Coral catastophe?

The Great Barrier Reef is in worst state that previously thought and fingers are pointing to ocean acidification...
26 February 2016

Interview with 

Cat Dixon, Sea Life London Aquarium and Dr Rebecca Albright, Stanford University


This week, news broke that The Great Barrier reef is in worse shape than Coral fraggingpreviously thought owing to ocean acidification. The Great Barrier Reef is one of many populations of corals world wide. And although they look like plants, corals are actually colonies of animals. Tiny polyps, which are almost like miniscule jellyfish, cluster together and gradually build-up a calcium carbonate exoskeleton. Living alongside them are algae, which feed the coral by capturing the energy in sunlight. Georgia Mills went to find out more about these unusual animals, and the problems they face...

Georgia - The Great Barrier Reef may be world famous for it's coral but it's a little bit out of the way, so I journeyed to Sea Life London Aquarium to have a look at some for myself...

I was taken through the blue fish filled corridors, past the sharks, on to the behind the scenes tour and in a room full of very loud water pumping systems, amongst the jellyfish and the rays, I found a tank of corals and, conveniently, someone who could tell me about them.

Cat - Hiya.  My names Cat Dixon, I'm a senior aquarist at Sea Life London Aquarium. Coral reefs are very, very important  and they are home to about 25% of all marine life providing shelter, feeding grounds, and nurseries for a wide, wide range of marine organisms.  And the biodiversity of coral reefs is actually believed to be one of the highest on the planet, more than even rain forests.

Georgia - We're currently standing in front of a big green tank with several samples of coral in it.  So what am I looking at here?

Cat - This is where we frag and grow our corals.  So we take a large piece of coral, break a little bit off, and then grow it up here. Some of them we actually get from Heathrow customs that have been confiscated at the airport and others we get from other sites.

Georgia - When I think of corals, I tend to think of quite brightly coloured things.  These in here, they all look a bit brown.  Why are these not brightly coloured?

Cat - At the moment, because it's early in the morning, the lights aren't on yet, so when the lights come on, all the algae will come out and they'll will be a lot brighter.

Georgia - Well as much as I like it in this room - there's loads of jelly fish over there, there's corals, there's loads of sea plants - shall we go somewhere a bit quieter.

Cat - Yes let's do that...

Georgia - Lovely...

Cat - So yes, there are many threats facing coral reefs at the moment.  Some of these include destructive fishing practices, like bottom trawling can dredge up the bottom of the sea and damage the corals.  Pollution - farm run off can be toxic to corals and also smother them with algal blooms and then they can't have access to sunlight.  And also climate change is a quite a big threat that corals are facing at the moment..

Georgia - And the reason why climate change is such a big worry is because it attacks the coral in multiple ways. Firstly, there's coral bleaching, which is where increased temperatures are causing coral to actually expel the algae that provides them with their colour and their energy; this leaves them unable to grow properly.  Secondly, there's a bigger risk of catastrophic weather events physically damaging the reefs.  And thirdly, there's something call ocean acidification...

Cat - Ocean acidification is where the excess carbon dioxide in the atmosphere is actually being absorbed into the oceans and this is forming, with the seawater, carbonic acid which is reducing the Ph of the ocean.  This, in turn, is forming with carbonate ions that the corals would usually bond with to create their calcium skeletons and, therefore, they are not able to grow and build there skeletons as they should be.

Georgia - Scientists know from lab experiments that high acidity harms coral growth but is the small Ph change in the ocean actually causing any problems for the corals, or could it be one of the many other human impacts that's stunting their growth?

A study just out in the journal Nature has taken the science outside of the lab and into the ocean and has finally revealed the answer.  I called up the lead author, Dr Rebecca Albright while she was at the AGU Ocean Science meeting...

Rebecca - We wanted to effectively restore the chemistry of seawater that was flowing over a coral reef community in their natural environment, two conditions that would have been expected under preindustrial scenarios and then monitor how the reef responded.  We did this by adding sodium hydroxide, which is a base or effectively an antacid, to the seawater to increase the alkalinity of that seawater that was flowing over the coral reef community and this temporarily kind of reversed ocean acidification and then we monitored the calcification response.  And what we found was that when seawater chemistry was restored closer to preindustrial conditions, coral reef calcification was enhanced.  So these results really represent the first piece of strong evidence that ocean acidification is already impairing coral reef growth.

Georgia - As well as this evidence, this study also shows that if you restore acidity back to normal, the corals can grow again.  So, could this be the answer to our problems?  Could we use Rebecca's technique to engineer the oceans to be like they once were?

Rebecca - Alkalinisation of the oceans has been suggested as a geoengineering technique to mitigate ocean acidification impacts.  However, we are very much of the opinion that this is not a scaleable solution to mitigating ocean acidification impacts for global marine ecosystems over the long term.  The Great Barrier Reef itself is over 2,000 kilometers long and ocean acidification is a chronic problem that continues to worsen as the oceans continue to absorb carbon dioxide from the atmosphere.  So, it's really important to realise that the only solution for mitigating ocean acidification impacts, and preserving coral reef ecosystems into the future is to drastically cut carbon dioxide emissions.

Georgia - This was a sentiment Cat back at Sea Life agreed with as corals are clearly worth keeping, whether they're in the Great Barrier Reef or on the shores of the UK.

Cat - There's some in Scotland and Ireland.

Georgia - Oh, that's too far away.  I was hoping you were going to say the Thames...

Cat - No, I'm afraid not!


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