Ecosystem History of the Southwest Coast-Shark River Slough Outflow Area

The objectives of this project are to document impacts of changes in salinity, water quality, coastal plant and animal communities and other critical ecosystem parameters on a subdecadal-centennial scale in the southwest coastal region (from Whitewater Bay, north to the 10,000 Islands), and to correlate these changes with natural events and resource management practices. Emphasis will be placed on 1) determining the amount, timing and sources of freshwater influx (groundwater vs. runoff) into the coastal ecosystem prior to and since significant anthropogenic alteration of flow; and 2) determining whether the rate of mangrove and brackish marsh migration inland has increased since 20th century water diversion and what role sealevel rise might play in the migration.

First, the environmental preferences and distributions of modern fauna and flora are established through analyses of modern samples in south Florida estuaries and coastal systems. Much of these data have already been obtained through project work conducted in Florida Bay and the terrestrial Everglades starting in 1995. These modern data are used as proxies for interpreting the historical data from Pb-210 and C-14 dated sediment cores based on assemblage analysis. On the basis of USGS data obtained from cores in Florida Bay and Biscayne Bay, the temporal span of the cores should be at a minimum the last 150 years; this is in agreement with University of Miami data showing sedimentation rates in Whitewater Bay to be approximately 1cm/year. For the estuarine/coastal ecosystems, a multidisciplinary, multiproxy approach will be utilized on cores from a transect from Whitewater Bay north to 10,000 Islands. Biochemical analyses of shells and chemical analyses of sediments will be used to refine data on salinity and nutrient supply, and isotopic analyses of shells will determine sources of water influx into the system. Nutrient analyses will be conducted to determine historical patterns of nutrient influx. To examine the inland migration of the mangrove/coastal marsh ecotone, transects from the mouth of the Shark and Harney Rivers inland into Shark River slough will be taken. These cores will be evaluated for floral remains, nutrients, charcoal, and if present, faunal remains.

This project will provide 1) baseline data for restoration managers and hydrologic modelers on the amount and sources of freshwater influx into the southwest coastal zone and the quality of the water, 2) the relative position of the coastal marsh-mangrove ecotone at different periods in the past, and 3) data to test probabilities of system response to restoration changes.

本项目旨在记录西南沿海区域（白水湾向北延伸至万岛群岛）亚十年至百年尺度内，盐度(salinity)、水质(water quality)、沿海动植物群落及其他关键生态系统参数变化所带来的影响，并将此类变化与自然事件及资源管理实践相关联。研究重点将聚焦于两方面：其一，明确在人类活动显著改变水流之前及之后，输入沿海生态系统的淡水输入(freshwater influx)的总量、时序与来源（地下水(groundwater)与地表径流(runoff)）；其二，厘清自20世纪调水工程(water diversion)实施以来，红树(mangrove)与咸淡水沼泽(brackish marsh)向内陆迁移的速率是否有所提升，以及海平面上升(sealevel rise)在该迁移过程中发挥了何种作用。

首先，通过对佛罗里达南部河口湾(estuaries)与沿海系统的现代样本开展分析，确定现代动植物群的环境偏好与分布特征。自1995年起，研究团队已通过在佛罗里达湾与陆地大沼泽地(Everglades)开展的项目工作获取了其中大部分数据。此类现代数据将作为替代指标，用于通过组合分析(assemblage analysis)解读基于铅210(Pb-210)与碳14(C-14)定年的沉积物岩芯(Sediment Cores)中的历史数据。基于从美国地质调查局(USGS)佛罗里达湾与比斯克亚湾(Biscayne Bay)获取的岩芯数据，这些沉积物岩芯的时间跨度至少可追溯至过去150年；这一结论与迈阿密大学的观测数据一致，后者显示白水湾的沉积速率约为1厘米/年。

针对河口/沿海生态系统，研究团队将对从白水湾向北延伸至万岛群岛的断面(transect)岩芯采用多学科(multidisciplinary)、多替代指标(multiproxy)的研究方法。将通过壳体的生化分析(biochemical analyses)与沉积物的化学分析，优化盐度与营养物供给(nutrient supply)相关数据；同时通过壳体的同位素分析(isotopic analyses)，确定系统内淡水输入的来源。还将开展营养物分析，以厘清历史时期营养物输入的变化模式。为探究红树/沿海沼泽生态交错带(ecotone)的内陆迁移情况，研究团队将设置从鲨鱼河与哈尼河河口向内陆延伸至鲨鱼河沼泽水道(slough)的断面。将对这些岩芯开展植物残体、营养物、炭屑以及（若存在的）动物残体的分析检测。

本项目将产出三类成果：其一，为修复管理者(restoration managers)与水文建模人员(hydrologic modelers)提供西南沿海区域淡水输入的总量、来源及水质的基准数据；其二，明确历史不同时期沿海沼泽-红树生态交错带的相对位置；其三，提供用于验证生态系统对修复措施响应概率的相关数据。