Aside from rivers and estuaries, water also flows below-ground from land to the ocean through coastal and submarine aquifers. While the global fresh submarine groundwater discharge (SGD) is less than 1% of river discharge, it is chemically important as groundwater nutrient inputs are 25% of riverine inputs. This land-ocean connectivity is important for sensitive ecosystems such as coral reefs if the groundwater delivers solutes that are either necessary for or harmful to reef life.
Here, we present the interesting but potentially common situation of dramatic SGD in a volcanically active area in the Philippines which has been identified as the world’s most biodiverse coastal area and whose coral reefs provide for local communities. We studied coastal and submarine thermal springs associated with high fluxes of acidic waters and carbon dioxide, some of which are within or close to thriving coral reefs. The SGD fluxes are amongst the largest in the world and the SGD carbon dioxide fluxes overwhelm coastal carbon budgets.
The presentation delivers explanations for the high SGD, discussing the mechanics and different sources and pathways of water, by bringing together multiple lines of evidence from different methods including deep diving, drones, novel sensors, geochemical tracers, thermal remote sensing, and modeling.
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M. Bayani Cardenas is a hydrology professor in the Department of Earth and Planetary Sciences of the Jackson School of Geosciences at the University of Texas at Austin. His research seeks to understand flow and transport processes across different hydrologic settings, water quality and quantity problems, and scales, using a combination of theoretical, computational, and observational methods. He received his education from the University of the Philippines, the University of Nebraska, and the New Mexico Institute of Mining and Technology.