The Central Great Barrier Reef as a Net Source of Climatically Relevant Biogenic Volatile Organic Compounds

Abstract

Biogenic volatile organic compounds (BVOCs) such as dimethyl sulfide (DMS), methanethiol (MeSH), isoprene, and monoterpenes partly control the Earth's radiation budget. As such, measuring coral-reef BVOC emissions are important for understanding the impact of future climate and shading interventions that are being developed as part of the Reef Restoration and Adaptation Program to protect the Australian Great Barrier Reef (GBR). Here we report high temporal resolution BVOC concentrations and fluxes from the central GBR in the austral summer of 2021–2022, including the first flux estimates of MeSH, isoprene, and monoterpenes from reef systems, using a proton-transfer-reaction quadrupole mass spectrometer. Median fluxes of DMS, MeSH, isoprene, and monoterpenes across the two voyages were 4.26 ± 2.53, 0.94 ± 0.64, 0.05 ± 0.03, and 0.03 ± 0.03 μmol m−2 d−1, respectively, indicating that the central GBR is a net source of climatically relevant BVOCs in summer. Dissolved concentrations of BVOCs were positively correlated with sea surface temperature and proximity to the coast, which was most likely due to a coastward gradient for chl-a and nutrient concentrations. Predictably, wind speed and dissolved BVOC concentrations were the main drivers of BVOC fluxes. This study adds to our understanding of ocean-atmosphere exchange processes in coral reef systems and will help improve model predictions of the local climate of the GBR under future climate change scenarios.