Marcelo Ardon Sayao

The proposed research is for continuing our unique long-term study of the consequences of climate change on lowland tropical streams in Costa Rica. We now have over 30 years of data that shows the occurrence of climate-driven acidification events in lowland streams. Our previous LTREB research indicates that an influx of soil-derived CO2 via subsurface flow paths contributes to those pH declines, signaling a tight coupling among rainfall, terrestrial, and aquatic ecosystems. Climate-driven acidification events are stronger and more common in solute-poor, poorly-buffered, streams than in solute-rich, well-buffered, streams - another characteristic of the study landscape. Here we propose to continue working towards testing this hypothesis by (1) assessing the relation among daily, seasonal, annual, and decadal patterns in stream water chemistry with major climate events (e.g., El Niño and La Niña - ENSO), by (2) assessing biotic responses to climate-driven acidification, and by (3) experimentally buffering a low-solute stream against climate-driven acidification related to ENSO events. Climate trends and global circulation models predict changes in the frequency and intensity of weather extremes. For Central America, models predict greater seasonality, similar to patterns observed during ENSO years. In the Caribbean lowlands of Costa Rica, El Niño events result in abnormally low precipitation during the dry season, while La Niña results is high precipitation. Our own dataset from lowland Costa Rican rainforest streams, combined with additional long-term data from our terrestrial ecology colleagues, has shown that decreased precipitation during the dry season can decrease carbon sequestration and increase the acidity of streams. Our studies suggest that despite showing the capacity to withstand low pH, both macroinvertebrates and algal assemblages are shaped by climate driven acidification. In this proposal, we build on continuous stream water chemistry and benthic insect data to examine the mechanisms and consequences of changing precipitation regimes on the acidity and biotic response of tropical streams.

Overview The proposed research will further our unique long-term study of the consequences of climate change on lowland tropical streams in Costa Rica. Using our 25+ year dataset, we identified the occurrence of climate-driven acidification events in lowland streams. Based on previous LTREB research, we hypothesized that an influx of soil-derived CO2 via subsurface flow paths contributes to those pH declines, signaling a tight coupling between rainfall, terrestrial, and aquatic ecosystems. Climate-driven acidification events are stronger and more common in low-solute poorly-buffered streams than in solute-rich buffered streams, another characteristic of the study landscape. Here we propose to evaluate and further develop this hypothesis by (1) assessing the relation between daily, seasonal, annual, and decadal patterns in stream water chemistry with major climate events (e.g., ENSO), by (2) assessing biotic responses to climate-driven acidification, and by (3) experimentally buffering a low-solute stream against climate-driven acidification related to the ongoing large ENSO event. Intellectual merit Climate trends and global circulation models predict changes in the frequency and intensity of weather extremes. For Central America, models predict greater seasonality, similar to patterns observed during ENSO years. ENSO events result in abnormally low precipitation during the dry season in the Caribbean lowlands of Costa Rica. Our own 20+ year dataset from Costa Rican rainforest streams, combined with additional long-term data from our terrestrial ecology colleagues, has shown that decreased precipitation during the dry season can decrease carbon sequestration and increase the acidity of streams. Our studies suggest that despite showing the capacity to withstand low pH, both macroinvertebrates and algal assemblages are shaped by climate driven acidification. In this proposal, we build on 20+ years of continuous stream water chemistry and 15+ years of benthic insect data to examine the mechanisms and consequences of changing precipitation regimes on the acidity and biotic response of tropical streams. Broader impacts Our program has 4 main goals regarding broader impacts. (1) Research on climate change effects in Central America. We will continue to share these datasets via special sessions at annual meetings and the Luquillo LTER web interphase. (2) Graduate and undergraduate training. We will continue providing research opportunities to students interested in tropical stream ecology (Since 1997: >30 undergrads, 15 graduate students, 3 postdocs, and >60 peer-reviewed publications). Our proposed project will have an important positive impact on minority student training by enrolling students from Puerto Rico and from mainland institutions. PI Ramirez directs an REU site in Puerto Rico and encourage students interested in stream ecosystems to develop experimental projects around the topic of acidification during an initial summer in Puerto Rico. They will be offered the opportunity to apply for a second summer experience to conduct a comparative study at La Selva. Co-PI Small teaches an undergraduate field course at La Selva connected to this LTREB project. (3) Support early career researchers. Both, Ard?n and Small are tenure-track faculty at their institutions. They will build on their past experiences with the project to continue their careers and to maintain an expertise in tropical streams. (4) Environmental Outreach. We will maintain our environmental outreach program, Water for Life/Agua para la Vida, which includes outreach activities in local communities and an internationally accessible web page equipped with teaching tools on river conservation and water quality/quantity issues. We will also develop a citizen science project using the iNaturalist mobile device application (www.inaturalist.org). The project will involve the naturalist guides and the thousands of visitors to La Selva in collecting natural history data about dragonflies and damselflies within La Selva. Using the iNaturalist app on their m

Coastal wetlands provide important ecosystem services, such as flood protection, habitat for wildlife, and water quality improvement. Despite the recognition of their valuable services, local land use and global climate change are driving the loss of coastal wetlands. This project will examine the capacity of North Carolina coastal wetlands to continue to provide ecosystem services under a changing climate. The project will use remote sensing, tree ring analyses, field surveys and experiments, and new statistical methods to examine the response of both forested wetlands and marshes to droughts, storms, and increasing salinity. Past research has tended to focus on either forested wetlands or marshes, rarely has the response of both wetland types been studied together. This project will adapt recently developed methods to identify “early warning signals” that could help forecast the loss of coastal wetlands. It will advance theoretical understanding of the structure and function of wetlands, while answering management relevant questions to help prevent wetland loss. The project will engage middle school teachers, undergraduate and graduate students, and citizen scientists in long-term ecological research by creating new curricula, field based exercises, a graduate course, and a citizen science mobile device application. The project will support three graduate students, five undergraduate students, and five middle school teachers over five years. The project will also advance the career of a young investigator that is a member of an underrepresented group.

Climate change is transforming the outer edge of the Southern US coastal plain. Lower-lying parts of this region, characterized by extensive freshwater-dependent ecosystems, will be largely inundated by gradual sea level rise by the end of this century. In the interim, however, ocean waters are already penetrating and influencing freshwater-dependent coastal landscapes due to a combination of human and natural factors. This landward movement of salinity from the coast onto the coastal plain or “saltwater intrusion” represents the leading edge of climate change for many coastal landscapes. The salinization of surface waters and adjacent lands may lead to significant reductions in crop and timber yields in managed ecosystems, significant declines in ecosystem carbon sequestration in unmanaged ecosystems, and degradation of coastal water quality due to extraction of soil nutrients by seasalts. As this region and similar regions worldwide transform in response to and, indeed, in advance of rising seas, the sustainability of these coastal landscapes, now and for decades to come, hinges largely on a sophisticated understanding of the coupled human and natural processes influencing salinization of surface waters and adjacent lands. This project focuses specifically on saltwater intrusion across the Albemarle-Pamlico peninsula of North Carolina, and it will accomplish the 3 primary goals of NSF Coastal SEES: First, the project will provide a comprehensive toolset to enable place-based, system-level understanding of coastal systems at multiple spatial and temporal scales. Second, it will yield outcomes with predictive value in coastal systems that are easily understood by stakeholders while representing complex interactions between climate, hydrology, land use, and ecological processes. Third, by focusing on how information influences individual preferences, the project will identify pathways by which outcomes could be used to enhance coastal sustainability. Together, these activities will help guide sustainable management of this region and similarly affected regions over the next several decades to centuries.

This study aims to assess the extent of standing dead trees (i.e. snags) that could facilitate CO2, CH4, and N2O export from soils in coastal forested wetlands along the Albemarle Pamlico Peninsula in North Carolina. The specific research areas for sampling will focus on ghost forests around the APP where snags outnumber live trees. These areas include Palmetto Peartree 2 Preserve, Alligator River National Wildlife Refuge, Swanquarter National Wildlife Refuge, Pocosin Lakes National Wildlife Refuge, and Gull Rock Game Lands. Knowledge of the extent of greenhouse gases emitted from snags could lead to management strategies to reduce emissions from wetlands. The chamber-scale measurements will help understand GHG drivers and pathways to better predict across the broader landscape. This research will address the following: • Update extent of ghost forests along the Albemarle Pamlico Peninsula • Understand the magnitude and drivers of greenhouse gas emissions • Determine the amount greenhouse gas flux in ghost forests

This study aims to assess the extent of standing dead trees (i.e. snags) that could facilitate CO2, CH4, and N2O export from soils in coastal forested wetlands along the Albemarle Pamlico Peninsula in North Carolina. The specific research areas for sampling will focus on ghost forests around the APP where snags outnumber live trees. These areas include Palmetto Peartree 2 Preserve, Alligator River National Wildlife Refuge, Swanquarter National Wildlife Refuge, Pocosin Lakes National Wildlife Refuge, and Gull Rock Game Lands. Knowledge of the extent of greenhouse gases emitted from snags could lead to management strategies to reduce emissions from wetlands. The chamber-scale measurements will help understand GHG drivers and pathways to better predict across the broader landscape. This research will address the following: • Update extent of ghost forests along the Albemarle Pamlico Peninsula • Understand the magnitude and drivers of greenhouse gas emissions • Determine the amount greenhouse gas flux in ghost forests