Isoprene is the most abundant biogenic volatile organic compound (BVOC) on the planet, with annual emissions accounting for up to half of all BVOC emissions. Isoprene has been measured extensively in terrestrial habitats where it is highly abundant; however, there is limited knowledge on marine systems where it is found at lower concentrations. Here, we report for the first time isoprene fluxes from coral reef permeable carbonate sediments with a cover of microphytobenthos (MPB) from Heron and Lizard Islands, on the southern and northern ends of the Great Barrier Reef, respectively. Using advective and diffusive benthic chambers, we measured isoprene fluxes over full diel cycles on both islands. Net effluxes of isoprene from the sediment to the water column were observed at both Heron Island (mean: 10.0 ± 1.1 nmol m² h⁻¹) and Lizard Island (mean: 3.9 ± 0.9 nmol m² h⁻¹). Light isoprene fluxes were much higher on Heron Island than on Lizard Island and both islands had lower isoprene emissions in the dark. Higher isoprene fluxes during the day reflects the role of MPB photosynthesis in isoprene production. Lower isoprene fluxes at night is most likely due to isoprene consumption by microbial activity or less production in the absence of photosynthesis. The contribution of benthic isoprene emissions from coral reef carbonate sands worldwide (0.52 Gg C y⁻¹) were estimated to represent less than 0.005% of the global marine atmospheric fluxes (11,600 Gg C y⁻¹).

异戊二烯是地球上最丰富的生物挥发性有机化合物（BVOC），年排放量占所有BVOC排放量的一半。异戊二烯已经在高度丰富的陆地生境中被广泛测量。但是，对海洋系统中浓度较低的知识知之甚少。在这里，我们首次报告了珊瑚礁可渗透碳酸盐沉积物中的异戊二烯通量，其覆盖物分别来自大堡礁南端和北端的苍鹭和蜥蜴群岛的微植物底栖动物（MPB）。使用对流和扩散底栖室，我们在两个岛上的整个diel周期内测量了异戊二烯通量。在两个苍鹭岛都观察到异戊二烯从沉积物到水柱的净流出（平均值：10.0±1.1 nmol m ² h ^-1）和蜥蜴岛（平均值：3.9±0.9 nmol m ²  h ^-1）。苍鹭岛上的异戊二烯光通量比蜥蜴岛上的异戊二烯通量高得多，并且两个岛屿在黑暗中的异戊二烯排放量都较低。白天较高的异戊二烯通量反映了MPB光合作用在异戊二烯生产中的作用。夜间较低的异戊二烯通量很可能是由于微生物活动消耗异戊二烯或在没有光合作用的情况下产量降低。据估计，全世界珊瑚礁碳酸盐砂的底栖异戊二烯排放量（0.52 Gg C y ^-1）的贡献不足全球海洋大气通量（11,600 Gg C y ^-1）的0.005％。