Standard Presentation (15 mins) Australian Marine Sciences Association 2022

Spatial distribution of Symbiodiniaceae communities across the Great Barrier Reef in two species of Pocilloporids (#275)

Josephine JV Nielsen 1 , Kate M Quigley 2 , Ira R Cooke 3 , Jan M Strugnell 4 , David J Suggett 5 , Line K Bay 2
  1. James Cook University and Australian Institute of Marine Science, Douglas, QLD, Australia
  2. Australian Institute of Marine Science, Cape Cleveland, QLD, Australia
  3. CPHMVS, James Cook University, Douglas, QLD, Australia
  4. CSE, James Cook University, Douglas, QLD, Australia
  5. Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia

Associations between corals and their photosynthetic symbiotic algae (Symbiodiniaceae) influence overall thermal tolerance where harbouring specific Symbiodiniaceae taxa can confer >1oC of heat tolerance to the coral holobiont. However, the natural occurrence of heat tolerant Symbiodiniaceae is not well-documented for most coral species on the Great Barrier Reef (GBR).

Here, we aim to describe the spatial distribution of Symbiodiniaceae communities within two common coral species (Pocillopora meandrina and P. verrucosa) across the GBR spanning over 12o latitude (>1,500 km). We then discuss how changing Symbiodiniaceae community compositions influence the response of each species under an acute heat stress (Max Monthly Mean temperature, +6oC and +9oC).

Following experimental heat exposure, photosynthetic efficiency was significantly decreased across the GBR (P. meandrina 21-98%; P. verrucosa 7-95%) with the greatest decrease occurring in both species in the far northern Princess Charlotte Bay and the least reduction in the southern Capricorn Bunker group. Symbiont densities and chlorophyll content also experienced significant declines reef-wide. These trends are then discussed relative to observed changes in Symbiodiniaceae communities. Together, these findings highlight the role of specific Symbiodiniaceae taxa in conferring thermal tolerance examined across multiple symbiont-driven measures of physiological responses to heat stress across a reef-scape.