Te Herenga Waka–Victoria University of Wellington Professor of Marine Biology Simon Davy says a better understanding of the internal partnership corals have with certain types of algae could help them withstand a warming climate.
The difficulty is determining how best to draw on the strengths of that idiosyncratic relationship.
An expert in coral reef ecology and the biology and physiology of cnidarian-dinoflagellate symbiosis—the partnership between corals and algae—Professor Davy is the President of the International Symbiosis Society.
He is co-author of a just-published review paper in Trends in Microbiology, along with postdoctoral researchers Dr Sabrina Rosset and Dr Clinton Oakley, and overseas colleagues.
In the paper, Professor Davy says coral reefs are in crisis, with massive global loss predicted by the end of the century.
Research to better comprehend “communication” between the two organisms is essential to develop tools for coral reef conservation, including gene-editing to create “more thermally resistant pairings of corals and symbiotic algae”.
“There is some emerging literature on this, but we currently lack sufficient knowledge of the fundamental pathways involved to make rapid progress.”
Professor Davy is investigating this relationship in a project supported by a Marsden Fund grant from government funding managed by the Royal Society Te Apārangi.
“The cnidarian–dinoflagellate symbiosis is of huge importance as it underpins the success of coral reefs, yet we know very little about how the host cnidarian and its dinoflagellate partners communicate with each other to form a functionally integrated unit.
“Many cnidarians—which also include jellyfish and sea anemones—are dependent on the metabolic benefits provided by symbiotic dinoflagellates of the family Symbiodiniaceae, which live inside their host’s gastrodermal cells.
“This symbiosis is of immense global value, as it forms the basis of the coral reef ecosystem. These reefs may not survive this century as a result of accelerating stressors that cause ‘bleaching’, in which the symbiosis becomes dysfunctional and the dinoflagellate symbionts are lost from their host corals.”
There are a number of potential solutions for protecting coral reefs, he says.
“They include switching symbionts for more thermally-resistant species, selective coral breeding, and the use of coral probiotics, where the diverse microbial communities associated with corals are manipulated to reduce susceptibility to bleaching.
“However, careful consideration is needed of the potential ecological, ethical and societal impacts of such approaches, for example where experimentally modified corals are released back into the wild.”
It could take years to decades to fully develop robust technologies to boost the health of reefs.
“We still have much to learn about host-symbiont communication, but in particular we lack knowledge of exactly what signalling pathways operate in the symbiosis, as well as how and where signals are synthesised and perceived. Such gaps in core knowledge entirely limit our understanding of how this communication facilitates symbiosis onset and maintenance.”
There are many questions still to be answered, Professor Davy says.
“Such as, what inter-partner molecular signals enable the establishment and persistence of a successful symbiosis, how do these signals differ between those corals which can form relationships with multiple or few types of symbiotic algae, and how is inter-partner communication modified by environmental stress?
“Ultimately, we want to know how can we manipulate inter-partner signalling pathways to engineer more thermally resistant corals, and the foundational work we’re conducting in our current Marsden-funded project will go a significant way towards achieving this goal.”