River, Aquifer and Coastal Water Vulnerability on Tropical Volcanic Islands of French Polynesia (South Central Pacific Ocean)
Résumé
Submarine fresh groundwater discharge (SFGD) is an essential driver of coastal water quality as well as a prominent pathway of nutrients and eventually other chemicals to the reef and coastal ocean. Here we synthetize recent studies dealing with some environmental disturbances and vulnerability reported on rivers, SFGDs and lagoons [see Leroi (2016), Knee et al. (2016), Salvat et al. (2016), Andréfouët and Adjeroud (2019) and Haßler et al. (2019)] on the tropical volcanic Society Islands in the South central Pacific Ocean, that are the most urbanized and populated parts of French Polynesia. Compared globally, the level of pollution threats linked to anthropogenic land use is low in French Polynesia but can be very different between islands and archipelagos and even remote areas can be impacted.
We emphasize and discuss the Tahiti, Moorea and Raiatea cases studied from a point-source angle where relatively elevated nitrate amounts were detected in SFGDs mainly associated with septic waste/manure and/or crop fertilizers inputs into fresh water (Tahiti and Moorea) as well as pesticides and herbicides contamination of stream and bay waters (Raiatea). In addition, we bring up leaching and runoff of soils from agricultural land as potentially widespread and relevant source of herbicides to coral reef organisms in Tahiti and Moorea.