Positive data on coral reefs coping with ocean acidification (audio)

According to a report published in Nature: Climate Change, coralline algae, which acts as a sort of glue that holds coral organisms themselves together, is more resistant to ocean acidification that previously thought.

The reports’ lead author, Merinda Nash, a doctoral student at the Australia National University in Canberra, tells Bruce Hill it’s some rare positive data about reef systems and their ability to survive.

Presenter: Bruce Hill

Speaker: Merinda Nash, a doctoral student at the ANU in Canberra

NASH: We’re looking at coraline algae and algae are part of the plant kingdom, whereas corals are effectively an animal, even though they do have symbiotic algae. So our research specifically relates to coraline algae, which helps build the structural part of the reef. Some corals are looking OK, and that’s really species-specific, so that’s not actually our research.

HILL: So what did your research find about the way that coraline algae can survive high ocean acidity?

NASH: What we found is that we discovered this extra mineral dolomite in the coraline algae. Now what’s important about that is that prior to our discovery, everybody had thought that this coraline algae was made up of magnesium that was was thought to be and is very susceptible to dissolution. So there was a lot of concern that the coraline algae, which plays a key role in building the reef and binding corals together, that this would be the first thing to dissolve as CO2 went up and that that would impact the reef structure. So we found that this presence of dolamide actually reduced the dissolutiion rate significantly to about one tenth the rate of the algae without the dolomite, so that’s quite good news.

HILL: So does this mean that the coral could actually prove a bit more resistant to ocean acidification than we thought before?

NASH: Well, as I mentioned, our research was looking at the algae, not the coral, so and this is quite difficult it seems for most people trying to understand the difference. So the best analogy that I can give is that the algae that we look at is like the cement in the house made of bricks and the coral are the bricks. So if you could imagine a house that had bricks and no cement. It wouldn’t be a very strong structure. So the coraline algae with dolomite look to be quite resistant, but what happens to the corals will be a different story.

HILL: So we’re talking here about essentially the concrete or the glue that holds the bricks together. The bricks are still in trouble from acidification though, is that right?

NASH: It looks that way. There’s a lot of research being done now that’s showing the different species have different susceptibility and there’s some very interesting research showing resistant increasing I guess across generations and that there can be protection for some species that are able to control their PH, but that’s still fairly new, the research showing the resistance to PH species. But it does look like that the corals are still going to be quite impacted by the rising temperature and acidity.

HILL: So this is more or less good news or better news than we’ve been having for coral reef systems, but it’s not necessarily saying, don’t worry, panics over. It’s all going to be fine?

NASH: Yeah, don’t go back to driving your V8s just yet.

What is really good about this is for a lot of the Pacific Islands that are coral atolls, that face high energy waves all the time, a lot of those islands are actually protected by ridges that are built just about entirely out of coraline algae in the top couple of metres. So, for example, one of the islands we looked at Rodrigues which is in the Indian Ocean. The top four metres of that reef isn’t predominantly coraline algae and there’s a ridge that comes up about nearly a metre that is just coraline algae and that forms the highest engery point of the reef. So where the waves are strongest is where the algae with the dolomite loves to grow. So it has a really critical role protecting shorelines and human communities on the shore from the worst affects of the high wave energy.

HILL: There’s still an awful lot about coral reef systems that we don’t understand?

NASH: Yes, you’ve absolutely got that right, Bruce. Some of the other work I’ve been involved in is the latest CSIRO Marine Report Card on Ocean Acidification and as one of the authors on that, I’ve seen the latest research that’s been done and it’s quite clear that while we are starting to understand a lot of the impacts, The more we dig into it, I think the more we realise that we don’t understand it and how much further is to go.

ABC Radio Australia, 10 December 2012. Audio.

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