浮游植物群落对营养盐水平变动的弹性响应及其机制

Generally, the response of phytoplankton biomass to initial nutrient reduction is not sensitive or lags behind the reduction during treatment process of eutrophic lakes, which increases the uncertainty for expected treating effect. The resilience response (compensatory dynamics) of phytoplankton community to the variation in nutrient level is the primary reason for the insensitivity or the lag. Oppositely, the collapse of resilience in phytoplankton community indicates the shift of ecosystem regime. However, it is limited for the understanding on the process and mechanisms of the resilience response of phytoplankton community to variation in nutrient level. In the study, we will integrate the long-term time series data (>25 years), field investigation data (>80 lakes) and simulated experiment in situ to (1) elaborate the relationship between the phytoplankton community turnover rate and the change rate of biomass during the nutrient reduction, and analyze potential affecting factors and their contributions for the relationship; (2) compare the difference in compensatory dynamics and functional traits of dominant species between nutrient reduction process in eutrophic lake and enrichment process in oligotrophic lake, and reveal the mechanisms of resilience response of phytoplankton community to the variation in nutrient level; (3) predict the nutrient thresholds inducing the collapse of resilience in phytoplankton community. This study will be helpful not only to understand the response process and mechanisms of phytoplankton community stability to variation in nutrient level, but also to direct the protection of healthy lakes and the treatment of eutrophic lakes.

富营养湖泊治理过程中，浮游植物生物量对于最初污染负荷削减的响应通常不敏感或具有滞后性，这增加了湖泊治理预期的不确定性。浮游植物群落对营养盐水平变动的弹性响应，即物种间的补偿作用，是保障生物量稳定维持的重要因素，弹性的坍塌则将导致系统状态的转变。目前关于浮游植物群落弹性响应营养盐变动的过程和机制仍不清楚，本项目将结合长序列数据（25年）、面上数据（>80个湖泊）和原位模拟实验，阐明富营养湖泊营养盐削减过程中浮游植物群落结构转换速率与生物量滞后响应的关系及其影响因素和贡献；揭示富营养水体寡营养化和寡营养水体富营养化两个过程中浮游植物群落补偿动力学和优势物种功能特性的差异，明确浮游植物群落弹性响应营养盐变动的生态学和功能特性机制；构建关联营养盐-群落结构-生物量的经验模型，模拟预测浮游植物群落弹性坍塌的关键营养盐阈值。此研究对于指导良好湖泊的管理和富营养湖泊的修复具有重要的理论和应用价值。

富营养湖泊治理过程中，浮游植物生物量对于最初污染负荷削减的响应通常不敏感或具有滞后性，这增加了湖泊治理预期的不确定性。浮游植物群落对营养盐水平变动的弹性响应，即物种间的补偿作用，是保障生物量稳定维持的重要因素，弹性的坍塌则将导致系统状态的转变。目前关于浮游植物群落弹性响应营养盐变动的过程和机制仍不清楚，本项目结合长序列数据、面上数据和原位模拟实验，阐明了富营养湖泊营养盐削减过程中，营养盐仍是浮游植物群落结构转换速率与生物量的主要驱动因素，气象因素其次；浮游植物种间补偿效应是富营养化湖泊中浮游植物群落生物量稳定维持的主要生态学机制，而浮游植物种群的功能特性权衡是浮游植物优势种生物量稳定维持的主要生理学机制。富营养化湖泊营养盐削减过程中，浮游植物生物量稳定性机制逐渐改变，由超富营养水平的群落优势度效应转变为富营养水平的种间补偿效应，最后转为寡中营养水平的Portfolio效应。浮游植物生物量在总磷在0.05-0.10 mg/L之间受种间补偿效应驱动，稳定性高，当总磷浓度低于0.05 mg/L时，浮游植物群落稳定性坍塌，生物量将快速下降。此研究提升了我们对于湖泊浮游植物生物量稳定维持机制的认识，对于指导良好湖泊的管理和富营养湖泊的修复具有重要的理论和应用价值。