Abstract
The impact of coastal acidification on sediment nitrous oxide (N2O) and methane (CH4) fluxes is largely unknown. We exposed temperate estuarine sediments to moderate (pH 7.3) and extreme (pH 6.3) acidification. Sediments were collected from two sites—one exposed to high and the other to low nitrogen loading. We demonstrate that low pH has a strong effect on greenhouse gas fluxes. The response, in terms of both magnitude and direction, was site specific. Sediments from the high nitrogen loading site exhibited increased N2O fluxes and decreased CH4 fluxes under moderate and extreme acidification. In contrast, sediments from the low nitrogen loading site exhibited decreased N2O fluxes under moderate and extreme acidification while CH4 fluxes both decreased (moderate) and increased (extreme). This study highlights the dynamic response of sediment N2O and CH4 fluxes to low pH and emphasizes the need for deeper understanding of ofcoastal acidification impacts on sediment biogeochemistry.
Scientific Significance Statement
Estuaries are increasingly exposed to low pH conditions (i.e., coastal acidification) largely driven by rising temperatures, increased precipitation, and excess nutrient loading. The impact of coastal acidification on sediment biogeochemical processes, including those responsible for the production or consumption of greenhouse gases (GHGs) are largely unknown. Here, we show that sediment fluxes of two powerful GHGs (nitrous oxide: N2O and methane: CH4) respond rapidly to low pH conditions. In addition, the magnitude and direction of this response varies within an estuary, even at sites with similar pH exposure histories. Overall, this study highlights the need to incorporate current and future pH conditions in forecasting models and in the development of coastal GHG budgets.
Mazur C. I. & Fulweiler R. W., in press. Coastal acidification alters estuarine sediment nitrous oxide and methane fluxes. Limnology and Oceanography Letters. Article.
