Biswas Saswati, Tiwari Pankaj Kumar, Kang Yun, Pal Samares
Department of Mathematics, University of Kalyani, Kalyani - 741235, India.
Science and Mathematics Faculty, Arizona State University, Mesa, AZ 85212, USA.
Math Biosci Eng. 2019 Nov 20;17(2):1272-1317. doi: 10.3934/mbe.2020065.
In the present study, we investigate the selective feeding of zooplankton on phytoplankton infected by free-viruses in the presence of environmental toxins in the marine ecosystem. The environmental toxins assume to decrease the growth rate of susceptible phytoplankton, and increase the death rate of infected phytoplankton and zooplankton. Global sensitivity analysis identifies important parameters of the system having crucial impact on the aquatic health. The coexistence equilibrium of the system stabilizes on increasing the parameters related to inhibition of phytoplankton growth due to environmental toxins and the force of infection, and destabilizes on increasing the carrying capacity of susceptible phytoplankton and preference of zooplankton on infected phytoplankton. The chance of extinction of free-viruses increases on increasing the preference of zooplankton on infected phytoplankton or decreasing the force of infection. Moreover, if the input rate of environmental toxins is high, then the system becomes zooplankton-free for higher values of force of infection. On increasing the values of preference of zooplankton on infected phytoplankton, the system exhibits transition from stable coexistence to oscillations around coexistence equilibrium to oscillations around disease-free equilibrium. We observe that the presence of free-viruses and environmental toxins in the system drive zooplankton population to very low equilibrium values but the ecological balance of the aquatic food web can be maintained by modulating the decay (depletion) rate of free-viruses (environmental toxins).
在本研究中，我们调查了海洋生态系统中存在环境毒素时浮游动物对受游离病毒感染的浮游植物的选择性摄食情况。假定环境毒素会降低易感浮游植物的生长速率，并增加受感染浮游植物和浮游动物的死亡率。全局敏感性分析确定了对水生健康有至关重要影响的系统重要参数。随着与环境毒素导致的浮游植物生长抑制和感染力相关的参数增加，系统的共存平衡趋于稳定；而随着易感浮游植物的承载能力以及浮游动物对受感染浮游植物的偏好增加，共存平衡则趋于不稳定。浮游动物对受感染浮游植物的偏好增加或感染力降低时，游离病毒灭绝的可能性会增加。此外，如果环境毒素的输入速率较高，那么对于较高的感染力值，系统将变为无浮游动物状态。随着浮游动物对受感染浮游植物偏好值的增加，系统呈现出从稳定共存到围绕共存平衡振荡再到围绕无病平衡振荡的转变。我们观察到，系统中游离病毒和环境毒素的存在会使浮游动物种群达到非常低的平衡值，但通过调节游离病毒（环境毒素）的衰减（消耗）速率，可以维持水生食物网的生态平衡。
