A short story about corals #2

This photo has nothing to do with the topic but it attracts your curiosity “Niark Niark” (evil laugh).

Hello curious reader,

Hope you are doing good and ready to dive again in the incredible world of corals.
Last time we spoke about polyps and zooxanthellae, remember? If not check rapidly the 1st story about corals! Don’t be lazy, it’s worth it!

We are far to understand all the mysteries that hide corals and we’ll probably never know them, like every nature forms. However, let’s try to discuss about the things we know for the moment.
We’ve seen that corals are true builders. But they are not only simple builders: they are colourful builders! Red, pink, brown, green, yellow… they are colours for everybody! And guess where come from all these rainbows of colours?
Yes, exactly my attentive reader! They came from the tiny algae who live inside the polyps: the zooxanthellae (most of the tropical hard corals possess this symbiont).
The algae give colours to the corals just like chlorophyll does for plants. In exchange the polyps protect his precious host with a calcareous structure. Isn’t that poetic? Like the beast protecting the beauty, and the beauty bringing colours to embellish the beast…
But like in every fairy-tale, they are villains. And one of this bad guy is called “rising level of CO2 in the atmosphere” (weird name huh?). He can split into two dangerous mini-villains called: “Acidification of the ocean” and “Global warming”. I’m sure you heard about them (someone telling me in the ear flap that they are both send by the evillest of all: the anthropogenic effect).
Galaxea sp coral (Chloé Pozas-Schacre)

Hydnophora sp coral (Chloé Pozas-Schacre)














Acidification of the Ocean
The polyps to construct a calcareous skeleton, used as a fortress to protect him and his beauty, needs carbonate ion (CO32−). Carbon dioxide is increasing in the atmosphere with the impact of human activities, nothing new here.
But the problem is that our Ocean absorb a large quantity of this CO2 gas and change its chemistry. To make it simple the Ocean became more acid and the proportion of carbonate ions decrease drastically (for more detailed information ask for a chemist!). Yes, you get it, they don’t have the chemical compounds to build a solid structure! Exactly, like a snail without a shell. And what happen to a snail without shell? (No, he is not transforming into a slug; try to focus reader) He simply dies…

A nudibranch, Hypselodoris pulchella, in the sea which don’t have shell and don’t need to build anything.  Lucky him! (Chloé Pozas-Schacre)

Global warming
Yes, I know… “Enough about the Global warming, since the last 50 years everybody talks about it! Let’s make it fast! Because of The Global warming as you know, the water temperature increase, the trick is that polyps are very sensible to change in temperature. They get stressed and eject the zooxanthellae from their body. This is what we called “coral bleaching”. The polyp loses his algae and so his colours. However, there is still hope! If he adapts to the new condition (in this case thermic one), he can absorb new zooxanthellae and retrieve a normal coral colouration. The problem is that the change in temperature are fast and the corals barely have time to adapt. So often the coral never find new algae to live with and then die (for the moment scientists estimate that most of them died after 2-3 weeks without zooxanthellae).

Kind of sad for a love story… Can we modify the destiny of the lovers?
Maybe reader, maybe…

To be continued!

Léopold

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