Holecene Paleoenvironmental Reconstruction from the Shark River Estuary, Everglades, Florida

Abstract

This dissertation examines the paleoecological records from the Shark River Estuary in the southwestern part of the Everglades National Park (ENP), Florida, with primary goal of reconstructing the Holocene history of the coastal mangrove ecosystem in the Florida Coastal Everglades. Roughly 15 meters of sediments were collected from 4 study sites and subjected to loss-on ignition, palynological, and X-ray fluorescence analyses. According to the literature, the earliest communities of Rhizophora mangle (red mangrove) occurred prior to 8,000 cal yr BP in the south-central area of the Belize Barrier Reef Platform. Between 7,000 and 5,000 cal yr BP, Rhizophora was established in the Caribbean coast of South America and Central America. With warmer winter sea-surface temperature and a decreased rate of sea-level rise between 5,000 and 3,000 cal yr BP, Rhizophora eventually colonized the coastlines of the Yucatan, South Florida, and Bermuda. Statistical analysis of 25 modern pollen spectra from the Everglades National Park shows that different wetland sub-environments in the Everglades can be identified based on their palynological signature. Accordingly, palynological data from sediment cores can be used to accurately reconstruct past wetland responses to a variety of environmental and climatic changes in the Everglades. Multi-proxy analyses of sediment cores from four study sites along the Shark River Estuary reveal that the mid-Holocene sea-level rise is the dominant cause of vegetation change. The Shark River Estuary underwent three major transformations during the last six millennia: (1) Short-hydroperiod marl prairies were progressively replaced by long hydroperiod prairies and sloughs from ¡­5,700 to 3,800 cal yr BP. (2) Long hydroperiod prairies and sloughs were replaced by brackish marsh from 3,800 to 2,000 cal yr BP. (3) A significant expansion of mangroves occurred over the last 2,000 years. In addition to Hurricane Wilma in 2005, the southwestern Everglades were directly impacted by at least six major hurricanes at ~3,000, 1,700, 950, 580, 350, and 120 cal yr BP. At ~1,100 cal yr BP, as the shoreline became stabilized, a mixed mangrove forest was formed at the mouth of the Shark River.