Shelf Sea Biogeochemistry blog

Showing posts with label RRS Discovery. Show all posts
Showing posts with label RRS Discovery. Show all posts

Sunday 30 August 2015

Working on the night shift

The scientists on RRS Discovery work all hours.  The ship is expensive to run and the Shelf Seas Biogeochemistry (SSB) Project has a lot of different tasks to achieve and it would not be possible to do this without working 24 hours a day.

What this means is that a small fraction of the scientists and crew on board need to adjust to working during the night. The shift that I have been allocated runs from 6 pm to 6 am. Getting into the swing of it is hard as your body clock adjusts but this is the third cruise in this project where I have been asked to work the night shift so I am getting used to it.  There are a few downsides: we miss all lunches and most breakfasts (although food is left out for us), we don’t see that much sunlight, and everyone’s day finishes as ours begins but there are lots of positives.

1.-   Sunset

Sunsets at sea are spectacular things.  The air is clear, the sky turns multi-coloured and the light reflects off the clouds. 

A spectacular sunset.
 2.- The big fauna comes out at night

 A lot of the larger creatures like the cover of darkness. So far on this cruise we’ve seen two different types of shark, a sunfish, dolphins, a whale, garfish and many jellyfish. A lot of the fauna get attracted to the lights on the boat that shine on the water while we are working. This means that as they approach the boat they are easy to spot. We regularly watch dolphins play around our sediment corer as it hits the water.

3.- The lab is quieter
The controlled temperature laboratory we use on board is possibly the busiest part of the ship.  It is a small lab in the middle of the ship where we keep the sediment we collect that is kept at the same temperature as the bottom of the sea. There are ten people working in there and bench and floor space is very limited.  All the space that will be used is planned out months in advance but when lots of people are working in there it can become very cramped. During the night shift the majority of those who use the lab are asleep so we get the chance to work knowing we won’t be in anyone’s way.

4.- Getting involved with everyone’s work
Because there are so few people working at night we all help to collect each other’s samples.  Over the three cruises I have had the chance to trawl for epibenthic megafauna (looking for large rarer invertebrates that live on the sediment surface), use a sediment profile imager (SPI) to make cross section images of the sediment water interface and helped deploy a large in situ flume (a device that sits on the seabed and creates a current that runs in a circle to look at how the mud and sand behave under different conditions).

SPI camera,
5.- Snacktime
The kitchen does not run 24 hours, so when we work nights there is no lunch put on. We eat dinner for breakfast and breakfast for dinner.  You can get lunch put aside but sometimes it’s more fun to create snacks from the leftovers of dinner, toast and buffet bar. Salad mountains, rum and raisin ice-cream granola, peanut butter, jam, banana and nutella sandwiches, potato salad baps, and anything you fancy.

6.- Sunrise
The sunrises are as spectacular as the sunsets, with the added knowledge that the nights work is almost over and it’s nearly time for bed as everyone else gets up.

Tuesday 18 August 2015

36 years of working on Discovery

By Peter Statham
Ocean and Earth Science, University of Southampton

When I first set foot on the old Royal Research Ship Discovery in 1979 in Cape Town I had little idea that in 2015 I would be on the Discovery once again but now on the most recent version of the vessel to carry this famous name. 

I am interested in the chemistry of the ocean and how chemical processes affect the biology and other parts of the marine system. This aspect of oceanography is important in terms of understanding how the sea works and can be impacted by climate change. 

On this trip we are studying where the essential nutrient iron comes from on the shelf and how it may move away into the open ocean.  In some areas the element is at such low concentrations that it limits plant growth and thus impacts ecosystems, so it is important to know where it comes from, and one potentially important source are the edges of shelf seas. 

Launching a glider from Discovery. Gliders move up and down through the water by altering their density and “glide” on their wings from one location to another in the upper ocean, whilst collecting data that is sent by satellite to shore when it is at the surface. This new model has a small propeller to help it occasionally overcome strong currents.
Whilst frequently demanding with long working hours I always enjoy the times at sea with the wide range of people on board, the constant challenges to be dealt with and the buzz when a long planned experiment finally works out.  Whilst new techniques such as satellites and gliders are developing rapidly, ships are still essential tools in the study of the oceans. Discovery is a world-class research platform for UK marine science that will support our new generation of oceanographers into the future.

Monday 17 August 2015

The animals on the seafloor of the Celtic Sea

Yesterday we recovered some nice trawls from the sandy site. We also managed to get some images of the animals that live on the seafloor of the Celtic Sea, which is about eighty miles north by northwest of Land's End.



Ophiuroid_brittle star

Paguroidea_Hermit crab



Echinoid_ Sea Urchin

We've now finished most of the sediment sampling work at both our muddy and sandy sites. Tomorrow will likely be a busy day as we expect to pick up some lander, buoy and mooring equipment.

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.

Friday 24 July 2015

Diagnosing Transmission Problems

By  Julie Wood, NMF Technician

Thursday marked the end of the second iron transect of the cruise and for the technicians, it certainly was an eventful transect.

As technicians, one of the most important pieces of equipment we are responsible for is the CTD. This is a short name for the large metal frame carrying conductivity, temperature and pressure (measuring depth) sensors along with a whole suite of other instruments such as sensors to measure current, turbidity and fluorescence. It also carries large water bottles which can capture water from any depth visited.

On this cruise, we have two CTDs. One is a normal stainless steel frame with 20L bottles, while the other is made of titanium with 10L water bottles. Apart from titanium, this second frame contains as little metal as possible because it is used to collect water for investigating trace metals. The 10L water bottles are kept in the trace metal laboratory on the ship. Before each trace metal CTD, they are individually carried out to the frame to limit exposure to the metal on the ship.
Clean Sampling room with bottles

The CTD is lowered in the water by a wire of over 7000m long stored on a large drum. The cabling from the CTD is joined to the wire by an electrical splice near the mechanical termination (this is the conical part between the wire and the CTD frame). This allows real-time data from the sensors to be transmitted from the CTD along the wire. This means we can see profiles of ocean parameters while the CTD is in the water which can help the scientist select the depths that they would like to take water samples.

The first CTD of the iron transect was to commence on Tuesday morning at around 4am. Nick and Tom, the technicians on duty, prepared the CTD as usual for its journey down to 2400m. At around 1050m, the sensor readings indicated that the communications between the deck computer unit and the CTD had failed. The CTD was brought back on deck and the sensor readings all returned to normal. A second deployment was attempted for diagnostic purposes, however once the CTD was back in the water, the sensor readings stopped again confirming that there was a problem with the termination.
Julie and Dougal working on the CTD

The senior technician, Dougal, was called to assist in diagnosing and rectifying the fault. Based on the observations, initially 2m of cable was removed from the end of the wire. However, when the wire was tested, the electrical characteristics were found to be unsatisfactory. A further 400m of wire was removed and then the wire performed perfectly.

With assistance from Andy, the mechanical engineer, and Steve from the Glider group, the team started to build a new termination which is time consuming and requires attention to detail. A new mechanical termination needed to be put on along with a new electrical splice in order to communicate with the sensors. Both activities required concentration to ensure they were correctly and safely attached.

The final test, the load test, was performed on the new termination. This involved attaching the termination to the deck and progressively applying increasing force to a final weight of 1.2 tonnes. This ensures that it is well able to hold the CTD frame.

By 7:30pm, the titanium CTD was back in the water. Despite passing the load test, the first deployment following a new termination is always a nervous affair. The frame safely made it down to 2430m, just 20m shy of the bottom. All bottles were filled successfully with recovery of the CTD at 9:15pm.

The Metal Free CTD Winch

Unfortunately, this incident did caused delay to the science program. Some careful re-jigging of the timetable by the Principle Scientist meant that the iron line was still completed successfully. We deployed the titanium CTD at seven stations along the iron transect.

The final titanium CTD was retrieved on Thursday at 2pm, amid much excitement from the team of iron scientists collecting these water samples. With a completed transect, we hope they find lots of interesting features about iron on the shelf.