Hello, I am Mark Stinchcombe and I am the Principle Scientific Officer (or PSO for short) on the PAP cruise. Although I have taken part in well over 20 research cruises in my 12 years at the NOC, this is my first as PSO. You will have read all the blogs from the scientists, engineers and crew on board the RRS Discovery and will know that the ship works around the clock. There is always something happening, or about to happen.
As the PSO it is my job to make sure it all happens effectively and efficiently. Before the cruise starts I will have liaised with the cruise managers about what we are doing, where we are doing it, what we need to complete our science objectives and who will be coming to do the work. The cruise managers can then make sure the ship has the appropriate equipment on board and the right technicians to help us achieve those objectives.
During the cruise I need to be able to write a schedule of work that takes into account everyone’s scientific requirements. This needs to be communicated to the Bridge so the Captain and his officers know where the ship needs to be and what we’ll be doing but also to the crew on the deck so that Nathan can make sure there are operators for the many winches and cranes, the technicians so that Nick can make sure his team are available to provide the technical support needed in much of the work we do and of course the scientists themselves. This changes on a daily basis and 3 or 4 versions a day are not uncommon. I have to be able make change at short notice for many reasons, for example a sudden change in the weather.
Now the cruise has come to an end and we are steaming back to Southampton and I can take some time to look back and reflect on what we have achieved. We have completed 124 stations in only 15 days and this couldn’t be possible without the amazing show of teamwork that exists on board a research ship. We have deployed 11 CTDs, 13 megacores, 41 marine snow catchers, 10 SAPs, 17 camera frames and 2 trawls. We have had 10 PELAGRA deployments, 4 mooring deployments and 5 recoveries. Everyone has worked extremely hard through-out the cruise and there will be some great science produced from the samples collected.
I am extremely proud to have been the PSO on board the RRS Discovery and I would like to say a big thank you to the scientists, to Nick and his team of technicians and to Captain Antonio and his crew for all their hard work and for making my job that little bit easier.
After many nights of megacoring (see Marla’s blog) to sample macrofauna (tiny animals to be observed under a microscope), we finally got to collect some bigger specimens (megafauna). It was really interesting to witness the deployment of the trawl net (see Simone’s blog); all the manpower required to manoeuver the equipment, moving the cranes to carry the net soon to be thrown in the water. Watching crew and scientists combining their effort, step after step, like a very well organized ant colony is quite impressive.
Two nets were deployed four days apart. Each time the RRS Discovery dragged the net over night for 12 h, less on the actual seafloor in the central Porcupine Abyssal Plain (PAP), 4850 m below our feet. I couldn’t stop thinking about all the creatures we would recover. I already had an idea of what they would look like as I spent quite some time annotating photographs acquired with the Autonomous Underwater Vehicle (AUV) Autosub6000 in the same area for a different project, but seeing the animals ‘for real’ is a completely different story! The next morning after breakfast, we all got ready and went to the back deck to wait for the net to come up, with all sorts of expectations. It’s like a Christmas morning; what will we be hidden within the net? [If there’s anything at all???]. The first trawl arrived slowly on deck, carrying lots of benthic beasts (animals which live on the seabed), along with 2 tonnes of mud (Fig. 1a)! It doesn’t happen very often, and getting rid of all this sediment was quite a task! (Fortunately) my colleagues sorted all the animals on deck (Fig. 1b) so I could start examine a subset of our catch, sheltered in the lab (Fig. 1c). And indeed, observing all these creatures, living almost 5 km under the surface of the water in a cold and completely dark environment, was astonishing (Fig. 2). Contrary to what was long thought until a few decades ago, deep-sea populations are rich and varied: sea cucumbers, sea stars, anemones, sea spiders, etc. The animals found in the deepest parts of our planet are not as colourful as those in shelf waters because they don’t need to ‘waste’ energy producing pigments. However a few exhibit catching colours like the sea cucumber Psychropotes sp. which are all purple (they are also the largest specimen found on the deep-sea floor at PAP [up to 50 cm in length] and have a buoyant ‘tail’ which helps them floating above the seabed or navigate in the water, Fig. 3a), some isopods which are bright orange (third raw, first picture on Fig. 2), and some fish which are all black like the famous angler fish (third raw, fourth picture on Fig. 2) which possess a dorsal ‘antenna’ where a multitude of bioluminescent bacteria emit light to help the fish attract its preys. The second trawl catch was less muddy but nonetheless brought plenty of animals. Also we recovered loads of human artefacts such as two oil barrels and cans (more details in Andy’s blog). We found some anemones growing on top of a beer can (Fig. 3b,c) and a plastic sachet (Fig. 3d), showing how animals manage to survive in zones polluted by human activity.
Collecting some deep-sea benthic megafauna from PAP was a great opportunity for me. I started my PhD less than a year ago in the Deep-Seas department at the National Oceanography Centre, Southampton. For my project I would like to create a method for calculating the weight of animals based on their body shape using photographic data, thus regardless of their taxonomic identity. This will enable estimation of the biomass (mass of living animals) of benthic animals from various locations (NE Atlantic, Celtic Sea, NW Pacific). The method will consist of measuring the most representative length and diameter of each individual as if they were cylindrical. In fact it’s not as complicated as it sounds, but for doing so I need to validate my approach by comparing the weight and volume of ‘real’ animals and of those observed on photographs. For that reason, on board of the RRS Discovery I photographed and measured the weight (fresh wet weight) and volume of a few specimen (Fig. 4). If being rocked by the ship is comforting to fall asleep at night, it doesn’t ease rapid reading of the correct volume, but I managed to obtain my first self-acquired PhD data; which is always satisfying!
To finish my blog, I will just say how much I appreciate working at sea. It’s a challenge on all points of view given that working and living conditions are completely different than what we are usually accustomed back on land. But we learn a lot, for our own projects and from others, which is crucial in the world of science. Plus we get to meet new people sharing the same interests. Also if working on a very different schedule is hard, we were able to witness both sunset and sunrise almost every day and appreciate wildlife (dolphins, pilot whales) in their natural environment. Isolated on a ship in the middle of this vast blue ocean, the image of the sun showing up at the horizon on one hand, and the full moon in the absolute dark sky, like if both day and night were sharing the same place (Fig. 5), will forever stay in my mind.
“…if fish remain at rest during the night a great multitude of these creatures fall upon them and devour them. They are found in such numbers at the bottom of the seas as to devour any bait made of fish that remains any length of time upon the ground; fisherman frequently draw them out hanging like globes around the bait.” –Aristoteles (0330, book 4, chapter 10, translated by Cresswell, 1862)
Fours traps baited with dead mackerel, to mimic a natural food fall, just landed on the seemingly empty Abyssal seafloor (4850 m). However within 24 hours, these mackerel will be almost stripped bare, engulfed and devoured by Abyssal necrophagous amphipods (shrimp-like animals). These are not your typical amphipods. Armed with formidable claw-like legs and modified jaws, these are voracious feeders. They are capable of engulfing live prey, because when there is a meal to be had these amphipods turn up, sometimes in 10’s of thousands to devour a meal. Think Army ants in the jungle. In normal circumstances large mobile animals would be able to escape from amphipod predation, but if confined, they would succumb to the attacks. The amphipod, Eurythenes, have been seen to attack and feed voraciously on fish being brought up in (commercial) nets.
Why are we studying these animals?
Marine scavengers, or necrophages, are organisms that are able to detect and actively move towards carrion, eventually consuming all or part of a food fall. In the open ocean, when large fish or marine mammals die, their carcasses sink to the seabed, becoming a ‘food-fall’ for deep-sea scavengers. This provides a significant source of carbon needed to sustain deep-sea communities. Although the seafloor at the Porcupine Abyssal Plain receives an input of carbon (food) that originated at the surface as phytoplankton blooms and has sunk down to the deep sea, the benthic communities here are often food limited and rely on these alternative sources of carbon to sustain them.
At PAP, we have collected amphipods intermittently since 1985. We study community compositions; for example which species are present, the relative numbers of individuals (abundances), and reveal which are dominant (species with the highest abundances). Surprisingly this changes year on year. To better understand what factors may be driving this change we need to better understand links between upper ocean physical and biogeochemical processes, the supply of particulate organic carbon (POC) to the deep ocean, and the response of the benthic fauna (community changes in abundance, dominance).
To collect these tiny animals requires a concentrated effort from a lot of people—and I am very grateful to everyone for their help!
Step 1) Prepare the traps- Each of the four traps contain bait (mackerel). The design of including two narrow funnels within the traps means that the amphipods are able to get in and eat the bait, but it would be difficult to get back out. This allows us to take a ‘snap shot’ of what was happening, and what amphipods were present 24 hours into the food fall.
Step 2) Deployment- The traps are deployed from the back of RRS Discovery. Once released, the traps and frame will sink at a rate of 50 metres per min until they reach the seabed (4850 m), this takes approximately 100 minutes, and the GPS position is noted. The traps will remain on the seafloor for 24 hours before they are released and recovered.
Step 3) Fire the release! After 24 hours a code is entered to arm and fire the release mechanism attached to the amphipod trap, then the weight (keeping the frame in place) is released, and the buoyancy spheres (5 in total) attached allow the frame to ascend up to the surface and keep it there until we can recover it.
Figure 4 Step 3: Entering the code to fire the release, allowing the traps to return to the surface.
Step 4) Searching for the Amphipod traps: when released, the traps will more or less, rise to the surface in the same location as when deployed. However, one of the days, the winds were blowing at 30 knots with a fast moving surface current, which meant that the traps had been blown off course by 4 miles! Once the trap location was triangulated, everyone available came up to the Bridge (best vantage point) to help search for the traps. Eagle-eyed Henry Ruhl saw the Amphipod trap first!
Step 5) Recovery! Once the Amphipod traps were located, the ship winch will pull the frame onboard. All hands are on deck as we remove the traps and then they are quickly taken to the cold room for processing. As we are conducting molecular studies on these animals, they must be kept as cold as possible, and must be preserved as quickly as possible to keep the integrity of the genetic sequence that we will later extract and analyse.
Step 6) Processing- The individual traps are taken apart in the cold room, to access the amphipods. The resulting samples are placed in Ethanol (alcohol) preserving them for later analyses.
Step 7) Further analysis of the samples- Using the microscope onboard, I am identifying the species, counting the individuals and photographing them. Preliminary results indicate that there are fewer numbers of individuals recorded this year than in previous PAP years. Although the same species are found within the Amphipod traps at PAP, often the ratio of one species to another changes. Understanding why is an area of future work and research.
Now that this year’s PAP cruise is nearing its end, there was time for us in the benthic team to reflect on our work. So far, we have deployed and successfully recovered two Amphipod traps to study the diversity of scavenging crustaceans (see Marla’s next blog), have collected our target number of megacore samples for analyses of the fauna living in the sediment and other parameters, such as micro-plastics, biomarkers and eDNA, and have also successfully completed two bottom trawls to sample the larger organisms (megafauna) that live on and slightly buried in the sediment of the Porcupine Abyssal Plain.
Trawling at the PAP Observatory site is carried out with a semi-balloon otter trawl. This type of trawl consists of a funnel-shaped net with a wide opening at one end and one closed-end where the organisms that enter the trawl are caught. At each side of the net above the net opening, one heavy otter board (also known as trawl door) is attached, which keeps the mouth of the net open while it is being towed along the seabed. Across its lower edge, the net contains chains to keep it in contact with the ground, and on top of the net a float is fixed to ensure that the vertical spread of the net is maintained.
For many of us in the benthic team it was the first time working with trawl samples, so we were curiously watching the activities on deck. On the RRS Discovery, trawls are deployed from the back of the ship, and, as is the case with many of our sampling equipment, it needs a coordinated effort by the ship’s crew, technicians and scientists to deploy and recover the trawl safely. First, the net is deployed and then the two otter boards are slowly lifted into the water using the ship’s impressive hydraulic winch system. Once the boards are in the water, the cable that connects the trawl system to the vessel is payed out slowly to the seafloor. Since we are sampling the seabed at 4850 m water depth, it takes about 4 hours for the net to reach the bottom, using up about 12 km of cable.
After 2-3 hours of sampling and another couple of hours to haul back the net, the catch is brought back on deck and the work of the benthic team can begin. Half of the team is starting to sieve out the sediment caught in the net to uncover the deep-sea creatures of the abyss. Depending on the amount of sediment caught, this may take several hours, as we found out after recovering our first trawl of the cruise. But the effort is worthwhile, revealing a variety of life forms like sea cucumbers and sea stars, squat lobsters, sea anemones, scale worms, sea spiders, sponges and bivalves.
The other half of the team is working in the lab, pre-sorting the catch into major taxa and preserving the animals for further taxonomic identification and counting on land. In addition, Rob is taking tissue samples from the animals to perform DNA analyses, while Noelie is measuring the animals to examine the relationship between the size of the organisms caught and their weight. We are also taking images of the different species collected to extend our image catalogue of the invertebrate megafauna of the Porcupine Abyssal Plain. The specimens themselves will be available for future study through the Discovery Collections, an internationally important historical collection of deep-sea marine invertebrate and fish specimens.
With the benthic samples collected during this cruise, we are extending the long-term time series benthic data set collected since 1986 from the PAP Sustained Observatory site. We are interested in understanding how the benthic assemblages of the abyssal plain change over time and what drives this change. Using the meteorological, geochemical and biological data collected by the other teams on board, we will examine the relationships between the dynamics in the atmosphere and those observed in the upper ocean and on the seabed. This information will help us to understand how variable the benthic system of the abyssal plain is and how it may respond to anthropogenic disturbances.
(The images were taken by Anna Belcher, Claire Laguionie and Simone Pfeifer)
My name is Andrew and I’m one of the science party on the research cruise DY050, which is currently at the Porcupine Abyssal Plain (PAP) site within the Atlantic Ocean. Now, I’ve just used the words ‘party’ and ‘cruise’ in the last sentence and that may give the impression that I’m on some easy going holiday – not the case. A research ship at sea is a 24 hr science machine. Every moment of time is scheduled to cram the most amount of work into it. Whenever there isn’t any sampling or a deployment it is almost always the case that something is being prepared and made ready for more sampling or deployments. There are no weekends, no bank holidays. Every day is a work day; there are only shifts and schedules.
It is relentless… and I really enjoy it.
We are well looked after on board. All our meals are made for us, washing machines are freely available and clean bed linen is provided weekly. My daily commute to work at home takes 40 mins. On the ship it is more like 40 s. All this combines to mean that more time is available to focus on what we are here to do, with very few distractions.
My work centres on the making and testing of miniaturised sensors that are designed to measure physical properties of the oceans, like temperature and exactly how salty it is. That may sound a little superficial but accurately knowing these things can tell us a lot about the energy being transferred around the world, where it is coming from and where it is going to. These sensors rely on measuring tiny changes in electrical output, like a mV or μA, and I normally test them under very controlled conditions in a lab. At sea I get to really put these sensors through their paces, sending them down into the deep and the dark – where they experience incredible pressures. This is invaluable for my work and each time I have used them at sea we have learnt something really important. So far they have performed very well but I’m always keen to push them further.
It’s also really good fun learning so much from everyone else on board. There is much more opportunity than normal to see each other’s work as a lot of us work at different institutions, labs and offices. Here we all continuously work amongst one another, helping each other whenever we can. Overall, it’s all really satisfying. The days can be long and the work hard but it is a very productive time.
Counting the number and types of the larger invertebrates on the seafloor at the Porcupine Abyssal Plain forms an important part of the time series studies. The processes we study in the surface waters at PAP affect the amount of food that reaches the seabed 4.8 km below, which is linked to changes in the number of invertebrates at the seabed. As well as the intended target, invertebrates such as sea cucumbers and sea stars, our seabed studies also reveal some of the impacts that humans have on the ocean. Despite being far out in the Atlantic, 4850 m deep and seemingly remote from human influence our samples bring up various items of litter.
This year, like every year, we have found glass bottles, plenty of broken glass, drink cans, wood and bits of crockery, presumably lost overboard from passing ships. We also find clinker every year. Perhaps this is more surprising to those who haven’t studied PAP before. Clinker is by far the most common item we collect from the seafloor. It is the remains of the burnt coal that was shovelled over the side by sailors on steam ships. It has been many years since steam ships sailed across the Atlantic but the evidence of their fuel remains lying on the seabed. The clinker even provides a rare hard surface on the soft, muddy seabed that animals like anemones can attach to, much like limpets and barnacles attached to rocks at the beach.
Perhaps the most remarkable artefact we collected at PAP this year is an old clay pipe. We found it as the mud was washed away from a sample. It is in excellent condition considering its journey to seabed at some unknown point in the past and its very recent return to the surface. We don’t know much about it but it certainly looks old so we have been wondering what the story of the pipe might be; perhaps a sailor dropped it over the side whilst setting the sails on a tall ship during an arduous Atlantic crossing or maybe on a calm day a passenger was tapping the tobacco out of the bowl on the rails and dropped it over the side. We think this must have been long before scientists started researching the deep seabed here at PAP, or perhaps it is much more recent, we don’t know. There are some markings on the pipe, most notably a leaf pattern on the bowl. Hopefully these markings will help provide some more information about it when we return home to Southampton at the end of the cruise.
Finding such an unusual insight into the past gives us the chance to reflect on our predecessors at sea who had far less technology and comfort than we have today on the modern Discovery. Perhaps more pertinent, it shows how long items made ashore and discarded by humans will persist in the deep sea.
We have been collecting sediment samples for a variety of coordinated ecological studies during this cruise, and these samples will add to the on-going time series studies at the PAP site. I am focusing on benthic microbiology and environmental DNA (eDNA) studies. The benthic communities at PAP experience episodic pulses of carbon-containing material originating from phytoplankton blooms at the surface. We are interested in understanding how microbial communities transform this material as it sinks and eventually settles on the sea floor. Since the majority of microbes cannot be cultured in the lab, we extract and process DNA from environmental samples to see who is there. We can also extract RNA from the same samples to determine which genes are being expressed at particular times and locations. This information tells us what the microbial communities are doing (metabolically) and which members are active.
We can also target animals by extracting DNA from water and sediment samples and amplifying and sequencing target genes out of the environment. All animals release DNA into the environment by shedding skin, releasing gametes, defecating, etc. We can detect this eDNA and use it to determine whether certain animals are present in the area. Since we have large databases of gene sequences from many animals, we can compare the environmental sequences to those in the database to match eDNA sequences to a particular organism. For very large areas that are very difficult to sample, like the deep-sea, developing automated technologies coupled with genetic monitoring techniques can help us to gather information about the animals present in an environment on a scale that we currently can’t achieve. These kinds of autonomous environmental DNA sniffers would be immensely helpful for cataloguing diversity and monitoring human impacts in marine protected areas. With the samples that we are collecting during this cruise, we will compare environmental genetic data to more classical methods of assessing these communities in order to get a handle on how variable our genetic estimates are compared to intensive classical ecological sampling. There are few deep-sea environments with such extensive historical ecological data as PAP, so this is an ideal setting for these types of studies.
I have also been taking tissue samples from various animals that we collect to perform phylogenetic analysis. Using the historical information contained in DNA, I will reconstruct the relationships among these animals. I’ve sampled holothurians (sea cucumbers), Asteroidea (sea stars), pyncogonids (sea spiders), munodopsis (squat lobsters), and Actiniaria (sea anemones). Working in conjunction with our morphological taxonomists, we will verify evolutionary relationships within these animal groups, identify new species, and ultimately add genetic information to the databases that we use to identify environmental sequences.
The National Oceanography Centre is a unique place that houses experts in taxonomy, ecology, evolution and genetics alongside engineers and our autonomous platform development teams allowing us to create a new generation of robotic ocean explorers. It will be interesting to see what the next 30 years at PAP will bring.
One day when I was cruising around the English Channel I happened to spot a curious looking ship floating on the water. It was pretty big and had all kinds of things dangling off the side which seemed to keep going up and down, in and out of the water…curious. I was already pretty far away from my favourite shoreline in Cornwall, but thought I would fly out just a little further to investigate…
What a hive of activity the ship was! Lots of those land folk scurrying around, back and forth, to and fro, and back and forth again. Some of them seemed to be trying to collect lots of the water in many, many tiny bottles – it didn’t seem like a very efficient way to do so, but probably a good thing as I wouldn’t like it if they collected the whole ocean! I was pretty cautious of these people to start with and hid in a corner, occasionally popping out to sneak a peak at what was going on. I watched curiously. What a bizarre bunch! During the day they seemed to be trying to fill as many of those small bottles as they could as if it was the most important thing in the world, but as it got dark everything seemed to change. Tired looking land folk were replaced by fresh faced land folk dressed in bright yellow! These didn’t seem to be interested in the water at all, and somehow managed to pull up mud from the sea! Mud! Where did they get that from? Cornwall was by now a long way away. I flew around a bit to try and work it out, but definitely no muddy shore in sight. Hmmm, perhaps that strange thing they put in the water was making the mud, yes that must be it, a mud maker. Sadly for me it didn’t seem to make many worms!
As time went on, I began to realise that these folks weren’t so scary and I was keen to be part of the action, so I decided to stay. The people were very nice to me, I was struggling to find my usual grub (the little puddles here just didn’t seem to have any worms in them) so they kindly gave me some snacks to keep me going, my particular favourite was grapes, nicely chopped up into bitesize pieces. Well, mostly they seemed to like me, all but that one curious lady, one of those mud loving night folk. Every time I tried to say hello to her and see what she was up to, she screamed and hid behind whatever object she could find. I tried my best to say hi and make friends, but there always seemed to be some obstacle in my path!
After a few days, I had fully settled into the swing of things and was starting to feel like one of the team. I’d make sure the deck was clear by circling around when they wanted to send that big bottle like object over the side, and often helped one of the guys in red suits who seemed to be wrestling some kind of giant coiled purple worm! I tried to taste a bit of it, but decided grapes were much better! To keep in shape, I flew laps around the ship every day before returning to my favourite spot near the entrance to the ship where my friends often hung out drinking something they called tea. I started to become one of the pack, everyone seemed to have a different nickname for me, Winston, Hamish, Horatio, Cyril, the list goes on.
They worked tirelessly night and day, all round the clock…they really seemed to love what they were doing. Some of them had made best friends with those giant water bottle things that they dunked in the water every day. That was particularly odd, they would dunk it in the water, bring it back up pretty quickly and then just leave it there as if they didn’t care anymore. But they would always return a couple of hours later, only to fill up another tiny bottle and let the rest of that precious water just drain away! Strange folk, they seemed awfully protective over these teenie tiny specs that had collected in the bottom of the bottle. I had a peak, but no tasty worms there either.
Right, must dash, it’s time for me to scurry around the deck and help the guys chuck those bottles in the water again. The action never stops here!
It’s 3am, the benthic (seafloor sediments) team is on deck of the RRS Discovery, anxiously awaiting the arrival of the Megacorer (sediment coring equipment) returning to the surface after a 4 hour journey to the seafloor and back. After descending 4850 m, the wire tension alerts us that the Megacorer has hit the seabed. Sea conditions are good, but the swell and winds have picked up, this movement may have caused a bad moment of contact between the Megacorer and the seafloor. We are anxious, because there is no way to know if the Megacorer fired successfully, and after the long wait, we may have empty tubes. The Megacorer is out of the water… and we are in luck! There is an audible cheer from the team as all corers have successfully fired.
However, long before this anxious wait for the Megacorer, there was a debate and decisions were made on what equipment would be the best for all samples. The seafloor at the Porcupine Abyssal Plain receives food (carbon) which originated at the surface as phytoplankton blooms and then has sunk down to the deep sea. The communities living here see huge fluctuations in food availability as seasons change, often it is feast or famine. To understand this link with surface processes to the seafloor, the PAP benthic team needs to obtain sediment for a number of different analyses: eDNA (traces of all DNA in the environment), micro-plastics (>5 mm plastic pieces), biomarkers (e.g. coloured pigments), meiofauna (microscopic animals), foraminifera (encrusting organisms) and macrofauna (tiny invertebrates like worms). In the past, boxcores were used to collect sediment for macrofauna and Mega (or multi) corers were used for all remaining analyses.
The debate itself has to do with the collection of macrofauna using Megacores versus boxcores. Outside of the world of benthic ecology you have probably never heard of this debate, however it impacts numerous disciplines. Since the 1970’s, the boxcorer has been the standard sampler for studies of deep-sea macrofauna. However, over the last decade, several studies have shown that using boxcorers negatively influences the data obtained and that alternatives, such as the Megacorer are a better option.
The boxcorer creates a “bow-wave” effect as it passes through the water column and collides with the seafloor. This influence on the organisms (and data collected) has been known for a long time but only recently calculated. Up to 50% of the animals from the top layer (1-3 cm where the density is highest) are lost, but importantly, this “bow effect” is not consistent among species. Making it impossible to tell what may have been lost from the sample. Another issue is in the quantitative handling of samples for later analyses. As a biologist, we are concerned with the number of different species within an area (diversity) and the number of individuals (abundances). This needs to be done in a consistent and measurable way to draw any conclusions about the ecosystem. Ideally, you want ‘slices’ of the seafloor sediments at different depths (0-1 cm, 1-3 cm… ) and then calculate the diversity and abundances.
The Megacorer is hydraulically dampened, meaning that top sediment layer is undisturbed, and therefore the fluffy phytodetritus (degraded remains of surface phytoplankton blooms) and surface fauna are intact. The real strength of the Megacorer, is that is allows a scientist to handle the sediment in a concise way. Each tube is 10 cm in diameter, it is easy to take slices at measured depths and then carry out analysis of the abundances of the fauna. The downside is that only a small area is sampled. This can be a problem in the abyssal depths (at PAP it is 4850 m) where the density of the animals is very low. You need to collect many cores to collect enough animals, and ship time is expensive. We need 16 Megacorer tubes to match the number of animals we would collect with one boxcore sample.
Also, a consideration is where long-term time-series data such as PAP are collected it raises the issue that if you change your sampling method, then you can no longer directly compare your historic data and modern data. However, there are two important points to be made: 1) technology changes and improves our ability to collect good quality samples. 2) the use of the Megacorer for macrofauna is not that new.
At the PAP, it is our Megacorer’s 20th birthday, it was the first of its kind, and has successfully collected macrofauna around the planet. Other science teams are now adapting it as the standard tool.
The surface buoy and a frame full of sensors were successfully deployed. Data from all the instruments will constantly update throughout the year. We can look at many years of data on our webpages at http://noc.ac.uk/pap
The dataset from the PAP sustained observatory is a huge resource that can be used to look at processes that happen on different time scales. With the meteorological data collected from the buoy and our biogeochemical sensors we can look at short-term events such as storms and their effect on the mixing of nutrients up to the surface through the winter. We can see how phytoplankton growth changes through the spring and summer (using the chlorophyll fluorescence and light data). Or look at year-to-year changes in the mixing and supply of nutrients that drive the growth of phytoplankton.
I am especially interested in using surface sensors to look at the exchange of gas between the atmosphere and ocean. The surface ocean takes up a large proportion of the carbon dioxide produced, especially in a productive region like this. The carbon dioxide increase in seawater is followed closely by a decrease in pH known as ‘ocean acidification’. The pH of seawater is not acidic, it is about 8.1, but there is a trend to lower pH. We can use open ocean observatories like PAP to study these trends.
As well as deploying the sensors we have collected many water samples from the surface to full depth. Some of these, such as dissolved oxygen and chlorophyll, are being analyzed using the equipment we set up onboard. Others we will take back to analyze in the laboratories ashore. We can check up on our sensors this way and also fill in the gaps for the many things sensors cannot (as yet) measure.
Highlights on this trip have been seeing the full range of activities possible on a short cruise, from the surface plankton sampling to the muddy depths. Also seeing the dolphins racing alongside the ship, meeting the visiting curlews. Oh, and the food!