scholarly journals Successional dynamics and alternative stable states in a saline activated sludge microbial community over 9 years

Microbiome ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Yulin Wang ◽  
Jun Ye ◽  
Feng Ju ◽  
Lei Liu ◽  
Joel A. Boyd ◽  
...  
Keyword(s):  
Microbial Community ◽  
Activated Sludge ◽  
Alternative Stable States ◽  
Treatment Plant ◽  
Stable State ◽  
Comparative Genomic ◽  
Operational Parameters ◽  
Stable States ◽  
Alternative Stable State ◽  
Analysis Of Dynamics

Abstract Background Microbial communities in both natural and applied settings reliably carry out myriads of functions, yet how stable these taxonomically diverse assemblages can be and what causes them to transition between states remains poorly understood. We studied monthly activated sludge (AS) samples collected over 9 years from a full-scale wastewater treatment plant to answer how complex AS communities evolve in the long term and how the community functions change when there is a disturbance in operational parameters. Results Here, we show that a microbial community in activated sludge (AS) system fluctuated around a stable average for 3 years but was then abruptly pushed into an alternative stable state by a simple transient disturbance (bleaching). While the taxonomic composition rapidly turned into a new state following the disturbance, the metabolic profile of the community and system performance remained remarkably stable. A total of 920 metagenome-assembled genomes (MAGs), representing approximately 70% of the community in the studied AS ecosystem, were recovered from the 97 monthly AS metagenomes. Comparative genomic analysis revealed an increased ability to aggregate in the cohorts of MAGs with correlated dynamics that are dominant after the bleaching event. Fine-scale analysis of dynamics also revealed cohorts that dominated during different periods and showed successional dynamics on seasonal and longer time scales due to temperature fluctuation and gradual changes in mean residence time in the reactor, respectively. Conclusions Our work highlights that communities can assume different stable states under highly similar environmental conditions and that a specific disturbance threshold may lead to a rapid shift in community composition.

scholarly journals Path-dependent institutions drive alternative stable states in conservation

2018 ◽  
Vol 116 (2) ◽  
pp. 689-694 ◽  
Author(s):  
Edward W. Tekwa ◽  
Eli P. Fenichel ◽  
Simon A. Levin ◽  
Malin L. Pinsky
Keyword(s):  
Renewable Resources ◽  
Path Dependence ◽  
Alternative Stable States ◽  
Stable State ◽  
Empirical Support ◽  
Stable States ◽  
Alternative Stable State ◽  
Important Challenge ◽  
Quantitative Analyses ◽  
Path Dependent

Understanding why some renewable resources are overharvested while others are conserved remains an important challenge. Most explanations focus on institutional or ecological differences among resources. Here, we provide theoretical and empirical evidence that conservation and overharvest can be alternative stable states within the same exclusive-resource management system because of path-dependent processes, including slow institutional adaptation. Surprisingly, this theory predicts that the alternative states of strong conservation or overharvest are most likely for resources that were previously thought to be easily conserved under optimal management or even open access. Quantitative analyses of harvest rates from 217 intensely managed fisheries supports the predictions. Fisheries’ harvest rates also showed transient dynamics characteristic of path dependence, as well as convergence to the alternative stable state after unexpected transitions. This statistical evidence for path dependence differs from previous empirical support that was based largely on case studies, experiments, and distributional analyses. Alternative stable states in conservation appear likely outcomes for many cooperatively managed renewable resources, which implies that achieving conservation outcomes hinges on harnessing existing policy tools to navigate transitions.

scholarly journals Shifting States, Altered Fates: Divergent Fuel Moisture Responses after High Frequency Wildfire in an Obligate Seeder Eucalypt Forest

Forests ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 436 ◽  
Author(s):  
Jamie Burton ◽  
Jane Cawson ◽  
Philip Noske ◽  
Gary Sheridan
Keyword(s):  
High Frequency ◽  
Alternative Stable States ◽  
Stable State ◽  
Fuel Moisture ◽  
Stable States ◽  
Alternative Stable State ◽  
Obligate Seeder ◽  
Time Since Fire ◽  
Mountain Ash ◽  
Moisture Dynamics

High frequency wildfires can shift the structure and composition of obligate seeder forests and initiate replacement with alternative vegetation states. In some forests, the alternative stable state is drier and more easily burned by subsequent fires, driving a positive feedback that promotes further wildfire and perpetuates alternative stable states. Mountain Ash (Eucalyptus regnans (F.Muell.)) forests are highly valued for their biodiversity, water, timber and carbon. Fires are a natural part of the lifecycle of these forests, but too frequent fires can eliminate Mountain Ash and trigger a transition to lower stature, non-eucalypt forests which are dominated by understorey species. This study sought to better understand the fuel moisture dynamics of alternative stable states resulting from high frequency wildfires. A vegetation mosaic in the Central Highlands, Victoria created a unique opportunity to measure fuel moisture in adjacent forest stands that differed in overstorey species composition and time since fire. Specifically, we measured fuel moisture and microclimate at two eucalypt sites (9 and 79 years old) and three non-eucalypt sites (two 9 year old and one 79 year old). Fuel availability, defined here as the number of days surface fuels were below 16% and dry enough to ignite and sustain fire, was calculated to estimate flammability. Fuel availability differed between sites, particularly as a function of time since fire, with recently burnt sites available to burn more often (4–17 versus 0–3 days). There were differences in fuel availability between non-eucalypt sites of the same age, suggesting that high frequency fire does not always lead to the same vegetation condition or outcome for fuel availability. This indicates there is potential for both positive and negative flammability feedbacks following state transition depending on the composition of the non-eucalypt state. This is the first study to provide empirical insight into the fuel moisture dynamics of alternative stable states in Mountain Ash forests.

scholarly journals Transient invaders can induce shifts between alternative stable states of microbial communities

2020 ◽  
Vol 6 (8) ◽  
pp. eaay8676 ◽  
Author(s):  
Daniel R. Amor ◽  
Christoph Ratzke ◽  
Jeff Gore
Keyword(s):  
Environmental Changes ◽  
Alternative Stable States ◽  
Stable State ◽  
Natural Soil ◽  
Stable States ◽  
Alternative Stable State ◽  
Community Shift ◽  
Invader Species ◽  
Potential Impact ◽  
And Function

Microbial dispersal often leads to the arrival of outsider organisms into ecosystems. When their arrival gives rise to successful invasions, outsider species establish within the resident community, which can markedly alter the ecosystem. Seemingly less influential, the potential impact of unsuccessful invaders that interact only transiently with the community has remained largely ignored. Here, we experimentally demonstrate that these transient invasions can induce a lasting transition to an alternative stable state, even when the invader species itself does not survive the transition. First, we develop a mechanistic understanding of how environmental changes caused by these transient invaders can drive a community shift in a simple, bistable model system. Beyond this, we show that transient invaders can also induce switches between stable states in more complex communities isolated from natural soil samples. Our results demonstrate that short-term interactions with an invader species can induce lasting shifts in community composition and function.

scholarly journals Transient invaders can induce shifts between alternative stable states of microbial communities

2019 ◽  
Author(s):  
Daniel R. Amor ◽  
Christoph Ratzke ◽  
Jeff Gore
Keyword(s):  
Community Composition ◽  
Environmental Changes ◽  
Alternative Stable States ◽  
Stable State ◽  
Natural Soil ◽  
Stable States ◽  
Alternative Stable State ◽  
Community Shift ◽  
Invader Species ◽  
And Function

AbstractMicrobial dispersal often leads to the arrival of outsider organisms into ecosystems. When their arrival give rise to successful invasions, outsider species establish within the resident community, which can dramatically alter the ecosystem. Seemingly less influential, the potential impact of unsuccessful invaders that interact only transiently with the community has remained largely ignored. Here, we experimentally demonstrate that such transient invasions can perturb the stability of microbial ecosystems and induce a lasting transition to an alternative stable state, even when the invader species itself does not survive the transition. First, we develop a mechanistic understanding of how environmental changes caused by such transient invaders can drive a community shift in a simple, bistable model system. Beyond this, we show that transient invaders can also induce switches between stable states in more complex communities isolated from natural soil samples. Our results demonstrate that short-term interactions with an invader species can induce lasting shifts in community composition and function.One Sentence SummaryTransient invaders can cause lasting shifts in community composition and function.

scholarly journals Niche Differentiation among Three Closely RelatedCompetibacteraceaeClades at a Full-Scale Activated Sludge Wastewater Treatment Plant and Putative Linkages to Process Performance

2018 ◽  
Vol 85 (5) ◽  
Author(s):  
Veronica R. Brand ◽  
Laurel D. Crosby ◽  
Craig S. Criddle
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Wastewater Treatment Plant ◽  
Treatment Plant ◽  
Niche Differentiation ◽  
Full Scale ◽  
Pure Oxygen ◽  
Operational Parameters ◽  
Metabolic Potential ◽  
Operational Conditions

ABSTRACTMultiple clades within a microbial taxon often coexist within natural and engineered environments. Because closely related clades have similar metabolic potential, it is unclear how diversity is sustained and what factors drive niche differentiation. In this study, we retrieved three near-complete Competibacter lineage genomes from activated sludge metagenomes at a full-scale pure oxygen activated sludge wastewater treatment plant. The three genomes represent unique taxa within theCompetibacteraceae. A comparison of the genomes revealed differences in capacity for exopolysaccharide (EPS) biosynthesis, glucose fermentation to lactate, and motility. Using quantitative PCR (qPCR), we monitored these clades over a 2-year period. The clade possessing genes for motility and lacking genes for EPS biosynthesis (CPB_P15) was dominant during periods of suspended solids in the effluent. Further analysis of operational parameters indicate that the dominance of the CPB_P15 clade is associated with low-return activated sludge recycle rates and low wasting rates, conditions that maintain relatively high levels of biomass within the system.IMPORTANCEMembers of the Competibacter lineage are relevant in biotechnology as glycogen-accumulating organisms (GAOs). Here, we document the presence of threeCompetibacteraceaeclades in a full-scale activated sludge wastewater treatment plant and their linkage to specific operational conditions. We find evidence for niche differentiation among the three clades with temporal variability in clade dominance that correlates with operational changes at the treatment plant. Specifically, we observe episodic dominance of a likely motile clade during periods of elevated effluent turbidity, as well as episodic dominance of closely related nonmotile clades that likely enhance floc formation during periods of low effluent turbidity.

Mental disorders, network models, and dynamical systems

2017 ◽  
Author(s):  
Denny Borsboom
Keyword(s):  
Mental Disorders ◽  
Alternative Stable States ◽  
Stable State ◽  
Network Models ◽  
External Shocks ◽  
Stable States ◽  
Adverse Life Events ◽  
Healthy State ◽  
Strongly Connected ◽  
Network Approaches

Network approaches have been proposed as an alternative way of thinking about relations between symptoms of mental disorders. Unlike traditional psychometric approaches, network models view these associations as the result of direct interactions between symptoms. Disorders are defined as alternative stable states of a network due to increased connectivity between symptoms. This increased connectivity creates a pattern of reinforcement, so the system can get stuck in a state of prolonged activation. Mental health is defined as the stable state of a weakly connected network. Although symptomatology may be temporarily increased in a healthy network (e.g., due to adverse life events), as the influence of a shock wanes the network will spontaneously return to its healthy state. Strongly connected networks, however, may transition into disordered states upon similar external shocks, and may not naturally recover. Thus, the proposed definitions yield plausible conceptualizations of resilience and vulnerability.

scholarly journals Activated Sludge Microbial Community and Treatment Performance of Wastewater Treatment Plants in Industrial and Municipal Zones

2020 ◽  
Vol 17 (2) ◽  
pp. 436 ◽  
Author(s):  
Yongkui Yang ◽  
Longfei Wang ◽  
Feng Xiang ◽  
Lin Zhao ◽  
Zhi Qiao
Keyword(s):  
Wastewater Treatment ◽  
Microbial Community ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Wastewater Treatment Plants ◽  
Treatment Plant ◽  
Wastewater Sludge ◽  
Community Diversity ◽  
Nitrogen And Phosphorus ◽  
Metabolic Functions

Controlling wastewater pollution from centralized industrial zones is important for reducing overall water pollution. Microbial community structure and diversity can adversely affect wastewater treatment plant (WWTP) performance and stability. Therefore, we studied microbial structure, diversity, and metabolic functions in WWTPs that treat industrial or municipal wastewater. Sludge microbial community diversity and richness were the lowest for the industrial WWTPs, indicating that industrial influents inhibited bacterial growth. The sludge of industrial WWTP had low Nitrospira populations, indicating that influent composition affected nitrification and denitrification. The sludge of industrial WWTPs had high metabolic functions associated with xenobiotic and amino acid metabolism. Furthermore, bacterial richness was positively correlated with conventional pollutants (e.g., carbon, nitrogen, and phosphorus), but negatively correlated with total dissolved solids. This study was expected to provide a more comprehensive understanding of activated sludge microbial communities in full-scale industrial and municipal WWTPs.

scholarly journals At what spatial scales are alternative stable states relevant in highly interconnected ecosystems?

2019 ◽  
Author(s):  
Vadim A. Karatayev ◽  
Marissa L. Baskett
Keyword(s):  
Spatial Scales ◽  
Alternative Stable States ◽  
Stable State ◽  
Environmental Stochasticity ◽  
Rocky Reef ◽  
Alternative States ◽  
Stable States ◽  
Long Distance ◽  
Rocky Reefs ◽  
Model Predictions

AbstractWhether ecosystems recover from disturbance depends on the presence of alternative stable states, which are theoretically possible in simple models of many systems. However, definitive empirical evidence for this phenomenon remains limited to demographically closed ecosystems such as lakes. In more interconnected systems such as temperate rocky reefs, the local relevance of alternative stable states might erode as immigration overwhelms local feedbacks and produces a single stable state. At larger spatial scales, dispersal might counter localized disturbance and feedbacks to synchronize states throughout a region. Here, we quantify how interconnectedness affects the relevance of alternative stable states using dynamical models of California rocky reef communities that incorporate observed environmental stochasticity and feedback loops in kelp-urchin-predator interactions. Our models demonstrate the potential for localized alternative states despite high interconnectedness likely due to feedbacks affecting dispersers as they settle into local communities. Regionally, such feedbacks affecting settlement can produce a mosaic of alternative stable states that span local (10-20km) scales despite the synchronizing effect of long-distance dispersal. The specific spatial scale and duration of each state predominantly depend on the scales of environmental variation and on local dynamics (here, fishing). Model predictions reflect observed scales of community states in California rocky reefs and suggest how alternative states co-occur in the wide array of marine and terrestrial systems with settlement feedbacks.

scholarly journals Different coastal marsh sites reflect similar topographic conditions for bare patches and vegetation recovery

2020 ◽  
Author(s):  
Chen Wang ◽  
Lennert Schepers ◽  
Matthew L. Kirwan ◽  
Enrica Belluco ◽  
Andrea D'Alpaos ◽  
...  
Keyword(s):  
Stable State ◽  
Venice Lagoon ◽  
State Theory ◽  
Sediment Supply ◽  
Coastal Marsh ◽  
Tidal Range ◽  
Unstable State ◽  
Stable States ◽  
Alternative Stable State ◽  
Subsequent Loss

Abstract. The presence of bare patches within otherwise vegetated coastal marshes is sometimes considered to be a symptom of marsh die-back and the subsequent loss of important ecosystem services. Here we studied the topographical conditions determining the presence and revegetation of bare patches in three marsh sites with contrasting tidal range, sediment supply and plant species: the Scheldt Estuary (the Netherlands), Venice Lagoon (Italy), and Blackwater Marshes (Maryland, USA). We analyzed topographic properties of bare patches, including elevation, size, distance and connectivity to channels based on GIS analyses of aerial and LIDAR imagery. Our results demonstrate that across the different marsh sites, bare patches connected to channels occur most frequently at the lowest elevations and farthest distance from the main channels. Bare patches disconnected from channels occur most frequently at intermediate elevations and distances from channels, and vegetated marshes dominate at highest elevations and shortest distances from channels. Revegetation in bare patches is observed in only one site with the highest tidal range and highest sediment availability, and preferentially occurs from the edges of small unconnected bare patches at intermediate elevations and intermediate distances from channels. Our results are discussed within the alternative stable state theory. We suggest the existence of two stable states, a high-elevated vegetated state close to channels that tends to remain high and vegetated, and a low-elevated state of bare connected patches far from channels that tends to remain bare, with an unstable state at intermediate channel distances where bare patches may form and rapidly become revegetated.

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