亚热带暴雨事件的河海界面生物地球化学响应

Extreme weather events like rain storm were predicted to be increased as a result of global climate change. However, effects of storm event on subtropical aquatic system are poorly understood. In this study, biogeochemical responses to storm events will be investigated in the Jiulong River-Estuary system. A multiple-survey approach for both river and estuary area through fixed-point continuous monitoring, ferry-based cruise, buoy real-time observation is implemented during various storm events, as well as baseflow periods for comparation. We then develop an integrated dataset of biogenic elements (various forms of nitrogen, phosphorus, silicon), physiochemical characteristics, meteorology and hydrology, and phytoplankton (biomass and community). Using time-series analysis, spatial analysis, isotope tracer and lab experiments, our analyses emphasize riverine export of water and materials, nutrient-discharge pattern, and change in nutrient behavior and key biogeochemical process (e.g., nitrification, denitrification, and sediment nutrient exchange). Short term ecological response will be monitored based on buoy real-time observations. The objectives of the study is to examine the extent of biogeochemical response in river-sea interface to storm runoff, and to link estuarine primary production with the drastic nutrient dynamic and non-linear addition of ammoninum. This study aims at understanding the watershed-estuary relationship and associated ecological effects in the context of increasing human and climate perturbation.

聚焦亚热带极端天气（暴雨事件）的河海生物地球化学过程，针对九龙江河流－河口系统，开展河流－河口同步综合观测（定点过程性观测、船基走航大面调查、锚式浮标阵列实时观测），获取从河流到河口区的综合数据集（生源要素、理化因子、气象水文、浮游生物等）。基于时间序列分析、空间分析、同位素示踪和培养试验，研究暴雨条件下河流水和物质输送过程、流量－营养物输出量关系、河口混合区营养盐氮磷生物地球化学行为和关键过程（硝化、反硝化和沉积物释放）变化。基于浮标实时观测，捕捉河口生态系统的短期响应信号。探明河海界面营养盐生物地球化学行为和相关过程对暴雨径流输入的响应范围和程度，以及氮磷的脉冲式输入和氨氮的不等比例增加对河口初级生产的影响。研究目标是深入理解人类活动和气候变化干拢下的亚热带流域－河口关系和河口生态环境效应。

项目聚焦亚热带极端天气（暴雨事件）的河海生物地球化学过程。设计河流、河口同步观测策略，实现高时间分辨率生物地球化学测量。综合运用定点过程性观测、船基走航大面调查、锚式浮标实时观测，成功捕捉到不同量级降雨事件（包括台风暴雨）洪水过程营养盐和颗粒物参数随时间的变化。探明了亚热带地区暴雨条件下河流流量和物质的输送关系，发现气象条件（降雨）和水文过程（流量）控制了营养盐输出通量以及稀释与富集格局。对比分析了河口混合区营养盐氮磷硅的生物地球化学行为（添加或去除）和关键界面通量（河流-河口界面、河口-近海界面）在暴雨事件和常态时的显著差异。研究发现暴雨事件显著增强最大浑浊带对颗粒态磷的滞留，但增加了溶解态氮和磷的向海输出。发现暴雨径流携带更多的陆源氨氮及无机磷（包括大量颗粒结合态磷进入河口后释放为无机磷），导致营养盐供给结构发生变化，可引发库区和河口湾生态系统的藻华过程。.该项目注重现场观测，克服台风暴雨恶劣天气，获得宝贵的、十分丰富的第一手生物地球化学测量数据，取得一系列创新性成果，推进了关于人类活动和气候变化影响流域－河口关系及生态环境效应的科学认知。