Since we left port just over one week ago we have been busy, very busy, collecting seawater samples for trace metal analysis. Whilst deploying the various pieces of equipment we have for sampling I have seen seals kissing, squid jumping, Mahi Mahi, small tuna, the ubiquitous flying fish and even a shark! However, the fish I have seen the most of is the device we have for sampling the uppermost surface waters called a towed fish. This particular fish is made from stainless steel and looks like a torpedo. In the plastic nose of the torpedo is a plastic tube through which we pump seawater into the clean lab container for trace metal clean sampling. When the fish is in the water you can see the long thin wake it makes as the wire and tube cut through the water (Figure 1).
The way we sample deeper waters, down to 5 or 6 km, is with the 24 bottles on the “CTD” rosette. This is also loaded with instruments to measure the temperature, conductivity and the oxygen and chlorophyll content of the seawater (Figure 2 and 3). The bottles are triggered from a computer in the comfort of the lab to close at depths we determine after seeing what the above water properties look like at each station. This way we sample distinct water masses and biological zones. We also have a specially made trace metal clean CTD on board but this will have to wait for me to get a better photo.
But it is not only seawater we sample. Yesterday we collected over one litre of rain water during about one hour (Figure 3). This will tell us about the trace metals delivered to the ocean by wet deposition, otherwise known as rain. Dry deposition collection will surely be the subject of another blog.