Mercury Cycling in Coastal Ecosystems: Insights from Stable Isotopes of Dissolved Organic Carbon in Hurricane-Impacted Ecosystems

Mercury (Hg) is a global pollutant due to its atmospheric transport, its conversion into neurotoxic methylmercury (MeHg), and its biomagnification in food webs. Climate-driven events like hurricanes and sea-level rise can cause salinization of coastal freshwater wetlands (FW), leading to the formation of "ghost forests" (GF) and eventual conversion to salt marshes (SM). These transitions, along with storm surges, may significantly impact Hg cycling in these ecosystems, however, the effects are poorly understood. We conducted 15 field sampling to evaluate aqueous total mercury (THg) and MeHg along a salinity gradient on the Albemarle Pamlico Peninsula, North Carolina, which experienced two major hurricanes (Florence, 2018 and Dorian, 2019). Overall, THg increased from open water (OW) to FW sites, with the lowest THg level recorded in OW (1.90±1.52 ng/L) and the highest in FW (8.02±3.44 ng/L). MeHg levels were consistent across sites, except for significantly lower concentrations in OW. Post-hurricane data showed shifts in both THg and MeHg levels in which a strong positive correlation between THg and DOC was observed at FW (p<0.001) while an inverse relationship was found between THg and chloride (p<0.001). Our results suggest that habitat transitions due to salinization and storm surges increase the likelihood of Hg methylation due to the increased supplies of sulfate from seasalt and mobility. Thus, future climate scenarios likely exacerbate Hg pollution and elevates its risk in these coastal ecosystems.

Presentation Preference: Oral

Primary Presenter: Yener Ulus, Auburn Univesity at Montgomery (yulus@aum.edu)

Authors:

Yener Ulus, Auburn University at Montgomery  (yulus@aum.edu)

Martin Tsui, Chinese University of Hong Kong  (mtktsui@cuhk.edu.hk)

Marcelo Ardon, North Carolina State University  (mlardons@ncsu.edu)