基于概率-动力学模型的亚热带湖库浮游藻类种群增长动力学机制研究

At present, the mechanism of phytoplankton blooms is one of the most important problems to be solved in the eutrophication control of lakes and reservoirs in China. It is the key for solving this problem to reveal the mechanism of phytoplankton growth, by which we can accurately predict the phytoplankton blooms. This proposal takes phytoplankton growth dynamics for subtropical lakes and reservoirs as the research object, and does researches including collecting and analyzing data, modeling, and numerical simulation. Based on theories including population dynamic, probability, and hydrodynamic, the new probabilistic-dynamic models are proposed, which can describe the phytoplankton growth process for subtropical lakes and reservoirs. Phytoplankton growth is modeled using numerical simulation, and then to predict phytoplankton density from the viewpoint of probability distribution. By dynamic analysis and sensitivity analysis, it is studied how key ecological factors and their uncertainty influence the phytoplankton growth. This proposal is expected to propose some modeling method, analysis method, and simulation algorithm corresponding to probabilistic-dynamic models for phytoplankton growth in subtropical lakes and reservoirs, and reveal dynamic mechanism of phytoplankton growth. The findings from this proposal can provide some scientific basis and technical support to establish early warning and forecasting system for phytoplankton blooms, and then to reveal mechanism of phytoplankton blooms.

目前，浮游藻类水华暴发与成灾机理是我国湖库富营养化防治领域亟待攻克的重要问题之一，揭示浮游藻类种群的增长机制是解决该问题的关键，也是精准预测水华暴发的前提。本项目以亚热带湖库水域浮游藻类种群增长的动力学规律为研究对象，开展野外数据监测与统计分析、模型构建及计算机模拟仿真等方面的研究。基于种群动力学、概率论及水动力学等理论，构建符合亚热带湖库浮游藻类种群增长规律的概率-动力学新模型；利用计算机仿真模拟浮游藻类种群增长的动力学过程，从概率分布的角度预测浮游藻类种群密度的变化；运用动力学分析和敏感性分析，研究并揭示关键生态因子及其不确定性对浮游藻类种群增长的影响机制。本项目预期将提出系列亚热带湖库浮游藻类种群增长概率-动力学模型的建模方法、分析方法及模拟算法，阐明湖库浮游藻类种群增长的动力学机制。项目研究成果将为亚热带湖库浮游藻类水华预警预测系统的建立和暴发机理的解析提供科学依据和技术支撑。

目前，浮游藻类水华暴发与成灾机理是我国湖库富营养化防治领域亟待攻克的重要问题之一，揭示浮游藻类种群的增长机制是解决该问题的关键，也是精准预测水华暴发的前提。本项目以亚热带湖库浮游藻类种群增长动力学 规律为研究对象，开展了野外数据监测与分析、浮游藻类种群增长动力学模型构建、动力学分析及数值模拟等研究。在不考虑环境随机变化情况下，研究发现浮游藻类死亡率、浮游动物年龄结构等因子能导致模型展现出丰富的动力学行为，例如Hopf分岔、鞍结分岔、同宿分岔、Bogdanov-Taken分岔等。针对浮游藻类种群分布问题，构建了浮游藻类种群增长与扩散的对流-反应-扩散模型，获得了模型发生图灵失稳和对流失稳的临界条件，研究表明在水动力驱动下浮游藻类种群会形成局部均匀斑图、带状斑图等斑块分布，并且研究发现带状斑图是由不同波长、不同波速及不同振幅的行波共存而形成。当考虑生态因子受气候、天气等因素影响而具有随机性时，构建了浮游藻类种群增长概率-动力学模型，研究表明这些生态因子变化所服从的随机分布对浮游藻类种群密度变化有显著影响，在一定条件下较强的随机扰动能导致种群灭绝，而较小的扰动则可能更有利于种群共存。此外，研究发现在生态因子随机性扰动和脉冲控制扰动耦合作用更容易导致种群灭绝，从而影响水生态系统的稳定性 。本项目提出了亚热带湖库浮游藻类种群增长动力学模型构建、分析及模拟的相关方法，为量化生态因子对浮游藻类种群增长规律的影响提供新思路和方法基础，同时为 亚热带湖库浮游藻类水华预警预测系统的建立和暴发机理的解析提供科学依据和技术支撑。