The Eclipse and a Rescue Attempt

Louis Byrne, British Oceanographic Data Centre, NOC

The eclipse viewed from the RRS Discovery (photo by Helen Smith)

Friday started much the same as the previous two days with a 0600 shift  changeover followed by some clear blue skies (with a few white clouds) and more spatial survey. At 0800 we took a break from the spatial survey for about an hour to watch the eclipse as we moved between sampling sites, and a couple of the pictures we took have been provided in the blog. Following the eclipse we continued surveying till one, at which point there was a break to attempt to rescue the NOC-L (National Oceanography Centre, Liverpool) Lander which we had lost on recovery a few days ago.

Steve and Owain attempting to get the Lander back on deck

When deployed the Lander is dropped first, followed by approximately 50 metres of wire and then a heavy weight, which is attached to a surface buoy to mark the position of the lander and make it easier to retrieve. Unfortunately the rope to the surface buoy was detached from the Lander, meaning that to retrieve it we first had to trawl for the wire connecting the Lander to the anchor weight, and then somehow get the tangled mess back on deck.

The Lander is recovered!

The rescue attempt took a few hours, but after some fantastic work by CPO (Chief Petty Officer) Steve, Owain (National Marine Facilities) and the rest of the deck crew the Lander was rescued from the bottom of the Celtic sea and back on deck. If the rescue of the Lander wasn’t impressive enough, we were in for another surprise as somehow, the ultra-fragile oxygen sensor attached to the mooring managed to survive the rescue attempt and made it back to deck in one piece. I am told you really have to work with these things to understand just how unlikely it was that this happened. Following the Lander recovery it was back to the spatial survey, with approximately 12 stations to go before we are free of our sampling shackles and can head to CANDYFLOSS.

Deployment of SPI camera to the ocan's seabed.

Louis Byrne, British Oceanographic Data Centre, NOC

Until Saturday when we are scheduled to depart to CANDYFLOSS we are finishing a spatial survey between the four benthic sites which we have been working at thus far. The work which we are doing at the four benthic stations helps us to understand how processes such as nutrient resuspension and carbon storage work in four different types of marine sediment (mud, sandy mud, muddy sand and sand). The purpose of the spatial survey is to put the data which we have been collecting at sites A, I, G and H into context and to look at gradients in sediment type between the main sites. To do this the program has created a network of 70 locations between the four sites. Our task is to sample as many as we can before we run out of time and head to CANDYFLOSS.

Image taken by a SPI camera

At each station we do two NIOZ cores and a SPI camera, which is an instrument that is lowered to the seabed and dropped into the sediment. It contains a prism to reflect the light 90 degrees so that when an image is taken by the camera, you get an image of the sediment and the overlying water. These images are then analysed to get an idea of the sediment type at that location and inspected for any signs of animal life.

Map of Celtic Sea showing four main benthic sites and CANDYFLOSS. Map created by Kirsty Morris (National Oceanography Centre, Southampton)

From the sediment samples brought up by the NIOZ cores, we can find out the sediment type at that particular location, and a variety of measurements are taken including organic carbon, nutrient and chlorophyll concentrations, as well as particle size, porosity (the space between the grains of the sediment) and the oxygen concentrations in the water between the grains of sediment.

Coring while performing the spatial survey

All of these measurements combined will give us a good idea of how carbon and nutrients are being cycled in the shelf seas over a wide area of the Celtic Sea, with the hope that these data can be extrapolated to cover all of the shelf seas around the UK and parts of continental Europe. This will then give us a much better understanding of the nutrient cycle in this area of the world, and we will be able to estimate how much carbon from the atmosphere is being stored in UK sediments.

Kirsty Morris operating the SPI camera just before it hits the seabed.