LTREB Renewal: Twenty-three years of tidal marsh response to environmental change

Smithsonian Institution, Washington DC

Investigators

Abstract

Tidal wetlands make up the ecological fabric of coastal and estuarine ecosystems providing ecosystem services such as nourishing food chains, filtering water, and protecting coastal populations. Climate predictions agree that sea level will rise globally over the next century, threatening these critical habitats. The current loss of thousands of hectares of low-lying coastal wetlands to shallow, open water each year threatens fisheries, wildlife habitat, water quality, and infrastructure. This project will examine how elevated atmospheric carbon dioxide, nitrogen pollution, climate change, sea-level rise and plant invasion interact to influence the sustainability of tidal marsh ecosystems. The wealth of long-term global change research at the study site affords an unprecedented comparison of the relative importance of these factors. The research project will engage citizen volunteers, high school students, undergraduate interns, and graduate students, contributing to education and training of a broad group in a subject of pressing societal need. The information garnered from the proposed research will inform management practices aimed at protecting and restoring coastal wetlands. The balance of carbon gain and carbon loss ultimately determines the capacity of a tidal wetland to increase elevation at a rate that matches sea-level rise, and thus persist in a rapidly changing environment. This project will test hypotheses about the consequences of changes in atmospheric carbon dioxide, sea level, nitrogen pollution, and climate for carbon assimilation by plants and carbon mineralization by microbes in a coastal marsh ecosystem. Twenty-three years of data from this project show that effects that appear important in the short term may be obviated or reversed when longer-term trends are considered. The researchers will use complementary experiments that manipulate carbon dioxide and nitrogen to assess the effects of plant traits on ecosystem responses, based on the central hypothesis that changes in plant community composition will mediate the most important effects of global change on ecosystem sustainability. Results will contribute to a new model that identifies relative sea level as the global change factor that supersedes all others, followed by N addition, and finally elevated CO2. The ranking of these global change factors is based on their capacity to restructure plant community composition within the bounds of natural variability.