Shelf Sea Biogeochemistry blog

Sunday, 30 November 2014

Last of the Snowcatchers

Ocean research cruise blog of Jonathan Sharples


The weather eased off very quickly during yesterday, ending up with winds less than 10 knots. We arrived back at the mooring site in the central Celtic Sea and began a last set of sample collection and experiments, mainly focused on the zooplankton and on the particles settling down through the water.

The Marine Snowcatcher worked well. We’re getting better at operating it, though we think that is mainly a result of calmer weather. We are still not completely convinced that the deeper samples collected with the Snowcatcher are always from the depth that we think we have triggered the catcher to shut – if the ship is pitching at all it’s possible for the catcher to shut while it is being lowered through the water to the sample depth. However, we can solve that by collecting nutrient and salt samples from the catcher and comparing those with what we see in the CTD data to tell us the depth that the Snowcatcher sample was really taken.

last snowcatcher
Elena Garcia-Martin, from the University of East Anglia, and Darren Clark, from the Plymouth Marine Laboratory, are working on last these samples. They are measuring how the different sizes of particles, and their different components (carbon, nitrogen phosphorus), and being recycled by bacteria. The deep bacteria are acclimatised to darkness, so they have to be collected after sunset, extracted from the Snowcatcher carefully so that they don’t get fried by the ship’s deck lights, and taken into a darkroom laboratory for analysis.

Elena and Clare sampling particles

One last set of measurements to do here this morning, then we head off towards Plymouth. Should arrive just south of the Eddystone lighthouse about 0600 tomorrow.

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