Vianney Denis: Trophic plasticity of corals

Vianney Denis, Associate Professor at National Taiwan University in Taiwan, discusses his recently accepted paper, “Trophic plasticity of mixtrophic corals under contrasting environments.”

Coral Reefs In Taiwan | With disctinctive environmental conditions all around the country, Taiwan offers a natural laboratory to test hypotheses related to the transformation of coral reef ecosystems in the Anthropocene

About the paper

To be picky or to not be picky? That is an important question when it comes to corals’ diet. Our paper explored the trophic plasticity of important mixotrophs -organisms able to blend autotrophic and heterotrophic nutrition- at the base of the highly complex reef habitats. It is now well established that all coral species do not have the same diet and that from those differences could originate contrasting responses to environmental stressors. Yet, aside from considerably simplifying the way the coral diet is categorized, most previous works on the topic have also overlooked the variability existing among individuals and upon which natural selection could act.

Using natural stable isotopes of carbon and nitrogen, we identified disparate trophic behaviours among corals. Not only does trophic plasticity occurred among species but also within species as individuals responded to changes in environmental conditions. Eventually, we distinguished trophic strategies among corals with species spanning along a gradient of specificity from generalist to specialist.

Our paper provides new and important insight into the coral diet emphasizing the importance of trophic plasticity. It calls for greater consideration of intraspecific variability when foreseeing species’ fates. It could be particularly useful for avoiding unrealistic predictions based on the average response of coral colonies with direct implications in guiding the choice of species to use in reef restoration programs.

Reef surveys | Benthic communities are examined for their composition, functions and roles. The laboratory investigated reefs from shallow to mesophotic depths and from low- to high- latitudes.
Reef surveys | Benthic communities are examined for their composition, functions and roles. The laboratory investigated reefs from shallow to mesophotic depths and from low- to high- latitudes.

About the research

How can we picture the “survival of the fittest” if we average living organism responses to stressors at the species level? Our research puts a greater emphasis on the diversity of responses observed within conspecifics because we believe the individual coral holobiont -the animal host and its associated microorganisms- corresponds actually to the true ecological unit upon which natural selection operates. From organisms to the ecosystems, we are looking for the outliers, fringes, and extremes. The trajectory that the reefs will take in the future is probably not unique. The direction followed could partly depend on the survivorship and the resilience of those freaks with possible consequences on how seascapes will look like tomorrow.

Vianney DENIS | Looking at tiny coral-associated hydroids (Zanclea spp) at Green Island, Taiwan
Vianney DENIS | Looking at tiny coral-associated hydroids (Zanclea spp) at Green Island, Taiwan

About the Author

I had always wanted to work in ecology but my wish to work on coral reefs came much later during my master’s degree. Back then, I was already a diver and enjoyed the 4 °C gloomy waters of the abandoned mines from the North of France. From a fortunate encounter, I got the opportunity to survey reefs in Indonesia: stunning! After that, you can imagine it was difficult to move away from the tropics. I was converted and I continued in this direction. Currently, I am an Associate Professor at National Taiwan University in Taiwan. It may surprise many people but we have very nice reefs there thriving from tropical to subtropical latitudes, from shallow to mesophotic depths, and growing under a variety of human settings. My research focuses on the physiological ecology of reef organisms and the ecology of reef communities. Taiwan offers an amazing natural laboratory to test many hypotheses related to the transformation of coral reef ecosystems in the Anthropocene. As a reef ecologist and avid diver, witnessing the decline of the ecosystems I am caring for motivates me every day to be more convincing in my work. Yet, global immobilism may often be frustrating. Somehow, humans are not so different from corals, and our fate may also reside in our ability to be plastic in the face of the situation we are in now.

Read the research in full here

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s