30 Chapter 1 GREENHOUSE GAS METHANE IN THE CONTEXT OF COASTAL ECOSYSTEMS Methane (CH₄) is a potent greenhouse gas and plays a significant role in global warming, contributing to climate change (Saunois et al., 2016; Saunois et al., 2024). Despite a shorter atmospheric lifetime (~ 12 years) than of carbon dioxide (CO₂) (up to 200 years), methane has a global warming potential approximately 80 times over a 20-year period, making it a critical component for climate change modelling (Inman, 2008; IPCC, 2014, 2023; Pachauri et al., 2014). Coastal ecosystems, particularly wetlands, are hotspots for methane production due to high organic matter input and the reduced, anoxic conditions in sediments processes (Malone & Newton, 2020; Wallenius et al., 2021; Wells et al., 2020) (Figure 1). Furthermore, they are dynamic zones where methane emissions are prevalent due to complex carbon, nitrogen and sulfur cycling (Siefert & Plattner, 2004). Organic matter deposition and the anoxic conditions in sediments create ideal environments for methanogenesis - the biological process through for which methanogenic archaea produce methane. Methanogenesis is fueled by a variety of substrates, including acetate, methanol, hydrogen and dimethyl sulfide (Kurth et al., 2020). Agriculture, waste, and fossil fuel activities, along with aquatic ecosystems, are the primary contributors to methane emissions. The main methane sinks include atmospheric chemical reactions, soils, and (potentially) certain engineered biotechnological systems (Figure 1) (Rosentreter et al., 2021; Saunois et al., 2024). However, not all methane produced in these natural anoxic layers escapes into the atmosphere. A large portion is consumed by methane-oxidizing microorganisms in both anoxic and oxic zones, creating a natural biofilter that mitigates greenhouse gas emissions (Glodowska et al., 2022; Guerrero-Cruz et al., 2021; Kalyuzhnaya et al., 2019; Venetz et al., 2023; Welte et al., 2016) (Figure 1). The microbial methane oxidation occurs across various ecosystems, including oceans, wetlands, soils, and lakes, as well as engineered systems such as Waste Water Treatment Plants (Figure 1) (Rosentreter et al., 2021; Saunois et al., 2024; Wang et al., 2017).
RkJQdWJsaXNoZXIy MTk4NDMw