MCR LTER: Coral Reef: River chemistry dynamics in 2018 and 2019; data for Neumann et al., 2025 Scientific Reports

Rivers are the dominant avenue by which terrestrial efflux is transported to marine systems. Human activities on land, such as agriculture and infrastructure development, may impact coral reefs by disrupting historic biogeochemical processes of nearshore reef habitats. To identify how land use impacts rivers, and therefore nearshore lagoons, water chemistry was measured at a series of rivers around the island of Moorea, French Polynesia, in 2018 and 2019. Nitrate, Nitrite, Silicate, Phosphate, and Total Suspended Solids were evaluated at least weekly during sampling campaigns in rainy and dry seasons of both years. TSS was elevated following recent precipitation and negatively associated with watershed size. Phosphate was associated with Total Suspended Solids, presumably because of the phosphate-rich soils on Moorea. Dissolved Inorganic Nitrate was higher during the rainy season in watersheds with a high degree of land clearing. These results reinforce the importance of terrestrial factors for biogeochemistry of nearshore marine systems.