Estimating Late 19th Century Hydrology in the Greater Everglades Ecosystem: An Integration of Paleoecologic Data and Models

Abstract

Determining hydrologic conditions prior to instrumental records is a challenge for restoration of freshwater ecosystems worldwide. Paleoecologic data provide this information on past conditions and when these data are used to adjust hydrologic models, allow conditions to be hindcast that may not be directly estimated from the paleo-data alone. In this context, the paleo-data provide real-world estimates as input to the models. Restoration of the Greater Everglades Ecosystem requires this understanding of the hydrology of the natural system prior to significant alterations due to water management and land use. Large scale models such as the Natural Systems Model (NSM 4.6.2) have been used by the South Florida Water Management District and other agencies responsible for restoration to estimate past hydrologic conditions; however, these models typically portray a drier natural system for the beginning of the 20th century than what is indicated by paleoecologic analyses and historical data. The purpose of this study is to estimate pre-20th century water levels, hydroperiods and flow in the freshwater wetlands of the Everglades by using pollen assemblage data in three sediment cores to adjust the Natural Systems Model. This study is designed to further test estimates of flow through the Everglades derived from analysis of sediment cores collected in Florida Bay. The results demonstrate that the NSM 4.6.2 underestimates water levels and hydroperiods in the Everglades compared to the paleoadjusted NSM 4.6.2 model outputs. Flow models that use the paleo-adjusted water levels as input indicate flow through Shark River Slough in the late 19th century was approximately two times flow between 1990 and 2000, and flow through Taylor Slough was approximately three times flow between 1990 and 2000. The flow estimates derived from this study agree with the estimates derived from earlier studies using estuarine cores. This integration of paleoecologic information and hydrologic models provides resource managers with the best available estimates of past conditions and allows them to set realistic targets for restoration of freshwater ecosystems.

Widespread habitat loss leads to ecosystem‐scale decrease in trophic function

“…Florida Bay is an expansive estuary consisting of shallow mud banks and interconnected basins with vast seagrass beds mainly comprised of Thalassia testudinum , Halodule wrightii , and Syringodium filiforme , located between the Everglades and the Florida Keys (Krause et al., 2023). Human modification has drastically altered freshwater flows resulting in chronic hypersalinity, which in combination with high temperatures, has led to two large‐scale die‐offs in the last 40 years (Hall et al., 2016; Marshall et al., 2020; Robblee et al., 1991). The first die‐off began in 1987 (Fourqurean & Robblee, 1999; Robblee et al., 1991), and recovery to pre‐die‐off benthic communities did not occur until 2010 (Hall et al., 2021).…”

Primed and cued: long-term acoustic telemetry links interannual and seasonal variations in freshwater flows to the spawning migrations of Common Snook in the Florida Everglades

“…Alterations to the natural hydrology have occurred over the last century due to drainage and impoundment for urban and agricultural development that have reduced the volume of freshwater entering the system [67]. Paleo-based estimates indicate that historic flow levels were 2.1 times greater than those currently found [68,69]. Despite these changes, the historic wet/dry seasonal pattern has been retained, and > 75% of the system's rainfall occurs during the wet season in May through October, with a dry season of November to April [65,66,70,71].…”

Increasing Salt Marsh Elevation Using Sediment Augmentation: Critical Insights from Surface Sediments and Sediment Cores

“…Such records cannot capture the naturally variability in the ecosystem (Manzano et al 2020). The analysis of sediment cores provides one means of furnishing long-term records of pre-disturbance wetland conditions, rates and trajectories of change in physical and biological characteristics, and natural variability in wetland characteristics and processes (Liu et al 2022;Manzano et al 2020;Marshall et al 2020;Gell 2017;Gell et al 2019).…”