The physiology of coral reef calcifiers under local and global stressors

Anthropogenic activities have caused coral reefs worldwide to face extreme changes in their environment at both global and local scales. This thesis covers the effects of ocean acidification (OA) and eutrophication through increased dissolved organic carbon (DOC) availability on coral reef calcifiers. In this thesis the individual and combined effects of OA as increased dissolved inorganic carbon (DIC) and high availability of DOC on the physiology of reef building corals from the Great Barrier Reef and calcifying green algae from the Indo-Pacific and the Caribbean are investigated. More specifically, calcification processes, photosynthesis and nitrogen fixation of the coral holobiont and calcifying green algae were investigated. This thesis revealed that the physiology of the calcifiers investigated is negatively affected by both high DIC and DOC concentrations. These findings will be crucial to be able to investigate future reef changes under high DIC and increased DOC concentrations. Our findings on calcification rates and calcification structures can be used as indicators of environmental change and as future predictors.