Non-methane hydrocarbons (NMHCs) are generally C1 to C5 alkanes (e.g. ethane [H₃C-CH₃]), alkenes (e.g. isoprene [H₂C=C(CH₃)CH=CH₂]) and alkynes (e.g. propyne [H₃C-C=CH]). These reactive trace gases have an influence on the oxidising capacity of the atmosphere via their reactions with hydroxyl radicals [OH], ozone [O₃], and nitrate [NO₃]. The importance of anthropogenic emissions of NMHCs and biogenic emissions of monoterpenes (e.g. geraniol, menthol) and isoprene from the terrestrial biosphere has long been recognised and extensively studied. However, the ocean as a source of reactive species such as isoprene has only recently been identified. The emission of isoprene and other NMHCs from the ocean may provide a significant source of reactive organics to the atmosphere over the oceans remote from land.

Previous work carried out in our group by Dr. Wendy Broadgate showed a seasonal cycle of isoprene and other NMHCs in the North Sea and Southern Ocean (Broadgate et al. 1997). Our current focus is on the role of phytoplankton in the production of ethene (ethylene; [H₂C=CH₂]). This trace gas is recognized as a hormone in terrestrial plants, where the different stages of development are regulated by the hormones abscissic acid, auxines, cytokinins, gibberellins and the gaseous ethene. Exposure to ethene affects plant growth, development, and physiology, most notably the ripening of fruits, inhibition of stem and root elongation, promotion of seed germination and flowering, senescence of leaves and flowers, and sex determination. Little is known about the metabolic pathways that result in formation of ethene in the sea and its role in the chemical ecology of marine algae is unknown.