藻源性颗粒沉降胁迫下湖滨区苦草生长响应机制研究

The degradation of submerged vegetation along the lakeside area under the stress of algal bloom is now a serious environmental issue for many lake ecosystems. However, the detailed mechanism of the degradation is still unclear. This program focuses on the variations of the physical and chemical environmental conditions and the enrichment of sulfides around the rhizosphere caused by the algal-induced particulate matter. In addition, the response mechanism of the submerged vegetation to this process will also be studied. The Vallisneria natans, one of the dominant species in Lake Taihu, will be chosen for the study. Field investigations and indoor simulated experiments will be carried out to analyze the spatial and temporal variations of the physical and chemical environmental conditions and the enrichment of sulfides around the rhizosphere caused by the algal-induced particulate matter. Thereby, the formation process of sulfides around the rhizosphere of the Vallisneria natans will be expounded. The high resolution micro-interface system will be used to analyze the distribution, transfer, and enrichment of sulfides in the root of the Vallisneria natans. On the basis of these studies, the response mechanism of Vallisneria natans to the enrichment of sulfides during different growth phases will be further investigated. The response mechanism of Vallisneria natans to the deposition of algal-induced particulate matter is supposed to be revealed after these studies. The accomplishment of the study is supposed to further complete the degradation mechanism of submerged vegetation along the lakeside area under the stress of algal bloom, and to provide scientific basis for the recovery and conservation of submerged vegetation in eutrophic lakes.

藻类暴发胁迫下湖滨水域沉水植被退化是湖泊生态系统面临的严峻环境问题，然而，其退化机制尚不明确。本研究关注湖滨区域沉降藻源性颗粒降解导致的根际物化环境变化及还原态硫富集过程，以及此过程中沉水植物生长的响应机制。拟选择太湖沉水植物优势种苦草作为对象，通过野外调查及室内模拟实验，分析藻源性颗粒沉降驱动下苦草根际泥水界面环境要素特征及还原态硫产率和通量时空变化规律，阐明苦草根际还原态硫形成过程。并结合高分辨率微界面测试系统，获取还原态硫在苦草根系微界面的分布、迁移及累积特征。在此基础上，进一步剖析苦草不同生长阶段对根系还原态硫富集的响应特征，揭示藻源性颗粒沉降胁迫下苦草生长响应机制，以期丰富和完善藻类暴发影响下的湖滨水域沉水植被退化机制，为富营养化湖泊沉水植被恢复及保育提供科学依据。

藻类暴发胁迫下湖滨带沉水植被退化是湖泊生态系统面临的严峻环境问题，然而，其退化机制尚不明确。本研究关注湖滨带沉降藻源性颗粒降解导致的根际物化环境变化及还原态硫富集过程，以及此过程中沉水植物生长的响应机制。选择太湖竺山湾、梅梁湾、东太湖等典型藻型及草型湖滨带区域，进行了持续的野外观测研究。结果表明，藻型湖滨带颗粒物沉降通量显著高于草型区域，尤其是在藻类大规模爆发的季节，藻源性沉降颗粒通量是草型区域的10倍以上。藻源性颗粒沉降后在泥水界面形成的薄层富含大量藻体，在沉降后将快速发生衰亡、降解过程，此过程导致泥水界面氧迅速消耗，沉积物和上覆水体中还原态硫含量迅速上升。其中，无机态还原硫和有机态还原硫分别是湖滨带水体致黑和致臭的主要物质。对颗粒物中还原态硫形态解析结果显示，夏、秋季以酸可挥发性硫（AVS）为主，春季和冬季则以黄铁矿硫（CRS）为主。沉降藻源性颗粒衰亡降解导致的氧消耗和还原态硫浓度上升，导致苦草植株生物量和活性快速下降，在20天内即可发生植株衰亡、腐败现象。富营养湖滨带藻颗粒的大量聚积、沉降是导致沉水植物衰亡、退化的主要原因之一。在藻类暴发季节，应使用相应措施降低湖滨湿地中藻颗粒浓度，以缓解对沉水植物的胁迫作用。