The Flexibility of Coral-algal Symbiosis - Briareum asbestinum

A study by PhD candidate, Shelby Boyer. Here's a summary of what Shelby is doing - In my study I am looking at the octocoral Briareum asbestinum and it’s endosymbiotic algae, Symbiodinium. I want to know if the light environment will influence the type of symbiont that Briareum larvae acquire. So, we collected Briareum larvae right off of the parental colony and raised them in the lab in filtered sea water. When they metamorphosed into the polyp form, I treated them with different symbiont types: A, B and D. I also used mixed infections, AB, AD and BD to see if one type of algae excludes another or if the coral selects one type over another. I want to know if a low or high light environment will change the outcome of this selection. This type of information will be important for researchers and managers to understand in order to face the challenges of warming oceans and coral bleaching.

Newly settled B. asbestinum polyps on dead gorgonian axis (their preferred settlement substrate)

Close up of a newly settled B. asbestinum polyps on dead gorgonian axis (their preferred settlement substrate)
Close up of the experimental set-up showing the "light" and "shade" environments.


Experimental set-up with light and shade treatments

Cassiopea xamachana

Meanwhile, Rachel has been busy collecting and rearing embryos from the upside-down jelly fish, Cassiopea xamachana.

C. xamachana do not obtain their symbionts until the polyp stage (shown here). These polyps (known as scyphistomae) will be reared in the lab and exposed to different strains of Symbiodinium. Once the polyps are infected with symbionts, they will be placed in different habitats to see if the symbiont type will change under different field conditions

Once the larvae have metamorphosed into polyps, the branches will be place in containers and exposed to different strains of Symbiodinium in the experimental set-up shown here.

Briareum asbestinum

We have had success in collecting larvae from the octocoral, B. asbestinum. The larvae of this soft coral are brooded on the surface of the colony where divers can easily collect them using a syringe. Unlike the adult Briareum, these larvae do not have symbionts and must acquire them from the environment once they have metamorphosed into polyps.

The developing larvae are reared in the lab where they settle onto dead octocoral axis.