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Periphyton that lives attached to seagrass leaves is generally a source of autochthonous energy in the waters and has a major role in the food chain system that supports the primary productivity of seagrass beds. The aim of the current study was to study the extent to which mercury (Hg) levels affect the ecosystem by looking at Hg accumulation in the periphyton. This study used the method of species composition analysis, the density of epiphytic periphyton algae on seagrass, and analyzed the level of pollution in the Talawan Bajo estuary waters based on the bioaccumulation of mercury content in the periphyton and analyzed the periphyton as a bioindicator of the level of Hg pollution in the waters. The first stage was to identify the types of seagrass and periphyton and analyze the composition and density; diversity index, uniformity and dominance of periphyton. The second stage of this study included observation of the accumulation of heavy metal Hg on a laboratory scale and visualization of periphyton cells using TEMcell. Based on the results of the analysis, it was shown that the environmental conditions of the Talawaan Bajo estuary were polluted by heavy metal Hg because the Hg content accumulated in seagrass and periphyton exceeded the quality standards for aquatic biota. It was concluded that the environmental conditions of the Talawaan Bajo estuary were contaminated with heavy metal Hg because the Hg content accumulated in seagrass and periphyton exceeded the quality standards for aquatic biota. Hg contamination in aquatic ecosystems affects the life of biota in the environment, especially damage to tissue structures. [ABSTRACT FROM AUTHOR]

Ecosystems are increasingly challenged by the multiple facets of climate change, coupled with intensifying land‐use pressures. These co‐occurring stressors can interact in complex ways, but we lack an empirical understanding of the impact of higher‐order interactions on temporal patterns. Using 128 flow‐through circular stream mesocosms, we investigated the individual and combined effects of two climatic stressors (CO2 enrichment, flow variability) and two land‐use‐related stressors (siltation, light—as lack of shading) on algal communities and net ecosystem productivity (NPP) in a full‐factorial design. The sediment pulses coincided with high flow to mimic erosion events, whereas CO2 and light disturbances were applied continuously, as they would in nature. Sediment emerged as a key stressor for algal biomass. Land‐use stressors had more pervasive individual effects, whereas climate‐change‐related stressors were more important in up to three‐way interactions with other stressors. However, CO2 was a key driver of NPP, followed by sediment and light, whereas flow variability was only important in interactions with other stressors. The effects of sediment and flow on algal biomass depended strongly on their temporal patterns. The combined effect of an increasing number of stressors on algal biomass appeared to reach saturation with three active stressors, with no apparent additional effect caused by the fourth stressor. Synthesis. Sediment emerged as a key stressor in streams. Despite the mounting evidence and the multitude of available mitigation strategies, this problem persists worldwide. The complex interactions uncovered in our study illustrate context‐dependency that can be masked in two‐factor experiments. Our findings also highlighted that temporal patterns of individual and co‐occurring stressors can determine the ecological outcome. [ABSTRACT FROM AUTHOR]

Amphibian larvae can affect the structure and functioning of freshwater ecosystems, but their effects have been little explored although amphibian biodiversity is rapidly declining. Given that larvae of different amphibian species belong to different trophic levels, their effects on freshwater communities and processes can be expected to differ, with herbivores likely having direct effects on algae and predators having indirect effects through trophic cascades. We explored this question through a mesocosm experiment conducted in montane ponds, using an anuran and a urodele species affected by emergent diseases. We used different scenarios of reduction and loss of one or both species, and compared them to a control scenario representing a typical amphibian community in the study area composed of four species, with total larval density held constant. Loss of the anuran resulted in lower chlorophyll concentration and algal density, likely due to replacement by more efficient grazers. Loss of the urodele produced similar trends but weaker, possibly due to an increase of invertebrate grazing activity in the absence of this predator. Our study shows how the loss of amphibian species can alter the structure of montane ponds, but also how the mechanisms involved and the intensity of effects differ for different species. [ABSTRACT FROM AUTHOR]

Controlled sediment flushing operations (CSFOs) allow to recover reservoirs storage loss while rebalancing the sediment flux interrupted by dams but, at the same time, may cause unacceptable ecological impact. In this study, we investigated the responses of the food web of an upland stream to a CSFO, focusing on the effects of fine sediment deposition detected in three different mesohabitats, i.e., a pool, a riffle, and a step-pool. The field campaign lasted two years and included repeated measurements of fine sediment deposits, and sampling of periphyton, benthic macroinvertebrates and fishes. A moderate and patchy deposition occurred due to the CSFO with short and medium-term ecological impact on the lower trophic levels of the food web, which may affect the whole ecosystem functioning. The monitoring of all available mesohabitats in the investigated stream allowed to detect variations in the ecological response to CSFO, providing a more adequate assessment of the impact. As expected, sedimentation was larger in the pool but, in contrast to our hypotheses, the impact was lower and the recovery was longer for the benthic organisms inhabiting the riffle. In the case of fishes, no lethal impact of both brown trout and bullhead was recorded in the short term but the occurrence of longer lasting effects could not be excluded. To date, this is one of the few studies dealing with a detailed integrative assessment of the downstream impact of sediment management from reservoir on both abiotic and biotic components of stream ecosystem. [ABSTRACT FROM AUTHOR]

A study of diatoms in eight watercourses (four spawning rivers and four streams) in the area of the Ozernovsky Mining and Metallurgical Complex (MMC) on the Kamchatka Peninsula was carried out for the first time. A total of 174 taxa were identified, and a comparative analysis of periphyton species diversity at the sampling stations was carried out. A new species for science was proposed: Gomphonema anissimovae Glushchenko, Kezlya & Kulikovskiy sp. nov. The composition and quantitative characteristics of plankton were analysed only in samples collected from rivers. It was shown that all rivers are oligotrophic in terms of phytoplankton biomass. The work includes lists of taxa with indication of their abundance, as well as illustrative material of found diatom taxa, which will provide an opportunity to monitor changes in planktonic and periphyton microalgae communities in the studied watercourses in the context of potentially high anthropogenic load from industry. [ABSTRACT FROM AUTHOR]

Blooms of toxin-producing cyanobacteria are an enduring public health threat in lakes and rivers. In addition to more commonly studied planktonic taxa in lakes, attached cyanobacteria covering riverbeds and lake littoral zones can produce anatoxins, potent neurotoxins of growing concern. However, relative to planktonic blooms, the geographical and temporal extent and ecology of anatoxin-producing benthic cyanobacteria are poorly documented. To increase understanding of the distribution of these cyanobacteria and their relationships with physicochemical variables, we surveyed sites throughout the Klamath River watershed in Northern California, USA, for anatoxins from benthic mats. We used visual surveys, composite mat samples, water samples, and samples of transported coarse particulate organic matter (CPOM) to quantify benthic cyanobacteria and anatoxin extent. Benthic anatoxins were widespread, adding to a growing body of evidence that anatoxins from benthic cyanobacteria may be more common than previously recognized. Anatoxin concentrations were highest in benthic mats compared with water column and CPOM samples. Anatoxin detection frequency, as indicated by anatoxin synthetase genes, was high in both transported CPOM and benthic mats (74 and 86%, respectively), and transported CPOM anatoxin concentrations reflected benthic mat anatoxin concentrations and cover. Relationships between observed taxa, toxin concentrations, and genetic source tracking indicated that Microcoleus was the dominant anatoxin producer. Clear, low-nutrient tributaries supported anatoxin concentrations as high as, and in some cases higher than, mainstem sites that had higher nutrients. Weak, negative relationships among water quality parameters and anatoxins suggest that some aspects of the tributary streams not captured in this analysis promote the proliferation of benthic Microcoleus and associated anatoxin production. Monitoring benthic mats, including the use of nets targeting sloughed benthic material, can inform public health notifications and document changes in the proliferation of benthic cyanobacteria and associated cyanotoxin production in rivers. [ABSTRACT FROM AUTHOR]

Understanding the relationship between a dam's size and its ecological effects is important for prioritization of river restoration efforts based on dam removal. Although much is known about the effects of large storage dams, this information may not be applicable to small dams, which represent the vast majority of dams being considered for removal. To better understand how dam effects vary with size, we conducted a multidisciplinary study of the downstream effect of dams on a range of ecological characteristics including geomorphology, water chemistry, periphyton, riparian vegetation, benthic macroinvertebrates, and fish. We related dam size variables to the downstream–upstream fractional difference in measured ecological characteristics for 16 dams in the mid‐Atlantic region ranging from 0.9 to 57 m high, with hydraulic residence times (HRTs) ranging from 30 min to 1.5 years. For a range of physical attributes, larger dams had larger effects. For example, the water surface width below dams was greater below large dams. By contrast, there was no effect of dam size on sediment grain size, though the fraction of fine‐grained bed material was lower below dams independently of dam size. Larger dams tended to reduce water quality more, with decreased downstream dissolved oxygen and increased temperature. Larger dams decreased inorganic nutrients (N, P, Si), but increased particulate nutrients (N, P) in downstream reaches. Aquatic organisms tended to have greater dissimilarity in species composition below larger dams (for fish and periphyton), lower taxonomic diversity (for macroinvertebrates), and greater pollution tolerance (for periphyton and macroinvertebrates). Plants responded differently below large and small dams, with fewer invasive species below large dams, but more below small dams. Overall, these results demonstrate that larger dams have much greater impact on the ecosystem components we measured, and hence their removal has the greatest potential for restoring river ecosystems. [ABSTRACT FROM AUTHOR]

Context: Understanding the effects of environmental filters on the beta diversity of periphytic algae is fundamental to understanding the functioning of tropical reservoirs. Aim: To investigate how the presence and morphological complexity of macrophytes drives the increase in beta diversity of periphytic algae and whether environmental filters have direct effects on periphytic algae. Methods: Periphytic algae were collected from macrophyte stands quarterly in the Jazigo reservoir, north-eastern Brazil. Alpha and beta diversity were measured between the different structural complexities of macrophytes. Key results: Alpha and beta diversity, and turnover of periphytic algae were higher in macrophytes of higher complexity (Pontederia crassipes and Ludwigia helminthorrhiza) and nestedness was higher in macrophytes of lower complexity (Cyperus articulatus). Beta diversity was driven primarily by physical and chemical variables. Dissolved inorganic nitrogen, macrophyte complexity, temperature, macroinvertebrates, light and dissolved oxygen explained the beta diversity of periphytic algae. Conclusions: These results suggest that environmental filters and the structural complexity of macrophytes are determinants for the increase in alpha and beta diversity of periphytic algae. Macrophytes with greater morphological complexity favour increased availability of niches and microhabitats, and greater diversity of periphytic algae. Implications: Habitat simplification is one of the main threats to reducing biodiversity and homogenisation of aquatic communities. The aim was to explore how environmental filters act on the diversity of periphytic algae in tropical aquatic ecosystems. In this study, we analysed how environmental filters act on the biodiversity of periphytic algae in a tropical reservoir. We discovered that physical and chemical filters directly influence the alpha and beta diversity of periphytic algae and the importance of the presence of aquatic macrophytes. [ABSTRACT FROM AUTHOR]

Abstract Even though the use of organochlorine pesticides has been prohibited since the last century their presence is still being recorded around the world. In the upper La Antigua watershed, Veracruz, Mexico we have reported concentrations of these contaminants in different compartments of the riverine ecosystems. This is of relevance due to their potential disruptive endocrine effect on the vertebrates drinking the water or feeding in the riverine area. In this study we evaluated concentrations of organochlorine pesticides (OCPs) in streams running throughout mountain cloud forest and two different types of land use, pasture lands and coffee plantations. Water and periphyton samples were collected during the wet and the dry seasons from streams located in independent micro-basins. Spatial explicit analyzes show that the concentrations measured are independent of the distribution of the streams in the geographical area sampled. However seasonal differences were found during the dry season in the water and during the rainy season in periphyton. While OCPs in water support the idea that micro-basins can be used as independent monitoring units, OCPs in periphyton can be indicators of the effect of different land use. Some concentrations of all the OCPs registered had values above the limits for tap water.

Periphyton that lives attached to seagrass leaves is generally a source of autochthonous energy in the waters and has a major role in the food chain system that supports the primary productivity of seagrass beds. The aim of the current study was to study the extent to which Hg levels affect the ecosystem by looking at Hg accumulation in the periphyton. This study used the method of species composition analysis, the density of epiphytic periphyton algae on seagrass, and analyzed the level of pollution in the Talawan Bajo estuary waters based on the bioaccumulation of mercury (Hg) content in the periphyton and analyzed the periphyton as a bioindicator of the level of Hg pollution in the waters. The first stage was to identify the types of seagrass and periphyton and analyze the composition and density; diversity index, uniformity and dominance of periphyton. The second stage of this study included observation of the accumulation of heavy metal Hg on a laboratory scale and visualization of periphyton cells using TEMcell. Based on the results of the analysis, it was shown that the environmental conditions of the Talawaan Bajo estuary were polluted by heavy metal Hg because the Hg content accumulated in seagrass and periphyton exceeded the quality standards for aquatic biota. It was concluded that the environmental conditions of the Talawaan Bajo estuary were contaminated with heavy metal Hg because the Hg content accumulated in seagrass and periphyton exceeded the quality standards for aquatic biota. Hg contamination in aquatic ecosystems affects the life of biota in the environment, especially damage to tissue structures.

Abstract Controlled sediment flushing operations (CSFOs) allow to recover reservoirs storage loss while rebalancing the sediment flux interrupted by dams but, at the same time, may cause unacceptable ecological impact. In this study, we investigated the responses of the food web of an upland stream to a CSFO, focusing on the effects of fine sediment deposition detected in three different mesohabitats, i.e., a pool, a riffle, and a step-pool. The field campaign lasted two years and included repeated measurements of fine sediment deposits, and sampling of periphyton, benthic macroinvertebrates and fishes. A moderate and patchy deposition occurred due to the CSFO with short and medium-term ecological impact on the lower trophic levels of the food web, which may affect the whole ecosystem functioning. The monitoring of all available mesohabitats in the investigated stream allowed to detect variations in the ecological response to CSFO, providing a more adequate assessment of the impact. As expected, sedimentation was larger in the pool but, in contrast to our hypotheses, the impact was lower and the recovery was longer for the benthic organisms inhabiting the riffle. In the case of fishes, no lethal impact of both brown trout and bullhead was recorded in the short term but the occurrence of longer lasting effects could not be excluded. To date, this is one of the few studies dealing with a detailed integrative assessment of the downstream impact of sediment management from reservoir on both abiotic and biotic components of stream ecosystem.

Periphyton communities are fundamental components of freshwater ecosystems that influence water quality, nutrient cycling, and productivity. Additionally, periphyton communities serve as valuable food sources in aquaculture. The periphyton communities on two substrates—heather mats and geotextiles—were compared in four temperate fishponds. After 51 days of immersion, the geotextiles exhibited significantly greater fluorescence, indicating a greater abundance of algae and cyanobacteria. Conversely, the abundance (and biomass) of periphyton invertebrates on heather mats was greater than that on geotextiles, and the difference became more pronounced over time. These differences resulted from significantly greater dipteran larval abundances (biomasses) on the heather mats than on the geotextiles. This study suggested that heather mats can significantly enhance food abundance and availability within the water column under Central European conditions. [ABSTRACT FROM AUTHOR]

The dissemination of antibiotic resistance (AR) through various environments and the role of AR hotspots in public health crises are gaining increasing attention. Aquatic biofilms are speculated to play a significant role in AR spread due to their collection of diverse microorganisms and facilitation of horizontal gene transfer (HGT). However, few studies have characterized the AR genes (resistome) present in natural river biofilms. The goal of this study was to use MinION long-read sequencing to analyze the microbiome, resistome, and mobile genetic elements (MGEs) in periphyton (epilithic biofilms) (n = 56) from a multiuse watershed in Ohio, to elucidate the role of periphyton in clinically relevant AR. Key members of the periphyton microbiome included Flavobacterium and Aeromonas. Overall, periphyton microbial communities shifted with season and location. Specifically, species of Porphyrobacter and Cyanobacteria were more abundant in biofilms during the summer season. Potentially pathogenic bacteria, including the family Enterobacteriaceae, the fish pathogen Pseudomonas koreensis, and the human pathogen Shigella flexneri,weremore abundant in sites downstream of the large city, Columbus, OH, than upstream. The periphyton resistome carried diverse AR genes for a variety of classes, but had minimal clinical relevance. Escherichia, Escherichia coli, and Muvirus were common hosts of AR genes (ARGs) and MGEs. Pseudomonas and Cyanobacteria were frequently MGE hosts, but not AR genes, indicating the potentially important role of these taxa in HGT within and around biofilms. While the sequencing depth in this study was relatively shallow, these findings highlight the mobility potential for the transmission of ARGs in river biofilms. [ABSTRACT FROM AUTHOR]

Global warming can affect biomass accumulation and the dynamics of periphytic communities, potentially altering their role in aquatic ecosystem functioning. We conducted a 38-day mesocosm experiment to investigate the effects of an increase in winter temperature on periphyton biomass accumulation under eutrophic conditions. We evaluated the warming effect on colonization phases, identifying the most affected phase. The experiment had two treatments (control: current winter temperature of 23.5 ℃, warming: + 5.7 ℃ under IPCC scenario). It was carried out in growth chambers under controlled temperature, light, and humidity. Periphyton and water samplings were performed on days 3, 6, 9, 13, 17, 21, 27, and 38. The increase in temperature did not affect the organic matter accrual rate of the periphyton. However, it negatively affected the net and gross accrual rate of the algal biomass. Ash-free dry mass and chlorophyll-a ratio in the periphyton increased at higher temperatures, indicating a decrease in autotrophic components in the periphyton in the warming treatment. We detected losses in algal biomass during the intermediate and advanced colonization phases. Our results showed a decrease in periphytic algal biomass with an increase in average temperature in winter. In conclusion, a warming scenario can negatively influence periphyton biomass in eutrophic ecosystems, where algal growth in the community is generally unfavorable. [ABSTRACT FROM AUTHOR]

Lake Jošava (Croatia) is a shallow reservoir surrounded by agricultural land. In the present study, the trophic cascade was tested by examining the effects of stocking with common carp on plankton and periphytic microphytes. Before stocking, the phytoplankton community was dominated by the chrysophyte Synura uvella. In the epilithon and epiphyton, the predominant diatoms were prostrate, stalk-forming, and motile taxa representing an important food source for adult copepods. After stocking, phytoplankton biomass declined and the community shifted towards small centric diatoms, allowing the small-bodied zooplankton to exploit them. The lower biomass of adult copepods allowed rotifers to proliferate and exploit phytoplankton, while small cladocerans and nauplii fed primarily on epilithon. One month after stocking, phytoplankton was dominated by cryptophytes, small centric diatoms and chlorophytes, which were an important food for rotifers, while none of the zooplankton groups showed a significant relationship with the epilithic and epiphytic communities. By the end of the experiment, food was scarce due to reduced biomass of autotrophs, and zooplankton possibly began to feed on other sources. Our results add to the knowledge about the trophic cascade hypothesis in small shallow reservoirs. [ABSTRACT FROM AUTHOR]

Management of fed-fish culture practices, at present, stands on two broad feed categories, (i) formulated proteinaceous aquafeeds and (ii) the natural resources. Judicious use of the later is gaining popularity since it offers sustainability to fish culture. Polyculture often targets phyto- and zooplanktonic resources, but mostly ignores periphyton. This review discusses the works on feed diversification performed independently at different times. Fishes, viz. Cyprinus carpio, Labeo rohita and Amblypharyngodon mola were projected as potential candidates for resource - nutrient management with feed diversification in rice fish culture. With C. carpio the rice fish culture called Aji Gnui Assonii in terrace water-logged rice field of Apatani Plateau, Arunachal Pradesh (India) is referred as self-substrating aquaculture practice. This monoculture practice experiences high carp productivity since there remains surplus of resources below the threshold level in these rice fields. Similarly, L. rohita, explores periphytic resources in ponds when substrates are installed. As a result, filter feeders get more foraging aquatic phase intensifying the resources for exploration in pond. This concept is suggested for rice fields with water depth above 50 cm where rice stems act as substrate. With trenches or refuge canals, resource intensification may be managed for more cultivable fishes in rice fields with <50 cm water depth. This model of resource intensification further allows inclusion of Small Indigenous Fish Species (SIFs)-which are rich source of many micronutrients. Thus, integration of SIFs confers huge potentiality for intensification of nutrients, especially protein and micronutrients in rice fields. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Introduction: Water depth (WD) and snail abundance (SA) are two key factors affecting the growth of submersed aquatic plants in freshwater lake ecosystems. Changes in WD and SA drive changes in nutrients and other primary producers that may have direct or indirect effects on submersed plant growth, but which factor dominates the impact of both on aquatic plants has not been fully studied. Methods: To investigate the dominant factors that influence aquatic plant growth in plateau lakes, a one-year field study was conducted to study the growth of three dominant submersed macrophyte (i.e., Vallisneria natans, Potamogeton maackianus, and Potamogeton lucens) in Erhai Lake. Results: The results show that, the biomass of the three dominant plants, P.maackianus, is the highest, followed by P.lucens, and V.natans is the lowest. Meanwhile, periphyton and snails attached to P.maackianus are also the highest. Furthermore, WD had a positive effect on the biomass of two submersed macrophyte species of canopy-type P.maackianus and P.lucens, while it had a negative effect on rosette-type V.natans. Snail directly inhibited periphyton attached on V.natans and thereby increasing the biomass of aquatic plants, but the effect of snails on the biomass of the other two aquatic plants is not through inhibition of periphyton attached to their plants. Discussion: The dominant factors affecting the biomass of submersed macrophyte in Erhai Lake were determined, as well as the direct and indirect mechanisms of WD and snails on the biomass of dominant submersed macrophyte. Understanding the mechanisms that dominate aquatic plant change will have implications for lake management and restoration. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The present study explores the use of periphyton to ameliorate toxic properties of arsenic (As) to Labeo rohita and also assesses the human food safety aspects. Fish were introduced to arsenite [As(III)] contaminated water (0.3 and 3 mg/L) along with periphyton. Biochemical, physiological and immunological parameters, including gene expression, were assessed after 30 days of exposure. Periphyton incorporation significantly improved (p < 0.05) the adverse effects of As on respiration, NH3 excretion and brain AChE activity by reducing oxidative stress and As bioaccumulation. The presence of periphyton in As(III) exposed fish (3 mg/L) increased the immune response (Immunoglobulin M and Complement C3) in the serum and the regulation of the respective immune genes in the anterior kidney was found to be similar to the control. A speciation study using LC-ICP-MS confirmed the high accumulation of As by periphyton (5.0–31.9 μg/g) as arsenate [As (V)], resulting in a lower amount of As in fish muscle. The calculated human health risk indices, Target Hazard Quotient (THQ) and Target Cancer risk (TCR) indicate that fish grown in periphyton-treated water may lower the human health risks associated with As. The study signifies the importance of periphyton-based aquaculture systems in As contaminated regions for safe fish production with enhanced yield. [ABSTRACT FROM AUTHOR]

Periphyton is a complex community composed of diverse prokaryotes and eukaryotes; understanding the characteristics of microbial communities within periphyton becomes crucial for biogeochemical cycles and energy dynamics of aquatic ecosystems. To further elucidate the community characteristics of periphyton across varied aquatic habitats, including unpolluted ecologically restored lakes, aquaculture ponds, and areas adjacent to domestic and industrial wastewater treatment plant outfalls, we explored the composition and diversity of prokaryotic and eukaryotic communities in periphyton by employing Illumina MiSeq sequencing. Our findings indicated that the prokaryotic communities were predominantly composed of Proteobacteria (40.92%), Bacteroidota (21.01%), and Cyanobacteria (10.12%), whereas the eukaryotic communities were primarily characterized by the dominance of Bacillariophyta (24.09%), Chlorophyta (20.83%), and Annelida (15.31%). Notably, Flavobacterium emerged as a widely distributed genus among the prokaryotic community. Unclassified_Tobrilidae exhibited higher abundance in unpolluted ecologically restored lakes. Chaetogaster and Nais were enriched in aquaculture ponds and domestic wastewater treatment plant outfall area, respectively, while Surirella and Gomphonema dominated industrial sewage treatment plant outfall area. The alpha diversity of eukaryotes was higher in unpolluted ecologically restored lakes. pH and nitrogen content ( NO 2 - - N , NO 3 - - N , and TN) significantly explained the variations for prokaryotic and eukaryotic community structures, respectively. Eukaryotic communities exhibited a more pronounced response to habitat variations compared to prokaryotic communities. Moreover, the association networks revealed an intensive positive correlation between dominant Bacillariophyta and Bacteroidota. This study provided useful data for identifying keystone species and understanding their ecological functions. [ABSTRACT FROM AUTHOR]

Ecological assessments of the effects of hydropower plants (HPPs) are often limited to aspects of entrainment, mortality, injuries, and passage of fish, whereas the effects on riverine habitats and biological communities in proximity to these structures are hardly documented.In this study, aquatic communities comprising fish, macroinvertebrates, macrophytes and periphyton as well as physical and hydromorphological parameters were investigated in upstream and downstream river sections at five transverse structures at different seasons before and after the installation of an innovative HPP.At all study sites, significant differences in the aquatic community composition between the assessed upstream and downstream sections were found after HPP construction, indicating distinct serial discontinuity.Raising the damming target at the sites Großweil and Au deteriorated the habitat conditions in the upstream area close to the weir and presumably influenced in particular the macroinvertebrate community, where a significant decrease in the density of rheophilic mayfly, stonefly and caddisfly larvae was observed after HPP construction.Synthesis and applications: The installation of different types of innovative HPPs has not improved the habitat conditions for rheophilic species, contrary to the promises raised by the developers of these concepts. Conversely, retrofitting existing weirs accompanied by further damming even significantly increased the effects of serial discontinuity and deteriorated the habitat conditions for rheophilic species in upstream sections. As evident from the findings of this study, habitat and biological community effects resulting from serial discontinuity should become better integrated into ecological assessments of HPP developments. [ABSTRACT FROM AUTHOR]

The study examined the impacts of varying protein levels and additional substrate area for periphyton formation on the growth and survival of whiteleg shrimp postlarvae reared in a biofloc system. Shrimp postlarvae were stocked in eighteen 100L tanks each filled with 60L of seawater (28 = salinity). In a 3×2 factorial arrangement, the experimental diets were formulated to contain three varying dietary protein levels (25, 35, and 45% CP). Shrimp diets were prepared and supplied during the subsequent interval of the trial. The dietary protein levels were subjected to study in combinations with two different levels of periphyton surface areas (no periphyton P0% and P100% tank surface area). Different dietary protein and substrate addition levels significantly influenced growth performance, feed utilization, and survival. The dietary protein level in the diets of shrimp postlarvae reared in the Biofloc system can be reduced from 45 to 35% CP without negative effects on growth and feed conversion response. Regardless of the dietary protein level, results indicated much greater benefits for adding periphyton substrate to the shrimp-rearing system. Survival ranged between 76.67 and 91.33% and increased significantly from 84.33 (without substrate) to 91.56% (100% additional substrate area) regardless of the dietary protein level. Irrespective of substrate levels, they were 83.667, 88.167, and 92.0% for 25, 35 and 45% of CP, respectively. Likewise, periphyton enhances the immunity gene expressions of L. vannamei. The artificial substrate has economic advantages and is easy to establish. Although the positive impact for white leg shrimp, there is no interaction between the percentages of protein levels and the presence of absent artificial substrate. [ABSTRACT FROM AUTHOR]

Periphyton is a complex biological community comprising microorganisms and organisms from different physiological groups that collectively attach to various submerged surfaces in wetland ecosystems. Periphytic biofilms play a critical role in the wetland ecosystem’s dynamicity and possess a considerable capacity for decontamination. The following article examines the various aspects of periphytic biofilms’ capacity for removing some of the most critical environmental pollutants, including organic pollutants, pharmaceuticals, heavy metals, microplastics, and excess nutrients. The paper provides comprehensive discussions on the critical pollutant removal mechanisms employed by the periphytic communities. Additionally, the paper endeavors to contribute to the available knowledge regarding utilizing and developing periphyton-derived bioremediation technologies by presenting the most recent research findings, discussing common challenges in periphyton’s biotechnological application, and delineating crucial research gaps to postulate future research questions. Applying periphyton in pollutant removal aligns with the most recent paradigm of bioremediation technologies advocating the use of microbial consortia instead of single microbial species. In this regard, research results convey that the simultaneous presence of multiple microbial groups together in a biological community (such as periphyton) increases the microorganisms’ resistance to unfavorable environmental conditions and enhances the biological community’s capacity for decontamination. Based on the studies presented in this article, periphytic biological communities can employ different mechanisms to transform and biodegrade a wide array of pollutants. [ABSTRACT FROM AUTHOR]

Extensive pesticide use for agriculture can diffusely pollute aquatic ecosystems through leaching and runoff events and has the potential to negatively affect non-target organisms. Atrazine and S-metolachlor are two widely used herbicides often detected in high concentrations in rivers that drain nearby agricultural lands. Previous studies focused on concentration-response exposure of algal monospecific cultures, over a short exposure period, with classical descriptors such as cell density, mortality or photosynthetic efficiency as response variables. In this study, we exposed algal biofilms (periphyton) to a concentration gradient of atrazine and S-metolachlor for 14 days. We focused on fatty acid composition as the main concentration-response descriptor, and we also measured chlorophyll a fluorescence. Results showed that atrazine increased cyanobacteria and diatom chlorophyll a fluorescence. Both herbicides caused dissimilarities in fatty acid profiles between control and high exposure concentrations, but S-metolachlor had a stronger effect than atrazine on the observed increase or reduction in saturated fatty acids (SFAs) and very long-chain fatty acids (VLCFAs), respectively. Our study demonstrates that two commonly used herbicides, atrazine and S-metolachlor, can negatively affect the taxonomic composition and fatty acid profiles of stream periphyton, thereby altering the nutritional quality of this resource for primary consumers. [ABSTRACT FROM AUTHOR]

Abstract 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.

Our study aims to investigate the longitudinal effects of two land-cover transitions on the periphytic algal community. We utilized datasets from three different studies conducted over a 5-year interval in a tropical headwater stream. The studied stream traverses two abrupt adjacent transitions from an upstream forest to a pasture and back to a downstream forest remnant. We performed a high-spatial resolution sampling and used generalized additive models (GAMs) to capture the non-linear gradient response of algal metrics to distance from land-cover transitions. Algal biomass presented a lagged response to increased light availability along the pasture section and decreased along a shorter distance in the downstream forest. Most algal metrics presented a lagged response to transitions, with chlorophyll-a taking up to 375 m to reach the maximum values inside the pasture and up to 300 m to return to reference conditions inside the downstream forest. In the downstream forested section, diatom richness and abundance were similar to the upstream forested section but did not return to reference conditions. The results were consistent across years. Our results indicate that, while riparian forest remnants can play an important role in buffering impacts related to land-cover changes in low order streams, both the magnitude and directionality of these effects might be influenced by longitudinal effects caused by the flow of water. Riparian forest remnants can have a longitudinal effect in stream conditions, influencing environmental characteristics even over non-forested reaches, to where the forest conditions can be propagated downstream by the flow of water.

Population growth and increasing production demands threaten the highly diverse Andean freshwater ecosystems. Biological indicators constitute a valuable tool for evaluating the ecological quality of freshwater ecosystems under different pressures. Diatom and macroinvertebrate assemblages are the most used bioindicators to assess water pollution, whereby these biotic groups occupy the first and second trophic levels and respond to habitat pollution. Several studies have explored the response of these communities to water pollution in other regions, but no studies have examined their performance in Andean rivers. In this context, this research aimed to evaluate the responses and relationships of both groups of bioindicators in the Upper Guayllabamba basin. We collected macroinvertebrate and diatom samples from nine sites in this basin during the dry and wet seasons, calculated trophic indices for both groups, and related them to environmental characteristics. The results indicated that both bioindicators were sensitive to changes in land use and nutrients. Epilithic diatoms were more sensitive to changes in water chemistry and macroinvertebrates to changes in fluvial habitat and land use. The index based on macroinvertebrates better-detected changes in quality classes between sites and seasons. Therefore, both indices gave complementary information, and their joint use seems suitable in Andean streams. [ABSTRACT FROM AUTHOR]

Background: Periphyton-based aquaculture improves water quality, provides a natural food supplement, limits harmful bacteria, provides a safe haven for shrimp to escape, and adds living space. The impacts of diverse natural substrates on periphyton formation were examined under earthen lined pond seawater systems as a first step in analysing the sustainability of periphytonbased shrimp production. Methods: Natural substrates such as coconut coir, coconut shell and split bamboo pole were placed inside the earthen lined pond filled with seawater for duration of 45 days. Periphyton samples were obtained from each type of substrate on the 15th, 30th and 45th days of the experiment. For all substrates, periphyton biomass and chlorophyll ‘a’ pigment in the periphyton were measured at depths of 0 to 40 cm, 40 to 80 cm and 80 to 120 cm. Physico-chemical parameters of experiment pond water were recorded during periphyton samplings. Result: During the experiment, coconut coir showed higher periphyton biomass in terms of dry matter (DM) (3.4995 0.31201 mg/cm²) and chlorophyll ‘a’ pigment (3.2949 0. 27076 mg/cm²). Duncan’s Multiple Range Test and One Way ANOVA of diverse data reveal a significant difference (P 0.05) between the substrates in periphyton biomass and chlorophyll ‘a’ pigment. In all three substrates, a Student’s ‘t’ test analysis shows that the upper 0 to 40 cm depth yields more periphyton biomass and chlorophyll ‘a’ content than the other levels. Coconut coir was the best natural substrate for periphyton growth among the three. [ABSTRACT FROM AUTHOR]

Stream periphytons are candidate ecosystem engineers in proglacial margins. Here, we quantify the extent to which they are engineers for the case of hillslope‐fed tributaries in the terrace zones of proglacial margin alluvial plains. Candidate ecosystem engineering effects relate to periphyton‐driven changes in (1) vertical infiltration of water, which in turn could aid plant colonization and hence local surface stabilization, and (2) near‐bed hydraulics, notably near‐bed turbulence properties. We ran two flume experiments in parallel in the proglacial margin of the Otemma glacier (Switzerland), reproducing the environmental conditions found in terrace streams. In both experiments, we followed periphyton development on initially bare sediments for 28 days. Then, whilst the experiment continued undisturbed in one flume, in the second and over a further 26 days, we introduced disturbances in the form of desiccation events. Throughout the entire experiment length, we collected imagery for close‐range SfM‐MVS photogrammetry, data on vertical infiltration, and near‐bed hydraulics. The experiments showed that periphyton development significantly changed the streambed properties. First, periphyton development over the timescale of a few days reduced bed roughness and clogged the benthic interstitial space, reducing water infiltration. These effects were insensitive to the disturbance regime. Second, the changes in streambed roughness modified the near‐bed turbulent structures, and this resulted in a reduction of bursting events and in the modification of the turbulent kinetic energy at the near‐bed layer. The latter, however, appeared to be less important in these environments as compared with the impacts on infiltration. Given the low water retaining capacity of glacial sediments, the observation that periphyton can reduce vertical infiltration explains wider observations of their importance in glacial floodplains where vegetation succession is critically constrained by water availability. The relatively reduced impacts on near‐bed turbulence also contribute to explaining why disturbance in proglacial margin streams remains a key limit on ecological succession. [ABSTRACT FROM AUTHOR]

Fish culture sustainability is improved by reducing the fish product content in aquafeeds. Marine periphyton can be used dually for biofiltering mariculture effluent and fish nutrition. The feasibility of periphyton substituting for fishmeal in aquafeed requires evidence. Toward this goal, four iso-protein (42%) and iso-lipid (10%) aquafeeds for grey mullet (Mugil cephalus) were formulated. A control periphyton-free diet consisted of 32% fishmeal, while in the other three diets, periphyton replaced 25%, 50%, or 100% of the fishmeal. Fish were cultured over 104 days with the four diets while measuring their weight gain, specific growth rate, feed conversion ratio, protein uptake, and production value. In a subsequent 35-day trial, and the utilization and digestibility of the feed and dietary amino and fatty acids were measured after feeding fish with the four diets consisting of 1% of Cr2O3 as an indigestible marker. The content of protein, lipids, carbohydrates, and ash in the feed and fish was measured using acceptable protocols while fatty acids and amino acids were measured via gas chromatography and high-performance liquid chromatography, respectively. Economic analyses of the reduction in feed and fish production costs were performed using data from the IndexMundi database and research results. Reducing the fishmeal content to 16% did not negatively affect their growth, feed conversion, or protein uptake. The digestibility of dietary protein and lipids was high under the low-fishmeal diets. Eliminating fishmeal from aquafeed inhibited growth, presumably due to a metabolic deficit in the biosynthesis of long-chain polyunsaturated fatty acids under high-salinity conditions. Economically, dietary periphyton reduced the mullet's aquafeed and production costs, saving USD 0.8 per kg of produced fish with the low-fishmeal (16%) diet. This diet also reduced the fish-in:fish-out ratio to 2.8. The dual use of periphyton improves fish culture sustainability by recirculating nutrients, saving costs, and reducing the fish-in:fish-out ratio. [ABSTRACT FROM AUTHOR]

Resource quantity controls biodiversity across spatial scales; however, the importance of resource quality to cross‐scale patterns in species richness has seldom been explored. We evaluated the relationship between stream basal resource quantity (periphyton chlorophyll a) and invertebrate richness and compared this to the relationship of resource quality (periphyton stoichiometry) and richness at local and regional scales across 27 North American streams. At the local scale, invertebrate richness peaked at intermediate levels of chlorophyll a, but had a shallow negative relationship with periphyton C:P and N:P. However, at the regional scale, richness had a strong negative relationship with chlorophyll a and periphyton C:P and N:P. The divergent relationships of periphyton chlorophyll a and stoichiometry with invertebrate richness suggest that autochthonous resource quantity limits diversity more than quality, consistent with patterns of eutrophication. Collectively, we provide evidence that patterns in resource quantity and quality play important, yet differing roles in shaping freshwater biodiversity across spatial scale. [ABSTRACT FROM AUTHOR]

The subclass Cyrtophoria is a group of morphologically specialized ciliates with diverse characteristics, which can be found in a variety of aquatic and terrestrial habitats. In the present study, two cyrtophorian ciliates, Aegyria oliva Claparède & Lachmann, 1859 and A. peculiaris sp. nov., isolated from coastal waters of China, were investigated based on microscopic observations of live and protargol-stained specimens, and SSU rRNA gene sequence analyses. For A. oliva, the type species of the genus, detailed morphometric data, and improved diagnosis are provided. The new species, Aegyria peculiaris sp. nov. is characterized by a body size of 70–115 × 30–65 μm in vivo, an inverted oval body shape with a protrusion at the anterior left and a posterior bulge on the dorsal side, 45–58 somatic kineties, 31–46 nematodesmal rods, 4–6 transpodial segments, and about six contractile vacuoles. Phylogenetic analyses unveiled a close relationship between the newly identified species and A. foissneri, thereby confirming the monophyly of the genus Aegyria. [ABSTRACT FROM AUTHOR]

Assemblages of infralittoral periphytic algae are understudied due partially to the historical emphasis on phytoplankton and other water-column characteristics to evaluate the integrity of lentic systems. We tested the null hypothesis that characteristics of epilithic algal assemblages at infralittoral sites in reservoirs of Middle and East Tennessee do not infer trophic state. One infralittoral site in five mesotrophic and five eutrophic reservoirs in Middle and East Tennessee was sampled to determine the relative abundance of the most common epilithic diatoms and soft algae, concentrations of epilithic chlorophyll (chl) a, and water concentrations of chl a, total phosphorus (TP), and total nitrogen (TN). The concentration of epilithic chl a correlates significantly to the concentration of TP but not to TN as determined by the probability values for Pearson's correlation coefficients. The water concentration of chl a does not correlate significantly to concentrations of TP, TN, or epilithic chl a. Trophic-state indicator values for 162 epilithic diatom taxa and 102 epilithic soft-algal taxa are calculated as the abundance-weighted average of the concentration of epilithic chl a normalized between 0 and 100. The trophic-state indicator values indicate the relationship of the abundance of algal taxa to trophic state and contribute to our limited knowledge of the effects of eutrophication on infralittoral algal taxa. Trophic-state indices are calculated as the mean abundance-weighted average of trophic-state indicator values for algal taxa of an assemblage. The index values infer the trophic state of the sites and are the first to use epilithic concentrations of chl a as opposed to water-column characteristics to indicate trophic-state optima for periphytic algae of lentic systems. The indices are easy to calculate and provide novel tools to help evaluate and monitor the trophic state of infralittoral sites in reservoirs of Middle and East Tennessee. [ABSTRACT FROM AUTHOR]

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.

Sewage fungus is a classic bioindicator of organic pollution in streams and rivers. However, it has received limited scientific interest in recent decades, despite persistent occurrence in lotic ecosystems. The aim of this review is to provide an up-to-date assessment of sewage fungus, its composition and structure, and the environmental factors that influence its growth to support future research and mitigation interventions. We advocate for the term “undesirable river biofilm” (URB) to more accurately characterise the composition, location, and environmental consequences of sewage fungus. These filamentous or gelatinous growths found on the banks and beds of flowing watercourses are composed predominantly of bacteria, not fungi. Based on modern genomic analyses, we now know that URBs are composed of a diversity of microbial taxa, including those that have long been associated with sewage fungus (e.g. Sphaerotilus, Beggiatoa, and Zoogloea) and newer associated taxa (e.g. Rhodoferax and Thiothrix). While organic pollution is generally considered the main trigger, this review highlights the importance of other environmental factors, such as water velocity, river substrate, pollutant composition and loading, and shading, in the occurrence and persistence of URBs. To illustrate the widespread and continued presence of URBs in rivers, environmental surveillance data for England's rivers were analysed. Between 2000 and 2020, environment officers documented 6,025 occurrences of URBs as part of a wider water quality incident reporting programme. Thus, URBs persist even in countries with stringent water quality standards and comprehensive wastewater infrastructure, suggesting they may continue to be a significant issue globally, despite limited public or scientific focus. We argue that in addition to tackling point discharge of organic pollutants, greater emphasis should be placed on understanding the impact of intermittent and diffuse pollution and altered environmental conditions on river ecosystems. To safeguard river ecosystems, a holistic approach is needed that considers pollution in combination with wider river functioning (e.g. river hydrology, geomorphology, biogeochemical processing, and riparian zones) and climate change. Future areas for study into the URB phenomenon are suggested, including more comprehensive monitoring of URBs specifically and river biofilm health generally.

Abstract Predation and competition are among the most important factors affecting sandfish, Holothuria scabra, growth and survival in ocean‐based production systems. In this study, the potential predators and competitors of sandfish juveniles reared at two sites in the Philippines using the floating hapa ocean nursery system were assessed. A total of 26 species of potential predators and competitors from 16 different families of fishes, molluscs and crustaceans were recorded. These taxa were dominated by the opisthobranch Stylocheilus striatus at Bolinao (north–west Luzon) and the isopod Cymodoce sp. at Maliwaliw (eastern Visayas). Highest number of potential predators and competitors that recruited and/or migrated to the inside of floating hapa nets was recorded on day 23 at Bolinao and day 30 at Maliwaliw, then decreased over the 69‐day duration of the study. Mean length, absolute growth rates (AGRs) and survival of sandfish juveniles reared in floating hapas at the two sites varied during the study. AGRs were highest at 1.17 ± 0.06 mm day−1 at Bolinao, and 1 ± 0.08 mm day−1 at Maliwaliw, by days 23 and 60, respectively. Mean lengths of sandfish juveniles reared at Bolinao and Maliwaliw by the end of the study were 46.7 ± 0.15 and 58.8 ± 2.4 mm, respectively, and survival at both sites was high at 96% by the end of the study. Negative correlations were observed between the number of individual predators and competitors, and survival and growth rates of sandfish juveniles reared at Bolinao and Maliwaliw, respectively. Our results highlight the importance of predator and competitor management measures and appropriate site selection to optimize growth performance and survival of sandfish juveniles reared in ocean‐based culture production systems.

Abstract In the present study, a taxonomic review was conducted on representatives of the genus Tetmemorus (Desmidiaceae, Zygnematophyceae) documented within Brazilian territory. This review involved compiling data from the literature and analyzing samples collected throughout the Bahia State, updating our knowledge about this genus in Brazil. For each identified taxon, we provided information such as description, distribution across biomes and states, watersheds, ecological aspects (including habitat and community types), a list of examined (and excluded) materials, and taxonomic comments. Additionally, a taxonomic key for all species reported in Brazil was provided. Through this comprehensive review, we identified a total of eight Tetmemorus taxa occurring in Brazilian territory, comprising five species (T. brebissonii, T. furcatus, T. granulatus, T. laevis, T. planctonicus) and three non-typical varieties (T. brebissonii var. minor, T. laevis var. borgei, T. laevis var. minutus).

Organochlorine pesticides (OCPs) have been widely used around the world due to their high-efficiency and broad-spectrum insecticidal effects. However, they pose a severe threat to ecosystems and human health due to their easy bioaccumulation and high toxicity. Periphyton is ubiquitous in the submerged substrates surface. It plays a crucial role in carbon, nutrients elements cycling and contaminants transformation in environment. Periphyton can remove OCPs through bioadsorption, bioaccumulation and biodegradation, which alters the fate of OCPs in environment. This review presents a comprehensive summary of OCPs occurrence, global cycle, potential harm in environment, and their removal by periphyton. The OCPs residual have been detected frequently in different environmental medias such as water, soil, atmosphere, sediment, and organisms. Their harm is depending on their physicochemical properties and the exposure route. The main compositions and functions of periphyton have been summarized. Moreover, the artificial cultivation methods of periphyton in laboratory and in-situ field are compared. In addition, the mechanisms of periphyton-mediated OCPs removal and the main factors impacting OCPs removal are also discussed. Periphyton could self-regulate its biological communities to adapt to the OCPs and environment, and then regenerate new species to degrade OCPs. Finally, the prospect of OCPs removal by periphyton and future studies are also proposed. This review provides a systematic introduction on current knowledge of OCPs occurrence, cycle, potential harm in environment, and their removal by periphyton. [ABSTRACT FROM AUTHOR]

Biofilms are complex microecosystems with valuable ecological roles that can shelter a variety of microorganisms. Spirochetes from the genus Leptospira have been observed to form biofilms in vitro, in rural environments, and in the kidneys of reservoir rats. The genus Leptospira is composed of pathogenic and non-pathogenic species, and the description of new species is ongoing due to the advent of whole genome sequencing. Leptospires have increasingly been isolated from water and soil samples. To investigate the presence of Leptospira in environmental biofilms, we collected three distinct samples of biofilms formed in an urban setting with poor sanitation: Pau da Lima, in Salvador, Bahia, Brazil. All biofilm samples were negative for the presence of pathogenic leptospires via conventional PCR, but cultures containing saprophytic Leptospira were identified. Whole genomes were generated and analyzed for twenty isolates obtained from these biofilms. For species identification, we used digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) analysis. The obtained isolates were classified into seven presumptive species from the saprophytic S1 clade. ANI and dDDH analysis suggest that three of those seven species were new. Classical phenotypic tests confirmed the novel isolated bacteria as saprophytic Leptospira. The isolates presented typical morphology and ultrastructure according to scanning electron microscopy and formed biofilms under in vitro conditions. Our data indicate that a diversity of saprophytic Leptospira species survive in the Brazilian poorly sanitized urban environment, in a biofilm lifestyle. We believe our results contribute to a better understanding of Leptospira biology and ecology, considering biofilms as natural environmental reservoirs for leptospires. [ABSTRACT FROM AUTHOR]

Periphyton is a ubiquitous niche in aquatic environments and can be a significant source of dissolved organic matter (DOM) production and leaching, especially in such environment as the Everglades, a slow-water flow wetland in Florida, USA. We employed an array of methods, including compositional analysis, 3-dimensional excitation emission matrix (3-D EEM) fluorescence spectroscopy, and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, to perform quantitative and qualitative analyses on the DOM produced by periphyton and DOM in surrounding surface water and periphyton overlying water for comparison purposes. Higher dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) contents in periphyton pore water than surface water and periphyton overlying water indicated the remarkable contribution from periphyton-produced DOM. Higher total protein, carbohydrate, and thiol contents in periphyton pore water than in surface water and periphyton overlying water underscored the possibility of periphyton pore water DOM leached from periphyton. These results agreed with 3-D EEM and ATR-FTIR analyses that showed the prevalence of possible microbial source of periphyton pore water DOM as indicated by higher fluorescence index (FI) than surface water and periphyton overlying water. Similarly, the size-fractionated DOM from surface water demonstrated terrestrial sources, and periphyton pore water demonstrated microbial sources regardless of their differences in size based on their FI values. The types of periphyton affect the production and composition of DOM, as evidenced by higher total protein, carbohydrate, and chlorophyll-a (Chl-a) contents in floating mat on the water surface than in epiphyton attached to submerged phytoplankton, probably because the former is photo-synthetically more productive than the latter due to different light availability. This study provided fundamental information on periphyton DOM that is essential for further investigating its role in carbon cycle and its biogeochemistry. [ABSTRACT FROM AUTHOR]

Anthropogenic pollutants, such as excessive nutrients and marine plastic debris (MPDs), can significantly affect marine micro-ecosystems, including phytoplankton and periphyton. However, there have been few studies about the impacts of these pollutants on microalgal community. We aimed to assess these impacts by 1000-L mesocosm experiments that simulated the influx of nutrients and MPDs in autumn (natural seawater: control, low nutrient: LN group, high nutrient: HN group). The phytoplankton biomass in water increased rapidly in the LN group (maximum 21.7 μg L−1) and HN group (maximum 14.6 μg L−1), resulting in a succession from Cryptomonas spp. to Pseudo-nitzschia spp.. Interestingly, although the threefold difference in nutrient addition between the LN and HN groups, the phytoplankton biomass was similar (cumulative biomass during the entire experiment: 68.9 μg L−1 in LN group and 70.7 μg L−1 in HN group). On the other hand, on day 15 the periphyton biomass on the PP plates was 12.7-times higher in HN group than in LN group. Also, the estimated periphyton biomass of mesocosm wall was significantly different between LN group (4,696 µg cm−2) and HN group (59,835 µg cm−2), in relation to the lack of phytoplankton biomass relative to nutrient addition. In particular, the species-specific characteristics of Cylindrotheca closterium, which grow well even in low nutrients, and the relatively weak solar irradiance in autumn helped to increase the periphyton biomass. Therefore, these findings suggest that the influx of MPDs and nutrients can change the community structure of microalgae, leading to an increase in the periphyton ratio, and this change can have negative consequences on the marine ecosystem by potentially reducing primary productivity. Our mesocosm experiments provide important ecological insights regarding the time-series changes of phytoplankton in the water column and of microalgae attached to MPD when nutrients and plastic debris are introduced into coastal waters through river discharge after rainfall during autumn in temperate regions. [ABSTRACT FROM AUTHOR]

Floodplain lakes are highly productive and biodiverse ecosystems whose food webs depend on a variety of autochthonous and allochthonous resources. Thus far, the role of attached algae, and epiphytes in particular has been understudied, although often high densities of macrophytes in these lakes may provide extensive substrate for attached algal growth. Our goal was to evaluate spatial and temporal variability in food web dynamics of three floodplain lakes permanently connected to the Usumacinta River, with emphasis on the role of epiphytes as a carbon source for upper trophic levels. To achieve this, we analyzed the physicochemical properties of water and stable isotopes of fish and invertebrate consumers and potential autochthonous (macrophytes, phytoplankton, epiphytes, epipelon) and allochthonous (terrestrial organic matter) basal resources during the rainy and dry seasons. The mixing model output highlighted the crucial role of epiphytes as the main energy pathway supporting secondary production year-round, while aquatic macrophytes were of secondary importance. The contribution of terrestrial organic matter to consumers was low, mostly limited to invertebrates, and overall increased from the rainy to the dry season, countering expectations of higher allochthony following strong seasonal flow pulses. Community-wide metrics further revealed higher trophic diversity among invertebrates as compared to fish. Our findings highlight the importance of preserving epiphytic energy pathways and macrophyte-periphyton linkages, as they provide key support to food webs of these vital fishery ecosystems. [ABSTRACT FROM AUTHOR]

Residual concentrations of pesticides are commonly found outside the intended area of application in Ontario's surface waters. Periphyton are a vital dietary component for grazing organisms in aquatic ecosystems but can also accumulate substantial levels of pesticides from the surrounding water. Consequently, grazing aquatic organisms are likely subjected to pesticide exposure through the consumption of pesticide‐contaminated periphyton. The objectives of the present study were to determine if pesticides partition into periphyton in riverine environments across southern Ontario and, if so, to determine the toxicity of pesticides in periphyton when fed to the grazing mayfly Neocloeon triangulifer. Sites with low, medium, and high pesticide exposure based on historic water quality monitoring data were selected to incorporate a pesticide exposure gradient into the study design. Artificial substrate samplers were utilized to colonize periphyton in situ, which were then analyzed for the presence of approximately 500 pesticides. The results demonstrate that periphyton are capable of accumulating pesticides in agricultural streams. A novel 7‐day toxicity test method was created to investigate the effects of pesticides partitioned into periphyton when fed to N. triangulifer. Periphyton collected from the field sites were fed to N. triangulifer and survival and biomass production recorded. Survival and biomass production significantly decreased when fed periphyton colonized in streams with catchments dominated by agricultural land use (p < 0.05). However, the relationship between pesticide concentration and survival or biomass production was not consistent. Using field‐colonized periphyton allowed us to assess the dietary toxicity of environmentally relevant concentrations of pesticide mixtures; however, nutrition and taxonomic composition of the periphyton may vary between sites. Environ Toxicol Chem 2023;42:2143–2157. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]