Symbiotic Versus Non-symbiotic Octocorals: Physiological and Ecological Implications

What is it about?

Octocorals are a major component of the sessile benthic fauna worldwide, especially important in tropical regions, such as the Indo-Pacific and Caribbean, where together with hard corals they represent the most common group of macrobenthic animals of coral reefs. Despite their importance, little is known about their physiology, specifically the importance of their symbiotic relationship with the algal endosymbiont from the genus Symbiodinium, and the advantages/ disadvantages associated with this symbiosis. In symbiotic species, the energetic contribution from Symbiodinium to the host might increase their resistance and/or recovery from stressful conditions, but the presence of these algal endosymbionts also limits octocoral distribution to the photic zone, where light is available. During the past few decades, octocorals have gained dominance in some tropical areas where scleractinian corals have declined due to climate change and local perturbations, increasing the need for research related to this understudied group. This chapter summarizes the current knowledge available about the ecology and physiology of octocorals, focusing on differences that are the result of the presence or absence of endosymbionts, and discusses the implications of having endosymbionts in the context of how octocorals may respond to global climate change.

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