INTRODUCTION

The current massive effort to restore south Florida, guided by the Comprehensive Everglades Restoration Plan (CERP), lists restoration of the timing, quantity and quality of the natural flow of freshwater as one its primary goals.  Before restoration can occur, however, the baseline conditions of the environment prior to significant human alteration must be established and the range of variation within the natural system must be determined.  This information can then be used by resource managers to establish targets and performance measures for restoration.

Figure 1. Satellite image map of Biscayne Bay, Florida, showing sites where USGS cores were collected and the boundary of Biscayne National Park (blue dashed line). Image cropped from John W. Jones and others (2001) . [larger image]

The information generated by this research addresses the needs of the many entities involved in managing Biscayne Bay, primarily Biscayne National Park and South Florida Water Management District (SFWMD).  SFWMD's Water Management Plan for south Florida includes the establishment of minimum flows and water levels for different bodies of water within the District, including Biscayne Bay (with an emphasis on central and southern Biscayne Bay) (www.sfwmd.gov/org/wsd/mfl/biscaynebay).  The purpose of the Biscayne Bay Coastal Wetlands Project (BBCW) of the Comprehensive Everglades Restoration Plan (CERP) is "to rehydrate wetlands and reduce point source discharge to Biscayne Bay" (http://www.evergladesplan.org/pm/projects/proj_28_biscayne_bay.cfm) and the project identifies the need to "define target freshwater flows for Biscayne Bay and the wetlands."  Biscayne National Park, like all National Parks, was charged by the Organic Act of 1916 with “conserving the scenery and the natural and historic objects, and the wildlife therein and to provide for the enjoyment of the same in such means as will leave them unimpaired for the enjoyment of future generations.”  One of the Park’s management goals is to understand how the conditions of the resources have changed over time.  Our research provides these agencies with long-term spatial and temporal data on changes to the ecosystem that allow them to establish minimum flow values, targets, and performance measures based on centuries of data and to understand how to conserve and protect the resource.

In order to achieve our project objectives, we have examined a total of eleven cores, six collected specifically for the current project.  This report is divided into three sections to discuss three different categories of cores:  (1) mudbank cores; (2) wetland cores; and (3) near-shore cores.  Three of the eleven cores were collected from mudbanks in central and southern Biscayne Bay in 2002, and the bulk of these analyses were discussed in Wingard and others (2003); however, some additional analyses completed since the publication of that report are described here in the "Additional Analyses of Mudbank Cores" section.  Two wetland cores were collected in order to examine changes to the wetland ecosystems bordering the bay; these are discussed in section entitled "Patterns of Change in the Wetlands at Military Canal."  In order to determine more accurately the role of freshwater influx on the patterns seen in the mudbank cores, three additional cores were collected in 2003 at sites located in near-shore areas in close proximity to historical freshwater drainage; the preliminary results of these analyses are reported in the "Patterns of Change at Near-shore Sites" section.

The multiproxy, multicore approach utilized in this study has been successfully used in Florida Bay (Brewster-Wingard and others, 1998; Brewster-Wingard and Ishman, 1999; Nelsen and others, 2002; Wardlaw, 2001) and will be utilized to address issues in other areas of south Florida in the future.  By understanding the past - the natural range of variation within an ecosystem - we can set realistic goals for restoration, and through the past we can potentially understand the future and how the system will respond to restoration efforts.