Studying Ocean Acidification at PAP

Written by Sue Hartman.

The amount of biologically active dissolved gases in the surface ocean, such as oxygen and carbon dioxide, changes throughout the year. This seasonal change is influenced by temperature and the growth of plankton. The sensors that we have deployed track changes in all of these variables along with changes in the nutrients that influence the plankton growth.

Figure 1.  ‘Team CO2’ – setting up the new equipment to measure seawater and atmospheric carbon dioxide.

We now have a long time series of measurements and can see both the seasonal and year to year variations. Examples of the data are on the PAP website www.noc.ac.uk/pap/data. The cold, productive waters of the North Atlantic are especially interesting to study changes in carbon dioxide; this area is a sink for this important greenhouse gas. Whilst this oceanic sink may reduce the atmospheric carbon dioxide the water acidity is increasing and this can have harmful effects on some species. A process very similar to adding dissolved carbon dioxide to water to make soda water. We can track the increase in ocean acidification (a decrease in pH) through direct measurements of pH as well as measuring carbon dioxide.

 

 

Figure 2.  The box for atmospheric carbon dioxide measurements high up on the buoy mast.

 

The data will be calibrated using the bottle samples – once they have been measured back at NOC. Each year we collect bottle samples to full ocean depth to give us profiles of oxygen, nutrients, carbon dioxide and pH. All of these measurements are used to monitor the influence of ocean acidification at depth and to consider changes in relation to the longer time series.  Currently we are also setting up an underway system to measure carbon dioxide, temperature, salinity and oxygen with the sensors that we have on board to compare with the ships underway systems.

 

 

 

Figure 3. The pelagic team sampling from the CTD rosette for oxygen, nutrients, dissolved inorganic carbon, chlorophyll and temperature.

Gaining experience on the high seas!

If someone had told me in May of 2016 that in two years time I’d be on a research cruise to the PAP-SO, I would not have had a clue what they were talking about. At that time I’d been working for 4 years on commercial fishing boats as a fisheries biologist in Alaska and only just starting to look for other opportunities, particularly in higher education.

I hadn’t even heard of NOC, the James Cook, or the University of Southampton. Yet here I stand, an inexperienced masters student with the deep seas benthic group taking full advantage of every opportunity; slicing megacore samples, cutting through fish for amphipods, putting together traps, sieving zooplankton, labeling everything, asking questions, and peering over other people’s shoulders.

Blessed with inexperience, every moment is a learning opportunity. Even at the birthday celebration onboard I had a discussion that pertained to my masters thesis and European conservation efforts. The easiest way to start a conversation is asking someone about their day, and in doing so learn the many aspects of studies being conducted onboard. Lunch topics have included individual projects (who knew there was deep sea fungus?), HyBIS, how courses work in different countries, funding, the CTD sensors, amphipods, holothurians, tardigrades, abyssal fishes, writing proposals, the prospective trawls, and how everyone has gotten to being a part of the cruise. Just walking down the hall yesterday I peered into a bucket containing a portion of a deep zooplankton tow and saw a chaetognath and a very active amphipod. I helped with a zooplankton night tow and saw a couple hundred active amphipods, copepods, glowing blue flashes, and even a few pteropods!

Going through the cores every night could become monotonous, but the benthic gang turns up some tunes and most nights there is something to investigate at the top of a core. The excitement of seeing something, really anything from those depths, instantly has all of us crowd a core. Is it a foram? A polychaete? More green fluff? In the past day we’ve added pteropod test, large xenophyophore, and unknown ascidean to the list! Just this morning the group collected two unknown items from the top of the sediment, including the unknown ascidean, which looks like a beautiful, nearly blooming flower under the microscope.

Surrounded by interesting equipment, samples, and people aboard the RRS James Cook, I’m soaking it all in and enjoying.

 

Written by Virginia Biede.