It has been a very long few since we left Mauritius. The seas have been very rough and many people on the ship, me included, were overcome with sea sickness for the first two days. Luckily, the medicine has finally worked and the seas have gotten calmer, so we are all back to feeling well.
Despite all of the sea sickness, we have been making very good progress on our planned sampling and we are actually ahead of schedule. This means that I have spent a lot of my time trying to keep up with the pace of sampling.
For my research, we use an instrument called a CTD that measures conductivity, temperature, and depth. Conductivity is directly related to the salinity of the water. Salinity along with temperature can then be used to calculate the density of the water, which is a primary driving force for ocean currents. The CTD is a package of electronic instruments attached inside a metal frame work called a rosette. There are also water sampling bottles called Niskins surrounding this metal framework.
The entire CTD rosette is deployed off the side of the research vessel and lowered to just above the ocean floor, which is called a CTD cast. When the CTD rosette is deployed, all of the Niskin bottles are open on the top and the bottom, so water will flow through them. While the CTD is being lowered, we will receive live data from the electronic sensors attached to the rosette. Then, when the CTD rosette is being brought back up, we can send signals through the cable to close each Niskin bottle individually. This allows us to collect water at various depths in the water column.
Once the CTD rosette is back on the ship, all of the water collected will be analyzed for a variety of parameters. However, there is a very specific order to which we can sample the water out of the Niskin bottles. This order is driven by the fact that some chemical and biological parameters being measured are more sensitive than others to interactions with the atmosphere or timing once the Niskin bottle is opened. Therefore, everyone must wait until it is their turn to sample from the Niskins.
Once I collect my samples from the Niskins, I bring them back to my lab space to process them for a variety of variables. In processing my samples, I reuse the same lab equipment for each set of samples. Therefore, once I have completed my analysis on a sample set, which usually takes about three or mpre hours, then I need to clean all of the lab equipment that I just used and reset everything for the next station. It typically takes about two hours to get all of my gear cleaned and prepped for the next sampling location. Usually, by the time I am done, there is about thirty minutes of rest before another CTD rosette is back on the boat and ready to be sampled. Although I will be taking samples from a majority of the CTD casts, I will not sample all of them because I do need to sleep sometimes.
The photos below include the CTD rosette that we are using on the R/V Isabu and a snapshot of some of the live data we obtain while the CTD rosette is being lowered in the ocean.
