significantly loss of epipelon biomass. No change in the N:P ratio led to a significant increase in algal biomass in the epipelon. In conclusion, changes in the N:P molar ratio can affect the growth of phytoplankton and epipelic algae under eutrophic conditions. Our results suggest that photosynthetic biomass increase in the epipelon depends on an optimal relationship between light and P.

Response of periphytic algae community structure characteristics to hydrodynamic conditions in an open channel

Response of periphytic algae community structure characteristics to hydrodynamic conditions in an open channel

Microbial metabolomic responses to changes in temperature and salinity along the western Antarctic Peninsula.

Seasonal cycles within the marginal ice zones in polar regions include large shifts in temperature and salinity that strongly influence microbial abundance and physiology. However, the combined effects of concurrent temperature and salinity change on microbial community structure and biochemical composition during transitions between seawater and sea ice are not well understood. Coastal marine communities along the western Antarctic Peninsula were sampled and surface seawater was incubated at combinations of temperature and salinity mimicking the formation (cold, salty) and melting (warm, fresh) of sea ice to evaluate how these factors may shape community composition and particulate metabolite pools during seasonal transitions. Bacterial and algal community structures were tightly coupled to each other and distinct across sea-ice, seawater, and sea-ice-meltwater field samples, with unique metabolite profiles in each habitat. During short-term (approximately 10-day) incubations of seawater microbial communities under different temperature and salinity conditions, community compositions changed minimally while metabolite pools shifted greatly, strongly accumulating compatible solutes like proline and glycine betaine under cold and salty conditions. Lower salinities reduced total metabolite concentrations in particulate matter, which may indicate a release of metabolites into the labile dissolved organic matter pool. Low salinity also increased acylcarnitine concentrations in particulate matter, suggesting a potential for fatty acid degradation and reduced nutritional value at the base of the food web during freshening. Our findings have consequences for food web dynamics, microbial interactions, and carbon cycling as polar regions undergo rapid climate change.

Toxic effects of environmentally persistent free radicals (EPFRs) on the surface of tire wear particles on freshwater biofilms: The alleviating role after sewage-incubation-aging

The aquatic ecological risks posed by the surface-active components of tire wear particles (TWPs) are not fully understood. This study aimed to determine the acute (24 h exposure) aquatic toxicity effects of TWPs on freshwater biofilms in terms of total organic carbon (TOC), chlorophyll-a (Chl-a) abundance, quantum yield (ФM), and adenosine triphosphate (ATP). Three types of TWP were tested: TWPs produced via the typical wear of tires and roads (i.e., rolling friction (R-TWPs) and sliding friction (S-TWPs)) and cryogenically milled tire treads (C-TWPs). The results showed that the surface structural properties of the three TWPs differed significantly in morphology, bare composition, functional groups, and surface-active components (environmental persistent free radicals). The exposure of biofilms to the TWPs increased TOC and ATP at low concentrations (1 mg L−1) but inhibited them at high concentrations (50 mg L−1). All TWP types inhibited biofilm photosynthesis (reduced Chl-a and ФM) and altered the community structure of algae to varying degrees; in addition, the toxicity mechanisms of the TWPs contributed to the accumulation of reactive oxygen species and cell membrane (or cell-wall) fragmentation, leading to lactate dehydrogenase release. S-TWPs were the most toxic because their surface carried the highest environmental persistent free radicals. R-TWPs were the second most toxic, which was attributed to their smaller particle size. The toxicity of all TWPs was tested after sewage incubation aging. The results showed that the toxicity of all TWPs reduced as the sewage covered their surface components and active sites. This process also reduced the differences in toxicity among the TWPs. This study filled a research gap in our understanding of aquatic toxicity caused by the surface structural properties of tire microplastics and has implications for the study of microplastic biotoxicity mechanisms.

Analysis of the Impact of Stormwater Systems on Receiving Waters Based on the Analysis of Algal Community Structure

Analysis of the Impact of Stormwater Systems on Receiving Waters Based on the Analysis of Algal Community Structure

Spatial Difference in the Marine Algal Community of Yeongil Bay Inner and Outer Areas on the East Coast of Korea

This study examined the seasonal and spatial changes in the marine algal community structure in the outer and inner areas of the intertidal zone of Yeongil Bay. A seasonal survey was conducted at 13 intertidal sites in Yeongil Bay between August 2021 and July 2022. Algal samples were collected using a destructive approach, and the marine algal community was analyzed based on species composition, biomass, and the important value (IV) index. To confirm the differences between the outer and inner areas, ANOSIM and SIMPER analyses were conducted based on the biomass and IV indices of the marine algal species. The marine algal communities in the outer and inner areas of Yeongil Bay differed because of the high contribution of Ulva spp., as determined using the IV index. Our findings suggest that there was an influx of nutrients into Yeongil Bay from the Hyeongsan River, which had remained in the inner area for an extended period because of the slow current. This allowed Ulva spp., an opportunistic species, to bloom quickly and dominate the marine algal communities in the inner area. These results indicate a difference in the structure of marine algal communities between the outer and inner areas owing to the proliferation of Ulva spp. Therefore, Ulva spp. can be used as a target species to monitor the marine environment of Yeongil Bay.

Effects of mesohabitat, grazing and substratum roughness on locally common and rare diatom species

Abstract Habitat type and grazing are key factors controlling benthic diatom communities. Nonetheless, the strength of grazing may depend on the habitat complexity at fine (substratum roughness) and meso scales (mesohabitat type). The interaction between grazers and physical conditions may thus be an important factor shaping benthic diatom communities. Several investigations have evaluated how habitat type, grazing and substratum roughness separately affect the biomass, species richness and community structure of algal communities. However, how these factors act together remains poorly understood, particularly for sets of common and rare species. The latter is important for understanding whether common and rare species are affected differently by environmental filters at the local scale. We investigated the effects of mesohabitat type, grazer occurrence and substratum roughness as well as their interactions on benthic diatom communities in a split‐split‐plot field experiment consisting of hierarchical treatments: (i) mesohabitat (pools and riffles); (ii) grazer occurrence (presence or absence of grazers >1 cm in size); and (iii) substratum roughness (smooth and rough substrata). We analysed the entire community and also datasets of common and rare species. Here, we define common and rare species based on their abundance–occupancy relationships, with rare species presenting low mean abundance per experimental unit (between 0.025 and 8.2) and low occupancy (between 2.5% and 25%). Substratum roughness was the main factor explaining differences in species richness, with higher species richness found on rough than on smooth substrata for both the complete dataset and for common and rare species. There was evidence that the interactions between mesohabitat and grazer occurrence and between mesohabitat and substratum roughness affected community structure (relative abundances) for the complete dataset and for common species, whereas the three‐way interaction between mesohabitat, grazer and substratum roughness affected community structure of rare species. Our findings emphasise that crevices are important microhabitats that allow the establishment of both common and rare species. Furthermore, our results suggest that physical differences between mesohabitats influenced the effect of grazers on the community structure of common and rare species. For common species, the effects of this interaction were difficult to depict, but we found a change in the second‐most‐common species between mesohabitats and depending on the occurrence of grazers. For rare species, grazers more clearly affected community structure on smooth substrata in riffles than in pools. Our results demonstrate that local patterns of common and rare diatom species resulted from distinct combinations of the evaluated environmental filters. Together, our results highlight how multifactorial field experiments are key to understanding the main environmental filters driving the species richness and community structure of benthic diatom communities.