Before I get into the specifics of what happened on our cruise (it was, um, challenging) I thought I’d provide an illustrated guide to how we do what we do out at sea.
Our lab mostly samples from deep-sea hydrothermal vent systems – think of geothermal areas like Yellowstone or Rotorua, but at the bottom of the ocean, usually associated with volcanism (which can provide a depressing sequel when you return to a site and find it paved over with fresh basalt, as we spent an Awful Lot of time doing on the telepresence cruise I worked on last July. A week and a half of seaflood basalt. That’s a lot of basalt. Basalt is boring.)
Because it’s at the bottom of the sea, water can be ejected at temperatures well above boiling – the pressure stops it turning to gas – but for our purposes of growing microorganisms, we sample from fluid that’s between about 10 and 50 degrees celcius, as it’s more likely to contain living cells. This requires a sampler which can take in fluid and then keep it sealed up and air-free – it’s anaerobic when we sample it – right until it gets to us in the lab. We rely on one designed and built by the very hard-working Dr. David Butterfield of the University of Washington, which I sadly forgot to get a picture of, but rest assured it basically makes our job possible (and a bunch of other people’s.)
First, though, you need a ship, because our vent site is well off the coast – about five hundred kilometres.
The Langseth is actually a seismic topography ship in the normal course of things; that’s what all those tubes and reels are for, a system of air-guns that are shot into the ocean and the bouncing sound off the sea-floor recorded. That big watch-tower in the middle is the Marine Mammal Observation platform, so they can call off operations if marine mammals are in the vicinity. It has a great view, but we weren’t allowed up it while at sea (very wisely, I’m sure.)
To find a hydrothermal vent system, if you aren’t sure it’s there already, you use what’s called a CTD. CTD stands for Conductivity, Temperature, and Depth and it’s an instrument lowered off a cable which measures changes in those properties of seawater. Changes in conductivity and temperature are what indicate a plume of hydrothermal vent fluid is rising to the surface. The telepresence cruise in the Galapagos spent a lot of time doing CTD casts, because we didn’t know where the vents were; at Axial Volcano, our site this year, we didn’t need to because we know where the vent fields are. CTDs were done anyway to contribute to ongoing monitoring of the plumes from these vent fields, and we took samples from background seawater as controls for our microbial growth experiments (you shouldn’t expect to find bacteria that can grow at above 55C – our minimum temperature – in background seawater, or very few.)
To sample from hydrothermal vents, you need a robotic or human-operated submersible that can go down to them and stick a sampling probe in. In our case, the (robotic, but human-directed) submersible was JASON/Medea.
JASON is the main vehicle, with manipulator arms, plenty of sample storage space (the fluid sampler is on the back and I don’t have a photo of it, but you can see the
milk crates and bungee cords high-tech sample storage units on the front). With JASON, we can sample fluids and return them to the surface; take samples of rocks and animals; and deploy and retrieve monitoring equipment.
It takes six trailer-trucks of equipment and a very skilled team to operate JASON, and when it’s in the water it’s a 24-hour operation until it returns. That means we scientists (separate from the JASON team) are on 4-on, 8-off watches for science operations, data logging (90% of which is “started sample”, “ended sample”, and “starfish”) and video logging (A.K.A. Turning On The DVD Recorders, because you would be surprised how much science relies on hacking existing technology, especially my favourite hack of all – the JASON Science HD Cam controller.)
Our shift was 12-4, midday and midnight. On top of processing the samples JASON brought up, this means “cruises” do not involve a lot of sleep. Or relaxation. On the third hand, the food was excellent.
And so we sailed out to sea, parked up, dove JASON 1500m down to the vent sites on the seafloor, and sampled. The short version of our cruise is that we got quite a few samples, did some good science, and had fun when we weren’t stumbling around zombie-eyed. The long version is…well, you’ll see.