2019 Cruise - DY103

Microbial genomics at sea: developing new approaches for ecological monitoring at PAP

C R Young

This is my 5th consecutive year as a member of the science team for the PAP research cruise. Every year, I collect various types of samples for genetic analysis. I collect water samples from the CTD Niskin bottles, sediment samples from the megacorer, and preserve samples of organisms from the trawl. We preserve these samples, usually by freezing at -80C, for processing back at the National Oceanography Centre.

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Megacore slicing for microbial ecology

Our focus is on the ecology and evolution of the organisms that we find here. We study a broad range of organisms by applying a variety of genetic, genomic, and computational biology tools. By sequencing the genes and genomes of larger animals like sea cucumbers, molluscs, and crustaceans, we can identify new species, tell how these species are related to one another, how they move between populations, and even which of their genes have been affected by natural selection in the past. By bulk sequencing whole communities of microscopic organisms like bacteria, we can understand how they are contributing to the cycling of organic material and what roles they play in the benthic food web.

My group has been studying environmental microbiology at PAP over the past several years. We have generated data from hundreds of water and sediment samples, and we have even described the gut microbiomes of many of the species of sea cucumbers that we find here. All of this data together will help us to understand the ecological roles of these different types of microbes. Usually, we collect the samples to be process back home, but this year we tried something new.

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Robyn filtering seawater in the temperature-controlled lab.

This year, I brought aboard a graduate student that I’m co-advising under the NEXUS doctoral training program, Robyn Samuel, to help with the sample processing. Robyn has been filtering the water samples from the CTD and extracting DNA from these samples. We collect water from various depths and study the microbial communities by sequencing their genomes. This year we are performing our genomic sequencing on board the ship using a MinION sequencer. This is a genomic sequencer that plugs into a USB port on your computer that can generate information from billions of nucleotides (the building blocks of DNA) in a sample over the course of a couple of days. It works by drawing a single strand of DNA from the sample through a nanopore and measuring the electrical current that passes through the pore. The temporal variation in electrical signal as the DNA molecule is drawn through the nanopore is then translated into DNA sequence by software using sophisticated machine-learning algorithms such as deep-neural nets. This near real-time data allows us to understand the composition of our samples while we are still at sea, and we can adjust our sampling strategy based on what we see in the sample.

 

(Left) MinION genome sequencer   (Right) Inside of the MinION sequencer showing the flowcell into which the sample is loaded.

Applying these technologies at PAP are a first step towards our ultimate goal of performing sequencing on observatory assets like the mooring our on autonomous underwater vehicles. Like our environmental sensors that continuously send real-time data back to NOC without having to have scientists at sea making the measurements, one day we hope to be beaming genomic data back, allowing us to monitor microbial communities from shore all year around. For example, we can visually detect blooms of the coccolithophore E. huxleyi from space [their calcium carbonate scales (coccoliths) make up the white cliffs of the southern UK], but we cannot see all of the other microorganisms associated with these blooms. Coupling satellite imagery of surface blooms with real-time genetic data would allow us to better understand the ecology of these and other surface events. We know even less about microorganisms in the deep-sea, and these technologies will allow us to construct a better picture of the dynamics of these enigmatic communities.

Whether we are measuring ecological dynamics on the scale of hours or decades, at the surface or 4800m below in the sediments, the value of long-term observatories such as PAP is all about temporal dynamics. We visit PAP once a year, and have done so for over 30 years. We hope to use technology to eventually generate continuous ecological data during the times of the year that we aren’t able to be out here on the ship. There is immense scientific value generated by sustained ocean observatories that allow us to understand how our oceans are changing on a decadal scale, and our efforts to expand the data the PAP-SO generates to include microbial genomics will undoubtedly generate new (and likely unforeseen) insights over the next 30.

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2019 Cruise - DY103

Homeward Bound

By Sue Hartman

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As I write we are on our way home from the PAP site. Everyone is either busy writing up reports or packing away equipment. Our last activity was to deploy a sediment trap, in the early hours of the morning. However, some systems continue to gather data for us, such as the underway carbon measurements.

The trip has been successful and we recovered and deployed various autonomous systems and collected many samples. A full set of data is sent from the buoy, via a satellite link. Analysing this ‘near real time’ data, and looking at the collected samples, will keep us busy for a while. The sediment trap time series itself now spans thirty years and will be used to look at both short and long term variations in carbon fluxes from the surface to the ocean depths.

Despite nearly 30 years of seagoing this was my first experience of being ‘principal scientist’. It meant being involved in decision making, choosing station timings and generally having to step away from just working on just one thing! It helped that there were some very experienced people on board though and there was also a general willingness for everyone to pull together and make the cruise a success.

The weather helped too! Rarely are the seas so calm and the weather so sunny around the PAP site. No time was lost to the weather, which is quite unusual.  Of course, the sunshine can be a distraction too, especially when there are whales and dolphins around. We plan to return to the site as early as April next year, just before the spring bloom. However, the data from our Met Office buoy suggests it may not be so calm here at that time of year!

Thanks to everyone on-board for all your support, especially to the galley for some wonderful food. We will ‘demob’ in our home port Southampton; always a busy day unloading equipment (and people). I am looking forward to seeing my family and friends again, though some people still have long journeys to make. Hoping to keep up collaborations with our new ship board colleagues, be they from Plymouth, Belgium or even Colombia and I wish everyone a safe journey home.

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2019 Cruise - DY103

Long-term ocean observations: an international challenge

The Porcupine Abyssal Plain Sustained Observatory (PAP-SO) is one of very few long-term time-series study sites at abyssal depths in the world’s oceans. Over thirty years it has made many important contributions to helping scientists understand the functioning of the largest ecosystem on our planet. This is highlighted by nearly 300 scientific publications written about data collected at PAP including many important contributions to wide ranging scientific disciplines. NOC scientists, engineers and our international collaborators are incredibly proud to operate this site and make the data and findings available to scientists and other stakeholders around the world. Those of us out here on RRS Discovery at the moment are particularly excited to be continuing this important work.

Long-term observations of the oceans, as we make at PAP-SO, are essential if we are to collect the data we need to address important societal concerns such as climate change and the sustainable management of our oceans. Scientists from around the world (including from NOC) recently published a paper about the global needs for ocean observations. The paper highlighted that long-term multidisciplinary scientific observation, like we do at PAP-SO, is exactly the type of work needed to address these important questions.

To enhance ocean observation we can link up with other ocean observatories to share expertise, address science questions using data from multiple sites and encourage the dissemination of information about the oceans to those who need it. PAP is one of eleven ocean observatories that make up the European Multidisciplinary Seafloor and water column Observatory (EMSO). EMSO is a European Research infrastructure Consortium (EMSO ERIC) with observatories in the Atlantic, Mediterranean and Black Sea. It aims to provide the ocean observations needed to understand European seas.

Working together, these different observatories are measuring extensive parameters throughout the water column to the seabed, from a broad range of scientific disciplines including meteorology, physical oceanography, biogeochemistry, ecology and geo-hazards. This enables us to learn quickly from each other’s experience in the engineering needed to manage, maintain and develop the future of these important observatory infrastructures so that we can produce science of global importance. This is an important step toward increasing the global ocean observations required to meet some of our biggest challenges.

 

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The PAP-1 mooring after being deployed during the DY103 cruise. The mooring hosts sensors on the surface buoy and on a sensor frame that hangs 30 m below the buoy. It provides data that is key to understanding the rest of the system at the Porcupine Abyssal Plain Sustained Observatory (PAP-SO)

 

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Great skill and teamwork are needed to deploy the PAP-1 mooring that includes the surface buoy and the sensor frame that hangs 30 m below it, all in 4850 m water depth.

 

 

2019 Cruise - DY103

A Beginners’ Guide to Work Aboard a Research Vessel

Hello. my name is Toby Mortimer, and I am currently an MRes student at the University of Portsmouth, UK, where I am studying the variations of Phosphorus speciations in shelf sea sediments with my supervisor. When it was mentioned at the start of my MRes year that I could experience 2-3 weeks working on a boat, I was intrigued. When it was said a few months later that I could participate on board and help with sampling, meet amazing scientists and workers to collect data and help and possibly see numerous whales along the way, I was elated. As someone who enjoys new experiences, lab work and seeing charismatic megafauna in the flesh, I could not let this opportunity pass!

As this was my first ever time participating in a research cruise, arriving at the NOC on Thursday the 20th June was slightly daunting. And then I first saw the RRS Discovery. Never before have I taken so many photographs of boats before, but I was loving life. I knew this journey would be excellent if I was drunk with excitement just being on the docks looking at a research vessel. Upon moving into my cabin, I spent the first night meeting a number of highly interesting and amusing people.

The days of travelling to the PAP site provided me with my first opportunities to observethe numerous labs, processes and equipment that occur onboard the vessel. “Pleasantly overwhelmed” would be a nice way to sum everything up. In truth, the number of different surveys, benthic cores, chemical/biological analyses and more occurring was fascinating, and of course, really ruddy cool.

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 It also gave me the chance to see the Scilly Isles and the Needles of the Isle of Wight, as well as plenty of opportunities to show off to my friends and family at home (Without mentioning that the travelling swell wiped me out for half a day).

 

The 23rd introduced me to the first CTD cast from the RRS Discovery. As part of my second year of university, I had once experienced a CTD cast in the river Itchen, but this was to far greater depths. A CTD contains a rosette of 24x20l Niskin bottles, which can be fired at specified water depths. These water samples can be used for multiple fields of analysis, but I have been focusing on the concentrations and masses of chlorophyll, aswell as Particulate Organic and Inorganic Carbon (POC/PIC).

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With expert training from the ever-fabulous NOC staff, I was introduced to my filtration station for the next 2 weeks and eagerly began filtering innumerable litres of seawater. While POC and PIC samples are to be analysed at NOC upon return, chlorophyll samples have been kept in 8ml acetone in a fridge overnight, then analysed in a fluorometer in duplicate.

This cruise has also introduced me to Star Oddi sensors. These small probe-like white sensors are placed in casings and then strapped with cable ties to the frame of the CTD, which collect data at specific intervals for temperature, depth and tilt angle of the frame. As a self-styled Star Oddi Master and Technician, I was tasked with programming, maintaining and attaching these sensors to the frame, a job which I am currently relishing. Having collected data from retrieved PAP#1 Buoy Star Oddis, I have since calibrated and attached different sensors to the New PAP#1 buoy, which I had the great pleasure of watching being re-deployed yesterday for another year and are currently collecting data at 10 minute intervals.

Post/Pre-deployment of PAP #1 buoy!

With less than a week now remaining of our 18 day exploration, I have truly been blessed to work alongside such incredible people, use incredible machines and equipment and eat truly incredible food. My love of the sea is indeed coming out in full colours on the ship, as I’m often seen staring out of portholes looking at the waves (and always hoping a glimpse of a whale) when not at work. I look forwards to the rest of the time and work aboard this fine vessel, and hopefully many more to come!

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2019 Cruise - DY103

ICOS inter-comparison at DY103

Hello, we are Sue and Hannelore, from NOC and VLIZ (Flanders Marine Institute) and we are sailing on RSS Discovery cruise DY103 around the PAP site in the North Atlantic. We are both involved in the project called ICOS (Integrated Carbon Observation System https://www.icos-ri.eu/ ) and we look after fixed ocean stations (PAP and the VLIZ Thornton Buoy). The PAP site is one of the longest biogeochemical time series records in Europe and one of the main components is a surface mooring and buoy equipped to determine many physical and biogeochemical variables including measurements of greenhouses gases and ocean acidification.

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Back in November 2018 we started talking to each other about the cruise. The idea had been raised to setup an inter-comparison exercise to test different systems to measure carbon chemistry while we were on board the ship. Since the ship is equipped with a surface sea water supply we decided to compare various systems that we have to measure the carbon dioxide, pH and alkalinity of the surface ocean.
However, things were not as simple as they looked. We had to think about gas connections, distance between the water supply and intake of the seawater to minimize temperature differences, make sure there are enough drains, the safest place to put the equipment, freighting equipment …..all before we set foot on Discovery… Once on board we spent some time connecting up the gas and water supplies (which sounds easier than it was ), and making sure the equipment worked.

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And here we are sailing the North Atlantic, with our underway systems. For those who want the details we have a Picarro analyzer and Kongsberg Contros FT (owned by VLIZ); Pro-Oceanus sensors (supplied by NOC) and a ship fitted Dartcom system (owned by the Plymouth Marine Laboratory) all measuring the carbon dioxide. We are also measuring alkalinity of the seawater (using a Kongsberg Contros HydroFia from VLIZ and a custom made system from the engineering group from NOC).


However, we are not only comparing systems against each other. We are also comparing our measurements with the sensors on the buoy and a frame below that – these systems will be left in place for the whole year. The ultimate aim is to improve our estimates of the exchange of carbon dioxide between the atmosphere and the seawater in this productive part of the North Atlantic. It will also help in our studies of ocean acidification and how this varies with the changing seasons and from year to year.
Two more wet chemical sensors developed at NOC, one for pH and one for alkalinity, are attached to the CTD rosette. We match up the data with spot samples taken from the Niskin bottles that are fired at various depths down to nearly 5000m. Through our collaboration and comparisons, we will also look at how we sample the water and then analyse those samples. We are already learning so much from each other and we will have plenty more to find out from the samples that we take back to our various laboratories for analysis.

While the inter- comparison exercise of the various instruments and methodologies keeps on going we safely retrieved the PAP Buoy. As we write this the final touches are being made for re-deployment. We will be very excited to see the buoy being deployed again. And last but not least we still have some critical analysis to complete on board!

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2019 Cruise - DY103

Eclectic cruising at the PAP-SO

by Corinne Pebody

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One of the fabulous aspects of the PAP-SO is how it brings scientists and science together. We work in different fields with different equipment but are united in our desire to identify and understand the processes that drive our oceans.  The focus of our work here is sea floor to sea surface mooring, instrumented on the surface buoy, a complex frame at 30m and at intervals down to 500m. A second mooring collects data from 3000m to 4850m (seabed). A third, a seabed lander collects data from the abyssal plain. We change round the equipment once a year and this provides an excellent opportunity to gather samples and data that can’t be collected via our moorings.

For example today, Monday, we started with HYBIS (a remotely operated vehicle with camera systems and attachments) rescuing the bathysnap (a seabed camera system) that we deployed last year- but failed to release on command. Following this we recovered an amphipod trap that we deployed 2 days ago and while the animals were being sorted in one of the laboratories, the next activities on deck were two CTDs in a row. The CTD (Conductivity, Temperature, Depth sensored frame with a rosette of niskin (water sampling) bottles) is the work horse of our scientific cruises. It gathers data about the physics and biochemistry of the ocean beneath us and collects water samples so we can verify the data collected and provide water for experiments.

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We also use these CTD dips to benchmark the instruments that we intend to deploy on our mooring for the next year. Each instrument has its own bias and only by comparing them to the CTD can we trust the numbers that they generate and such trust is imperative if we are to make qualified statements on any trends or change that we see at our Observatory.  On this cruise we are also collecting water for colleagues who are looking at sinking particles. This ties in very closely with our sustained interest in the carbon cycle particularly here in the open ocean. The PAP-SO is our insight into the Northeast Atlantic and we have been studying its behaviour for thirty years. Only by establishing and maintaining long term time series such at the PAP-SO can we hope to measure any change or trends in the carbon cycle that affects our climate and us.

Currently there is a mega core descending to the seabed 4850 m below us. In four hours when it is back on board and the samples are being carefully processed and preserved, it will be the turn of the plankton net.

This cruise is later in the season than we have been the last few years and I can see a real difference in the zooplankton collected; far fewer copepods and meso zooplankton and many more amphipods, mostly Themisto which is a much larger animal than all copepods.

Earlier today I was checking a sensor that measures chlorophyll so we can measure the microscopic algae that grow here in the spring and summer, a phosphate sensor so we can measure the nutrients that these plants uptake, and checking data from our oxygen sensors so we track how this changes over the seasons. At the same time, colleagues from Belgium and the UK were checking nitrate, which is another nutrient that the tiny algae need to grow and another colleague was measuring the amount of carbon that the ocean has dissolved at different depths. We all work in the same lab and so can share our concerns and discoveries and grow our science together.

The multi-stranded measurements we make here are diverse and yet entwined with each other and with us. The enthusiasm that we all have, carries us through long hours and multiple set backs away from our homes and families. The energy that everyone brings to their work, whether scientific, engineering or shipside, is contagious and I always find our PAP cruise to be incredibly affirming; our science really does matter.

If you want to find out more about the data that we collect and the work that we do please visit our website

http://projects.noc.ac.uk/pap/

2019 Cruise - DY103

Sampling for marine fungi at the Porcupine Abyssal Plain

Marine mushrooms??

I’m Kim, a research assistant in the Cunliffe group at the Marine Biological Association in Plymouth. There aren’t actually any marine mushrooms as such, but there are fungi living in the oceans! I work on project called MYCO-CARB which aims to reveal the secrets of these marine fungi which we refer to as mycoplankton. Mycoplankton are part of the marine microbial community that carry out important functions such as carbon cycling, however, unlike other microorganisms (e.g. phytoplankton) mycoplankton have not been widely studied.  I am here on Discovery with one of our MRes students Cordelia collecting samples at the Porcupine Abyssal Plain (PAP) in order to answer questions about how mycoplankton interact with their surroundings, how they fit into the marine carbon cycle and as a result start to better understand their role in the marine ecosystem.

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Cordelia Roberts and Kim Bird

Filtering for fungi

We are taking seawater samples throughout the water column from the surface right down to seafloor at ~4800 m during the CTD casts (check out the next blog to find out more about CTDs). Mycoplankton are microscopic and cannot be seen with the naked eye, so to find out what we have in our samples we must filter the water, and it is a lot of water. By the end of this trip we will have processed about 1 ton of seawater through filters with pores 250 times smaller than a human hair, as you can imagine this takes quite a lot of time and patience. We have several filtration manifolds set up to collect a range of different samples, it looks quite complex with all the tubing and funnels, but really the principle is quite simple; we use a pump to create a vacuum which then draws the seawater through the filter, anything in the seawater is then collected onto the filter.

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Fishing for fungi

Organic particles that are formed in the productive upper ocean which then sink through the water column are known as ‘marine snow’. Marine snow is a complex particle and can range from 1/2 a mm to cm’s in size and are composed of anything from gelatinous material to dead cells and even zooplankton poop. Marine snow is important because it transports nutrients to the deep sea and eventually the sea floor where it is stored. To find out if mycoplankton are interacting with these particles we are carrying out some experiments on board where we will be adding particles to seawater and seeing what fungi attach, kind of like fishing, as well as collecting some natural particles for comparison.

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Marine snow particle stained with Alcian blue

“I shall call him Squishy and he shall be mine”

One of the most exciting parts of our work onboard is cultivating mycoplankton from the particles we collect. We will be able to physically see some of the mycoplankton we are sampling, which can be all sorts of colours and textures. As well as being pretty to look at these cultures are important to our work. Only 6% of the marine snow produced ever reaches the seafloor, but we know very little about what happens to these particles on their journey through the water column. We hope to take some isolates back to the lab with us which will help us understand what types of particles they are degrading as a food source and the mechanisms they use to degrade complex particles like marine snow.

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Marine fungi strain from the MBA culture collection

It’s worth the wait

Not only do we have to be patient when collecting our samples, we also have to wait to find out what we have collected as the majority of our samples have to be analysed back at our lab in Plymouth. Once back on dry land we use molecular tools and sequencing technology to determine the abundance and composition of the mycoplankton community, and also identify which of them are alive and active. From these data we can build a picture of the mycoplankton community as a whole and tell what individual groups are most important in the ecosystem. One of the great advantages to sampling at a sustained observatory like PAP is all the other fantastic science that happens alongside ours year after year, by working with other science groups we will now be able to establish the impact of fungi on the marine carbon cycle.

2019 Cruise - DY103

Our eye in the abyss

Finally, the chance to live out one of my childhood dreams of being part of a scientific team on a Royal Research Ship. My PhD at the National Oceanography Centre (NOC) started in October last year, with the aim of studying deep-sea ecosystems. I have spent the last months preparing and annotating thousands of images taken by HyBIS on last year’s cruise. Now it is my turn to see behind the scenes, be part of the team conducting HyBIS dives and call myself a ‘proper’ scientist.

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Figure 1. Me and HyBIS ready to roll

The goal of HyBIS is to collect images at the Porcupine Abyssal Plain Sustained Observatory (PAP-SO). HyBIS is a modular robotic underwater vehicle (RUV) that is towed behind the ship to collect images of the seabed, capable of reaching 6000 m depth. The attached cable and fibre optics provide a live video link and the camera is programmed to take a picture every 5 seconds. The images collected on these missions are used to record environmental conditions of the deep-sea. The deep-sea is the largest ecosystem on earth that plays a crucial role in carbon cycling and regulating global processes. Not only do we want to observe this extreme and alien world, but it is necessary to understand how the ecosystem works to conserve the important habitat.

The primary food source for deep-sea organisms is the flux of particles that falls to the deep from surface waters, and the amount of particles that reach the seabed is affected by local climate. Monitoring the effects of climate change on deep-sea communities is one area of research conducted using HyBIS images. For example, we can count the number of organisms and how they change through time, and compare those changes with climate conditions that are also monitored at PAP-SO.

The night arrived to conduct the first HyBIS dive of the cruise. The RUV was launched overboard and the crew took some time to confirm it was receiving power, all systems were working and set up the camera and viewing screens. Many gather in the control room as HyBIS starts its descent, everyone eager to see the first images sent back from 4850 m deep into the abyss below us.

Figure 2. A couple of organisms seen during the HyBIS dive (Top), and an old trawl mark that has filled with phytodetritus and litter (bottom).

The camera reaches the sea-floor and the ship sets off at a steady 0.3 knots along a selected root. Audible ooh’s, ahh’s and wow’s can be heard around the lab as different organisms glide across the screen. The camera moves up and down with the waves and the winch attached to the cable has to be controlled throughout the dive. We want the camera to be close to the sea bed to be able to identify as many organisms as possible. But we also do not want to damage the ecosystem, or expensive equipment, by hitting the sea-floor. The hours go by quickly, being attentive to the images we are collecting and never knowing what will pass by our eye in the abyss next. From purple or spiky holothurians, red tentacles of anemones flowing in the current, to worms poking their heads out of their burrows to feed. The first HyBIS dive of my career has been a success. I hope to get more dives done during the cruise and look forward to getting the images back to NOC to start processing and annotating once more.

 

Written by Philip Smith

 

2019 Cruise - DY103

Preparation, preparation, preparation

Hello, my name is Helen and I’m the Head of Scientific Engineering at NMF. Though the title may be grand, in reality I joined NOC in February this year and this is my first time at sea as part of a scientific expedition. My job onboard this trip is to watch and learn from the team of experienced and enthusiastic technicians and scientists, bringing some practical context to the theory I’ve learned so far. “What does that mean?” I hear you cry……..basically I get to watch some cool science and engineering in action, help out where needed, and generally get in the way! Oh and not to boast, I’ve been told I make a cracking cup of tea.

Today’s learning experience has been the preparation and deployment of sediment trap moorings, the deployment of amphipod traps and the ongoing build of the soon to be deployed PAP 3 sensor frame.

For the sediment trap mooring, and mooring operations in general, lesson number one is “preparation, preparation, preparation!” The smooth, swift and most importantly safe deployment of the mooring starts several hours beforehand with the individual sections and pieces of equipment laid out and secured in sequential order on deck. This is followed by a safety brief and a toolbox talk for all people involved, then PPE on and off to work we go. With the evolution ably led by our moorings team veteran Steve Whittle, everything that should have gone over the side did, and critically in the correct order and position without a hitch. The whole operation took around 2 hours……….turns out it takes a while to deploy a few kilometres of rope!

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By comparison the amphipod traps deployment was a breeze, completed with half the number of people in a fraction of the time; but still with the same preparation beforehand.

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In the time between these operations, preparations are well underway for the PAP 3 buoy redeployment; testing and populating sensors on the buoy and sensor frame. This is a great task for anyone who enjoyed playing with Meccano as a kid (and I was definitely that kid).

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This evening promises coring and net operations, so lots of tea making, questions and getting in the way left to be had today.

2019 Cruise - DY103

Maintaining the CTD

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Watching the CTD rosette. Photo credit Chris Cardwell

I’m Tim, a trainee technician with the Sensors and Moorings team which in turn is part of the Scientific Engineering Group within the National Marine Facility (NMF). DY103 is an opportunity for me to get to grips with CTD operations under the watchful eyes of John Wynar, one of our most experienced techs.

The CTD is one of the main workhorses of ocean observation, measuring Conductivity (for salinity), Temperature and Depth whilst also collecting water samples at different depths with large 20 litre bottles.  I’m lucky to have John training me as he’s a very patient and forgiving man. Just the other day I forgot to empty one of the 20 litre CTD bottles resulting in him filling his boots with sea water as he cocked the bottles ready for the next cast. Oops.

After each CTD cast we carry out several checks to make sure everything is working as it should and is ready for the next cast, one of these checks is to test the insulation on the CTD wire. After the first deep cast we noticed the value was much lower than we would expect indicating a problem at the termination where the wiring harness for the CTD is connected to the ships CTD wire.

Peeling back the layers showed that the immense pressure found at 4810m had forced water into the termination and that we would need to cut the CTD wire and re-terminate. Water can travel a long way up a wire in very little time thanks to capillary action, this led to us needing to cut 120m off the end of the CTD wire to get back to dry cable.

The process of re-terminating the wire is time consuming but quite straightforward, the two pin tail is soldered to the CTD wire, covered in heat shrink tubing and wrapped in layer after layer of amalgamating tape and a sticky glue like substance called ScotchKote. Throughout this process we regularly test the insulation to ensure all is well, this time it’s looking really good and we are feeling confident. The electrical connection is finished off with a long thick piece of adhesive lined heat shrink to provide strength and prevent the soldered joint from failing due to fatigue.

Next comes the mechanical termination, we’ll be hanging the CTD frame off this wire which can weigh up to ton so the termination needs to be strong with no chance of it slipping or failing. A replacement CTD package would cost around £250,000 so we definitely don’t want to lose one. Wrestling with the wire to form it into a small loop we add three stainless steel clamps and progressively tighten the bolts using a torque wrench. Lastly we mark the wire so we can easily see if there is any slippage under load.

With the help of John, the ship’s CPOS (Chief Petty Officer – Scientific), we carry out a load test, two deck eyes are bolted into the deck, strops are attached along with a load cell, a chain block and finally the CTD termination. We submit our new termination to 0.5 Ton, 1.0 Ton, 1.5 Ton and finally 2 Ton holding for 5 minutes at each load to ensure it can safely handle the weight of the CTD package. Our termination passes the test and the paperwork is signed off saying it’s fit for use. I’m hoping it survives its next trip to the bottom of the ocean and this time remains waterproof.