Executive Summary : | Climate change has increased the frequency, duration, and intensity of heat waves in India. Altered weather patterns and increasing global temperatures, have intensified extreme heat events, resulting in considerable stress on natural ecosystems and socioeconomic conditions. Among these ecosystems, terrestrial-aquatic interfaces (TAIs), often referred to as "Blue carbon" ecosystems, are sensitive to climate change. Comprising mangroves, seagrasses, and salt marshes, these vital ecosystems cover a small area, but store approximately 50% of the carbon in marine sediments. Besides, direct drawdown of atmospheric CO2 via photosynthesis, these ecosystems serve as crucial hotspots for organic matter (OM) deposition from terrestrial and marine sources. However, the effects of climate change, such as irregular monsoon patterns and sea-level rise, pose significant threats to TAIs. These changes can lead to altered precipitation, reduced river discharge, increased evaporation, and seawater encroachment, transforming the physicochemical characteristics of these ecosystems. Such alterations affect the stability and resilience of TAIs, raising concerns about their capacity to continue sequestering carbon. Understanding the fate of organic matter with an increase in salinity is critical, as their impact on sulfate-reducing bacteria (SRB) is less constrained. Salinity exerts a significant influence on microbial processes, particularly on OM decomposition. The combined effect of sulfate reduction and methanogenesis promotes substantial OM decomposition as salinity increases from freshwater to oligohaline conditions (0.5–5 ppt) (Chambers et al., 2011). However, in euhaline conditions (up to 30 ppt), a rise in sulfate concentration suppresses methane (CH4) production as higher sulfate concentrations favor sulfate reducers, outcompeting methanogens and decreasing the rate of OM decomposition compared to oligohaline conditions (Weston et al., 2006; Chambers et al., 2011). This suggest that the impact of salinity is not straight forward.
Despite advancements in understanding the impact of salinity on OM decomposition, hypersaline environments remain poorly studied. As climate change continues to pose a significant threat to global ecosystems, comprehending how microbial processes, like sulfate reduction and organic matter decomposition, are affected by salinity changes becomes paramount for predicting and mitigating the impact of environmental alterations. Hypersaline environments are relatively rare natural phenomena, but the observed irregularities in precipitation patterns and the potential transformation of many TAIs into hypersaline environments necessitate urgent research to comprehend the preservation and reduce the emission of greenhouse gases to the atmosphere. The present research will contribute to a broader scientific understanding of the interplay between microbial processes, salinity, and climate change in TAIs. |