Nicole Dilernia
Project Title: Resolving the limits of reef forming corals to survive under ocean deoxygenation.
Supervisors: Dr. Emma Camp, Professor David Suggett, Dr. David Hughes, Professor Michael Kühl
Contact Detail: Nicole.J.Dilernia@student.uts.edu.au
Project Background: Degradation of coral reefs from ocean warming and acidification under local anthropogenic impacts and global climate change is well documented. However, as ocean temperatures continue to rise, reefs are subject to another – hidden and unstudied – stressor, deoxygenation. Climate forecasts suggest that future declines in dissolved oxygen (O2) concentrations will heavily impact temperate and tropical coral reefs, mangrove lagoons, and seagrass meadows. It is currently unclear whether and how different coral reef taxa exhibit capacity to withstand deoxygenation exposure, and in turn their potential to evolve greater tolerance to conditions that are considered “hypoxic” (< 2 mg/L). To understand how ocean deoxygenation could shape future form and functioning of coral reefs, it is time-critical to resolve tolerance thresholds to decreased O2 availability and identify the physiological traits underlying tolerance for diverse coral taxa and across a range of spatial scales (e.g. from within a coral colony, to across a reef system). The goal of my research is therefore to understand the extent with which reef-forming corals can tolerate reduced O2 availability, resolving lethal and sub-lethal hypoxia thresholds for coral taxa of differential morphologies and from different reef habitats and regions, and the variation of intra- (and inter-) colony “oxyregulation” capacity.
Project Aims: My project will specifically focus on spatial variances within, across and between key reef forming coral species (e.g., morphological differences and intra/inter-colony variance), and environments (e.g., reef versus mangrove). This will be achieved by applying new O2 performance assays developed for coral to resolve capacity for oxygen regulation and thresholds of hypoxia (low O2 stress) sensitivity, across the following objectives: (i) determine how changes in environmental O2 availability correspond to O2 concentrations retained in coral tissues (e.g., polyp tissue), and hence identify “oxyregulation” offset declines in external O2 availability for taxa with different morphologies (e.g., massive versus branching), (ii) establish how intra and/or inter-colony spatial variation affects thresholds of hypoxia in common coral species, (iii) determine whether and how thresholds of hypoxia change for coral species thriving across contrasting habitats with different inherent O2 availability (mangrove lagoons vs. reef flat), and (iv) determine whether and how thresholds of hypoxia change for coral species thriving across contrasting regions with different inherent O2 availability (e.g., GBR vs. Red Sea).