Mangrove Paleoecological Responses During Holocene Sea Level Changes: A Multiproxy Aapproach

红树林(由许多不同树种组成的沿海海洋森林)存在于热带和亚热带，处于海洋和陆地环境之间的过渡阶段；这种环境对海平面上升等环境变化特别敏感。许多沿海环境依赖红树林栖息地来减少侵蚀，缓冲飓风的影响，并为海洋生物提供栖息地。人们对红树林对未来海平面上升情景的反应感到担忧。然而，关于红树林的实验室和野外实验提供了一个有限的时间和空间视角来研究红树林对环境变化的反应。我们的研究提供了一种新的方法来研究过去红树林对全新世(最近10000年)环境变化的响应，在这段时间里，海平面已经上升。伯利兹目前连续的红树林泥炭储量是世界上最大的，为研究这一时期的红树林生态系统提供了特殊的资源。已经收集了一些泥炭岩芯，并将在这个拟议的项目期间进行分析。我们建议分析来自三个不同地点的岩芯，以形成一幅区域过去红树林生态的稳健图景。一个岩芯(约8米深)来自双礁，第二个岩芯(约8米深)来自烟草山脉。这些地点距离伯利兹大陆海岸约12公里，因此不太容易受到大陆热带植物物种的影响。此外，通过分析取自大陆沿海红树林的岩芯(约6米深)，我们将能够比较和对比海岸和岛屿红树林对全新世海平面变化的响应。生态系统的变化将通过研究保存在这些泥炭岩芯中的多条证据(过去植被的多个替代物)来确定，这些证据使用放射性碳测年来确定年代。泥炭岩芯将被分析，以寻找包括化石花粉计数在内的替代物，以跟踪植被组成的变化，以及将监测红树林随时间的生理变化的散装和复合特定稳定同位素(C和N)技术。通过分析每个地点的一套替代指标，我们将能够制定详细的历史记录，描述这些生态系统的重要方面，包括物种组成、植物形态和结构、营养状况和有效性、泥炭积累速率和生理胁迫等因素。通过分析多个站点和一个站点内的多个核心，我们将能够区分特定站点和区域趋势，这将使我们能够确定对整体生态系统变化的可靠评估。反过来，这些数据将与该地区全新世海平面变化的框架进行比较。我们相信，我们的地点是最好的地点之一，可以用来开发红树林生态系统的长期记录。归根结底，了解这些生态系统如何应对过去的环境变化对于评估热带生态系统将如何应对未来的环境变化非常重要。

Mangroves (coastal marine forests composed of a number of different tree species) exist in the tropics and sub-tropics at the transition between the ocean and terrestrial environment; a setting that is particularly sensitive to environmental changes such as sea-level rise. Many coastal environments depend on mangrove habitats to reduce erosion, buffer the influence of hurricanes and provide habitats for marine organisms. There is concern about the response of mangroves to future sea-level rise scenarios. However, laboratory and field experiments involving mangroves provide a limited temporal and spatial perspective of mangrove responses to environmental change. Our proposed research presents a novel approach to study past mangrove responses to environmental change throughout the Holocene (the last ~10,000 years), a period during which sea-level is known to have risen. The continuous deposits of mangrove peat present in Belize are the largest in the world and provide an exceptional resource to study past mangrove ecosystems over this period. A number of peat cores have already been collected and will be analyzed during this proposed project. We propose analyzing cores from three different sites to develop a robust picture of regional past mangrove ecology. One core (~8 m in depth) is from Twin Cays and a second core (~8 m in depth) is from Tobacco Range. These sites are ~12 km off of the mainland coast of Belize and are therefore less liable to be influenced by mainland tropical plant species. In addition, by analyzing a core (~6 m in depth) taken from coastal mangroves on the mainland, we will be able to compare and contrast coastal and island mangrove responses to Holocene sea-level changes. Ecosystem changes will be established by studying multiple lines of evidence (multiple proxies of the past vegetation) preserved in these peat cores, which are dated using radiocarbon dating. Peat cores will be analyzed for proxies that include counts of fossil pollen to track changes in vegetation composition, together with bulk and compound specific stable isotopic (C and N) techniques that will monitor physiological changes in mangroves with time. By analyzing a suite of proxies at each site, we will be able to develop detailed histories describing important aspects of these ecosystems, including factors such as species composition, plant morphology and structure, nutrient status and availability, peat accumulation rates, and physiological stress. By analyzing multiple sites, and multiple cores within a site, we will be able to distinguish between site-specific and regional trends, which will allow us to determine a robust assessment of overall ecosystem changes. In turn, these data will be compared with the framework of Holocene sea-level change for the region. We believe that our sites are among the best available to develop long-term records of mangrove ecosystems. Ultimately, knowledge of how these ecosystems responded to past environmental change is important in assessing how tropical ecosystems will function in response to future environmental changes.