We have now completely finished our work programme and have begun our 4100 nautical mile transit to Fiji. We have packed Anonyx back into its shipping container and our focus now is on producing our section of the cruise report, working through the remaining scavenger videos and of course, writing our PhDs. But it’s not all work.
Once work had finished on 14th May, the crew and lots of the scientists set about preparing a BBQ and party for the evening. This began at 5:30pm, with tables set out on the deck for one of the greatest views from a restaurant table you could imagine – the sun setting over the beautiful, calm Pacific ocean. Later there was music and dancing until the early hours of the morning, some staying up until sunrise.
The “equipment testing pool” which we are definitely not using as a swimming pool
There are lots of things to do, we have a ping pong table and table football – both of which can be a special challenge when the ship is rolling. We have had movie nights in the lounge area and card games in the bar, not to mention a few nights of shouting at videogames. Often we spend the evening having a beer on the top deck as the sun sets – something no one ever gets tired of, it’s different and spectacular every day. And finally, the crew put together the “testing pool” a few days ago, which lots of people have been “testing” in the sunshine.
After work beers on the top deck at sunsetSarah fishing from the aft deck, she and others have caught several tuna and mai mai, which we have eaten for dinner on a number of nights
There are now two cruises covered on this blog. Annabel, Marta and Andrew will be posting here from their vessel the RV Kilo Moana, which is sailing out of Hawaii today.
You can choose to follow both, or just one of our cruises, simply by using the categories in the righthand column. You can track the location of both vessels using the links in the menu above.
Anonyx is recovered at night for the first time. Credit: Robert Sommerfeldt
Author: Rob Harbour
The problems began on deck with the single acoustic releaser we have been using. Every now and then we need to remove the release from the lander, open the heavy titanium housing, replace the twelve alkaline batteries and clean and lubricate the o-rings. I had done this and sent a signal to the release to close the clasp around the ring that attaches it to the weight system. Once the ring and cable is attached, the release is put to sleep and reattached to the lander – the next time the release motor turns is to drop the weights at 4km underwater. As I carried it out to the lander a hint of doubt entered my mind and I decided I’d test it one more time before attaching it. I sent the release signal and instead of dropping the ring, the motor jammed. It took four more goes and some manual wiggling of the motor to unstick it – it’s likely that if this had happened on the seabed, the lander would have been stuck there.
Here the release is supposed to be in the open position; the raised block in the middle is meant to be straight so the slot in the metal rectangle can fall over it (it’s upside-down in the picture).
Since we have some spare parts on the broken release, we decided it was better to switch the working motor end with the jammed one, rather than risk it jamming and not coming back.
The lander was deployed at 8pm for a 24hr deployment; set to be our first night-time recovery. Generally we would avoid this, simply because it’s potentially more difficult to find in the dark if the radio beacon or strobe fails, and trickier for the helmsman (helms-person is more correct, since she’s a woman) to judge the lander’s distance from the ship as they steer towards it. To make things easier, I made a radar reflector from a catering-sized steel can of mushrooms, with the contents removed and the label peeled off – much to the amusement of everyone – and attached it to a long reflective pole on top of the lander.
At around 9pm the following evening, we dropped the hydrophone into the water and sent the enable signal to the release. It woke up and replied immediately as usual, so after checking its distance from us, we sent the release signal. Again, the release responded to say it had released. Unfortunately, when we checked the range, the lander was in the same place – at this stage we’d expect it to be leaving the seabed and returning to the surface. Over the next 20 minutes, we ranged and ranged again, sending the release signal another four times, but the lander stubbornly remained at a distance of 4377m from us. Fearing the worst, and holding up the programme of other deployments, we decided to come back to it after the next deployment. When we tried again, the range reported that the lander was more than a thousand metres closer to the surface than it had been before – it was on its way! Later the video showed it had taken 30 minutes to heave free of extremely sticky mud.
Anonyx’s strobe flashes in the distance under the stars. Credit Robert Sommerfeldt.
We stood on the bridge and awaited its arrival. When it popped up, the strobe was clearly visible flashing in the darkness, and happily the radar screen showed a solid green lump where it bounced off my mushroom-can reflector. Lena skilfully steered the ship towards the lander, and the crew plucked it from the water. We were very happy to see the fish had been completely eaten, making the deployment a complete success.
We were due to deploy one more time, but since we have now encountered serious problems with both releases, and been stuck-fast in the mud, it was decided that we should quit while we’re ahead. So Anonyx is safely back on deck and ready to be dismantled and packed back into its shipping container for our arrival in Fiji in just under three weeks.
Two sediment traps rescued after three years in the abyss
Author: Rob Harbour
Three years ago, my supervisor Prof. Andrew Sweetman and Prof. Craig Smith deployed two sediment traps in the British license area, around four hours journey from our current position in the German area. Each of the traps consists of a large funnel with 21 bottles underneath that open and close in a programmed series, capturing the settling sediment. This provides data on the rate of sedimentation over the course of a year, as well as carbon cycle monitoring and various biochemistry analyses. The two traps are deployed in-line, the first at a depth close to the seabed, the second hanging around 130m above it. They are weighed down with a recycled train wheel and connected to an acoustic release similar to the one on our Anonyx lander.
The flag and floats of the sediment traps appear on the surface
Unfortunately, due to funding constraints, the traps were never recovered and have remained deployed for three years, two years longer than intended. The acoustic release batteries are rated to just two years, but the manufacturer suggested there could be up to 20% of their power remaining after three years. If we were lucky, this could be enough to drop the weight and allow the trap to return to the surface.
A rescue mission was very kindly agreed by BGR and we set out to try to bring up the traps. Henning (a technical engineer) and I spent 1.5 hrs constantly pinging the release from two different deck units, with no response whatsoever. Disappointed, we were just discussing giving up, when Abner spotted the floats on the surface. The release may have had enough power to let go of the weight, but not enough to respond to us – it probably released right away since the ascent time was estimated to be between 80-100 mins. The traps were hoisted onto the deck and the samples secured. They will be sent back home to Hawaii when we arrive in Fiji.
Milena found a new arrival on our last deployment, we think this creepy looking fish is a bathysaurus, or deep-sea lizard fish. It’s a predator that lays completely motionless, waiting for something nice to eat to swim past. It’s pretty big too, that tuna is around 40cm long and 1.8kg.
I spotted this beautiful baby whale shark this morning, just 2.5m long (they grow up to 12m), it stayed with us for 20 mins or so, circling around the back of the ship.
The multi-net as it’s recovered from a trip to 4000m. There are five nets, connected to an electronically signalled closing device in the big silver box at the top.
Author: Rob Harbour
This piece of equipment is designed to take biological samples from the water column. The large metal box at the top contains mechanisms for opening and closing each of the five nets; this is done remotely from a deck unit on the ship.* At the bottom of each net is a container that collects any animals caught in the net.
A tiny part of one sample from the surface waters showing a large variety of animals, from copepods and shrimps to chaetognaths and polychaetes. Taken with my phone down the microscope!
Each net has a mesh size of 100µm, designed to catch a variety of zooplankton, although they have caught a few small fish in some of the deployments. The multi-net is lowered to 4000m, where the first of the nets is opened. The device is then winched from 4000m to 3000m, collecting anything in the water column as it goes, before the net is closed again and the second net is opened. This process continues so that samples are taken from five depth ranges: 4000m-3000m, 3000m-2000m, 2000-700m, 700m-150m and 150m-surface.
The penultimate depth range might seem a little random, but a sample is taken from 700-150m for a good reason – this allows a full sample to be taken within something called the Oxygen Minimum Zone. As the name suggests this is a layer of water containing a very low oxygen concentration. The oxygen in the water is significantly depleted by the respiration of zooplankton and other animals in the water column as they graze on photosynthetic plankton from the sunny surface waters, and also from bacterial decomposition (when there’s lots of this activity we call the region ‘highly productive’). One of the reasons this layer is so thick in the Pacific is that the water masses here are very old, they have been gently propelled by oceanic currents from their formation in the cold waters of the poles, travelling for around 500 years, to where we find them now (for comparison, North Atlantic water masses are around 275 years old). Since they have travelled so far, there has been lots more time for animals living in the water to respire the oxygen. Of course this oxygen is replaced to an extent with photosynthetic activity, but this is not a uniform phenomena, so we find different OMZ thicknesses in different areas of the ocean.
Hauling the multi-net back on board
Back on board the Sonne, the containers at the bottom of each net are sieved over progressively smaller sieves, 1mm, 300µm and 40µm, the fractions fixed in ethanol for later identification. The data for this experiment is also being used to create the large DNA barcoding library mentioned in the box corer article. Collections have been made in the North Sea, the Indian Ocean and now the Pacific; one day they hope to be able to take a cup of zooplankton and identify every animal in it, automatically. For now there’s a lot of taxonomy and DNA extraction to do back in the lab.
* for the nerds: the winch line they use has a coaxial data cable in the core which provides control over the net closing mechanisms and also transfers data from the CTD – a device which measures conductivity, temperature and depth, amongst other things.
The weights drop after we signal the acoustic release, creating a cloud of sediment before the lander lifts from the seabed, leaving scattered eelpouts in its wake.
Author: Rob Harbour
We are now on deployment number 8, and have enough weights to make 11 deployments in total. If all goes to plan this will give us 10 successful deployments – the minimum for the statistical power we’re looking for. Everything has gone extremely well so far, deployment and recovery has been optimised to an art, and the fish are ravenous for the bait we’re feeding them. We travelled 60 nautical miles away from the first deployment site and they seem even more keen here, regularly stripping the tuna down to a skeleton with only the gills left intact (I guess those bits are unpleasant even to hungry fish).
Totally stripped (although if we’re honest the head fell off during the ascent to the surface)
Since the camera records at regular 10 minute intervals for 2 minutes, by carefully timing the release signal we have managed to capture on video the moment the lander drops the weights and leaves the bottom. This has been both interesting and hilarious. We had expected the lander would rocket off the bottom the moment the weights release, but this is sometimes not the case. In one example it took 32 seconds for it to heave free of the muddy sediment, where its legs appear to be buried up to 30cm; this explains why sometimes when we ask for its range just after release, it reports being in the same place (this can be rather worrying for a moment). We have enjoyed watching the sleepy eelpouts flung unceremoniously from their amphipod dinner, they seem not to react in the slightest as they’re smothered with the plume of sediment created by the weight drop, then whisked away.
The box corer, armed and ready to be sent to the seafloor.
Author: Rob Harbour
This will be the first of several posts to describe the other work that’s being carried out during the cruise. First up, box coring.
Collecting nodules from the sediment surface
The nodules are washed and stored for later experiments
Box coring is being carried out on this cruise for the purposes of a resource assessment, or put simply, to make an accurate estimate of the weight of manganese nodules there are within a certain area. That is of course what the geologists will tell you, the biologists have other things in mind; they will look at the abundance and richness of different animal species living within the top 10cm of the sediment, as well as community and food web structure. Additionally, they will take DNA from each of the animals to build a large ‘barcoding’ database; with this they will be able to take bulk samples (lots of animals) and run them all together, identifying all the species within the sample by DNA alone. 80% of the species found on this cruise are expected to be new to science, so this database will be an invaluable resource once completed.
The box corer takes cube-shaped chunks from the sediment. The box itself is 50cm3 and generally it penetrates to around 40cm depth into the seabed. First, the box corer is armed with the swing door open and sent to the bottom on the winch line. When it lands on the seabed, the weights on the top force the box into the sediment. When the device is lifted again, the vacuum created in the top of the box, sealed by muddy sediment, stops the contents from falling out and the door swings shut to avoid loss on the way back to the surface.
Labels are added for photographing
Sections of sediment are taken from each depth layer
Removing the top 10cm for biological samples
Once the box corer is back on board the Sonne and the box has been removed from the device, a team of geologists and biologists begin a number of sampling tasks. First, the top of the box is lifted and the surface water is siphoned off into containers and fixed with denatured ethanol (when we say fixed, we are talking about halting biological processes so that our samples don’t rot away in storage). All of the manganese nodules from the surface of the sediment are picked off, rinsed, measured and stored for later experiments – any animals found on them are given to the biologists for identification.
The geologists then use syringes to remove sections of sediment from each depth layer; later these will be analysed for a number of criteria like total organic carbon, carbonate content, geochemistry, bulk density and grain size. The biologists sample the top 10cm in three layers; they sieve the sediment to capture any animals that are larger than 300µm (we call these the macrofauna) and fix them in either formalin or ethanol, depending on the future analysis they intend to carry out.
Nothing is wasted, the remaining sediment is taken home to Germany where there are several experimental teams waiting to run tests on it. Planned experiments include exploring the hydro-acoustic properties of deep sea sediment and measuring the affects and distribution of the plume following sediment disturbance.
A megalodon tooth found in the dredge from 4km depth, next to a modern shark tooth. These huge sharks were up to 18m long, making them the biggest predator that’s ever lived. This tooth is at least 2.3 million years old, which is when megalodon went extinct.
Marine Benthic Ecology, Biogeochemistry and In Situ Technology Group 