Final Report Summary - CORALCHANGE (Factors controlling carbonate production and destruction of cold-water coral reefs of the NE Atlantic)
Uptake of anthropogenic CO2 by the oceans is altering seawater chemistry with potentially serious consequences for calcifying organisms due to the reduction of seawater pH and carbonate ion concentration (ocean acidification, OA). Calcium carbonate (CaCO3)-rich ecosystems, such as shallow and deep-sea coral reefs, coralline and shellfish beds, are of central importance as they directly respond to climate change, contribute to structural complexity, create habitat for associated organisms, significantly contribute to biogeochemical cycles, and provide diverse services to human society. Thus, their damage or loss due to adverse conditions will have serious repercussions. Their survival and sustainability directly depends on the balance between constructive (accretion) and destructive processes (physical, chemical, and biological erosion). Cold-water corals (CWC) are thought to be particularly vulnerable to OA because they inhabit deep and cold waters where the aragonite saturation state (Ωa) is low. Given global climate change, two important questions are (1) what are the environmental controls of reef framework growth? and (2) how might cold-water corals be affected by environmental change? This project addressed these questions by studying the biological erosion (bioerosion) processes of carbonate substrates in coastal and deep-sea environments in the warm-temperate setting of the Azores region; and by studying growth dynamics of important cold-water corals in the Azores and their relationship to environmental factors. The project also included laboratory experiments on the effects of predicted increases in carbon dioxide partial pressure (pCO2) on the calcification, basal metabolism (measured as respiration rates) and gene expression responses of CWC species. The parasitic behaviour of zoanthids associated with CWC was also investigated as it raises questions on their importance as a natural cause of coral mortality, and on how can they affect coral population structure. The ultimate goal of the project is to improve predictions of how these coldwater corals will respond to future environmental changes and whether reefs will be able to maintain a positive balance between carbonate construction and destruction processes.
