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Volatilomics, the examination of all biogenic volatile organic compounds (BVOCs) emitted by an organism or system, holds potential as a novel screening tool for taxonomy, fitness, and ecological functioning. Volatilomics has been largely applied to terrestrial environments, but highly productive coastal marine systems, which are major sources of specific BVOCs, such as dimethyl sulfide, have been largely neglected. Volatilomic measurements are highly method-dependent, with different instrumentation impacting the diversity of identified BVOCs-therefore, understanding these biases is critical to reconcile studies. Here, we investigated BVOCs emitted by two species of coral endosymbiotic microalgae (Symbiodinium tridacnidorum and Durusdinium trenchii) using gas chromatography-mass spectrometry (GC-MS) and comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC x GC-TOFMS). Seven chemical classes were detected by both instruments, the most common being aromatic hydrocarbons. However, GC x GC resolved seven times more BVOCs than GC-MS (290 vs. 40), with a higher proportion of compounds tentatively identified (173 vs. 14). Notably, nine chemical classes were exclusively identified by GC x GC, including alkane, alkene, aldehyde, ester, and nitrile BVOCs-each potentially fulfilling undescribed functions in marine organisms. The microalgal species investigated shared a large proportion of BVOCs, and this result was consistent across instruments (97 and 98% shared compounds via GC x GC and GC-MS, respectively), suggesting consistent retrieval of general patterns between instruments. This method comparison is the first of its kind in marine systems and confirms the greater analytical power of GC x GC, required to help resolve complex BVOC emissions and the identification of their roles in marine systems., Author(s): Axel Olander [sup.1] , Caitlin A. Lawson [sup.1] [sup.2] , Malcolm Possell [sup.3] , Jean-Baptiste Raina [sup.1] , Maiken Ueland [sup.4] , David J. Suggett [sup.1] Author Affiliations: (1) [...]

Introduction: Biogenic volatile organic compounds (BVOCs) are emitted by all organisms as intermediate or end-products of metabolic processes. Individual BVOCs perform important physiological, ecological and climatic functions, and collectively constitute the volatilome-which can be reflective of organism taxonomy and health. Although BVOC emissions of tropical benthic reef taxa have recently been the focus of multiple studies, emissions derived from their temperate counterparts have never been characterised., Objectives: Characterise the volatilomes of key competitors for benthic space among Australian temperate reefs., Methods: Six fragments/fronds of a temperate coral (Plesiastrea versipora) and a macroalga (Ecklonia radiata) from a Sydney reef site were placed within modified incubation chambers filled with seawater. Organism-produced BVOCs were captured on thermal desorption tubes using a purge-and-trap methodology, and were then analysed using GC × GC - TOFMS and multivariate tests., Results: Analysis detected 55 and 63 BVOCs from P. versipora and E. radiata respectively, with 30 of these common between species. Each taxon was characterised by a similar relative composition of chemical classes within their volatilomes. However, 14 and 10 volatiles were distinctly emitted by either E. radiata or P. versipora respectively, including the halogenated compounds iodomethane, tribromomethane, carbon tetrachloride and trichloromonofluoromethane. While macroalgal cover was 3.7 times greater than coral cover at the sampling site, P. versipora produced on average 17 times more BVOCs per cm 2 of live tissue, resulting in an estimated contribution to local BVOC emission that was 4.7 times higher than E. radiata., Conclusion: Shifts in benthic community composition could disproportionately impact local marine chemistry and affect how ecosystems contribute to broader BVOC emissions., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)