Doctoral Dissertation Research: Holocene Climate and Environmental History of Laguna Saladilla, Dominican Republic

湖泊沉积物记录为重建过去的环境和揭示未来自然环境如何响应与人类有关的气候变化提供了强有力的工具。与北美和欧洲的高纬度地区相比，加勒比地区存在的全新世古环境记录相对较少，这主要是因为湖泊较少，而且许多湖泊在干旱或人类改变或破坏期间容易干涸。拉古纳萨拉迪拉湖是伊斯帕尼奥拉岛上的一个大湖泊（面积2.2平方公里），距离多米尼加共和国北部海岸约5.3公里，靠近海地边境。由于受到科迪勒拉七纬带的东北信风和科迪勒拉中部的南方海风的庇护，拉古纳萨拉迪拉处于理想的位置，可以记录冬季定期进入该地区的极地爆发频率的变化。然而，随着时间的推移，七层断裂带向西伸展的运动使沉积物记录变得复杂。本博士论文研究项目将利用探地雷达（GPR）和2001年回收的10.4米长的沉积物岩心的环境指标研究相结合的方法，研究构造和气候过程对拉古纳萨拉迪拉盆地沉积物的影响。该博士生将使用探地雷达对湖泊沉积物进行时空表征，以量化湖泊沉积物发生变化的时间和地点。这些数据将与沉积物核心中的硅藻、花粉和微观木炭的分析一起使用，以确定湖泊沉积物的变化是由构造、气候还是两者共同驱动的。该学生还将沿着湖泊的样带收集水样和湖泊学数据，以表征当今硅藻群落的特征，并为解释过去硅藻分类群的变化提供更坚实的基础。在拉古纳萨拉迪拉进行的这项研究将提供过去8000年来加勒比地区气候变化的详细记录。研究结果对于评估伊斯帕尼奥拉岛的植被、火灾生态和水文资源如何响应过去的气候变化具有重要价值。这些重建将为评估未来与人类有关的气候变化的潜在生态影响提供有用的信息。探地雷达野外研究将检查可能的构造引起的沉积物供应变化，这在解释古环境代用物时经常被忽视。探地雷达在湖泊沉积物研究中尚未得到广泛应用，以往的研究大多是在高纬度地区进行的。因此，这个项目将有助于确定探地雷达在热带湖泊沉积物研究中的作用。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。

Lacustrine sediment records provide powerful tools for reconstructing past environments and revealing how the natural environment may respond to human-related climate change in the future. In comparison to the higher latitudes of North America and Europe, relatively few Holocene paleoenvironmental records exist in the Caribbean region, largely because of a paucity of lakes and the vulnerability of many lakes to dessication during droughts or alteration or destruction by humans. Laguna Saladilla is a large (2.2 square kilometers in area) lake on the island of Hispaniola, located approximately 5.3 km from the north coast of the Dominican Republic near the border with Haiti. Sheltered from the northeast trade winds by the Cordillera Septentrional and from sea breezes from the south by the Cordillera Central, Laguna Saladilla is ideally positioned to record changes in the frequency of polar outbreaks that periodically move into the region during the winter. Movement of the western extension of the Septentrional fault zone over time complicates the sediment record, however. This doctoral dissertation research project will examine the impacts of tectonic and climatic processes on the sediments of the Laguna Saladilla basin using a combination of ground-penetrating radar (GPR) and the study of environmental proxies in a 10.4 meter-long sediment core recovered in 2001. The doctoral student will perform both spatial and temporal characterizations of lake sediments using GPR to quantify where and when changes in the lake sediments have occurred. These data will be used in conjunction with analyses of diatoms, pollen, and microscopic charcoal in the sediment core to determine whether changes in lacustrine sediments are driven by tectonics, climate, or both. The student also will collect water samples and limnological data along transects across the lake to characterize the present-day diatom community and provide a firmer basis for interpreting changes in diatom taxa in the past.This research at Laguna Saladilla will produce a detailed record of Caribbean climate change over the past 8,000 years. Results will be valuable for assessing how the vegetation, fire ecology, and hydrological resources of Hispaniola have responded to changes in climate in the past. The reconstructions will provide information useful in assessing the potential ecological impacts of future human-related climate change. The GPR field study will examine possible tectonically induced shifts in sediment supply that often are overlooked in interpretations of paleoenvironmental proxies. GPR is not yet widely used in studies of lake sediments, and most previous research has been conducted at high latitudes. This project therefore will help establish a role for GPR in studies of tropical lake sediments. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.