Methyl chloride production by calcareous periphyton mats from the Florida Everglades

Abstract

Methyl chloride (CH3Cl) is a trace gas with natural and anthropogenic sources that plays an important role in stratospheric ozone catalytic cycles. Here, we report on research to quantify the production of CH3Cl in response to varying levels of salinity from calcareous periphyton mats found within the Florida Everglades, USA, the first measurements of their kind. Periphyton were collected from the Everglades and exposed to continuous, artificially simulated 12 h dark: 12 h light cycles, in both freshwater and varying concentrations of saltwater. Water samples were collected and analyzed to determine the resulting production rate of CH3Cl. We found that periphyton produced CH3Cl in both freshwater and all concentrations of saltwater (24 to 208 fmol CH3Cl gDW-1 periphyton h-1 after 24 h) and that there was a significant positive effect of salinity on the production rate of CH3Cl (r2 = 0.993, p < 0.001). Our results indicate that rising sea levels as predicted by climate models will increase production rates of CH3Cl in coastal periphyton wetlands that could be inundated with high salinity seawater. Furthermore, other natural sources of CH3Cl may also respond through similar mechanisms to sea level rise and salt water intrusion resulting from global climate change.