Although resource availability is important for coral reef nutrient cycling and trophic ecology, it is poorly understood how particulate resources may change following an oceanic heat stress event. Here, carbon and nitrogen concentrations and stable isotope values (δ13C and δ15N) of particulate organic matter (POM; 10 and 30 m) were compared from before and after the 2016 mass coral bleaching event in the Maldives, Indian Ocean. To characterize the trophic status of the post-bleaching water column, dissolved inorganic nutrients across shallow to mesophotic coral reefs (10–50 m) and plankton δ13C and δ15N were measured. Eight months after the mass bleaching, an oligotrophic water column with decreased particulate organic nitrogen and variable yet increased mean δ13C of POM was observed. Elemental and isotopic data of particulate resources from pre- and post-bleaching revealed three oceanographic regimes related to ocean mixing. This study highlights the importance of characterizing water column biogeochemistry to understand nutrient cycling in coral reef ecosystems especially post-disturbance.
Republic of Maldives