Response of carbon dioxide, water, and energy exchange of peat and marl wetlands in the Florida Everglades to changes in hydroperiod

Steven F. Oberbauer, Florida International University

Jessica L. Schedlbauer, Florida International University

Gregory Starr, University of Alabama

Abstract

Objective: Our specific objective for this renewal is to determine the causes for unexpected reduced wet season productivity of Everglades marsh while we continue our general objective to determine the total CO₂ balance and the relative magnitudes of macrophyte and periphyton CO₂ exchange processes in peat and marl forming wetlands in response to changes in hydroperiod, the dominant control over ecosystem structure and function.

Research Questions: 1) What are the causes for strong reductions in gross ecosystem productivity of Everglades marsh during the wet season, 2) What are the overall CO₂ balances and how do they vary inter-annually, what are the contributions of macrophyte and periphyton physiology and CaCO₃ formation to these balances, how do the these contributions change with hydroperiod, and how does macrophyte primary productivity vary with hydroperiod across the landscape?

Location: The research will be conducted in the two dominant marsh types of Everglades National Park, Florida. The two study sites are co-located with nutrient auto-samplers and productivity sample sites of the Florida Coastal Everglades LTER.

Methods: The project combines eddy covariance, chamber-based, and geochemical measurements of CO₂ flux with biometric and physiological approaches to estimate net and gross primary production and canopy structure at peat and marl sites in the Everglades. Concurrent hydrological and climate data will be analyzed using statistical and modeling approaches to evaluate the drivers of physiological and abiotic exchange of CO₂. An ecosystem productivity model will scale macrophyte productivity in response to hydrological variation across the landscape.

Deliverables: Everglades marsh was once the largest contiguous area of peat soils in the world, but much of that carbon has been lost as a result of anthropogenic changes in hydrology. Further large changes in the CO₂, H₂O, and energy balances will occur with forecast changes in precipitation, water management, and the planned restoration of historical water flows to the Everglades. Deliverables include: 1) the causal mechanism for the wet season decline in productivity found in both peat and marl marsh, 2) continuation of ongoing work will provide nearly four years of CO₂ exchange of Everglades wetlands that includes estimates of the relative contributions of the physiology of macrophytes and periphyton and calcium carbonate formation, and refined estimation of how the contribution of macrophyte CO₂ fluxes vary with hydroperiod across the landscape. With these data we will be able to begin to determine the degree of interannual variability and its causes.