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Map of locations of the East River study sites—both the upstream rock collection area and the downstream field experiment site
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The long-stalked Didymosphenia is capable of forming large blooms and is expanding its range. To better understand the colonization dynamics of this species, we investigated the role of substrate characteristics-rock roughness and biofilm condition-on Didymosphenia colonization in a montane Colorado stream. Rocks differing in roughness (shale and s...
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Citations
... (2) Different algae species have various resistance capacities to scouring. (3) A assemblages on natural substrata with higher roughness were reported to be mor sistant to disturbances than artificial substrates [18,28,29]. (4) The scouring effect w be enhanced by suspended sediment. ...
... (3) Algae assemblages on natural substrata with higher roughness were reported to be more resistant to disturbances than artificial substrates [18,28,29]. (4) The scouring effect would be enhanced by suspended sediment. ...
The decrease in periodic scouring of pulsed flows in regulated rivers can result in algal communities dominated by filamentous algae, not available as food sources for fish and macroinvertebrates. To study the pulsed flow velocity required to scour benthic algae from natural river beds, the removal effects on the algal biomass and resistances of different species were tested in a laboratory flume at different velocities of 0.8, 1.1, 1.4, 1.7, and 2.0 m/s. The removal of total algal biomass showed a significant positive relationship with increasing velocities, which reached 22% at 2.0 m/s. The biomass removal of green algae and diatoms was higher than that of blue–green algae. The flow velocity at 1.4 m/s had a clear removal effect on filamentous algae. The velocity higher than 1.7 m/s caused a significant increase in the removal percentage of total biomass dominated by diatoms and blue–green algae. To reduce the filamentous algae and retain the diatoms and blue–green algae, a range of near bed flow velocity was suggested to be 1.4–1.7 m/s. This range could serve as a reference for required pulsed flow velocity to reduce the growth of excessive or nuisance periphyton.
... AIS management is often extremely complex, with most situations requiring rapid responses to efficiently limit the spread; for one reason, AIS directly competes for the same habitat as some of the most demanded fish species. As reported by Bergey et al., D. geminata blooms are observed to thrive in rocky and lownutrient cold-water streams that are ideal for trout populations [56]. The immediate closure of some of the most demanded trout-fishing streams, regardless of their state of D. geminata infection, cost more than it would have to remain open at the time of this study. ...
Didymosphenia geminata is a species of freshwater diatom that is known as invasive and is propagating quickly around the world. While invasive species are generally considered a nuisance, this paper attempts to find useful applications for D. geminata in the biomedical field and wastewater remediation. Here, we highlight the polysaccharide-based stalks of D. geminata that enable versatile potential applications and uses as a biopolymer, in drug delivery and wound healing, and as biocompatible scaffolding in cell adhesion and proliferation. Furthermore, this review focuses on how the polysaccharide nature of stalks and their metal-adsorption capacity allows them to have excellent wastewater remediation potential. This work also aims to assess the economic impact of D. geminata, as an invasive species, on its immediate environment. Potential government measures and legislation are recommended to prevent the spread of D. geminata, emphasizing the importance of education and collaboration between stakeholders.
... These results confirmed our second hypothesis, that is, that direct effects of solar radiation and high temperatures enhanced pigmentary changes, leading to their degradation. According to previous studies (Bergey et al. 2010;Timoner et al. 2014;Zlatanovi c et al. 2018), incised streambed geomorphology and canopy cover perform a protective role in temporary streams when the biota is exposed to the environmental severity associated to nonflow periods. ...
Increased duration and frequency of droughts under global change may affect both temporary and formerly permanent watercourses. Streambed desiccation, cooccurring solar radiation, and high temperature all may affect the composition and metabolism of photoautotrophic organisms in benthic biofilms. To test these effects, we characterized the composition of pigments when biofilms were exposed to dry conditions, and compared this to pigments measured after flow resumed, as well as to others measured from permanent streams in the same region. This comparison revealed important differences in pigmentary composition based on flow conditions. Active chlorophylls decreased exponentially with the duration and severity of the nonflow period, while chlorophyll degradation products and protective carotenoids increased. Streams experiencing longer and more severe nonflow periods showed the highest dissimilarities in their biofilm pigmentary composition, and this pattern was maintained after flow resumed. Our results pointed to duration of nonflowing periods as the major driver of pigmentary composition, regardless of whether these were interrupted or not by short intervals of water flows. Multivariate changes in pigmentary composition between sampling periods highlighted the influence of the long‐term hydrological history on the relative abundance of different taxonomic groups and their associated pigments. Overall, pigmentary fingerprints are informative of the biofilm capacity to resist water flow interruption and of their ability to recover after water flow returns.
... Climatic variables such as temperature have a strong effect in the global spatial and temporal population dynamic of D. geminata (Montecino et al. 2016). Moreover, substrate composition may determine whether the diatom can adhere to a surface as it has been shown that rocks with intact biofilm are more likely to be colonized by D. geminata (Bergey et al. 2010). Research on D. geminata and other diatoms suggests that bacterial biofilm composition may contribute to successful attachment (Gärdes et al. 2011;Brandes et al. 2016). ...
The number of organisms that spread and invade new habitats has increased in recent decades as a result of drastic environmental changes such as climate change and anthropogenic activities. Microbial species invasions occur worldwide in terrestrial and aquatic systems and represent an emerging challenge to our understanding of the interplay between biodiversity and ecosystem functioning. Due to the difficulty of detecting and evaluating non-indigenous microorganisms, little is known about them and the processes that drive successful microbial invasions-especially when compared to macroinvasive species. Microalgae are one of the most abundant microorganisms in aquatic systems, and some are able to produce massive proliferations (mats) with significant impact on biodiversity and economic activities. Among microalgae invaders, Didymosphenia geminata is a benthic diatom that constitutes a major global threat for freshwater ecosystem conservation. Despite two decades of research, the cause of mat proliferations remains uncertain. It has been proposed that bacterial biofilm composition may contribute to successful attachment and consequently to proliferation. The aim of this work was to assess the bacterial diversity associated with the mat-forming diatom D. geminata in three aquatic ecosystems of the Chilean Patagonia by implementing genomic-based tools. Using a metabarcoding approach, we determined a core microbiota represented by 4 phyla, 16 families, and 20 genera. Proteobacteria (Alpha and Beta) and Bacteroidetes were the dominant phyla, followed by Cyanobacteria and Planctomycetes. At the lower taxonomic level, unidentified genera from the Comamonadacea family were the most abundant bacteria of the core microbiota. The bacterial composition we found was very similar, with some relative abundance changes, to that reported in a previous study of the bacterial diversity of biofilms from rivers contaminated with D. geminata in New Zealand. This geographical co-occurrence pattern between bacteria and D. geminata in different independent studies suggests that a specific microbiota may be associated with D. geminata distributions, establishment and proliferation. Our work serves as the starting point to design an experimental study that aims to determine whether these specific bacteria facilitate the establishment of the microalgae by creating favorable conditions or are the result of the diatom invasion.
... Other studies have indicated that D. geminata alters microenvironments and reduces fish populations [16] by altering fish community diets [17]. Also, it disturbs aquatic invertebrate communities and the filters of drinking water systems [18,19], although it is unknown whether the contamination effect is direct. Recently, the toxic effects of microalgae on contaminated river communities [14] and the effects on Salmo salar spermatozoon activation time have been described [20]. ...
... The conditions in which D. geminata is established are, and the subsequent development of rock snot is even more complex. The studies have focused mainly on the physicochemical conditions of the development of D. geminata [1,24], and very few investigations have incorporated other physical-hydrological factors, such as turbidity, runoff speed, shear stress, substrate [19,25] and the like. This view leads to many degrees of freedom for assessing the main factors that condition the establishment and proliferation of D. geminata. ...
... Studies from other groups have addressed these questions by making direct observations in rivers. Observing their characteristics to model the growth of D. geminata [31] and evaluating the effect of phosphorus as a nutrient function or process of D. geminata [27,29], the type of substrate required [19] or the effect of nutrients on the development of this diatom [32], such studies require observations in the field, which make it difficult to control environmental and seasonal variables, as well as requiring that the seasonality of the hydrologic regime be considered at the time of collection. In contrast, this project suggests a D. geminata maintenance system that would allow D. geminata studies in the laboratory and provide the basis for generating systems that could test the conditions of D. geminata development or control. ...
... This organism was recorded in low numbers since XIX century, in several rivers of the Northern Hemisphere. During the last decades, new reports of D. geminata events and of nuisance blooms formation have occurred under a broader spectrum of environmental conditions, across many new temperate locations around the globe (Kawecka and Sanecki 2003;Spaulding and Elwell 2007;Bhatt et al. 2008;Bergey et al. 2010). ...
Didymosphenia geminata is a stalked freshwater diatom, which forms large blooms in ultra-oligotrophic conditions, and it has been declared a nuisance species in many lotic systems worldwide. Its presence is verified in Argentine Patagonia since 2010. To understand the differences in the community of macroinvertebrates between non-invaded sites and D. geminata blooms, three non-invaded sites and three sites with 80–90% blooms coverage were sampled seasonally at Futaleufú River. Physical and chemical variables (pH, suspended solids, total dissolved solids, conductivity, dissolved oxygen, and nutrients) showed no significant differences between sites. Sites with D. geminata blooms were associated with significantly higher values of periphyton biomass and chlorophyll a. Macroinvertebrate community differed between D. geminata infected sites and sites with native periphyton. Higher total macroinvertebrate density, higher tolerant groups (Orthocladiinae and non-insect taxa) density, and total richness were found in the presence of blooms. Trophic structure changed at D. geminata blooms, where shredders and collector-gatherers increased in abundance. The diatom blooms may constitute a new complex micro-habitat that provides refuge from harsh current and predators, as well as new foraging opportunities, producing a bottom-up effect on the benthic community.
... W 9 4 D cm artificial substrates of Tennessee gray flagstone (i.e., sandstone composed primarily of feldspar and quartz) placed at each sampling site. Artificial substrates were utilized to ensure uniform substrate morphology, reduce sampling bias and increase the likelihood of mat colonization (Smayda 1978;Bergey et al. 2010). Natural substrates lack smooth, dimple-free surfaces and can bias algal biomass calculations leading to oversampling when harvesting known areas of (Smayda 1978). ...
... Natural substrates lack smooth, dimple-free surfaces and can bias algal biomass calculations leading to oversampling when harvesting known areas of (Smayda 1978). Additionally, Bergey et al. (2010) found that D. geminata biomass was generally higher on rougher sandstone compared to smoother shale substrates, and therefore sandstone tiles were used for artificial substrates to facilitate colonization. Artificial substrates were placed at sampling sites in Fall 2014 (i.e., one season prior to sampling) to allow sufficient D. geminata inundation prior to harvest. ...
The diatom Didymosphenia geminata is known to alter benthic habitat and macroinvertebrate diversity and community structure. Associations between macroinvertebrate communities and D. geminata biomass in riffle and run mesohabitats were investigated in the South Fork Holston River in Tennessee and Virginia, USA. We found that low current velocity, low turbidity, and high dissolved oxygen (DO) were strong predictors of D. geminata mat presence. Didymosphenia geminata ash-free dry mass was significantly higher in run mesohabitats with low current velocity (CV) than in riffle mesohabitats with higher CV. Macroinvertebrate alpha diversity (Shannon Diversity H’) was only marginally significantly different between riffle and runs, while beta diversity (community composition) was highly significantly different between these mesohabitats. NMDS analyses found that D. geminata was a relatively unimportant predictor of changes in community structure relative to specific conductance, CV, DO, and turbidity. However, effects of D. geminata on macroinvertebrates appear to be very taxon specific with effects on individual taxa potentially masked by tailwater effects on general macroinvertebrate diversity in global analyses. We observed that taxon-specific effects include, but are not limited to, (1) reduction of bryophyte microhabitat utilized by dominant ephemeropterans, trichopterans, amphipods, coleopterans, and some chironomid genera in run mesohabitats from competition with D. geminata for substrate attachment space; and (2) differences in utilization of D. geminata mat biomass as a food resource and microhabitat for chironomids. Our insights into taxon-specific effects of D. geminata on macroinvertebrates open up multiple avenues for experimentation in which to validate our observational findings.
... 27,29,31−34 N. palea Cells Adhere Preferentially on Hydrophobic Surfaces. As diatoms are known to colonize surfaces of various physicochemical properties, 16,18 we compared the adhesive properties of N. palea cells toward hydrophobic and hydrophilic surfaces. We first investigated the macroscopic adhesion of diatoms, i.e., at the population scale. ...
Freshwater biofilms play an essential ecological role but they also adversely affect human activities through undesirable biofouling of artificial submerged structures. They form complex aggregates of microorganisms that colonize any type of substratum. In phototrophic biofilms, diatoms dominate in biomass and produce copious amount of extracellular polymeric substances (EPS) that make them efficient early colonizers. Therefore, a better understanding of diatoms adhesive properties is essential to develop new anti-biofouling strategies. In this context, we used atomic force microscopy (AFM) to decipher the topography and adhesive mechanisms of the common freshwater diatom Nitzschia palea. Images in physiological conditions revealed typical ultrastructural features with a few nanometers resolution. Using single-cell force spectroscopy, we showed that N. palea strongly adhere to hydrophobic surfaces as compared to hydrophilic ones. Chemical force spectroscopy with hydrophobic tips further confirmed that adhesion is governed by surface-associated hydrophobic EPS distributed in clusters at the frustule surface, and mostly composed of (glyco)-lipids as revealed by Raman spectroscopy. Collectively, our results demonstrate that AFM-based nanoscopy, combined with Raman spectroscopy, is a powerful tool to provide new insights into the adhesion mechanisms of diatoms.
... Didymo seems to alter microenvironments by inducing changes in invertebrate assemblages and drinking water filter systems (Bergey et al., 2010;Gillis and Chalifour, 2010;James and Chipps, 2016;Kilroy et al., 2009). Similarly, recent studies have described the toxic impacts of microalgae on the contaminated river communities of microcrustaceans (Larned and Kilroy, 2014), as well as their implications for Salmo salar spermatozoa activation times . ...
Didymosphenia geminata (Lyngbye) Schmidt, also referred to as Didymo, is an invasive diatom that forms nuisance mats. Since it was first reported in our country in approximately 2010, Didymo has expanded and colonized different rivers in the Zona Austral region of Chile. Its biology and effects on ecosystems are still being studied because Didymo is an invasive algal mat that forms in a range of systems from oligotrophic austral rivers to more subtropical systems. We aimed to evaluate the viability of two salmonid cell lines, CHSE-214 and SHK-1 (somatic and embryonic cell lines, respectively), in dilutions of river water alone and in river water contaminated with Didymo or polyphenols extracted from Didymo under controlled conditions. We developed an artificial river system (2 aquariums/replicate) from five different rivers from the central area (Bio-Bio) and Patagonia area (Futaleufú) of Chile to maintain Didymo in the benthic phase. The Didymo populations were maintained for six months in the water from the rivers, after which samples were obtained. Following the extraction of polyphenols from the Didymo samples maintained in the artificial rivers, toxicity assays (10 assays) were performed to determine cell viability. Our results indicated that the CHSE-214 cells were highly sensitive to increasing concentrations of Didymo extracts. We observed a 50% reduction in cell viability after 24 h of exposure to a 0.01 V/V dilution, and this treatment further reduced the proliferative capacity by 70% after 120 h. The SHK-1 cells were less responsive, showing only a 20% decrease in viability at 24 h and a lower cell proliferation rate (45%) after 120 h, which remained higher than that of the CHSE-214 cells. We conclude that certain cell types are sensitive to Didymo in rivers, suggesting that there are chronic effects on several aquatic species following exposure to these diatom substances. These effects should be further studied using this laboratory model to understand the full impact of Didymo on river ecosystems.
... Despite variation among solutes, benthic substrate composition and orientation influenced biofilm development, which controlled overall patterns of nutrient removal (as k) and demand (as v f ) among the 4 streams at ND-LEEF. Benthic substrate provides the habitat template for biofilm development in streams (Burkholder 1996), and biofilm structure and function can vary with stability, size, heterogeneity, chemical composition, and roughness of benthic substrate (Cardinale et al. 2002, Hoellein et al. 2007, Bergey et al. 2010, Besemer 2015. The streams at ND-LEEF were lined with rocks of similar geologic origin. ...
Substrate heterogeneity and biofilm colonization in streams vary across both time and space, but their relative contribution to reach-scale nutrient uptake is difficult to partition. We performed multiple short-term nutrient additions over a 4-mo colonization sequence in 4 small, groundwater-fed, experimental streams. We quantified the influence of substrate size (pea gravel vs cobble) and heterogeneity (alternating sections vs well mixed) on the uptake of NH 4 1 , NO 3 2 , and soluble reactive P (SRP) and transient storage properties. In general, the effect of benthic substrate on uptake velocity (v f) and areal nutrient uptake (U) were inversely related to substrate size, and both metrics were highest in the stream lined with pea gravel, lowest in cobble, and intermediate in streams with alternating and mixed substrates. Substrate trends were consistent among solute types, but the magnitude of uptake differed. Uptake generally was higher for NH 4 1 than for NO 3 2 and SRP in these open-canopy systems. Algal biomass controlled temporal patterns of nutrient uptake but reduced exchange of water between the stream channel and transient storage zone (k 1) such that k 1 decreased as nutrient uptake increased. Our results uniquely demonstrate that substrate heterogeneity and substrate-specific biofilms interact to influence biogeochemical cycling in streams, with implications for the role of substrate in restoring ecosystem function in impaired systems.
