Responses of calcifying macroalgae to ocean acidification

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The rapid reduction in carbonate saturation and seawater pH caused by ocean acidification has potential consequences for all marine biota. This PhD project focuses on the responses of coralline red algae and their associated biofilms. These critically important calcifying macroalgae (CM) are key primary producers, dominate hard surfaces from polar to tropical coral reefs to > 200 m deep, and are ecosystem engineers providing a substratum for many invertebrates. They produce a skeleton of high-Mg calcite which makes them particularly sensitive to the current changes in ocean chemistry. The effect of the associated biofilm on the growth of coralline algae and its response to ocean acidification is unknown. The aim of this project is to quantify the response of CMs to ocean acidification by asking the following questions: Does CM material not impacted by anthropogenic emissions exhibit a different skeletal morphology to fresh material? 2. Will CM growth rate vary along a latitudinal gradient due to different levels of photo-oxidative stress? 3. Will ocean acidification exacerbate the level of photo-oxidative stress in CMs by down regulated/inhibited productivity? 4. Will the balance between macroalgae and their predominantly non-calcifying biofilms shift as a result of OA? The project brings together Dr Perkins (Cardiff University), Dr Yallop (Bristol University) and Prof. Brodie (NHM, CASE partner), a consortium with expertise in micro- and macroalgal photophysiology, molecular biology and the global distribution of macroalgae. There will also be collaboration with Dr Bartsch (AWI Bremerhaven; BIOACID project). With field sites spanning a latitudinal gradient in the northeast Atlantic, the PhD will combine laboratory and field studies including molecular techniques, examination of skeletal morphology, measurements of photosynthesis and fluorescence, and comparative growth patterns to address the questions posed.