Cadmium and rising tides: Amplified greenhouse gas emissions from mangrove sediment

Mangrove ecosystems, renowned for their carbon sequestration capabilities, also contribute to the emission of greenhouse gases from their sediments. They are under stress from human activities and global changes, such as heavy metal pollution and rising sea levels , which can affect carbon stability and greenhouse gas emissions . However, the combined impact of these factors is not fully understood to date. This study assessed the impact of cadmium contamination at varying levels of inundation depths on the emission of CO 2 , N 2 O, and CH 4 from mangrove sediments. The findings indicated that increased inundation depth intensifies the effect of low cadmium concentrations on CO 2 emissions, with sediment CO 2 flux doubling from 3430 μmol m −2 h −1 to 6720 μmol m −2 h −1 . In contrast, deeper water levels reduced N 2 O emissions in the presence of high cadmium concentrations, lowering sediment N 2 O flux from 14.10 μmol m −2 h −1 to 10.13 μmol m −2 h −1 . These results highlight that the combined effects of rising inundation depth and cadmium pollution can enhance greenhouse gas emissions from mangrove sediments. It is crucial to consider the synergistic effects of pollution and rising sea levels on the stability of sediment carbon and gas emission rates in the conservation and management of mangroves. Such assessments will bolster efforts to protect blue carbon and achieve carbon neutrality in the future. • Rising sea-levels and Cd pollution increase GHG emission in mangrove sediment. • Increased water depth intensifies the effect of low Cd pollution on CO 2 emissions. • Increased water depth reduces N 2 O emissions in the presence of high Cd pollution.