Climate-induced shifts in sulfate dynamics regulate anaerobic methane oxidation in a coastal wetland

Anaerobic methane oxidation (AMO) is a key microbial pathway that mitigates methane emissions in coastal wetlands, but the response of AMO to changing global climate remains poorly understood. Here, we assessed the response of AMO to climate change in a brackish coastal wetland using a 5-year field manipulation of warming and elevated carbon dioxide (eCO₂). Sulfate (SO₄²⁻)–dependent AMO (S-DAMO) was the predominant AMO process at our study site due to tidal inputs of SO₄²⁻. However, SO₄²⁻ dynamics responded differently to the treatments; warming reduced SO₄²⁻ concentration by enhancing SO₄²⁻ reduction, while eCO₂ increased SO₄²⁻ concentration by enhancing SO₄²⁻ regeneration. S-DAMO rates mirrored these trends, with warming decreasing S-DAMO rates and eCO₂ stimulating them. These findings underscore the potential of climate change to alter soil AMO activities through changing SO₄²⁻ dynamics, highlighting the need to incorporate these processes in predictive models for more accurate representations of coastal wetland methane dynamics.