A Week on the RRS Discovery

It’s now been a whole week since my feet touched land, and what a busy week it’s been! My day usually starts about about 3 or 4am, when I have to get dressed and up on the main deck to sample from the CTD. The term CTD stands for “Conductivity Temperature Depth”, but is also used to refer to the actual piece of equipment that takes these measurements. Essentially, there’s a circular metal frame with 24 large bottles on it, called Niskin bottles. This is lowered into the water on a tow line, and as it sinks, it takes a profile of our chosen water column, so that we can see how the temperature, salinity and other characteristics change with depth. Once the CTD is at the bottom of our water column, it gets pulled back up and stops at specific depths and the Niskins are “fired”. All the Niskins go down open, and when they are fired, they shut tight and capture water. It means we can get access to water hundreds of meters down, though as someone who’s researching phytoplankton I don’t tend to sample water deeper than about 35m. The CTD is then brought back on to the deck, and we can use the taps installed in each Niskin to get the water out and into whatever container we need it in. This whole process takes about an hour to an hour and a half, depending on the depth of the water we’re looking at.

As well as just sampling the water we pass through, we’ve taken some of it on board to conduct big experiments, called bioassays. What we want to do is look at how a natural assemblage of plankton will react to ocean acidification. So we have 4 treatments, with our control at current CO2 levels, and the others being 3 different predictions for CO2 levels by the end of the century (ranging from moderate to worst case scenarios). The set up for this endeavour involved me and a few others getting up at around 2am to fill up about 80 bottles with seawater from the CTD. These bottles were labelled up, spiked with the right amount of acid/bicarbonate to shift the seawater chemistry, sealed up and put in our big incubator on the back deck. While it was tough work, and I was struggling from the odd sleep patterns, we were rewarded with a beautiful sunrise over the Irish coast. We all took a sample from another CTD cast to be our Time Zero measurements, and then sampled some of the bottles at our first time point, 2 days later. Yesterday we had the final time point, 4 days, and completed the first bioassay. We’re starting it all over again tomorrow, so I think it’s straight to bed after dinner for me today. The point of doing several bioassays over the cruise track is to see how different assemblages of microorganisms, preadapted to different environments, react to ocean acidification. So the results should be very interesting.

Sampling from the bioassays is hard work, because the amount of treatments means you end up with a lot of samples to analyse. The experiments I run are also time consuming (I have to split the samples into even smaller bottles, spike them with radioactive carbon, incubate them, filter them, fume them, and then put them in a scintillation counter) so my day’s hours are 4am till about 7pm. By that time I’m only too happy to curl up into bed and drift off ahead of the next early morning.

Yesterday was eventful in several ways. First of all, the CTD broke down, in the most fantastic way. One of the winches on the other side of the ship leaked hydraulic fluid, and it caught fire. It was also close to the container I work in, and I was actually about to head on up there to retrieve some samples when I was told to stay where I was! It was eventually sorted, but gave me an extra hour of down time. It worked out perfectly because I then heard that some dolphins had been spotted off the front deck! I was so excited, I grabbed my camera and my coat and made my way to the very front of the ship. By the time I got there, we thought they’d gone, but in no time at all, 4 common dolphins were playing at the front of the ship again. They were so beautiful, it was incredible the way they could just move through the water so effortlessly. They put on a little show for us and jumped and weaved around each other in the waves until eventually they disappeared into the blue.

By now we have fully circled the western coast of Ireland, and are now making our way along the Welsh coast. Tomorrow we are having to stop near Plymouth to make a boat transfer, they are bring out a piece they need to repair the CTD winch. We’ll also be in the Celtic Sea, meaning lots of more chances to see dolphins and maybe some basking sharks. That’s about it for my first week on a research vessel – or at least all I have the energy to write! I’m going to take a little break and head up to the front deck again with Evelyn, the post doc from our lab back in Essex. Perhaps I’ll spot somemore marine mammals… I’ll post again when week 2 is complete!

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