Studying radium concentrations in the muddy sendiments off the north west coast of Cornwall.

On Tuesday we continued with our coring as well as performing a few more CTDs.  Amber Annett (Edinburgh University) is taking water column samples from the CTD and sediment samples from an instrument called a megacorer, in order to study radium concentrations in the sediment and the overlying water, and she has written the following blog piece about her work.

Naturally occurring radium is a very useful element for studying many different shelf sea processes. This is because it is radioactive (no, not that dangerous sort of radioactive!), and we know the rate at which radium naturally decays. This means that radium can act as a kind of internal clock for a parcel of water, telling us how fast things happen.

Luckily, radium is also extremely rare in seawater, so even though it is a radioactive element it is present at concentrations thousands of times lower than anything we would need to worry about. Even though I use extremely sensitive detectors to measure radium (photo), because it is so rare I still need to sample a very large amount of water  to collect enough for a useful measurement– up to 150 litres for just one sample.

Amber's radium detectors on board the RRS Discovery

Radium comes from rocks, and there is plenty of lithogenic (rock) material in the sandy, muddy sediments on the UK continental shelf here off the north west coast of Cornwall. I am using a megacorer to collect pore water (water from in between the sand and mud particles inside marine sediments) and samples from the sediment-water interface, as well as a CTD to measure radium in the water column above. This lets me look at how much radium diffuses out of the sediments and into the sea, as well as how quickly this process occurs. This work is part of the trace metal group (SSB Work package 3), who are ultimately looking at how shelf seas can act as a source of iron, an essential nutrient for marine plant life, that is very scarce in many areas of the ocean. 

We will be using radium concentrations to help track iron that comes from sediments, where it goes and how fast it gets there.

Some very rare leisure time while heading into the next week at warp speed

Louis Byrne, British Oceanographic Data Centre, NOC

Over the weekend the weather has picked up a bit and we had couple of glorious days of sunshine complete with great sunsets such as the one pictured a few days ago. We have now moved from sampling the muddy and sandy sites A and G to site I which is the muddy sand site.

Helen Smith, Kirsty Morris, Natalie Hicks and Sarah Reynolds pointing at the location of sites I and H.

By Sunday we had managed to successfully complete all of the coring that we needed to do at site I, leaving only a few samples left to collect before we can move on to station H, the final of the four benthic sites (we are still planning on journeying to the shelf edge to a site called CANDYFLOSS, with the PSO (Principle Scientific Officer) Malcolm Woodward currently working hard on designing the TARDIS that will be taking us there).

Unfortunately there is no such thing as a weekend on a research cruise but some scientists have managed to carve out some very rare leisure time away. There is a film room with an extensive DVD collection (and the centre of RRS Discovery yoga), as well as a bar with a satellite TV where a few of us watched comic relief on Friday. The Kitchen-Galley is spacious and the food has been consistently delicious, indeed it will probably be the thing I miss most about the ship – Thank you Mark and Amy!

Mark, head chef on the RRS Discovery

 

Apart from the coring we also managed to complete most of the trawling that we need to do this trip. Three trawls are conducted per station and Steve Widdicombe of Plymouth Marine Laboratory (PML) will be analysing the animals that are brought up to try and estimate the biomass of marine animals that live on the sea floor. Some of the colourful creatures that we found in our nets have been photographed by Kirsty Morris (National Oceanography Centre).

A cuttlefish (photo by Kirsty Morris)

A shrimp caught in the trawl (photo by Kirsty Morris)

A spider crab (photo by Kirsty Morris)

We’re now heading into the next week at warp speed and are looking forward to completing the work at site I so that we can move to H and then to CANDYFLOSS, where as well as carrying out our usual coring, water sampling and other data collection tasks we will make a short detour to pick up and drop off some sea gliders (more about them later in the blog). 

The trawl net being brought back in (photo by Kirsty Morris)