沉积物环境变化对热带泰来草的影响过程与机制

Seagrasses support important ecosystem function and service for coastal areas. In recent years seagrass decline has been reported due to physical disturbances and eutrophication throughout the world. Researches about the combined effects of physical disturbances and eutrophication on seagrasses are still lack, although sediment physical environment changes and eutrophication effects on seagrasses have been studied separately for some seagrass species. In this project we aim to combine 3 comprehensive approaches: field monitoring, manipulative field experiments and mesocosm experiments to study: 1) in natural field conditions, the relationship between seagrass Thalassia hemprichii morphological, physiological parameters and environmental variables in Xincun Bay, Hainan Island. 2) response mechanisms of seagrass Thalassia hemprichii to sediment physical environment changes, such as burial and erosion, 3) the combined effects of physical disturbances and eutrophication on seagrass Thalassia hemprichii, 4) influences of iron content in sediment on reducing negative effects of eutrophication on seagrass Thalassia hemprichii. Under the conditions of gradually serious eutrophication, increasing reclamation engineering and more typhoon disasters in China, our results will support deeply understanding the combined effects of global climate change and human activities on seagrass decline, also provide scientific basis for ecological restoration of damaged seagrass beds.

海草床为海岸带区域提供关键的生态系统服务和功能。近年来，由于物理干扰和富营养化的影响，全球范围内海草衰退严重。虽然学术界对沉积物物理环境变化和富营养化对海草的影响机制进行了相关研究，但是沉积物物理环境变化和富营养化对海草的协同影响方面的研究还很缺乏。基于此，本项目拟选择海南新村湾热带海草床内的优势种泰来草作为研究对象，采用野外观测、野外围栏操控实验和室内模拟实验，研究自然条件下，海草生理指标和形态指标及其环境影响因素，分析海草对沉积物物理环境变化（掩埋和侵蚀）的响应机制；探讨沉积物掩埋和侵蚀以及沉积物有机物富集对海草的协同影响；评估沉积物铁含量对于缓解富营养化对海草负面影响的作用机制，在我国近岸水体富营养化日益严峻，围填海活动进一步扩大和台风等自然灾害日益频发的背景下，结果对于深入理解全球气候变化和人类活动对海草衰退的双重影响具有重要的科学意义，同时可以为受损海草床的生态修复提供科学依据。

海草床为海岸带区域提供关键的生态系统服务和功能。近年来，由于物理干扰和富营养化的影响，全球范围内海草衰退严重。本项目主要研究了自然条件下，热带海草泰来草指标及其环境影响因素，评估了热带海草泰来草对沉积物物理变化的响应机制，揭示了沉积物营养盐、有机物富集和铁添加对热带泰来草海草生态系统的影响。. 新村湾泰来草海草床海水盐度、温度、pH、氨氮浓度、磷酸盐浓度以及沉积物粒径均呈现显著的月度差异。泰来草海草叶片长度和宽度、根长度、根状茎节长和直径均呈现显著的月度差异。海水温度与泰来草叶片宽度显著正相关，盐度与泰来草叶片长度和根状茎节长显著正相关，盐度与泰来草根状茎直径显著负相关。. 营养盐、有机质和铁富集对海草生物量产生了显著的正面影响，都添加时海草地上生物量和地下生物量最高，营养盐和有机物富集促进了海草叶片的生长。同时，沉积物营养盐添加显著提高了沉积物有机碳含量，表明营养盐长期富集可能对海草床产生一定程度的负面影响。. 在波浪的影响下，沉积物侵蚀可能对海草床产生负面影响，沉积物侵蚀和波浪影响时间密切相关，有海草区域，沉积物保持时间比无海草区域保持时间长。由于缺乏根系间的支撑作用，像海菖蒲这种无茂密根状系统的海草种类维持沉积物稳定的能力不如根系茂密的种类。. 在全球气候变化和近岸水体富营养化背景下，应加强对受损海草床的长期监控，减小富营养化和海岸侵蚀对海草床的负面影响。