Dr Jonny Stark — Chief Investigator
The aim of the project is to create a future ocean scenario that we might expect to see by about the end of this century. So as we’re increasing the carbon dioxide concentration in the atmosphere about 1/3 of the carbon dioxide is being absorbed by the ocean. That increase in carbon dioxide in the ocean, causes a chemical change in the ocean and basically l makes it more acidic. It’s this process which is known as ocean acidification.
So aim of this experiment was to get some idea of how Southern Ocean communities, and in particular animals living on the sea floor might respond, what sort of changes we might expect to see by the end of this century under business as usual emissions scenario, which means we keep emitting more or less what we are now.
We are expecting an atmospheric concentration of about 1000ppm. It’s currently around 400. It’s only a 0.4pH change, but it is actually a very big change in pH and would have very serious implications for a lot of marine life. For example, it can affect everything from the reproduction, to the growth and development of many marine organisms.
So we were looking at everything from the very, very small so the microbial forms of life and bacteria, up to the macro, the larger invertebrates that you find on the seabed things like starfish, sea anemones, and those sorts of things.
The experiment ran for an eight week period. The basic experimental design was specially designed chambers. So these were placed on the seabed and they were acidified to a level that we expect to see by the end of this century, so roughly 2.5 times more acidic or a 0.4 pH change.
We had four chambers in total; two of those were acidified and two of those were control. So we could compare the acidified ones and see what kind of changes might have occurred in those communities living in the chambers.
Dr Glenn Johnstone — Project Leader
Every aspect of what we did with this project was something that we’ve not really come up against before. We were modifying and inventing ways to do this and it was really gratifying when they worked. It was really great to work with a team of people and use all their different skills to try and come up with a method to make sure that this all worked.
We use dry suits, we use surface supply and AGA masks. So unlike the normal half masks that you’d be used to, this covers your entire face. It allows a space that we can have a microphone, so we have communications and earpieces, we can talk to the other diver and we can also talk to the surface.
So underneath that dry suit, we’ve got a layer of thermals, then a fleece layer and then an even thicker fleece layer. And you’re probably wearing two gloves, two pairs of socks, each person just depends is a bit different, and we have three fingered gloves — you’ve got to learn to manipulate things underwater with three fingered gloves on. A dive at the depths we were at, which was about 12–14m, would last 50 mins. Water is always about −1.8 and under the sea ice there in that Bay it doesn’t vary over the year.
When we first got there, there was good visibility. The first dive that we did we had probably about 80–100m worth of visibility, which is remarkable anywhere in world. Then slowly over the season that decreases when you have the algal bloom. At the end of the season it was much less than when we started but wasn’t particularly dark — it can be if you’ve got a lot of snowfall. Though we had plenty of wind, which tends to clear the snow off the ice. So even though the ice was 2.2 metres thick there was plenty of light down there.
We were visited many times by Weddell seals and on one occasion in particular we were visited by one that had a fish in its mouth, which is not something any of us had ever seen before and proceeded to eat it right in front of us in the dive hole which was really special to see that.