Ocean Acidification Experiments

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Over the last four weeks I have been completely tied up with the sole reason for my being here in Antarctica, the Ocean Acidification Project. This season we have had nothing but excellent luck and perfect timing to help us achieve all of the goals that we set out to achieve in the short time we had available to us. This year the entire project team arrived at Davis together on Voyage 1 and all of our equipment was here waiting for us to turn on and get going. We anticipated that it would take us two weeks to get ourselves set up and ready to go and it only took us ten, even with resupply duties pulling us away at times.

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Through November and December the water around Davis Station is covered by a thick layer of fast ice. Last season this ice didn’t break out until the start of February, which is not convenient when we need to take our water samples in open water (the phytoplankton community under the ice is much simpler than the open water community and not what we wanted to look at). Over the winter, back at the Antarctic Division in Kingston, a strategy was devised to allow us to sample the open water even if the fast ice was still in. This involved the use of one of our helicopters equipped with a Bambi Bucket (commonly used by firefighters to air drop water on bush fires) and a 7000L holding tank to deliver the water to our minicosm facility. Again, fortune shone on us and we had excellent flying weather the day after we had finished setting up our equipment. It took approximately ten trips by the helicopter to fill the holding tank up, which was then transferred through plumbing down the hill into our six 650L minicosm tanks.

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It was quite an incredible feeling to see the helicopter delivering our water for us. This project had encountered some pretty serious obstacles, with its cancellation last season and the uncertainty throughout the year about whether we would be able to come down and finish what we started. This project also forms the basis for my PhD thesis, so you can imagine the relief seeing it all come together brings.

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After leaving the water to settle in our tanks overnight, and letting our phytoplankton get accustomed to their new home, we started sampling the next morning. Our project team is composed of six scientists and we all worked on different aspects of ocean acidification, using the same six tanks for our samples. For the first week our chemist slowly modified the CO2 in each of the tanks to reach our desired concentrations (based on future atmospheric CO2 projections), then we turned the lights up and let them grow for two weeks, whilst we took samples every 1-2 days for our various experiments.

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My responsibility was to test the health of the phytoplankton and bacterial community through tracking their ability to consume carbon. This is done by using a radioactive form of carbon, called carbon-14, which I add to my water samples and let the phytoplankton or bacteria (in two separate experiments) consume over a set period of time (1-2 hours). The phytoplankton consume carbon through photosynthesis, which requires me to incubate them under lights. After the set incubation period, I remove all of the carbon-14 that hasn’t been consumed and use a special instrument called a scintillation counter, which detects radioactive decay, to measure how much carbon-14 remains in my sample. This is the amount that has been consumed. On the same day we also took water samples to measure the number of phytoplankton and bacterial cells per millilitre, which I can use to calculate the amount of carbon consumed per cell in the sample. The more carbon consumed per cell, the more healthy the cells are.

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I also took a second set of water samples and added a fixative (gluteraldehyde) so that the cells don’t break down. These samples I ran through a different instrument, called a FlowCAM, that I like to think of as an automated microscope and cell counter. I will use the data captured on this instrument to get an idea of the phytoplankton species composition and cell numbers and be able to track how these change throughout the experiment and between the different tanks. Fixing the cells means that I can run the water samples through the instrument at a later date, which was necessary for me as the carbon-14 work would take me all day to complete. I ran the carbon-14 experiments every second day so I would catch up on my FlowCAM samples on my non-sampling days. This meant that I had to work every day that the experiment was running (18 days) and it was definitely a challenge going almost three weeks without a whole day off. I was fortunate to get out of the lab for two afternoons for a walk, otherwise I may have run out of steam.

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Everyone else in our science team was also working diligently on their experiments at the same time so the science building was buzzing with life. It was so nice to see everything running smoothly and we were all getting interesting results. We were all exhausted when we reached our final sampling day but I think we were all so happy to finally complete the experiments we’d been planning for so long. There was no time to rest tho, as the four scientists that hadn’t been here last year finally got to go out on a walk in the Vestfold Hills to complete their survival training and visit Watts Hut. As for me, I took a day off, the second one I’d had since we had arrived at Davis a month before. It was well deserved and appreciated.

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