JC142 cruise blog #2 – First Dives by Sarah Howarth (PhD student)

After two days transit we arrive at Tropic Seamount. The first piece of equipment to go overboard is the CTD (conductivity-temperature-depth) rosette. This is a series of bottles that can be lowered and then opened at specific depths to allow us to sample the seawater at different depth of the water column. With a rosette of 24 bottles that can carry 20L each, this is a lot of water to process! This time the water collected is used to sample the microbiology at different depths.

The Autonomous Underwater Vehicle (AUV), Autosub6000, is the next to go in for a 12-hour high-resolution mapping mission of the summit. This is vital information for later dives and allows us to pinpoint potentially exciting areas to explore in later dives.

Early morning start for the first AUV mission of the cruise to map the summit of Tropic Seamount.

Isis, the ROV on JC142, is used for seafloor observation and sampling, armed with 3 video cameras, 2 manipulator arms and a selection of tools that can be added depending on the main aim of the dive. Today’s aim is a 22-hour dive to deploy the lander and undertake reconnaissance on the SW area on the seamount summit. During dives seafloor observations from the ROV cameras of both the biology and geology are used to map changes in environment. 

Isis returns from the first dive for reconnaissance and the trial plume generation experiment. Samples are ready for sample processing- including one large sponge on an even larger FeMn crust slab.

First FeMn crust.

The geologists constantly ask resident marine biologist Lissette Victorero what the different sponges are called. A fish with legs adds 5 minutes entertainment to a 30 minute stretch of otherwise monotonous sediment. Sample collection is one of the most exciting exercises during dives and when the ROV comes up 22 hours later it’ s like Christmas has come early. With the ROV on deck the geologists and biologists collect the samples ready for cutting, bagging and distribution during the“sampling parties”.

The scientific party is split into two teams who do 12-hour shifts, from midnight to midday and vice versa. This allows for time at sea to be optimized and for round the clock investigations. The timetable for life on board is easiest to follow by the meals: one team lives by breakfast/lunch and the other by lunch/dinner. It does lead to some confusion saying “good morning” at midnight but it’s a good sign that you’ve settled into your shift pattern. Down-time is spent relaxing in the bar, watching movies, playing table football and most importantly, sleeping. 

Last Monday, we saw the super-moon, apparently the brightest and biggest since 1948. The sea was lit up by an eerie silvery light . With clear skies, the sight was quite breathtaking and drew lots of the ship’s company out on the foc’sle deck where there are no lights to spoil the effect.