PRODUCTION OF VOLATILE ORGANIC COMPOUNDS (VOCS) BY TEMPERATE MACROALGAE: THE USE OF SOLID PHASE MICROEXTRACTION (SPME) COUPLED TO GC-MS AS METHOD OF ANALYSIS
Volatile organic compounds (VOCs) are produced by macroalgae in response to environmental stresses. A novel approach using Solid Phase Microextraction (SPME) was used to quantify the production of several VOCs from eight common intertidal algal species from the UK (Ascophyllum nodosum (Linnaeus) Le Jolis, Fucus vesiculosus (Linnaeus), Fucus serratus (Linnaeus), Laminaria digitata (Hudson) Lamouroux, Ulva lactuca (Linnaeus), Ulva intestinalis (Linnaeus), formerly known as Enteromorpha, Palmariapalmata (Linnaeus) Kuntze and Griffithsiaflosculosa (J. Ellis) Batters). The volatile compounds included halogenated, sulphur containing, aldehydes, non-methane hydrocarbons (NMHC) and oxygenated species. Overall, the production of VOCs by these algae was not considerably different under illumination or in darkness; this suggests that the VOC production occurs during both algae photosynthesis and in other metabolic processes such as respiration or osmoregulation. Desiccation played an important role in the production of VOCs with greater production by macroalgae after desiccation. This production was related to the alga's normal position within the intertidal zone; there was a lower production of VOCs for species growing near the high water mark and a greater production for algae taken from the low tide position. There were also species differences in the VOC profiles and quantities released. For example, chlorinated and oxygenated compounds were principally released by the brown alga Ascophyllum nodosum, while green algae such as Ulva lactuca and Ulva intestinalis released greater amounts of brominated, sulphur containing compounds, aldehydes and non-methane hydrocarbons than the other algae tested. Thekelps (e.g. Laminaria digitata) had the greatest release of iodinated compounds such as diiodomethane. These processes make significant contributions to the VOCs in seawater and, by transfer to the atmosphere, in the coastal atmosphere.