Production of Dimethyl Sulphide (DMS) by Scleractinian Coral during Aerial Exposure – Effect of Temperature and Light

In this thesis I investigated how rates of DMS production in three Scleractinian corals were affected by both aerial exposure and different light and temperature regimes. Coral specimens were acclimated over a 1 month period prior to data collection. Gas samples were collected from corals both prior to and during emersion in a hermetically sealed vial system and DMS was content measured via gas chromatography. Major differences in DMS production during emersion were observed between species; Acropora inermis production increased significantly upon exposure (from ~20 to ~600 nmol/h/cm2) with Turbinaria reniformis also increasing but to a lesser degree. No significant increase was observed in Porites cylindrica. Prolonged acclimation to low light (~20 µmol photons/m²/s) resulted in a general decrease in DMS production in A. inermis and Turbinaria reniformis compared to control (~200 µmol photons/m²/s). The most dramatic effect was observed in T. reniformis where production was very low and in some cases not detected. The effect of temperature on DMS production was dependent on species and light, with either an increase, decrease or no measurable effect being observed. However the magnitude of this effect was smaller compared to other factors. Although interspecific differences in symbiont density, chlorophyll content and total DMSP were observed, no measurable effect of acclimation to light and temperature was recorded, suggesting that intraspecific differences in DMS production were not driven by changes in Symbiodinium physiology. The results of this study show that coral reefs exposed regularly at low tide can potentially act as significant contributors to the local DMS-flux. However, interspecific differences in response, as well as the effects of environmental factors, make predicting habitat-wide DMS production challenging. Further investigation into the mechanisms behind these responses is warranted to support potential reef-wide shifts in DMS production.