Work

Influence of hydroperiod and canopy cover on mercury accumulation and methylation in Carolina bay wetland sediments in the Southeastern United States

Year: 2025

Type: article

Abstract: Isolated wetlands are crucial to the global mercury (Hg) cycle due to their widespread distribution and variable hydrology. To quantify atmospheric Hg deposition, sediment accumulation, and Hg methylation, we collected surface sediments from 10 Carolina bay wetlands—including short- and long-hydroperiod bays during wet and dry seasons for total Hg (THg) and methylmercury (MeHg) analysis. THg and MeHg concentrations ranged from 23.2 to 224.8 ng/g and 0.4 to 5.5 ng/g, respectively, and %MeHg ranged from 0.4 to 3.1%. Short-hydroperiod bays had higher THg concentrations (116.4 ± 46.5 ng/g) than long-hydroperiod bays (72.7 ± 48.1 ng/g) under flooded conditions ( P = 0.001). MeHg concentrations were influenced by THg ( P < 0.0001) and were highest in long-hydroperiod bay center locations ( P = 0.002). The methylation potential (%MeHg) was inversely related to THg and covarying tree canopy cover ( P = 0.004). Our results indicate that short-hydroperiod bays tend to sequester higher concentrations of atmospheric Hg under flooded conditions than long-hydroperiod bays, however, long hydroperiods tend to enhance Hg methylation and MeHg production. Canopy cover shows a significant impact on Hg cycling within the Carolina bay ecosystem. Our study demonstrates that Hg accumulation and methylation in Carolina bay wetlands contribute to the biogeochemical cycling of Hg, as well as anaerobic Hg methylation under long hydroperiods and flooded conditions, which advances our understanding of Hg cycling across different wetland types. • Under flooded conditions, short-hydroperiod exhibited higher sediment THg concentrations than long-hydroperiod bays, likely influenced by canopy cover and internal Hg cycling. • Longer hydroperiods tend to enhance Hg methylation and MeHg production. • Canopy coverage enhances total Hg (THg) deposition but suppresses methylation potential (%MeHg). • Sediment MeHg concentrations peak in center locations of long-hydroperiod bays.

Source: Environmental Research

DOI: 10.1016/j.envres.2025.123139

Authors: Chongyang Qin, David E. Scott, Stacey L. Lance, Demetrius Calloway, Cara N. Love, Xiaoyu Xu

Institutions: University of Georgia, Gannan Normal University, University of Michigan, Princeton University

Language: English

Topic: Mercury impact and mitigation studies

Subfield: Health, Toxicology and Mutagenesis

Field: Environmental Science

Domain: Physical Sciences

SDGs: Life on land, Clean water and sanitation, Climate action

Open Access status: hybrid

Estimated APC paid: $3,880