CONSTRAINING SUBMARINE GROUNDWATER DISCHARGE TO CORAL REEFS FROM SALINITY, RADON AND SILICA SYSTEMATICS – INSIGHTS FROM MO’OREA AND TETIAROA, FRENCH POLYNESIA

Anthropogenic climate change has caused an increase in sea temperatures worldwide, which in turn has altered the ecosystem surrounding coral reefs and made them more susceptible to ocean acidification. Freshwater from nearby islands in the form of Submarine Groundwater Discharge (SGD) may have buffering capacities for these reefs through introduced alkalinity. This study presents a multi-methodological approach to quantifying SGD off the islands of Mo’orea and Tetiaroa, French Polynesia. Using salinity, radon, and dissolved silica analysis SGD will be mapped and quantified through coastal transects and time series analysis. Measurements over wet and dry seasons will further present a comprehensive view of how SGD fluctuates seasonally in this understudied region. Furthermore, by comparing a high volcanic island, Mo’orea, to a low coral atoll, Tetiaroa, this study hopes to elucidate limitations and strengths of the chosen methodologies that would otherwise be difficult to identify when used alone. By precisely quantifying SGD fluxes, more information on how groundwater is exiting both islands may provide vital information for long-term aquifer management as well as identifying if SGD has any impact on nearby coral reefs.