Chapter 13 - Nutrient inputs in to the coastal ocean associated with Submarine Groundwater Discharge (SGD) from the unconfined aquifers of Kayalpattinam, Southern coast of Tamil Nadu

Abstract

Submarine Groundwater Discharge (SGD) may be a major source of chemical contaminants that go from land to sea. We initially calculated SGD at the local scale in Kayalpattinam, a typical coast with fast industrial growth, using radon (222Rn), radium isotopes and associated nutrient fluxes. Then, to evaluate the large-scale consequences of SGD on nutrient budgets, we summarized SGD research. The SGD hotspots corresponded with the location of polluted near-shore waters indicated. Based on radon (222Rn) mass balance models, the total (fresh and saline) SGD flux in was calculated to be 0.14–0.20m3m−1day−1. We proposed the first estimate of SGD and related nutrient fluxes of the Kayalpattinam coast by integrating these findings with published data. These nutrient fluxes from SGD accounted for more than 50% of total dissolved inorganic nitrogen (DIN), Sodium Reactive phosphate (SRP), and silicate (DSi) inputs into coastal waterways, accounting for about 45% of the phosphorus needed for primary production. SGD had a considerably higher N/P ratio (78) than Redfield, which has major implications for phytoplankton growth and structure. SGD has the ability to impact water quality, control nutrient budgets, and drive primary production on a local, regional, and global scale.