The corals that my colleagues and I research in Mo‘orea, French Polynesia, are sea polyps that develop in symbiosis with unicellular algae known as zooxanthellae. Most of those corals’ vitamins come from the sugars produced by algal photosynthesis.
Often, human-built coral nurseries are situated on the backside of the ocean. Nonetheless, right here on the Centre for Island Analysis and Environmental Observatory (CRIOBE) in Mo‘orea, affiliated with the College of Perpignan in mainland France, we favor the floating cell timber that I’m within the image. These permit us to see the corals from all views. Additionally they make it straightforward to detect sure issues, corresponding to invasive algae.
On this image, there are two coral species — Acropora pulchra and Acropora cytherea. The pulchra has retained its darkish yellow color however the cytherea — which is often gentle brown or purple — has turned white.
This bleaching occurs when the water temperature rises above regular for an extended interval. This results in the coral expelling the microalgae. With out them, coral polyps flip white and starve to demise. This phenomenon is getting extra frequent and might destroy a complete colony in a number of months.
One in all my workforce’s important duties is to dive within the coral nurseries to measure varied parameters. Once we dive, we take a plastic sheet that helps us to establish every species. We register the water temperature, the color of the corals, whether or not there are indicators of bleaching and if any polyp has died.
Sure polyps appear to be extra resilient than others to temperature stress. We wish to study whether or not that is actually the case and, in that case, why. Discovering solutions would possibly assist us to guard corals, however after all what would actually assistance is an finish to air pollution and international warming.