Rain-derived particles and CDOM distribution along the east coast of New Caledonia

Heavy rainfall or tropical storms can dramatically increase chlorophyll-a concentration, turbidity, and colored dissolved organic matter (CDOM) in New Caledonia's lagoons, with effects detectable up to 50 km offshore. The eastern coast is more affected due to its geomorphology, frequent intense rains, and erosive lateritic formations from ultramafic rocks. Satellite imagery and oceanographic measurements reveal that these increases—visible as plumes extending offshore—affect deeper lagoon areas (>20 m) and extend to coral barrier reefs. While large particles settle near river outflows, fine particles (<10 µm), colloids, and CDOM are transported to reefs, potentially benefiting corals by shielding them from UV radiation or providing nutrients. However, the impact of trace metal distribution from these particles on coral health remains uncertain.

Röttgers, R., Frouin, R. J., Dupouy, C., Juillot, F., Lefèvre, J., Wattelez, G., Andreoli, R., Lille, D., & Murakami, H. (2018). Rain-derived particles and CDOM distribution along the east coast of New Caledonia. Remote Sensing of the Open and Coastal Ocean and Inland Waters, 22. https://doi.org/10.1117/12.2501807