Will young corals thrive with stronger symbiotic algae?

Corals depend on microbes for their survival and are well known for their relationship with photosynthetic single-celled algae. These micro algae provide food for the corals in return for shelter and essential nutrients, making a symbiotic, or mutually beneficial, relationship. 

Studies have shown that the types of micro-algal symbionts (Symbiodiniaceae) in the partnership affect the corals’ physiology; some help corals to grow quickly while others improve corals’ tolerance to warmer and extreme temperatures. This relationship is very delicate and in prolonged periods of high temperature and strong light, the micro-algae can be lost and coral bleaching occurs. This can lead to mass colony mortalities.  

Recent pioneering research at AIMS has demonstrated that micro-algal symbionts selectively cultured at elevated temperatures can transfer some heat tolerance to one coral species. Expanding the range of species that may benefit from this, as well as optimising methods to get these symbionts into corals needs more research. 

This project investigates if providing these beneficial symbionts very early in a coral’s life (i.e., larval and early settlement stage), can influence survival and growth over the first few months of life. In the SeaSim, we will supply four coral species with four different types of cultured symbionts, at different densities, at the larval stage and separately during the early settled stage.  

The survival and growth rates of coral juveniles from these symbiont inoculation strategies will be tracked over three months (October 2021 to February 2022) to assess the most favourable symbiont types and densities for each of the four coral species that are being tested. This will provide valuable data on the impacts of selectively cultured symbionts on the fitness of multiple coral species during early life stages and inform methods for optimizing the uptake of these symbionts by young corals. This knowledge is important to maximise success of planned coral aquaculture and restoration endeavours to re-seed degraded coral reefs.

Feature image credit: Katarina Damjanovic