Nutrients in submarine fresh groundwater discharge

Submarine groundwater discharge (SGD) happens when water flows underground from the land and emerges underwater in the ocean. This water can carry dissolved nutrients, metals, pollutants and other materials which can affect coral reefs.

In Tahiti and Moorea, most of the freshwater enters the groundwater at high altitudes where rainfall is highest, while the majority of the nutrients added in fresh groundwater comes from human activities at lower altitudes. Septic waste, manure, and fertilizer are the primary sources of elevated nutrients on both islands. This highlights the potential for human activities to impact the health of coral reefs even indirectly through the groundwater system.

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Haßler et al. 2019