BRC-BIO - The effect of sea-level rise on methane dynamics in coastal wetlands: Building undergraduate research opportunities in Hawai'i

Hawaii Pacific University, Honolulu HI

Investigators

Abstract

Wetlands contribute anywhere from 50 to 80% of natural methane gas emissions to the atmosphere. Some global models suggest that wetland methane emissions could double by 2100, but saltwater inputs are simultaneously changing the coastal landscape, which could reduce methane contributions. Therefore, the goal of this project is to conduct an ecosystem-scale experiment that teases apart the mechanisms behind how saltwater inputs influence water chemistry, microbial communities, and methane dynamics over two years. This project maximizes taxpayer investment by leveraging an existing saltwater introduction experiment being conducted by the U.S. Fish and Wildlife Service aimed at reducing invasive plant species and enhancing endangered waterbird habitat. Hawai‘i Pacific University undergraduate classes will be actively involved in this project, so that the next generation of leaders can gain hands-on experience in environmental science. This project will also support the mentorship and independent research projects of at least three undergraduate students and two Master’s students. Students will participate in real-life natural resource management research including field work, laboratory techniques, data analysis, and technical writing, all of which promote educational growth, workforce development, and a strong economy. Brackish wetlands are characterized by lower methane emissions as salinity increases, which has been attributed to sulfate-reducing bacteria outcompeting methanogens (microbes that produce methane). However, recent studies are challenging this paradigm. Intermediate salinities could provide a hotspot for methane emissions due to decreased methane consumption by methanotrophs, which are sensitive to salinity. Additionally, the effect of salinity on methane emissions may be primarily mediated by the dominant plant species. This project will test these three key hypotheses using two freshwater control ponds, two treatment ponds with varying salinities, and one naturally intertidal pond. These ponds will be sampled monthly for the first year following saltwater introduction and then every three months for the second year. This project will measure methane production rates, water-column concentrations, and chamber-based emissions along with dissolved inorganic nitrogen and phosphorus, dissolved organic carbon, and sulfate. Microbial communities will also be characterized using 16S amplicon-sequencing, and the abundance of key functional groups (methanogens, sulfate-reducers, methanotrophs) will be assessed using quantitative PCR. This project’s innovative experimental design will inform both scientific understanding and practical conservation efforts. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.