Award: DEB-1237517

The Florida Coastal Everglades (FCE) LTER program encompasses the subtropical freshwater wetlands, mangrove swamps, and shallow seagrass communities along the two main drainages of Everglades National Park. Since 2000, the FCE LTER program has transformed scientific understanding of the origins of coastal ecosystem productivity (growth rate of plant and animal biomass), particularly how nutrients regulate ecosystem responses to disturbances such as tropical storms, droughts, cold snaps, shifts in freshwater management, and sea-level rise. By pairing sustained long-term measurements with experiments, social-ecological studies, and modeling, the FCE LTER program fosters a mechanistic understanding of ecosystem function that influences policy, restoration, and management. The program is especially well-poised to address how the chronic stress of sea-level rise affects ecosystem sensitivity to disturbance legacies, social-ecological feedbacks, and regional freshwater allocation decisions. Intellectual Merit: Phase III of the FCE LTER program (2013-2018) was guided by four goals: (1) Water - assessing how accelerating sea-level rise interacts with political conflicts over freshwater restoration; (2) Ecosystem Dynamics - determining how freshwater and marine supplies change the accumulation of carbon by altering water chemistry, properties of detritus and soils, and production and composition of plants and animals; (3) Legacies - characterizing the effects of past climate and human disturbances, and; (4) Scenarios and Synthesis - using comparative studies and numerical modeling to study how freshwater restoration may reduce vulnerability to rapid climate change in coastal ecosystems. Water: Our long-term salinity measurements showed that saltwater continued to intrude into the FCE with rising sea levels and delayed freshwater restoration. However, increasing wet-season rainfall and projects to restore freshwater flows to the FCE over the last 5 years have recently increased water levels in freshwater marshes. Policy studies found improved agricultural practices and water treatment reduce the concentrations of phosphorus, the nutrient that limits plant productivity, in Everglades inflows. Most of the phosphorus coming into the FCE is from marine sources. These supplies are increasing with sea-level rise and saltwater intrusion through underlying limestone bedrock. Ecosystem Dynamics: Rising seas stimulate interior mangrove migration due to phosphorus intrusion. Interior movement of these productive forests will increase carbon capture, resulting in soil carbon and elevation gains. However, our experiments find that carbon losses can exceed increases where saltwater invades freshwater marshes, resulting in abrupt soil elevation loss that further promotes saltwater intrusion. Changes in marsh plant productivity will influence coastal food webs that are subsidized by episodic and seasonal connections to upstream detrital food supplies. Legacies: FCE LTER data reveal that multiple types of disturbances - including cold snaps, fires, droughts, floods, and tides - play a strong role in shaping coastal ecosystems. Tropical storms can be beneficial by dispersing mangrove propagules into disturbance-generated canopy gaps. They also deliver phosphorus-rich mineral deposits that promote mangrove transgression, increased soil elevation relative to sea level, and more rapid mangrove wetland recovery. Scenarios and Synthesis: The fate of massive coastal carbon stores is uncertain. The FCE LTER led comparative cross-site studies in subtropical and tropical karstic freshwater wetlands, mangrove forests, and seagrass communities - showing that carbon storage in mangrove forests far exceeds terrestrial woodlands. Our modeling studies show that the fate of massive stores of coastal "blue carbon" depends on how managers respond to global climate change. During FCE III, the FCE LTER produced 272 journal articles, 1 book, 25 book chapters, 5 thematic issues of journals, 32 dissertations, and 18 theses. The 176 data packages collected over the past 18 years are published in the Environmental Data Initiative (EDI) repository. Open access has led to new research and synthesis using FCE LTER datasets on flux tower, seagrass productivity, and water quality. The FCE LTER has also led international, open access LTER synthesis projects. Broader Impacts: Social-ecological, historical, and scenario studies associated with the FCE LTER contribute to understanding how decisions about Everglades restoration have been made. This has included fostering strong, lasting agency partnerships that ensure the integration of long-term research into policy, restoration, and management. Most of the undergraduate and K-12 students engaged in field and laboratory studies at FCE LTER are from the >90% majority-minority populations of Florida International University and Miami-Dade County Public Schools. Teachers are engaged in long-term research, creating experiential and data-based lessons for the K-12 Schoolyard. Undergraduates serve as mentors to high school students. Along with 12 partner institutions, FCE LTER promotes environmental literacy through an Everglades Artist in Residence program and long-term citizen science studies involving predator tracking and decomposition measurements. Early career scientists gain leadership experience by co-leading FCE LTER working groups. Graduate students take on leadership roles as mentors, representatives on the executive board, participants in Everglades Service-to-Activism and other science-policy communications workshops, and congressional visits. Last Modified: 03/23/2020 Submitted by: Evelyn E Gaiser