Ecology Department, College of Resources & Environments, Hunan Provincial Key Laboratory of Rural Ecosystem Health in Dongting Lake Area, Hunan Agricultural University, Changsha 410128, PR China.
Ecology Department, College of Resources & Environments, Hunan Provincial Key Laboratory of Rural Ecosystem Health in Dongting Lake Area, Hunan Agricultural University, Changsha 410128, PR China.
Sci Total Environ. 2024 Feb 25;913:169601. doi: 10.1016/j.scitotenv.2023.169601. Epub 2023 Dec 28.
Understanding how phytoplankton interacts with local and regional drivers as well as their feedbacks is a great challenge, and quantitative analyses of the regulating role of human activities and climate changes on these feedback loops are also limited. By using monthly monitoring dataset (2000-2017) from Lake Taihu and empirical dynamic modelling to construct causal networks, we quantified the strengths of causal feedbacks among phytoplankton, local environments, zooplankton, meteorology as well as global climate oscillation. Prevalent bidirectional causal linkages between phytoplankton biomass (chlorophyll a) and the tested drivers were found, providing holistic and quantitative evidence of the ubiquitous feedback loops. Phytoplankton biomass exhibited the highest feedbacks with total inorganic nitrogen and ammonia and the lowest with nitrate. The feedbacks between phytoplankton biomass and environmental factors from 2000 to 2017 could be classified into two groups: the local environments (e.g., nutrients, pH, transparency, zooplankton biomass)-driven enhancement loops promoting the response of the phytoplankton biomass, and the climate (e.g., wind speed)-driven regulatory loops suppressing it. The two counterbalanced groups modified the emergent macroecological patterns. Our findings revealed that the causal feedback networks loosened significantly after 2007 following nutrient loading reduction and unsuccessful biomanipulation restoration attempts by stocking carp. The strength of enhancement loops underwent marked decreases leading to reduced phytoplankton responses to the tested drivers, while the climate (decreasing wind speed, warming winter)-driven regulatory loops increased- like a tug-of-war. To counteract the self-amplifying feedback loops, the present eutrophication mitigation efforts, especially nutrient reduction, should be continued, and introduction of alternative measures to indirectly regulate the critical components (e.g., pH, Secchi depth, zooplankton biomass) of the loops would be beneficial.
了解浮游植物如何与地方和区域驱动因素相互作用及其反馈是一个巨大的挑战，定量分析人类活动和气候变化对这些反馈环的调节作用也受到限制。本研究通过使用太湖 2000-2017 年月度监测数据集和经验动态建模来构建因果网络，量化了浮游植物、地方环境、浮游动物、气象以及全球气候振荡之间因果反馈的强度。发现浮游植物生物量（叶绿素 a）与测试驱动因素之间普遍存在双向因果关系，为普遍存在的反馈环提供了整体和定量的证据。浮游植物生物量与总无机氮和氨的反馈最强，与硝酸盐的反馈最弱。2000-2017 年浮游植物生物量与环境因子之间的反馈可分为两类：地方环境（如营养物、pH 值、透明度、浮游动物生物量）驱动的增强环促进浮游植物生物量的响应，以及气候（如风速）驱动的调节环抑制它。这两个相互制衡的组修改了新兴的宏观生态模式。研究结果表明，自 2007 年以来，随着营养物负荷减少和放流鲤鱼不成功的生物操纵恢复尝试，因果反馈网络显著松弛。增强环的强度显著下降，导致浮游植物对测试驱动因素的响应减少，而气候（风速下降、冬季变暖）驱动的调节环增加——就像拔河比赛一样。为了抵消自我放大的反馈环，目前的富营养化缓解工作，特别是减少营养物，应该继续进行，并引入替代措施来间接调节关键组件（如 pH 值、塞奇深度、浮游动物生物量）将是有益的。
