By Alan Hughes, NOCS
Today marked our last day at our Northeast site, and the last sampling of this cruise. Work in the early hours of this morning began with a final Megacore deployment. This was to take samples for Natasha and Holly to study tiny worms living in the sediment. Noticeably, the cores here have a distinct brown layer at the surface, with grey mud below. The brown layer may represent mud that has been deposited during the Holocene – the geological period that covers approximately the last 10,000 years, and represents the current warm period in the global climate. If this is the case the sediment at the bottom of the cores could be over 20,000 years old.
The final Megacorer deployment returns 8 out of 8 perfect (and beautiful!) cores. The cores are 10 cm across.
Holly, Natasha and Tonya (left to right) in the Cold Room at 4 am, ready to start processing the cores. It was a long night.
After the coring, we recovered the Amphipod trap (or “Amphitrap”). Amphipods are tiny (generally a few millimetres long) shrimp-like animals, which occur in huge numbers in the sea. The Amphitrap attracts amphipods that feed on dead fish, and these tiny scavengers can reduce a dead fish down to its bones in less than a day. The Amphitrap has been extremely successful onboard this cruise, with three deployments at the Southeast site, and two at each of the other three sites. The animals caught in these traps will be carefully studied by Dr. Tammy Horton in Southampton. There are currently more than 800 species of scavenging amphipods known to science, although the large number of species has resulted in some confusion. These samples will be invaluable in helping to sort out the identification problems of these abundant animals, as well as determining the geographic range of many species. As the mid-Atlantic ridge has been so poorly sampled, it’s also quite possible that Tammy will find new species from these samples.
The Amphitrap.
: Claudia holding a sieve containing fish bones and hundreds of tiny amphipods captured by the Amphitrap.
Close up photographs of two amphipods, both Eurythenes gryllus, a species which we found at all four sites. Although amphipods are generally very difficult to identify, this species grows up to about 7 cm long, making it easy to spot. We found it in a variety of colours, although the white ones were more common in our samples.
After all the landers were safely onboard we took some last water samples, then just before lunch we set sail for Falmouth with the wind and the sea behind us. Our day didn’t end there, however, as in the afternoon we had a safety drill. After the General Alarm sounded, all the scientists and technicians mustered on the back deck. We then split into pairs, with one person in each pair being blindfolded. The blindfolded person then had to walk back to his cabin, with the other person making sure that they didn’t trip over anything, or fall down the stairs, etc. The pairs swapped roles then made their way back onto the aft deck. This drill is to make sure that people would be able to find their way of the ship if there was a power cut or if the ship was full of smoke. This was actually quite good fun, and made an enjoyable end to the working day.
: Jess and Pedro looking surprisingly happy at 6 am. They worked all night carrying out experiments to study the bioluminescence of small animals such as the amphipods recovered in the Amphitrap.
The PAL lander is welcomed back on deck.
Scientists muster on the back deck for the safety drill.
