skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Bifurcation Analysis of a New Aquatic Ecological Model with Aggregation Effect and Harvesting
In this paper, we investigated the dynamics of the interaction between Microcystis aeruginosa and filter-feeding fish in a new aquatic ecological model and considered the effects of aggregation and harvesting and focused on studying the critical threshold conditions through the analysis of saddle-node bifurcation, Hopf bifurcation, and Bogdanov–Takens bifurcation. We also conducted numerical simulations to illustrate our findings and provided biological interpretations. The results obtained indicate that the aggregation effect or harvesting can disrupt the coexistence of Microcystis aeruginosa and filter-feeding fish. The filter-feeding fish population may go extinct while the Microcystis aeruginosa population could survive. We identified the importance of finding an appropriate timing for harvesting Microcystis aeruginosa in order to promote the growth of the filter-feeding fish population. This optimal timing may be influenced by the carrying capacity of Microcystis aeruginosa. Taken together, our study sheds light on the dynamics of Microcystis aeruginosa and filter-feeding fish in an aquatic ecosystem, highlighting the critical role of aggregation, harvesting, and timing in determining the coexistence and survival of these species.  more » « less
Award ID(s):
1950254
PAR ID:
10561685
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
World Scientific Publishing Company
Date Published:
Journal Name:
International Journal of Bifurcation and Chaos
Volume:
33
Issue:
15
ISSN:
0218-1274
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, Toxins)
    Eutrophication of inland waters is expected to increase the frequency and severity of harmful algal blooms (HABs). Toxin-production associated with HABs has negative effects on human health and aquatic ecosystem functioning. Despite evidence that flagellates can ingest toxin-producing cyanobacteria, interactions between members of the microbial loop are underestimated in our understanding of the food web and algal bloom dynamics. Physical and allelopathic interactions between a mixotrophic flagellate (Cryptomonas sp.) and two strains of a cyanobacteria (Microcystis aeruginosa) were investigated in a full-factorial experiment in culture. The maximum population growth rate of the mixotroph (0.25 day−1) occurred during incubation with filtrate from toxic M. aeruginosa. Cryptomonas was able to ingest toxic and non-toxic M. aeruginosa at maximal rates of 0.5 and 0.3 cells day−1, respectively. The results establish that although Cryptomonas does not derive benefits from co-incubation with M. aeruginosa, it may obtain nutritional supplement from filtrate. We also provide evidence of a reduction in cyanotoxin concentration (microcystin-LR) when toxic M. aeruginosa is incubated with the mixotroph. Our work has implications for “trophic upgrading” within the microbial food web, where cyanobacterivory by nanoflagellates may improve food quality for higher trophic levels and detoxify secondary compounds. 
    more » « less
  2. ; ; (, Environmental Fluid Mechanics)
    Abstract Harmful algal blooms (HABs) pose significant threats to aquatic ecosystems and human health, necessitating efficient mitigation strategies. Although clay-algae aggregation has been widely used for controlling HABs, the slow sedimentation of clay-algae aggregates hampers its effectiveness. We examine how turbulence dynamics affect the formation and settling of clay-algae aggregates. Using a custom-designed plankton tower equipped with an oscillating grid and an in-situ imaging system, we investigated how varying dissipation rates of turbulent kinetic energy (ε = 8 × 10−9to 9 × 10−5m2/s3) affected the removal efficiency ofMicrocystis aeruginosaby laponite clay. In addition, we directly measured the settling velocity and size of clay-algae aggregates over time. The results demonstrate that turbulent mixing, on a time scale typical of the diurnal mixed layer of lakes, can enhance the removal efficiency of HABs by up to threefold. Higher turbulence dissipation rate,ε, leads to an increase in the settling velocity and size of clay-algae aggregates. We demonstrate that the maximum removal efficiency ofMicrocystis aeruginosais achieved when the ratio of the diameter of clay-algae aggregates is half the Kolmogorov length scale. Our findings highlight the importance of turbulence in enhancing clay-based HAB mitigation and provide actionable insights for field applications, such as leveraging natural wind-driven mixing or implementing mechanical agitation in the lakes’ surface mixed layer. This study bridges the gap between well-controlled laboratory experiments and real-world HAB implementation. 
    more » « less
  3. ; ; (, Mathematical Methods in the Applied Sciences)
    ABSTRACT Predator‐prey models, such as the Leslie‐Gower model, are essential for understanding population dynamics and stability within ecosystems. These models help explain the balance between species under natural conditions, but the inclusion of factors like the Allee effect and intraspecific competition adds complexity and realism to these interactions, enhancing our ability to predict system behavior under stress. To detect early indicators of population collapse, this study investigates the intricate dynamics of a modified Leslie‐Gower predator‐prey model with both Allee effect and intraspecific competition. We analyze the existence and stability of equilibria, as well as bifurcation phenomena, including saddle‐node bifurcations of codimension 2, Hopf bifurcations of codimension 2, and Bogdanov‐Takens bifurcations of codimension at least 4. Detailed transitions between bifurcation curves–specifically saddle‐node, Hopf, homoclinic, and limit cycle bifurcations–are also examined. We observe a novel transition phenomenon, where a system jumps from saddle‐node bifurcation to homoclinic and limit cycle bifurcations. This suggests that burst oscillations may serve as an early warning of system collapse rather than simply a tipping point. Our findings indicate that moderate levels of intraspecific competition or Allee effect support coexistence of both populations, while excessive levels may destabilize the entire biological system, leading to collapse. These insights offer valuable implications for ecological management and the early detection of risks in population dynamics. 
    more » « less
  4. ; ; ; ; ; ; (, Limnology and Oceanography Letters)
    Abstract Understanding how altered temperature regimes affect harmful cyanobacterial bloom formation is essential for managing aquatic ecosystems amidst ongoing climate warming. This is difficult because algal performance can depend on both current and past environments, as plastic physiological changes (acclimation) may lag behind environmental change. Here, we investigate how temperature variation on sub‐weekly timescales affects population growth and toxin production given acclimation. We studied four ecologically important freshwater cyanobacterial strains under low‐ and high‐nutrient conditions, measuring population growth rate after acclimation and new exposure to a range of temperatures. Cold‐acclimated populations (15.7°C) outperformed fully acclimated populations (held in constant conditions) across 65% of thermal environments, while hot‐acclimated populations (35.7–42.6°C) underperformed across 75% of thermal environments. Over a 5‐day period, cold‐acclimatedMicrocystis aeruginosaproduced ~2.5‐fold more microcystin than hot‐acclimated populations experiencing the same temperature perturbation. Our results suggest that thermal variation and physiology interact in underappreciated ways to influence cyanobacterial growth, toxin production, and likely bloom formation. 
    more » « less
  5. ; ; ; ; ; ; ; (, Applied and Environmental Microbiology)
    ABSTRACT The frequency and intensity of cyanobacterial blooms are increasing worldwide. Interactions between toxic cyanobacteria and aquatic microorganisms need to be critically evaluated to understand microbial drivers and modulators of the blooms. In this study, we applied 16S/18S rRNA gene sequencing and metabolomics analyses to measure the microbial community composition and metabolic responses of the cyanobacterium Microcystis aeruginosa in a coculture system receiving dissolved inorganic nitrogen and phosphorus (DIP) close to representative concentrations in Lake Taihu, China. M. aeruginosa secreted alkaline phosphatase using a DIP source produced by moribund and decaying microorganisms when the P source was insufficient. During this process, M. aeruginosa accumulated several intermediates in energy metabolism pathways to provide energy for sustained high growth rates and increased intracellular sugars to enhance its competitive capacity and ability to defend itself against microbial attack. It also produced a variety of toxic substances, including microcystins, to inhibit metabolite formation via energy metabolism pathways of aquatic microorganisms, leading to a negative effect on bacterial and eukaryotic microbial richness and diversity. Overall, compared with the monoculture system, the growth of M. aeruginosa was accelerated in coculture, while the growth of some cooccurring microorganisms was inhibited, with the diversity and richness of eukaryotic microorganisms being more negatively impacted than those of prokaryotic microorganisms. These findings provide valuable information for clarifying how M. aeruginosa can potentially modulate its associations with other microorganisms, with ramifications for its dominance in aquatic ecosystems. IMPORTANCE We measured the microbial community composition and metabolic responses of Microcystis aeruginosa in a microcosm coculture system receiving dissolved inorganic nitrogen and phosphorus (DIP) close to the average concentrations in Lake Taihu. In the coculture system, DIP is depleted and the growth and production of aquatic microorganisms can be stressed by a lack of DIP availability. M. aeruginosa could accelerate its growth via interactions with specific cooccurring microorganisms and the accumulation of several intermediates in energy metabolism-related pathways. Furthermore, M. aeruginosa can decrease the carbohydrate metabolism of cooccurring aquatic microorganisms and thus disrupt microbial activities in the coculture. This also had a negative effect on bacterial and eukaryotic microbial richness and diversity. Microcystin was capable of decreasing the biomass of total phytoplankton in aquatic microcosms. Overall, compared to the monoculture, the growth of total aquatic microorganisms is inhibited, with the diversity and richness of eukaryotic microorganisms being more negatively impacted than those of prokaryotic microorganisms. The only exception is M. aeruginosa in the coculture system, whose growth was accelerated. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email