Ocean Acidification

The land-based inputs in the form of river discharge, wastewater runoff, and submarine groundwater discharge (SGD) are among the major land-based natural pathways for the Coastal Ocean Acidification (COA). This study evaluates the direct influence of these land-based drivers, along with the aerosol deposition, and in-situ biogeochemical processes on COA along a highly populated tropical coastal area. The results suggest that spatially, aerosol deposition and in-situ biogeochemical processes in Kutch region are the major (72%) contributors to COA. In contrast, cumulative land runoff significantly (70%) contributes to COA in South Gujarat. Among these drivers, river water mixing causes the most significant pH decrease (0.093), while wastewater input results in the minimum pH drop (0.016) along the Gujarat coast. The seasonal nature of river water discharge, compared to continuous seepage of both fresh and recirculated (saline) SGD, highlights the role of SGD in COA. These findings align with the global studies represented SGD as one of the prominent land-based drivers for COA. Additionally, the low annual average pH (~ 7.954) along the Gujarat coast is attributed to the region’s macrotidal characteristics, which facilitate the release of sediment bound CO₂, leading to a reduction in pH levels. The findings from the current study emphasis the need for comprehensive data collection on physicochemical and biogeochemical parameters to accurately assess COA dynamics and quantification of spatial and seasonal impacts of each driver along the India’s west coast.

Reddy K. K., Busala S. K. K., Gupta G. V. M., Pandya D. & Chhag S., 2026. Quantifying the role of land-based inputs on coastal ocean acidification from a tropical semi-arid region. In: Ganugapenta S., Badimela U., Krishnan K. A. & Mejjad N. (Eds.), Coastal biogeochemistry and ecosystem shifts: tracing the impact of human activities, pp. 273-286. Cham: Springer Nature Switzerland. Chapter (restricted access).