Discovery leaving Southampton for cruise DY021

By Louis Byrne, British Oceanographic Data Centre, NOC

RRS Discovery docked in Southampton. Picture taken by Amber Annett

After a week of setting up where all manner of frames, sensors, analysers, buoys, containers, chemicals, supermassive autonomous vehicles and an array of bedraggled looking scientists have boarded the RRS Discovery it was finally time to leave the port of Southampton for the open sea!

Breakfast on the morning of departure is at 7:30 and is followed by a safety briefing and familiarisation before departure at 1015. Rumour had it that we were leaving port into fairly rough seas, and once we have escaped the shelter of Southampton docks those rumours turn out to be correct.  It is a bit of a baptism of fire for some of the scientists on board and I think many are feeling a little queasy. 

Before our stomachs have had time to settle it is time to practice the muster, which is similar to a fire drill, however once at the assembly point everyone is required to put on a life jacket, enter an orange life boat and consider how rubbish it would be if we actually had to use it,  52 people in a small orange box with no toilet, one small hatch for air and fishing rods which aren’t actually provided for us to catch fish, but to give us the psychological illusion that there actually something we can actually do ourselves to improve our chances of survival as we get tossed around like an orange cork in a gigantic tumble dryer (if today’s  seas are anything to go by). 

Mini Stable (left) and autosub (right) on deck departing Southampton. Picture taken by Richard Cooke, National Oceanography Centre, Liverpool.

The original plan was to conduct some equipment trials at a long term observation station near Plymouth called E1, however due to the state of the seas we’ll be skipping the trials station and heading straight out to the Celtic Sea and to site A, which we are expected to reach at 9PM tomorrow (Monday). As there is little left to do today a few of us hit the bar and tv room, just in time to watch England get mauled by Ireland in the 6 nations. All in all it’s been a pretty rough day.  Just before signing off there is time for a bonus question:

Who set off the Discovery’s fire alarm the night before departure by spraying deodorant in their cabin? Answer in the next blog.

Shelf Seas Biogeochemistry – A short introduction

By Louis Byrne, British Oceanographic Data Centre, NOC

We woke up on Monday to a sea which was perhaps even worse than Sunday. We were still a fair distance away from site A and were not scheduled to reach site A till approximately 2100 Monday evening. Due to the rough seas I spent the majority of the day hugging my toilet bowl, but not before making the rookie mistake of blocking my sink with the remains of my breakfast, which Geoff the Steward was not too happy about.  Due to a day spent in transit not much happened, and due to my sea-sickness I was not around to see what did, therefore I thought it would be a good time to introduce the reason why we’re rushing towards the Celtic Sea at a slow and steady speed of seven knots.

Although shelf seas make up only 5% of the ocean surface, they have been estimated to be the most valuable biome on earth, with high levels of primary productivity supporting diverse ecosystems. High concentrations of nutrients support the growth of phytoplankton, which are single celled marine organisms that photosynthesise like plants on land. Like plants on land, Phytoplankton are the base of the marine food web and they provide a diverse food source for many marine creatures, such as zooplankton.
 

Phytoplankton are the foundation of the oceanic food chain.

Zooplankton are tiny marine animals which are food for fish and countless other marine organisms, that are then in turn eaten by others. It is in this way that the sun’s energy fixed by phytoplankton on the surface of the water column is distributed throughout the marine ecosystem, underpinning more than 90% of global fisheries and offering many other important ecosystem services.

In addition to supporting the entire marine food web, the photosynthesis carried out by phytoplankton also removes significant amounts of carbon dioxide from our atmosphere.  Although tiny, phytoplankton have a disproportionately massive effect on our atmosphere, and are responsible for creating as much as half of the oxygen that we breathe, removing an equally large amount of carbon dioxide as they do it. Some of the carbon extracted by the phytoplankton will sink to the sea floor and be stored in the sediments (often for thousands of years!), reducing the overall concentration of carbon dioxide in our atmosphere.

In order for the shelf seas to sustain these high levels of production, the phytoplankton must be supplied with nutrients, but where do these nutrients come from? It is the need for us to better understand the role of shelf seas in the global nutrient cycle, how this supply of nutrients determines the shelf’s primary and secondary production and how this affects other processes such as carbon storage which has led to the Shelf Seas Biogeochemistry programme.

At 2100 on Monday night we reached site A and decided that the seas were too rough to sample that night. Therefore, an 0600 hours CTD cast was scheduled for the following morning, and we were hopeful that our cruise was about to get its first piece of data.

For those of you wishing to see the answer to yesterday’s question, the answer is Richard Cooke of the National Oceanography Centre, Liverpool.

Expeditions of Discovery find the secrets of the shelf seas

Shelf Sea Biogeochemistry and the recent pelagic cruise (DY018) were featured in an article 'The secrets of the shelf seas – one of Earth’s most important ecosystems' by The Observer newspaper. 

The sea off our coasts teems with microscopic life that breaks down the carbon dioxide we pump into the air. Now a series of expeditions aims to find out more.

Colony of salps floating under the RRS Discovery during DY018. Underwater photography courtesy of Claire Ostle (University of East Anglia).

Docked

Ocean research cruise blog of Jonathan Sharples

 

We finished up all of the sampling during yesterday afternoon, and headed in past the Needles lighthouse on the west corner of the Isle of Wight. The pilot was picked up just before Calshot Spit, and we steamed up Southampton Water. It was bitterly cold! Probably the coldest weather we had experienced all cruise.

The ship docked in Empress Dock, in front of the Oceanography Centre, just after 1700. As soon as the gangway was in place, and we’d got the announcement that the ship had been cleared by customs, off we all went – the entire science group headed off through the docks to the Platform Tavern.

And that’s it. A very busy morning ahead as we unload the ship, but normally we are able to get away by noon. The end of a very productive cruise, with remarkable weather allowing us to do a lot more than we expected.

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The Needles

Land sighted

Ocean research cruise blog of Jonathan Sharples 

 

We steamed along the south coast overnight, and at breakfast this morning we passed Lulworth Cove and then Swanage. There’s just one last bit of science left to do. We are crawling slowly into Poole Bay and Christchurch Bay, taking surface samples of seawater. Clare Davis, from the University of Liverpool, is processing these water samples for a couple of the Liverpool University PhD students. The students are researching the dispersion of organic matter from estuaries out into the ocean, and also looking at the relative supplies of nutrients from rivers and from the deep ocean to the shelf seas. These samples are also tying our work into another research project focussed on land catchments and river nutrients. Anouska Panton, a researcher working at the University of Southampton, will be carrying out fieldwork in Christchurch harbour today so that later we can link the data together with what we are collecting to get a broader picture of river-supplied nutrients and their fate in the autumnal shelf sea.

One important job we managed to clear yesterday was the cruise photo. We picked the right time for it, sat 20 miles off Plymouth with nice, sunny weather. Today wouldn’t have been as good – it’s windy and grey outside. But at least we can now see land, for the first time in three and a half weeks.

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DY018 people

Visitng E1

Ocean research cruise blog of Jonathan Sharples

 

We arrived at position E1, south of the Eddystone, at about 0600. This is a site regularly sampled by the Plymouth Marine Laboratory (PML), generally about once per month but more frequently recently in collaboration with the project we are working on. Scientists and technical staff at PML maintain a data-gathering buoy out here. We carried out 6 seabed cores this morning, and were then met by the two PML boats. Coring the seabed from the PML boats is difficult, so they are very happy that we can stop here for a few hours to collect these samples for them, and transfer the samples to their boats to be taken back to PML and analysed.

pml explorer alonside

It was also our last CTD profile here at E1, at 0630. And it was fully mixed from the surface down to the seabed! Not too surprising as E1 is fairly close to the permanently-mixed water of the English Channel, and it’s only 75 metres deep. So we expect it to become mixed relatively early in autumn. We’ll do some more zooplankton nets this afternoon – Sari Giering is keen to have a lst go at collecting some more of the trichodesmium nitrogen-fixing bacteria, this time to get some samples for some DNA analysis.

Nick shows us the engine room

The clear-up of the labs has begun. The ship has a fast turn-around in Southampton, so we need to be ready when we arrive tomorrow evening to get some of the larger bits of equipment and container labs off. Some of the scientists took some time to go on a tour of the ship’s engines. Nick, the 2nd enginner, showed us around those normally hidden parts of the ship that power us through the water, provide fine-control of the ship’s position when we are working a station, as well as powering all our instruments, making our freshwater, ventilating the ship, and treating the sewerage. Remember there are about 50 people living on this 100m-long metal box for several weeks at a time: the ship is like a small, very independent village.

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Last of the Snowcatchers

Ocean research cruise blog of Jonathan Sharples

 

The weather eased off very quickly during yesterday, ending up with winds less than 10 knots. We arrived back at the mooring site in the central Celtic Sea and began a last set of sample collection and experiments, mainly focused on the zooplankton and on the particles settling down through the water.

The Marine Snowcatcher worked well. We’re getting better at operating it, though we think that is mainly a result of calmer weather. We are still not completely convinced that the deeper samples collected with the Snowcatcher are always from the depth that we think we have triggered the catcher to shut – if the ship is pitching at all it’s possible for the catcher to shut while it is being lowered through the water to the sample depth. However, we can solve that by collecting nutrient and salt samples from the catcher and comparing those with what we see in the CTD data to tell us the depth that the Snowcatcher sample was really taken.

last snowcatcher

 
Elena Garcia-Martin, from the University of East Anglia, and Darren Clark, from the Plymouth Marine Laboratory, are working on last these samples. They are measuring how the different sizes of particles, and their different components (carbon, nitrogen phosphorus), and being recycled by bacteria. The deep bacteria are acclimatised to darkness, so they have to be collected after sunset, extracted from the Snowcatcher carefully so that they don’t get fried by the ship’s deck lights, and taken into a darkroom laboratory for analysis.

Elena and Clare sampling particles

One last set of measurements to do here this morning, then we head off towards Plymouth. Should arrive just south of the Eddystone lighthouse about 0600 tomorrow.

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Glorious mud

Ocean research cruise blog of Jonathan Sharples

 

We reached the northern-most station by about 7 pm last night. There was great excitement watching the data from the CTD as it was lowered through the water. If any site was going to have reached the fully mixed winter state by now, it was going to be this one. About a dozen of the scientists were crowded around the CTD computer in the main lab, willing the temperature of the water to stay the same as the CTD went lower. But there was a collective groan as a thermocline appeared at 66 metres below the surface. It’s a bit disappointing that we are not going to be out here to see that final transition to the winter mixed water, but I’m pleased that I appear to have generated so much enthusiasm for shelf sea physics amongst the crowd of biogeochemists on board.

box corer

Matthew Bone, from the University of East Anglia, is interested in the muddy seabed at this site. We collected 4 cores from the seabed using a large “box corer”. This is a large steel cylinder that is lowered down onto the seabed, and then pushed into the seabed by the large weights above it. When it is pulled out, a core of the seabed mud is held within the cylinder and brought on board. Matt has been working on measuring how the mud releases nutrients back into the water. This muddy area of seabed, in an area called the Celtic Deep, is an important fishing ground for a scampi that lives on, and burrows into, the mud. At one point last night the radar was showing 12 fishing vessels around us, within a distance of about 10 miles. One of the cores caught a scampi. It seems happy enough in the lab, busily shifting mud around the top of the core and tending a burrow. The plan is to release it later today when we pass over another area where we have in the past seen scampi on the seabed.

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mephrops

A windy morning

Ocean research cruise blog of Jonathan Sharples

 

A bit of weather more typical of November today and last night. We finished over-the-side work at about 7 pm yesterday, with winds of about 40 knots about to make use of the iron-free CTD unfeasible. The wind has dropped a little this morning, 30 knots of so, but the sea and wind are giving us a fairly good list to port as we steam between stations.

windy morning

We had to cancel the work planned for the first site this morning, as a fishing boat close by suddenly decided that the spot we had been sat on all night was exactly where he needed to drag his nets. Once we’d cleared away from where the fishing was, the winch that lowers the iron-free CTD suddenly threw us an error. The ship’s engineers are working on it now, and I decided that we’d lost enough time waiting around that site and should just head up to the next one. Timing is a bit tight today. Ideally we need to get up to our most northerly site by about 6 pm so that we can do some seabed sampling up to about midnight. That should give us time to head back for one last set of measurements back at the mooring site before we start to make our way into the English Channel.

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Heading north

Ocean research cruise blog of Jonathan Sharples

 

Another successful day yesterday, with the wirewalker mooring and both of the gliders recovered very quickly. Jo Hopkins immediately removed all of the instruments from the wirewalker, and strapped them to the CTD ready for the next time we lowered it through the water. This allows Jo to calibrate the wirewalker data with the data collected by the CTD, with the CTD data all calibrated against analysis of samples we collect in the sample bottles. Every profile of data we collect through the water with the CTD involves samples being collected for salt concentration, dissolved oxygen and chlorophyll. These samples are analysed against known, internationally-recognised standards and lab techniques, so that we can calibrate the sensors on the CTD and estimate the error associated with their measurements. This is a vital part of any science: no other scientist would allow us to publish our results if we couldn’t demonstrate that our measurements achieved acceptable standards.

omg glider recovery

We can measure salt concentration to within about 2 thousandths of a gramme in 1 kg of seawater. We need to know salt to this level of accuracy because it has, along with temperature, a big influence on how dense the seawater is. The sea is always attempting to sort itself out so that less dense water floats above denser water, so knowing salt and temperature can tell us a lot about how the water will be moving. I’ve mentioned dissolved oxygen before in the context of Chata’s work – biology both produces oxygen (when the microbial plants are glowing) and consumes oxygen (when bacteria break down the organic matter), so accurate data on the oxygen in the water tells us a lot about how the biology is operating. Chlorophyll in the ocean is the same green stuff that you see in leaves and grass – the chemical that plants use to collect energy from sunlight. Chlorophyll is particularly good for plants that live in the ocean. Sunlight is absorbed very quickly as it passes downward from the sea surface. All of the red light from the sun is absorbed within the first 1 metre below the sea surface. Blue light travels the deepest in the sea, and chlorophyll is well suited to capturing energy from blue light. Clearly this is an advantage for the microbial plants in the sea, as they are mixed through the upper few 10s of metres and need to maximise their chances of collecting the sun’s energy. But why should land-based plants use chlorophyll when they don’t have the problem of metres of ocean absorbing the light? Photosynthesis first evolved in the ocean. Land-based plants haven’t bothered to evolve a form of photosynthesis more suited to life above the sea, instead they just highjacked the system that the ocean’s microbial plants had developed. Quite literally. At the heart of the photosynthesising biochemical machinery in every leaf lies a light-capturing system that can be genetically traced right back to photosynthesising marine bacteria.

Billy does the salts

We’ve started to head north through the Celtic Sea now, stopping every 25 km or so to lower the CTD through the water and collect more information. The wind has picked up, with about 25-30 knots now. The sea is looking rough, but it’ll take a few hours for the swell to pick up and start to move us about.

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November weather

Ocean research cruise blog of Jonathan Sharples

 

The remarkable weather continued yesterday as we continued a series of measurements and zooplankton nets next to the moorings. A couple of scientists were even spotted sunbathing between net hauls. The wind continued to drop, and the sea finally reached a glassy state by sunset. Pretty good for November in the Celtic Sea.

The winning picture of the salps in the process of releasing faecal material into the water is below: look at the streaks of back trailing from the curl of colonial salps in the lower left of the picture. Some of these salp groups are reaching lengths close to 2 metres.

chain of salps

salps cought pooing

 This morning just as the sun came up we carried out one vertical profile with the CTD just next to the wirewalker mooring. That will provide Jo Hopkins with vital data for her to calibrate the instruments on the mooring. We are now pulling up the wirewalker, and will then head off to collect the 2 gliders that neeed to come back with us. The glider “pilot” back at the Oceanography Centre has sent instructions to the gliders to meet as at a specific location, so the gliders will have dutifully reached that position this morning and will now be bobbing about on the surface waiting for us.

ctd at down

The weather is due to close in tomorrow, with 25-30 knots of wind expected from mid afternoon through to mid afternoon on Friday. But the longer term forecast is suggesting a return to these calm, sunny conditions. Feels strange for this time of year, but none of us are complaining.

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More jellies

Ocean research cruise blog of Jonathan Sharples

 

The children at Churchtown Primary School are I gather busy working on the questions we asked them about sinking salp poo. The zooplankton group on board are getting very excited about their results, and already planning the scientific papers that they want to write. We collected more of the zooplankton yesterday so that we can make better estimates of the rate at which they eat and the rate at which they release the faecal pellets. In an attempt to get an idea of what these delicate organisms look like in the ocean we attached a few waterproof cameras to the CTD, and lowered them into the sea surface to record pictures for half an hour or so. I set the challenge to get a picture of a jellyfish or salp in the process of releasing faecal pellets into the water. There was a clear winner (Clare Ostle, from the University of East Anglia), but she was working very early this morning and is currently in bed – so I’ll get the photo for tomorrow.

an interesting bucket of jellies

Meanwhile, to help the kids at Churchtown think about this problem, the picture below has some good examples of the salps (the long, tubular jellies, connected in spirals) and the tiny jellyfish. Another rally interesting organism in this photo can also be seen, just about. The photo looks like it has a fine sprinkling of sawdust in it. These are tiny colonies of a photosynthesising bacteria called trichodesmium. It’s special in the ocean because it is a nitrogen fixer – it is able to use nitrogen gas dissolved in seawater, rather than the form of inorganic nitrogen (nitrate) that most phytoplankton need. That means they can grow in areas where nitrate is in very low concentrations, such as the large areas of open ocean in the sub-tropics. Finding them here is odd, because there is enough nitrate around and so the trichodesmium should not have any advantage compared to other phytoplankton. I’ll find out a bit more about them for another blog entry.


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salps and tiny jellyfish

The importance of zooplankton poo

Ocean research cruise blog of Jonathan Sharples

 

At dawn this morning we reached the end of the iron sampling transect, crossing onto the edge of the continental shelf at a depth of about 250 metres. Quite a stunning sunrise, with flat calm seas. Not what you’d expect for November. The dreadful-looking forecast for the end of the week also appears to have dissipated, so we might be able to push our work further north into the Celtic Sea.

end of iron transect

We are about to head southeast for an hour or so, to return to the shelf edge site that we spent 3 days on earlier in the cruise. We need to repeat some of the Snowcatcher work there, and also the zooplankton biologists on board want to find some more salps and jellyfish to try out some experiments to determine how much they are eating and also what happens to the waste material that they excrete. I’ve asked the children at Churchtown Primary School in Southport to have a think about this problem – how quickly does a salp waste pellet (i.e. a salp poo) sink through the sea? It’s an important thing for us to know about. A fast sinking particle doesn’t give the bacteria in the water much time to breakdown the organic material before the pellet reaches the seabed. A slow-sinking pellet can be broken down into inorganic material before it reaches the seabed, and that inorganic material is then returned to the water where it is accessible to the phytoplankton. Also, sinking quickly means that the carbon in the pellet is removed from the ocean surface (and the atmosphere) very quickly – you could argue that the stability of Earth’s climate owes a great deal to zooplankton poo.

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Measuring growth of the microbes

Ocean research cruise blog of Jonathan Sharples

 

Yesterday started with another of our pre-dawn set of measurements. Fundamental biological measurements we need from these pre-dawn CTDs are how fast the microbial plants (the phytoplankton) are absorbing and using carbon and nutrients, and how fast the bacteria are growing by using the organic matter available in the water. Think of these as the two ends of a food chain, with the phytoplankton converting the inorganic elements into organic material, and the bacteria breaking down the organic material back into the inorganic. Between them we have the zooplankton, and other marine animals, eating the organic material provided by the phytoplankton, and in turn providing waste material that the bacteria use.

Radioisotope lab1

Measuring uptake of elements by phytoplankton and bacteria requires very careful laboratory work. The method involves using tiny quantities of radioisotopes of the elements we are interested in (carbon, nitrogen, phosphate, silicate) and incubating samples of seawater that have been treated with these isotopes. After a set period of time the sample is filtered to collect the phytoplankton or bacteria, and the activity of the samples counted to tell us how much of the element the organisms used. We have two laboratories dedicated to this work on the ship. Alex Poulton (National Oceanography Centre, Southampton) and Kyle Mayers (University of Southampton) are working in one to measure the phytoplankton rates. Sharon McNeill from the Scottish Association for Marine Science in Oban is dealing with the bacteria rates.
We steamed quickly over to the deep ocean side of the shelf edge yesterday afternoon, and at about 8 pm we started the second of our line of sample stations to measure iron in the seawater. This line started in a deep canyon, and we are working up the wall of the canyon back towards the continental shelf.

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Radioisotope lab2

22 November, 2014 08:49

Ocean research cruise blog of Jonathan Sharples

 

We had a very successful day yesterday – managed to get through all that was planned, plus most of what I’d planned for the next day as well. Deploying the moorings began shortly after 0800. This tends to be a long, careful process as the mooring wire is gradually unwound over the stern, instruments are clamped onto it at the planned depths, buoys are slotted in at key stages to hold it all up in the water, and then finally the 500 kg clump of chain is attached and dropped into the sea. By lunchtime we had deployed the long temperature/salt logger mooring and also the bedframe with the current meters. The second current meter mooring has been delayed until today, while the techs sort out an issue with the memory cards that it uses. That allowed us to go and hunt for the wandering wirewalker mooring and also the glider that we deployed when we first got here from Falmouth, but which has refused to dive.

Both the wirewalker and the glider have been sending us regular position information via a satellite link, which meant that finding them and getting them on board was very quick. We arrived back at the mooring site just after sunset, ready to do some more zooplankton work.

It’s a lovely day today – a glorious sunrise (complete with dolphins) and an almost flat sea. However, we’ve just heard that the long-term forecast is looking a little grim. A particularly nasty-looking low pressure system is due this side of the Atlantic next weekend. Forecasts that far out tend to be a little uncertain, but it’s worrying enough for us to think carefully about when we can get back to this site to recover the wirewalker and the 2 gliders that are here.

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