A comparative study of deterministic and stochastic dynamics for a non-autonomous allelopathic phytoplankton model (original) (raw)

Structural Stability Ananlysis of an Algal Bloom Mathematical Model in Trophic Interaction

International Journal of Nonlinear Analysis: Real World Applications, 2010

The paper deals with the dynamical behavior of plankton population ecosystem, mainly found in Sunderban mangrove area. The ecosystem is represented by a set of two dimensional non-linear differential equations involving zooplankton-phytoplankton population. Plankton populations undergo dramatic changes in marine ecology. We propose a description of plankton communities as excitable systems which resemble the behavior of excitable media. The delay parameter dependency of the various ‘excitable’ phenomena, trigger mechanism, threshold, and slow recovery, is clear, and permits ready investigation of the influence of properties of the physical environment, including variations in nutrient fluxes, temperature or population levels. We have analyzed the stability and bifurcation of the model system with and without delay. We have shown the existence and uniqueness of limit cycles in the rapid growth of the plankton population. We also studied the model system into a stochastic one, by incorporating random fluctuations of the environment. And we study the stochastic stability of the dynamical system in mean square sense around the interior equilibrium.

A systematic approach to evaluate sustained stochastic oscillations

2011

Although the populations of biological systems are inherently discrete and their dynamics are strongly stochastic, it is usual to consider their limiting behaviour for large environments in order to study some of their features. Such limiting behaviour is described as the solution of a set of ordinary differential equations, i.e., a continuous and deterministic trajectory. It will be shown that this trajectory does not always average correctly the system behaviour, such as sustained oscillations, in the neighbourhood of deterministic equilibrium points. In order to overcome this mismatch, an alternative set of differential equations based on polar coordinates is proposed. This set of equations can be used to easily compute the average amplitude and frequency of stochastic oscillations.

Evaluation of sustained stochastic oscillations by means of a system of differential equations

2012

Several approaches exist to model the evolution of dynamical systems with large populations. These approaches can be roughly divided into microscopic ones, which are usually stochastic and discrete, and macroscopic ones, which are obtained as the limit behaviour when the populations tend to infinity and are usually deterministic and continuous. We study the dynamics obtained by both approaches in systems with one deterministic equilibrium. We show that such dynamics can exhibit rather different behaviour around the deterministic equilibrium, in particular, the limit behaviour can tend to an equilibrium while the stochastic discrete dynamics oscillates indefinitely. To evaluate such stochastic oscillations quantitatively, we propose a system of differential equations on polar coordinates. The solution of this system provides several measures of interest related to the stochastic oscillations, such as average amplitude and frequency.

Mathematical analysis of plankton population dynamics

Malaysian Journal of Fundamental and Applied Sciences

Harmful algal blooms (HABs) event that causes enormous economic loss and health effect raises concerns among environmentalists. In this paper, a mathematical model of interaction between nutrient, toxin-producing phytoplankton (TPP), non-toxic phytoplankton (NTP), zooplankton, and toxic chemicals is proposed to study on how the process of these HABs occurred. The model of interaction is represented by Ordinary Differential Equations (ODEs) and stability analysis of the model is conducted. Several conditions for the system to be stable around trivial and interior equilibrium point are obtained. From the analysis, it is observed that under nutrient limitation, the amounts of toxic chemicals secreted out by the TPP are increased. As a result, NTP population and zooplankton population are affected by the situation. If this situation is prolonged, this will result in the extinction of both populations. Overall, this study shows that TPP release more toxic chemicals when the nutrient is l...

Modelling and analysis of a phytoplankton–zooplankton system with continuous and discrete time

Mathematical and Computer Modelling of Dynamical Systems, 2016

In this study, a phytoplankton-zooplankton system has been modelled using a system of differential equations with piecewise constant arguments, which represents a new approach to modelling phytoplanktonzooplankton interaction. To analyse the dynamic behaviour of the model, we consider the solution of the system in a certain subinterval, which yields a system of difference equations. Some theoretical results on the boundedness character and local stability properties for the discrete dynamical system are obtained. In addition, we explain the biological dynamics of the bloom in the plankton model through Neimark-Sacker bifurcation and obtain the threshold values for different parameters that govern the periodic nature of the bloom. We conclude that, while other studies explained that the bloom depended on only one parameter, this study explains that the bloom depended on three different parameters, namely θ (rate of toxin production per phytoplankton), β (zooplankton growth efficiency) and K (environmental carrying capacity of phytoplankton).

Stochastically perturbed allelopathic phytoplankton model

Electronic Journal of Differential …, 2010

In this article we have considered a stochastic delay differential equation model for two species competitive phytoplankton system with allelopathic stimulation. We have extended the deterministic model system to a stochastic delay differential equation model system by incorporating multiplicative white noise terms in the growth equations for both species. We have studied the mean square stability of coexisting state using a suitable Lyapunov functional. Numerical simulation results are provided to validate the analytical findings.

Almost periodic solution of a non-autonomous model of phytoplankton allelopathy

Nonlinear Dynamics, 2012

In this paper, a non-autonomous two species competitive allelopathic phytoplankton model in presence of a discrete time delay is considered. We have obtained the sufficient conditions for permanence along with existence-uniqueness of an almost periodic solution. Sufficient conditions are derived for the existence of unique almost periodic solution. Analytical findings are supported through exhaustive numerical simulations. With the help of the numerical example, we have demonstrated that initial density dependent almost periodic co-existence is possible in some situations when parameter values fail to satisfy all the conditions of permanence.

The Stability Analysis of The Plankton Full Interaction Model

To further investigate our understanding of biological processes in mathematical terms, we study the full original model of prey and predator interactions studied previously by [1]. We consider three species populations: phytoplankton (P); microzooplankton (M); and the volatile chemical released (C).We previously considered C as constant, due to the fact that we used a short timescale experimentally to explore the effect of the signaling chemical released, DMS (C). To further elucidate the function of Infochemical-mediated plankton interaction and phytoplankton bloom formation, we explored the dynamics of the model across the full range of a few parameters, both numerically and analytically. All current result are compared to the results in our previous publications.

Resonance and frequency-locking phenomena in spatially extended phytoplankton–zooplankton system with additive noise and periodic forces

Journal of Statistical Mechanics: Theory and Experiment, 2008

It is shown that natural systems are undeniable subject to random fluctuations, arising from either environmental variability or internal effects. In this paper, we present a spatial version of phytoplankton-zooplankton model that includes some important factors such as external periodic forces, noise, and diffusion processes. The spatially extended phytoplankton-zooplankton system is from the original study by Scheffer [M Scheffer, Fish and nutrients interplay determines algal biomass: a minimal model, Oikos 62 (1991) 271-282]. Our results show that the spatially extended system exhibit a resonant patterns and frequency-locking phenomena. The system also shows that the noise and the external periodic forces play a constructive role in the Scheffer's model: first, the noise can enhance the oscillation of phytoplankton species' density and format a large clusters in the space when the noise intensity is within certain interval. Second, the external periodic forces can induce 4:1 and 1:1 frequency-locking and spatially homogeneous oscillation phenomena to appear. Finally, the resonant patterns are observed in the system when the spatial noises and external periodic forces are both turned on. Moreover, we found that the 4:1 frequency-locking transform into 1:1 frequency-locking when the noise intensity increased. In addition to elucidating our results outside the domain of Turing instability, we provide further analysis of Turing linear stability with the help of the numerical calculation by using the Maple software. Significantly, oscillations are enhanced in the system when the noise term presents. These results indicate that the oceanic plankton bloom may partly due to interplay between the stochastic factors and external forces instead of deterministic factors. These results also may help us to understand the effects arising from undeniable subject to random fluctuations in oceanic plankton bloom.

Random Excitations in Modelling of Algal Blooms in Estuarine Systems

International Journal of Ecological Modelling, 2011

This paper proposes and analyzes a non-linear model for the biological outbreaks that links the trophic structure of primary and secondary producers in the estuary. Some of the principles governing phyto- plankton growth, biomass, and species composition in two-layered pelagic ecosystems are explored using an idealized, steady-state, mathematical model. Algal blooms often occur in estuary due to excessive flow of nutrients from domestic drainage, industrial and agricultural waste, and this causes the decrease in the concentration of dissolved oxygen in the estuary. We propose a description about interesting marine estuary systems which resembles to the behaviour of real media and construct a non-linear mathematical model with the main purpose of considering the severity and duration of algal blooms in the ecological arena. Although the environmental and physical factors that unleashed the bloom, but ensuing duration and severity of an outbreak are largely due to the subsequent biological interplay between organism. Hence, it threatens the survival of other species of the ecosystem indirectly, and also it is responsible for the degradation of water quality in the estuary because of less oxygen content. We give the results that are qualitatively resemble with those observed in the estuary and thereby offers an insight for the factors that sustain a bloom.