General audience abstract from Carla's dissertation submitted to her PhD Committee:

"From the humid tropics to the freezing arctic, from coastal floodplains to high-elevation mountaintops, wetlands are ubiquitous ecosystems that serve unique functions. Wetlands attenuate flooding, filter nutrients, store carbon, and are biodiversity hotspots. They lie at the boundaries of terrestrial and aquatic ecosystems, thanks to the slow movement of water which allows for a slow, but significant, accumulation of soil carbon and leads to increased interactions between the water-soil interface. Wetlands are a carbon storage powerhouse, but their emissions of carbon dioxide and methane could potentially offset the carbon stored in their soil. In addition, climate and anthropogenic changes could disturb wetlands’ role as carbon sinks and change carbon emissions.

"In this dissertation, I address questions about the spatial and temporal variability of carbon dioxide and methane dynamics as well as identify the environmental drivers of this variability. I do this in two unique wetland ecosystem types: temperate headwater wetlands in the Delmarva Peninsula of Maryland, USA and in freshwater coastal wetlands of Puerto Rico. In Delmarva wetlands, I sampled across 20 wetlands and used high-frequency sensors to examine how carbon dioxide and methane and the processes that influence their production and uptake are changing over time and across sites. In Puerto Rican wetlands, I present the first sampling of greenhouse gases in freshwater tropical coastal wetlands and the first experiment of the impacts of salinization on carbon dioxide and methane production on the island with the goal of evaluating how coastal saltwater intrusion could influence wetland carbon cycling. 

"I find that small and coastal tropical wetlands are hotspots of CO2 and CH4 concentrations. In small, headwater wetlands, light and hydrology influence CO2 and CH4 but patterns and dominant processes vary across these small wetlands. Further, in freshwater coastal wetlands, CO2 and CH4 have different drivers, with CO2 being more strongly controlled by season and temperature while CH4 is related to changes in dissolved oxygen and solutes. Finally, I observed that salinization decreased CH4 production and increased CO2 production in tropical coastal wetlands.

"The findings from this dissertation highlight the potential of small, headwater wetlands and tropical wetlands to disproportionately contribute to global carbon cycling. Interestingly, the diverging drivers of CO2 and CH4 points to underlying differences in the biogeochemical processes and sources that control their availability and thus, warrant increased exploration. The different responses to a simulated disturbance also highlight the potential complexity in the response of wetland carbon cycling to anthropogenic and climatic disturbances."