RAPID: Degradation and Resilience of Seagrass Ecosystem Structure and Function following a Direct Impact by Hurricane Harvey

RAPID：飓风哈维直接影响后海草生态系统结构和功能的退化和恢复力

• 批准号: 1807143
• 负责人: Lauren Yeager
• 金额: $ 19.97万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-12-01 至 2019-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1807143&HistoricalAwards=false
• 关键词: RAPID; Degradation; Resilience; Seagrass; Ecosystem

Disturbance has long been recognized as a major organizing force in marine communities with the potential to shape biodiversity. Hurricanes provide a natural experiment to understand how acute physical disturbances (storm surge and wind energy) may interact with longer-term changes in environmental conditions (salinity or turbidity) to alter the structure and function of ecological communities. As models indicate that hurricane intensity and precipitation will increase with a warming climate, understanding the response and recovery of coastal ecosystems is of critical societal importance. Harvey made landfall as a Category Four hurricane on the Texas coast on August 25, 2017, bringing extreme rainfall as the storm stalled over the middle Texas coast. The heavy rainfall and freshwater run-off created a low salinity lens that continues to persist two months later. Seagrass ecosystems may be particularly vulnerable because they grow on shallow, soft-sediment bottoms (and thus are easily dislodged or buried) and because seagrasses are sensitive to changes in salinity and turbidity. The societal implications of seagrass loss are well recognized: seagrasses provide highly valuable ecosystem services of large economic value for estuarine and nearshore dependent fisheries, serve as nursery habitats, and sequester gigatons of carbon on a global scale. Using measurements of the health and function of the seagrass and of the community for which it is habitat, the PIs are assessing the impact of the hurricane and of the persistent freshwater lens. Context is provided by looking at non-impacted sites and by six prior years of data.This project addresses the overarching question: How do intense physical disturbances in conjunction with chronic chemophysical perturbations affect loss and recovery of seagrass community structure and function, including local production, trophic linkages, and metazoan community diversity? To understand the impacts of Hurricane Harvey on seagrass ecosystems across the middle Texas coast, the investigators are (1) documenting losses in physical habitat structure, (2) teasing apart independent and interactive effects of multiple stressors associated with storm events on biodiversity and ecosystem function, and (3) identifying factors that promote resilience following disturbance. A state-wide seagrass monitoring program with six years of data from areas within Harvey's path and surrounding seagrass systems will provide invaluable context. The investigators are measuring seagrass structure, employing a Before-After-Control-Impact design at sites that experienced severe physical damage and appropriate reference sites. In situ loggers deployed after the storm track the evolution of the low salinity event together with seagrass physiological stress measurements (e.g. chlorophyll fluorescence, pigment loss, reduced growth). Changes in seagrass habitat function is assessed through measurements of faunal biodiversity within impacted and reference sites sampled via cores, benthic push nets, and seine nets. Tethering assays of seagrass blades and common invertebrate prey enables comparison trophic interactions across sites that vary in disturbance impact. These data are used to create models of ecosystem response to an extreme disturbance event and identify factors that best predict recovery of the physical structure of the habitat and of associated ecosystem functions.

长期以来，干扰一直被认为是海洋群落的主要组织力量，具有塑造生物多样性的潜力。飓风提供了一个自然实验，以了解剧烈的物理扰动（风暴潮和风能）如何与环境条件（盐度或浊度）的长期变化相互作用，从而改变生态群落的结构和功能。模型表明，飓风强度和降水量将随着气候变暖而增加，因此了解沿海生态系统的响应和恢复具有至关重要的社会重要性。 2017 年 8 月 25 日，四级飓风哈维在德克萨斯州海岸登陆，风暴在德克萨斯州中部海岸停滞，带来了极端降雨。强降雨和淡水径流造成了低盐度透镜体，这种透镜体在两个月后仍持续存在。海草生态系统可能特别脆弱，因为它们生长在浅的软沉积物底部（因此很容易被移动或掩埋），而且海草对盐度和浊度的变化很敏感。海草损失的社会影响已得到充分认识：海草为河口和近岸依赖的渔业提供了具有巨大经济价值的高度有价值的生态系统服务，作为苗圃栖息地，并在全球范围内封存了数十亿吨的碳。通过对海草及其栖息地群落的健康和功能的测量，PI 正在评估飓风和持久性淡水透镜体的影响。通过查看未受影响的地点和前六年的数据来提供背景信息。该项目解决了一个首要问题：强烈的物理干扰与慢性化学物理扰动如何影响海草群落结构和功能的丧失和恢复，包括当地生产、营养联系和后生动物群落多样性？为了了解飓风哈维对德克萨斯州中部海岸海草生态系统的影响，研究人员正在（1）记录物理栖息地结构的损失，（2）梳理与风暴事件相关的多个压力源对生物多样性和生态系统功能的独立和交互影响，以及（3）确定促进干扰后恢复力的因素。 全州范围内的海草监测计划将提供哈维路径内区域和周围海草系统六年的数据，这将提供宝贵的背景信息。研究人员正在测量海草结构，在遭受严重物理损坏的地点和适当的参考地点采用“前后控制影响”设计。风暴后部署的现场记录仪跟踪低盐度事件的演变以及海草生理应激测量（例如叶绿素荧光、色素损失、生长减少）。海草栖息地功能的变化是通过对受影响地点和参考地点内通过岩心、底栖推网和围网采样的动物生物多样性进行测量来评估的。对海草叶片和常见无脊椎动物猎物的系留分析能够比较干扰影响不同的地点之间的营养相互作用。这些数据用于创建生态系统对极端干扰事件的响应模型，并确定最能预测栖息地物理结构和相关生态系统功能恢复的因素。

项目成果

In the wake of a major hurricane: Differential effects on early vs. late successional seagrass species

• DOI: 10.1002/lol2.10112
• 发表时间: 2019-10-01
• 期刊: LIMNOLOGY AND OCEANOGRAPHY LETTERS
• 影响因子: 7.8
• 作者: Congdon, Victoria M.;Bonsell, Christina;Dunton, Kenneth H.
• 通讯作者: Dunton, Kenneth H.