Comparative distribution of Volatile Organic Compounds across the surface oceans

Abstract

2018 Ocean Sciences Meeting, 11-16 February, in Portland, OregonThe oceans are a natural source of Volatile Organic Compounds (VOCs). Once emitted, VOCs play important roles in the atmosphere; they provide odour landscapes for marine animals, act as oxidant scavengers and are precursors for aerosols, which affect the Earth radiation budget by scattering solar radiation back to space and altering the properties and lifetimes of clouds. Out of all VOCs, we focus on those that typically are supersaturated in surface seawater: DMS (dimethyl sulphide), OCS, CS2, CH3I, CH2I2, CH2ClI, CHBr3, CH2Br2 and isoprene. We used gas chromatography mass spectrometry to obtain aqueous concentrations of VOCs during 5 cruises across: the Mediterranean Sea (HotMix, 2014), Atlantic Ocean (Trans-PEGASO, 2014 and ACE0, 2016) and Southern Ocean (PEGASO, 2015 and ACE, 2016-2017). We present how these compounds co-variate among them and with other oceanographic and atmospheric variables. We explore their relationship with chlorophyll a, phytoplankton taxonomy and physiology, bacterial abundances, coloured dissolved organic matter, temperature, salinity, wind speed and solar radiation as potential drivers of their production and cycling. Our results show that usually these compounds are in the lower picomolar range (nanomolar for the DMS), but there are certain hotspots with high concentrations like the Mauritanian up-welling (164.2±0.2 pM isoprene) or the South Georgia summer bloom (54.8±1.3 pM CHBr3). Although all VOCs are related directly or indirectly to plankton productivity, we found a pattern of most compounds with temperature and light in which colder and more mixed waters present lower volatile/Chl a ratiosPeer Reviewe