Natural Halogenated Methane Production in Mangrove Ecosystems

Abstract

As rising sea levels, extreme weather, and groundwater overuse increases seawater encroachment in coastal areas, it is important to understand the resulting shifts in soil chemistry in these environments. A previous examination of coastal wetlands found that as freshwater wetlands are converted to salt marshes by this increased marine influence, there is a corresponding uptick in the emission of chloro- and bromomethane, both sources of stratospheric ozone degradation. Found to be associated with the overlap of high levels of both organic carbon endemic to freshwater ecosystems and the halogens within seawater, this correlation prompted a thread of inquiry into mangrove forests. These forests are exceptional in their ability to sequester immense levels of organic carbon (despite the challenges of inhabiting a saline environment), to retain contaminants in protection of local communities, and to stabilize coastal sediments. Examining soil samples collected across varying depths and locations within two Panamanian mangrove forests, I will seek to understand the current rate and intensity of halomethane emission and postulate how heightened seawater exposure may impact this emission rate. I hypothesize that the increased coastal seawater encroachment resulting from rising sea levels and extreme weather will result in long term, substantial increases in the natural emission rate and intensity of halomethane from mangrove ecosystems.