Tropical
urbanized coastal regions are hotspots for the discharge
of nutrient-enriched groundwater, which can affect sensitive coastal
ecosystems. Here, we investigated how a beach modifies groundwater
nutrient loads in southern India (Varkala Beach), using flux measurements
and stable isotopes. Fresh groundwater was highly enriched in NO3 from sewage or manure. Submarine groundwater discharge and
nearshore groundwater discharge were equally important contributors
to coastal NO3 fluxes with 303 mmol NO3 m–1 day–1 in submarine and 334 mmol
NO3 m–1 day–1 in nearshore
groundwater discharge. However, N/P ratios in nearshore groundwater
discharge were up to 3 orders of magnitude greater than that in submarine
groundwater, which can promote harmful algae blooms. As groundwater
flowed through the beach, N/P ratios decreased toward Redfield ratios
due to the removal of 30–50% of NO3 due to denitrification
and production of PO4 due to mineralization of organic
matter. Overall, tropical beaches can be important natural biogeochemical
reactors that attenuate nitrogen pollution and modify N/P ratios in
submarine groundwater discharge.
The direct discharge of groundwater to sea through aquifer medium (Submarine Groundwater Discharge), has been recognized as a small but significant component of hydrological cycle as it often transfers considerable amount of nutrients and pollutants to the sea. Understanding on Submarine Groundwater Discharge (SGD) allows us to estimate optimum exploitation levels of coastal fresh groundwater and to locate feasible waste disposal sites in coastal zones. SGD is temporally and spatially variable as interactions between multiple forcing mechanisms vary at any given location and time. Thus, site-specific investigation is necessary to comprehensively evaluate the timing, magnitude, and importance of SGD in any region. The potential of thermal remote sensing (IR imagery) was resorted to target the possible SGD zones in the initial phase. Subsequently, hydrogeological, hydrochemical and resistivity surveys have provided adequate field evidences to delineate the direct discharge areas. Though sandy horizons form the main aquifer material, laterite and weathered/fractured rock were also found to be functioning as aquifer zones. Based on different field investigation techniques, a total of three areas such as, Gotheeswaram, Kappad and Koyilandi were identified as potential groundwater discharge zones in the Kozhikkode coastal aquifer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.