|Scientists collecting the samples from ROV Isis after she returns from a dive.|
We are really interested in these fluids, as their chemistry can provide us with information about the deep-ocean crust, the processes of hydrothermal circulation and the origins of many important elements in seawater. As a result, we are keen to collect pure fluids from within the vents, before they mix with seawater, as well as water samples from inside the black smoke.
For collecting fluids directly from within the chimneys, we use large syringes made from titanium, which can withstand the extremely high temperatures. The manipulator arms of the ROV insert the syringes right into the chimney, and we wait for our temperature sensors to reach about 350 °C to indicate that we are in pure hydrothermal fluid. We then fire the syringes, sucking the precious fluids into our sample barrels as you can see in the pictures below.
Throughout the world’s oceans there are hundreds of sites of hydrothermal activity, pumping fluids enriched in many different elements into seawater. Despite being a few miles down in the deep sea, these elements can be transported up through the water column in the rising hydrothermal plume, and swept away on ocean currents. Some of these elements are essential nutrients and stimulate primary production - the first rung of the food ladder - if they reach the surface waters.