蓝藻水华对螺形龟甲轮虫反捕食策略的影响

Anti-predator adaptation can be induced by predator in ecosystems, which is at the expense of reproduction of prey. In eutrophic lakes, cyanobacterial blooms have profound effects on populations and interactions of zooplankton. But it is unclear how cyanobacteria affects the prey-predator interactions between zooplankton and survival strategies of prey. This study hypothesizes that shelter from colonial cyanobacteria would weaken the predation pressure of cyclopoids on rotifer Keratella cochlearis, and this weakness would change the trade-off between defense and reproduction of K. cochlearis, leading to decreased defense and increased reproduction. Combined with historical data, field investigation and experiments, we first reveal the temporal and spatial variations of traits of defense and reproduction in K. cochlearis and quantify the effect of cyanobacteria on its anti-predator characteristics. Then we conduct the experiments to demonstrate the effects of selective and inducing predation on K. cochlearis in the condition of cyanobacteria. This study will further analyse the survival strategy of zooplankton in eutrophic lakes based on the ecological adaptation and evolution. The results will contribute to understand the effect of cyanobacterial blooms on prey-predator interactions and consequently ecological function.

富营养湖泊的蓝藻水华对浮游动物的种群和相互作用产生了很大的影响，然而蓝藻如何影响浮游动物间的捕食关系及被捕食者的反捕食策略，其机制尚不清楚。本研究以剑水蚤（捕食者）和螺形龟甲轮虫（被捕食者）为研究对象，假设富营养湖泊中蓝藻群体的庇护会削弱剑水蚤对螺形龟甲轮虫的捕食压力，捕食关系的削弱会影响螺形龟甲轮虫防御和繁殖的权衡关系，螺形龟甲轮虫防御减少，繁殖率增加。本项目结合历史数据、野外调查和室内实验，以功能性状为定量指标，分析自然条件下，螺形龟甲轮虫防御和繁殖性状的时空变化规律，量化蓝藻对螺形龟甲轮虫防御捕食的影响程度；在野外调查的基础上，用蓝藻进行干扰实验，分析剑水蚤直接捕食和间接诱导对螺形龟甲轮虫防御捕食的影响。本项目将从捕食关系导致的物种生态适应性和被捕食者的进化两个角度，分析富营养湖泊浮游动物的生存策略，结果有助于进一步认识蓝藻水华对捕食关系的影响，进而对生态系统功能产生影响。

人类活动导致的水体富营养化对浮游动物的种群和相互作用产生了很大的影响，然而人类活动的干扰下浮游动物的群落构建机制、以及富营养化导致的蓝藻增多如何影响浮游动物的反捕食策略，其原理尚不清楚。本项目以浮游动物为研究对象，基于长江中下游湖泊调查和太湖长时间序列监测的浮游动物数据，以浮游动物群落功能性状为定量指标，逐步深入地分析了浮游动物尤其是轮虫群落结构对湖泊富营养化、鱼类养殖和水体修复等的响应过程，以及以螺形龟甲轮虫为代表种，分析了蓝藻对其反捕食策略的影响模式。研究表明，轮虫是长江中下游湖泊的优势类群，营养水平和鱼类捕食均对浮游动物群落结构产生了重要影响。其内在机制在于轮虫的反捕食机制是以牺牲个体生长为代价的，而蓝藻丰富的环境下，蓝藻的隐蔽作用削弱了轮虫的反捕食策略的选择，有利于轮虫群落的发展。营养水平升高和环境异质性下降对浮游动物群落结构的影响会进一步削弱其下行控藻功能。而在营养削减后，轮虫群落的稳定性会增加。通过本项目的研究，认识到研究湖泊浮游生物的生存策略和群落演替机制对于深入理解环境变化对生态系统的影响至关重要。