Mangrove Creeks Are a Sink for Isoprene—A Functional Link Between Ecosystems

Abstract

AbstractIsoprene is an important biogenic volatile organic compound with atmospheric emissions contributing to climate regulation. Because isoprene is predominantly sourced terrestrially, there is limited knowledge on the role it might play in marine systems. Here, we report for the first time isoprene concentrations and tidal fluxes from two subtropical mangrove creeks in Moreton Bay, Queensland, Australia: Jacob's Creek and Turkey Boat Creek in 2017 and 2019. Isoprene concentrations tracked the tide height with higher concentrations at high tide and lower concentrations at low tide in both creek systems, showing that isoprene was imported into the creeks on the flood tide. Mangrove creeks in Moreton Bay were a sink (−9.53 ± 9.10 nmol m−2 h−1) for isoprene. Isoprene was most likely produced in the open water by either phytoplankton or nearby seagrass beds and then consumed by bacterial communities as a carbon source within the mangrove creek sediments. Mangrove creeks in Moreton Bay are estimated to uptake isoprene at a rate of −6 mg m−2 y−1, leading to a total global isoprene sink of −0.69 Gg C y−1. While only a small component of the global marine atmospheric flux of 11,600 Gg C y−1, isoprene constitutes an important functional link between marine ecosystems.