Shelf Sea Biogeochemistry blog

Showing posts with label Celtic Sea. Show all posts
Showing posts with label Celtic Sea. Show all posts

Saturday, 22 August 2015

Collecting images from the seafloor.

By Henry Ruhl

We have completed sediment core sampling at our four main study sites. This is a key achievement for the trip. We are now sampling one other site that allows us to cross-reference our findings with those of other studies and a long-term study station with the nickname Candyfloss. This site is closer to the continental shelf edge and open ocean than we have been for most of the trip. Marine life spotting has been good and we even laid eyes on the RRS James Cook about ten miles from us. The James Cook is researching life in the canyons that extend just beyond the shelf edge. We will soon return northward to for the more AUV deployments, the fourth deployment of the NOC lander, as well as a few other remaining tasks.

We are using the Autsub3 autonomous underwater vehicle (AUV) during our cruise to collect photographic images of the seafloor, as well as sonar-based images of the shape and texture of the seafloor. We have been running the AUV in a ‘mowing the lawn’ pattern of parallel lines that are about ~5km long. After checking our seafloor shape and texture mapping for any obstacles, we ‘fly’ the AUV as close as 2.5 meters from the seafloor to collect colour photographs in the moderately cloudy waters of the Celtic Sea.

The images will be geo-referenced, which effectively turns the photo into a map like you see in Google Earth. As you can see below, that 2.5 m height above the seafloor still gives us images that are very useful for determining the identity size, and location of all the observed images. This can provide a landscape scale view of the seafloor and its inhabitants, which we can then use to improve estimates of ecological and biogeochemical patterns and processes.

The seafloor and its inhabitants
AUV photographs are particularly useful in estimating the distribution of biomass of larger animals that are not sampled well by trawls or sediment cores. Observed animals include crabs, shrimps, and anemones as well as fish. The images above and below come from a Celtic Sea site where the seafloor is dominated by sandy mud.

The seafloor and its inhabitants

Monday, 10 August 2015

Measuring the metabolism of the seafloor

By  Megan Williams, National Oceanography Centre

Today we recovered our benthic lander. The frame had been deployed for two days and has nine instruments measuring a range of parameters including water velocity, nutrients, suspended sediment, sediment particle sizes, and benthic oxygen consumption. Our first deployment was at a site with sandy sediments.

Recovery of the benthic lander 

 The steps toward our first recovery were many (see pictures): after driving the instruments and frame down from the National Oceanography Centre in Liverpool to our sister location in Southampton, we built the frame and started attaching instruments, batteries, and routing cables. When the frame was in a state it could be moved (with fragile instruments not yet installed), the frame was driven to the mobilization dock and loaded onto the RRS Discovery. Once on the ship, we could install the fragile water sampler (which will be used for nutrients and suspended sediment measurements) and the eddy correlation system (which makes fast oxygen and velocity measurements near the bed). The eddy correlation system measures subtle turbulent currents (eddies) just above the seafloor with both up and downward elements as they move past the sensor as swirls of water 'rolling' over the seabed. The sum of the upward (positive) and downward (negative) movement of dissolved oxygen gives a measure of how much oxygen the seafloor is using (i.e. the metabolism of the seafloor).

With a planned deployment time, we programmed instruments to start, did last minute calibrations, and set up the mooring. The frame was then slowly lowered 100 meters (m) to the sea bed, a ground line was set out, and a weight and buoy are connected 300 m away so as to not interfere with measurements.

All has gone well so far! We have the frame back on the ship this afternoon. We have now started to collect all the data off the lander, changing batteries, and preparing for another deployment of the instruments at a site with muddy sediment.

Wednesday, 15 July 2015

Call of Duty - Receiving a distress call

This week we were all reminded that RRS Discovery is more than just a research ship. On the open ocean, every vessel has a responsibility to play their part in the safety of the rest of the sea-going community.

Sampling activities at our first process station; Central Celtic Sea (CCS), were drawing to a close. All on board were starting to get into the swing of things. Most operations had run smoothly so far, including two pre-dawn sampling points, which at this time of year begin at 02.00 am!

At approximately 13.00 pm many scientists and technicians were on deck sampling seawater from the midday CTD; the piece of equipment which is deployed over the side of the ship to collect water from many different depths. Although sampling at CCS was not yet complete we noticed the ships engines rumble to life and the ship beginning to move. Soon after, Captain Jo appeared on deck with some somewhat startling news, at least for those of us who are not seasoned seamen.

RRS Discovery had received a distress call. The hull of an upturned vessel had been sighted from an aircraft, and we were in close vicinity and were required to respond immediately. The steam west to the site of the incident took approximately 3 hours, and it was all eyes on deck to keep a look out for anything unusual. Needless to say the atmosphere was tense, but the crew were incredibly calm and professional.

Cargo Ship and spotter plane look on as the boat from Discovery investigates
upturned hull.

When recovered Goose Barnacles indicate that the rusty old open boat has
clearly been at sea for a considerable time!

At around 16.00 we spotted a tiny brownish speck bobbing in the swell; the hull of a very small upturned boat. A light aircraft from the Irish coast guard was surveying from above, and a large container ship had reached the scene first, but neither had the means to move in for a closer look. 

With a readily deployable rib, RRS Discovery is better prepared than most vessels for the situation. Three brave crew members rose to the challenge of boarding the rib; 2nd Officer Vanessa, 3rd Engineer Angus and Petty Officer Willie. Watched anxiously by the rest of us they motored out to make an inspection, where to everyone’s great relief they found that the boat had clearly been adrift for quite some time, and was not a recent capsize. It was reddish-orange with rust, spattered with white bird poo, and hundreds of barnacles clung to its submerged surfaces. Some skilful manoeuvring by both the crew on the rib and on board the Discovery brought the old wreck alongside, and it was carefully winched aboard, in order that it would not cause an alarm to be raised in the future. The biologists among us ogled the stalked goose barnacles; beautiful yet slightly repulsive as their fleshy parts struggled and groped in vain for cool seawater. Meanwhile, the trace metal group shuddered at the amount of rust on the deck, and gave it a wide berth. 

The boat has been carefully stowed atop Alex and Chris’s container lab. They look forward to the stench of rot that will inevitably ensue if the sun decides to make an appearance.

Sunday, 12 July 2015

SSB Cruise DY033: Leaving Southampton

This is first blog entry from Cruise DY033, which is the latest in the series of Shelf Sea Biogeochemistry (SSB) cruises. My name is Mark Moore and I am the principal scientist on this final pelagic focused cruise of the SSB programme.

We are all excited to see what has been happening since the last pelagic cruise in spring and will be looking forward to finding out how the characteristics of the water column have developed following the spring phytoplankton bloom, alongside performing a whole series of measurements and experiments aimed at developing a better understanding of what is going on in the post bloom summer period.

I was really impressed with how smoothly mobilisation for the cruise went.

The RRS Discovery leaving port in Southampton

Thanks to the hard work of all the scientists and crew, all the equipment was loaded, boxes unpacked and instruments set up in just 2 days, partly reflecting the fact that many of the people on board are now very well rehearsed having been on a series of these cruises. Indeed, I personally feel a bit like the newcomer, this being my first cruise within the SSB programme. So I am looking forward to finally being able to ‘get wet’ and be involved in the at sea work. The cruise is also a bit of a personal journey for me as we will be working in the Celtic Sea where I performed much of my PhD work (quite a few years ago now…).

Having left Southampton on Saturday evening (see picture), we have now transited down through the English Channel and are on route to our first working area around our array of moorings, many of which have been in place for more than 18 months collecting unique data which will form a central part of the programme. Although we already have a few underway systems running and recording data, the major science operations will commence early tomorrow with us adding some additional shorter duration moorings to the array alongside the deployment of some gliders.

Wednesday, 15 April 2015

Spring has sprung - here comes the bloom

Alex Poulton, National Oceanography Centre

After two weeks in the Celtic Sea we are seeing clear signs that the spring bloom has truly begun - nutrients are declining whilst levels of the pigment chlorophyll, used by phytoplankton for photosynthesis, are steadily rising. 

Just how green the water is at present (slightly cheating as this is a pigment extract rather than seawater). Photo: Chata Seguro.

The bloom appears to be patchy across the Celtic Sea; from the shelf edge where the bloom has not started to show strongly yet, to the central Celtic Sea (where our Candyfloss site is) where small phytoplankton are actively growing, to the northern Celtic Sea where we saw huge diatoms (images below) - a type of phytoplankton which often characterises blooms and productive waters - which were at least a hundred times larger than anything we have seen so far. 

Diatoms and zooplankton seen under the microscope. Photo: Chata Seguro.

A close up of one of the large diatoms we saw in the NE Celtic Sea. Photo: Chata Seguro. 

As the nutrient levels continue to decline we are keen to see what happens within the phytoplankton community: will there be a clear progression from large cells to smaller cells which needs less nutrients for growth, will the diatoms be succeeded by another phytoplankton group? How these changes are reflected in the rest of the ecosystem is a key question we will address over the next two weeks. For example, how will changes in which type of phytoplankton is present influence the different nutrients needed for their growth (nitrogen, phosphorus, silica), and will we see changes in the dominant types of zooplankton (tiny animals that eat the phytoplankton) across the Celtic Sea.

The ever present fog viewed from the bow of the RRS Discovery. Photo: Chata Seguro.

Though the bloom has arrived, we have lost the sun - a dense sea fog has descended on us over the last few days which means we can only see a hundred to two hundred metres in any direction (see image). The eerie silence that this has brought to the ship is broken up at regular intervals by the ear shattering sound of the ships horn announcing our presence. If the spring bloom didn’t know we were here before, you can be sure that it does now.

Monday, 13 April 2015

The breath of the ocean

My name is Jose Lozano and I am a PhD student from the University of Vigo, Spain. In this cruise (DY029), I work with  Elena Garcia, post-doc at the University of East Anglia, taking samples and doing  measurements of oxygen (O2) respiration in the Celtic Sea (Candyfloss) by using different methods, Optodes (optical sensor devices, which is designed to measure absolute oxygen concentration and % saturation), Electron Transport System and Winkler (a test used to determine the concentration of dissolved oxygen in water samples).

Net community production (NCP) is a measure of the net amount of carbon removed from the atmosphere, which represents the difference between Gross Primary Production (carried out by phytoplankton through the photosynthesis) and Dark Community Respiration (from both phyto and zooplankton). Plankton found in the world’s oceans are crucial to much of life on Earth. They are the foundation of the bountiful marine food web, produce half the world’s oxygen and suck up harmful carbon dioxide.  It is therefore vital for scientists to closely observe the oceanographic and biological variables related with these little buoyant organisms, temperature, nutrient content, light extinction or partial pressure existing in the water column.

During the cruise we have very busy schedules, not only the scientists but also the crew and  the technicians. They all work constantly, making the practice of science much easier, by cleaning, cooking, creating tools, or fixing devices. We, the scientists, couldn't make it without their support.

Dolphins, Photo: Jose Lozano

When you spend 24 hours a day in an oceanographic vessel, even in hours of rest, you feel very tempted to go on deck to chill out and breathe the fresh air at the stern. In a good day you can feel the ocean breathing gently and musically through the waves, the cool wind blowing on your face, you can observe the wildlife, the terns and the gannets flying over your head and families of common dolphins jumping playful just few meters away from the vessel. You can even see some land animals, such as owls, garden birds or little spiders, which are travelling with us on the ship. All these organisms, from the smallest diatom to the biggest marine mammal, breathe oxygen (though in the case of archaea or bacteria, other molecules may be used) in order to obtain energy from organic matter, so to be able to keep going.

Sandwich tern. Photo: Jose Lozano

Tuesday, 10 March 2015

Springtime phytoplankton blooms in the Celtic Sea

Louis Byrne, British Oceanographic Data Centre, NOC

The seasonal changes in the Celtic Sea primarily revolve around the development of water column stratification in spring and when it breaks down in late summer to early autumn.  Right now in March, the Celtic Sea is fully mixed, however with the days getting longer and warmer (we hope), the surface of the Celtic Sea is also warming. As the surface warms its density decreases and the water becomes lighter compared to the colder waters below which don’t have access to the suns heat. (Fig 1.) To help watch for these changes we have a daily set of sea surface chlorophyll and temperature satellite images sent from the NEODAAS team at PML to the ship, and any developments of blooms and changes to the temperature can be seen as they occur.

Fig. 1: Temperature profiles in the mid latitudes in the ocean. Dashed (- - - -) line is for the winter and the continuous line for the summer season

This will eventually result in the creation of two distinct bodies of water, with a warm surface layer resting above a colder layer below, much like a cocktail which often have two or three coloured layers sitting on top of one another.

As well as causing the onset in stratification, the increase in temperature and sunlight also causes a truly massive increase in the number of phytoplankton in an event known as a plankton bloom [many plankton blooms are so large they can be seen from space! (see Fig.2)]. This results in a feeding frenzy as zooplankton (Fig. 3) numbers surge and they are in turn eaten by other organisms, passing the energy down the food web.

Fig. 2: Plankton Bloom in the Celtic Sea. Captured by the Envisat's Medium Resolution Imaging Spectrometer (MERIS) on 23 May 2010. Credits ESA

The phytoplankton bloom starts just before the onset of stratification, and then continues in the surface layer as the water there is warmer and receives much more sunlight. Eventually the phytoplankton will use all of the nutrients available in the surface layer and most of the plankton will die off. When this happens their cells will fall through the water column, causing a large increase in the biological material available on the seabed.

"Copepodkils". Licensed under CC BY-SA 3.0 via Wikimedia Commons -
When stratification breaks down at the end of summer, the water column in the Celtic Sea is again fully mixed. The bottom layer of water is still nutrient rich and these nutrients are also mixed into the surface of the water column, and become available for photosynthesis. This causes a smaller phytoplankton bloom at the end of summer before the days darken, and the cycle is complete.

Thursday, 27 November 2014

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.

original post 

Monday, 24 November 2014

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.

Original post 

Friday, 21 November 2014

21 November, 2014 09:05

Ocean research cruise blog of Jonathan Sharples


We arrived at the central Celtic Sea mooring site yesterday at 0930. Recovering the moorings was delayed a couple of hours while we waited for the wind to drop a little, but we began pulling them out of the sea shortly after lunch.

We have a fairly complex array of instruments on the moorings out here. There’s a weather buoy, provided to our project by the UK Met Office, plus a Cefas Smartbuoy that samples the surface biology and chemistry. The Met Office buoy doesn’t need servicing – they are designed to stay at sea sending back weather information for about 2 years. The Cefas buoy is looked after by Cefas scientists also working on this project. That leaves 3 other components that we need to service. The first mooring is a vertical line of acoustic current meters, anchored to the seabed and stretched upward by large buoys. These current meters are being used to measure turbulence in the sea, which allows us to calculate the supplies of nutrients towards the sea surface and how carbon is being mixed downward.

curretn meter buoy recovery
The second mooring is a relatively simple steel frame containing two acoustic current meters; this frame sits on the seabed, with the current meters looking upward and every 5 minutes measuring the flow of water in a series of 4 metre thick layers throughout the entire depth. Finally, the most complex of the moorings is a line holding about 25 temperature and salt loggers, anchored to the seabed and stretched up towards the sea surface by several buoys. These loggers, sampling every 1 minute, show us how stratified the water is, where in the water the thermocline is, and also if there are any waves running along the thermocline. All 3 moorings came up OK, though the string of loggers popped up about 1 km away from where we expected it to appear, requiring a bit of nifty ship manoeuvring by the captain to grab the mooring before it drifted onto the Cefas buoy. Once everything was on board, the National Marine Facilities engineers, along with Jo Hopkins and Chris Balfour from the Oceanography Centre in Liverpool, downloaded data, re-batteried instruments, and got the new mooring wires wrapped onto the winches ready for deployment.

Original post 
bedframe recovery

Sunday, 23 March 2014

Collecting mud at Celtic Sea

Deploying Cefas lander - 23 March 2014

Mud from Benthic D site - 23 March 2014

Day grab for collecting mud! -23 March 2014