Research

Research in the lab focuses on linkages among the hydrological cycle, ecosystem processes, and human activities, with the goal of advancing natural resources conservation and management. Current work focuses on three primary topics:

1. Hydrological, Ecological and Human Drivers of Coastal Change
2. Social-Ecological Effects of Hydroelectric Dams in the Amazon
3. Wetland, Riverine, and Forest Ecohydrology

Hydrological, Ecological, and Human Drivers of Coastal Change

Coastal regions are susceptible to sea-level rise (SLR), increased temperatures, changing rainfall and extreme weather patterns, subsidence, and land-use change. Several projects in the lab are examining the interactive effects of SLR, climate change, groundwater supply, and land use on coastal ecosystems. Funding comes from the US Fish and Wildlife Service, US Geological Survey, FL Dept. of Economic Opportunity, FL Fish & Wildlife Conservation Commission, and FL SeaGrant.

Coastal Vegetation Dynamics: PhD student Amy Langston is investigating how SLR and a warming climate are driving reassembly trajectories of coastal vegetation. Her data on tree and understory vegetation in freshwater forest islands extend a 20-year dataset and reveal long-term trends of forest decline and marsh conversion. Amy’s field experiments on mangrove seedling success in relict freshwater islands show that, while climate change provides favorable conditions for mangrove establishment, crab predation and insect herbivory are strong top-down controls on mangrove encroachment into new areas. Check out her recent papers in Global Change Biology and Hydrobiologia!

Saltwater Intrusion and Coastal Ecohydrology: PhD student Katie Glodzik is studying how saltwater intrusion from SLR and decreased river flow are combining to threaten coastal ecosystems, particularly those modified by development. She investigates drivers and impacts of saltwater intrusion and altered hydrology in the coastal wetlands of Florida’s Big Bend region to meet three objectives: 1) to determine long-term trends and drivers of river discharge; 2) to evaluate the effect of coastal roads on salt marsh hydrology and ecology; and 3) to use physical and hydrological variables to predict coastal forest die-off. Preliminary results show that roads consistently decrease invertebrate densities in tidally-restricted marshes, while impacts to salinity and vegetation vary by road.

Salt-Stressed Forests: PhD student Elliott White works to understand how chronic low-level salinity affects the health and productivity of coastal bald cypress (Taxodium distichum) swamps. Elliott recently published a comprehensive review of saltwater intrusion and freshwater management in coastal wetlands, and he is collecting ecological and hydrological data at sites across the Gulf of Mexico from Texas to Florida to show how connections between groundwater salinity, forest productivity, and mortality vary by region. This study builds on Dr. Kaplan's previous work to understand interactions among surface water, groundwater, and vadose zone hydrology and salinity in coastal floodplain forests. Read those papers in the Journal of Environmental Quality, Water Resources Research, Journal of Hydrology, and Journal of Contaminant Hydrology.

Oysters and Fresh Water: Oyster reefs provide myriad ecosystem services, however their role in directing flow during non-storm conditions has been largely neglected. Dr. Kaplan and colleagues in ESSIE and Wildlife Ecology and Conservation hypothesize that reefs can influence salinity over large areas, providing a “keystone” ecosystem service. In an ongoing field and modeling study, we found long-term salinity differences of >30% between landward and seaward sides of a degraded reef in the Gulf of Mexico, supporting the role of reefs as local freshwater “dams”.

Hydrodynamic modeling suggests that the degraded reef likely detained more freshwater in the past, buffering the landward advance of high salinities, particularly during droughts. These results elucidate a poorly documented ecosystem service provided by oyster reefs; provide an estimate of the magnitude and spatial extent of this service; and offer quantitative information to guide future oyster reef restoration. Read the paper in PLOS ONE.

Social-Ecological Effects of Dams in the Amazon

The Amazon River watershed is the world’s largest river basin and provides >US$30 billion/yr in critical ecosystem services to local populations and humanity at large. The Amazon is also a relatively untapped source of “cheap”, low-carbon electricity for Latin America, and construction of >30 large hydroelectric dams and >170 small dams is currently underway in the Brazilian Amazon.

Changes in the Amazon’s freshwater ecosystems from the development of hydropower will have a cascade of physical, ecological, and social effects at local to global scales. Several projects in the lab seek to to improve our understanding of the effects of hydropower development on ecosystem services provided by the Amazon. Funding comes from the National Science Foundation and the University of Florida.

Dams and Hydrologic Change: MS student Kelsie Timpe demonstrated the extensive effects of hydroelectric dams in the Amazon region on hydrologic parameters calculated using the Indicators of Hydrologic Alteration (IHA) method applied to 33 small and large dams in the Brazilian Amazon. Her analysis provides the first holistic assessment of hydrological alterations caused by Amazonian dams and offers insight on the primary physical and management drivers of dam impacts.

Across all sites, results suggest that all ecologically important flow characteristics have been affected in dammed systems, but the most dramatic shifts were related to the frequency/duration and frequency/rate of change of pulse events. While each dam/river system are unique, some dams cause substantially greater hydrological alteration (HA, see figure below). Dam elevation and reservoir area were the best environmental predictors of HA. This study provides the basis for future interdisciplinary research to develop flow-ecology relationships needed to improve dam management in this mega-diverse region.

Interdisciplinary Research: A team of UF faculty from the Amazon Dams Network (ADN) was awarded the 2015 Water Institute Graduate Fellows (WIGF) Program to study the complex and interactive set of impacts brought about by the construction and operation of dams in the Amazon. The project brings together UF faculty from across the biophysical and social sciences (hydrology, fisheries, forest ecology, human health, human geography, and economics) and is led by Dr. Kaplan with co-PIs Stephanie Bohlman and Denis Valle, Kai Lorenzen, and Cynthia Simmons.

WIGF students include: Roberta de Carvalho and Alli Sabo (Geography), Jacy Hyde and Christine Swanson (School of Forest Resources and Economics), May Lehmensiek (School of Natural Resrouces and Environment), and my PhD student Trey Crouch (Environmental Engineering Sciences). Trey's research focuses on one of the most conspicuous dam impacts: sediment capture. Trey is investigating the effects of the Santo Antônio and Jirau dams on sediment transport in the Madeira River, which carries ~2.1 million tons of sediments per day. His research aims to develop tools to mitigate ecological impacts while maintaining electricity production.

Connecting Fish Catch and Hydrologic Change: Visiting scholar Alice Lima (PhD student at the Federal University of Rondônia, Brazil) worked with Dr. Kaplan to model fisheries production in the Madeira River. She found important hydrological controls on fish catch, but observed unique responses across the ten commercially important fish species, suggesting that dam operating rules need to closely mimic natural hydrologic regime in order to maintain the dynamics of these diverse ecosystems. Read the paper in Ecohydrology.

Amazon Dams Network: All the research described above builds on Dr. Kaplan's ongoing work with the Amazon Dams Network (ADN), an international, interdisciplinary group of researchers, students, and stakeholders studying the social-ecological effects of dams across the Amazon. Along with other faculty at the University of Florida (UF) and seven South American universities, Dr. Kaplan helps to lead the ADN. The group’s research and education outputs include interdisciplinary research proposals and manuscripts, integrative coursework, and seminars/workshops focused on interdisciplinary research and education.

Wetland, Riverine, and Forest Ecohydrology

Hydrological processes are known to affect a wide range of ecosystem functions and services. Increasingly, reciprocal feedbacks among hydrological and ecological processes are being identified, which can be critical in dictating system states. Research in the lab explores uni- and bi-directional interactions between the hydrologic cycle and ecological function in wetland, riverine, and forest ecosystems, with a focus on how humans affect these coupled processes. Funding comes from the US EPA, FL Dept. of Environmental Protection, St. Johns River Water Management District (WMD), Suwannee WMD, Southwest Florida WMD, South Florida WMD, North Florida WMD, FL Dept. of Environmental Protection, FL. Dept. of Agricultural and Consumer Services, and the University of Florida.

Florida's Changing Springs: In many Florida’s springs, submerged aquatic vegetation (SAV) has declined in abundance while benthic and epiphytic algae cover have increased. Multiple factors are likely interacting to produce these observed shifts, but the causes remain unclear. To better understand these factors, PhD student Nathan Reaver is applying dynamical system modeling to spring ecosystems. We constrain and parameterize models through in situ measurements of hydrologic phenomena, including: SAV, algal, and flow velocity interactions; reach-scale hydrologic properties using hydrologic tracers; and large-scale flow velocity and primary producer structure correlations using novel remote sensing techniques. Beyond specific application to FL springs, we use springs as ideal "natural laboratories" to explore fundamental drivers of ecosystem trajectories, function, and structure.

Upland-Wetland Connections: The perceived benefits of forest management are often limited to upland habitat improvement, but management that reduces forest biomass (e.g., thinning and prescribed fire) may also increase regional water yield and improve wetland hydrology and habitats. To quantify these effects, PhD student Kevin Henson is studying how selective thinning and fire in upland pine change water level and hydroperiod in geographically isolated wetlands embedded within these forests. Lower upland biomass should lead to less upland water use and greater wetland water depth and hydroperiod following treatment. Kevin will also model how these changes affect endemic amphibians that rely on these wetlands. This study builds from previous work to quantify water yield as a function of management, forest structure, and ecosystem water use. Read that paper in the Journal of the American Water Resources Association.

Isolated Wetlands and "Significant" Nexus: Recent rulings by the U.S. Supreme Court have limited federal protection over isolated wetlands, requiring documentation of a “significant nexus” to a navigable water body to ensure federal jurisdiction. Despite geographic isolation, isolated wetlands influence surficial aquifer dynamics that regulate baseflow to surface water systems. To explore the importance of this function at the landscape scale, Dr. Kaplan and colleagues in the School of Forest Resources and Conservation and Virginia Tech integrated models of soil moisture, upland water table, and wetland stage to simulate the hydrology of a low-relief, depressional landscape. Read the paper in Water Resources Research.

Hydrologic Processes in Patterned Peatlands: Identifying the mechanisms that drive development of self-organized patterned landscapes is essential for guiding ecosystem management and restoration. In this work, Dr. Kaplan and colleagues in the School of Forest Resources and Conservation tested the hypothesis that feedbacks between patch anisotropy and hydroperiod may explain development of the flow- parallel ridge-slough mosaic of the Everglades (Florida, USA). Read the papers in Geophysical Research Letters, HESS, HESS, Water Resources Research, and Landscape Ecology.

Tropical Wetland Ecosystem Services: Rapid increases in population and growing food demand are causing widespread deterioration of tropical wetlands globally, and an increased focus on the role and function of these imperiled ecosystems is required. In this study, high-resolution, spatially distributed surface water and meteorological data were combined with a detailed topographical survey to quantify the wetland water balance, hydroperiod, and seasonal variability of wetland area, volume, and residence time. Read the papers in Wetlands and Wetlands Ecology and Management.