Monday, 10 December 2012

3 - Plume Hunting

For the last two nights we have been deploying the CTD (conductivity, temperature and depth) profiler. The CTD is the most versatile and well-used piece of oceanographic equipment on the ship. It was by using a combination of CTD and novel new sensors from Japanese colleagues in 2009/2010 that we were able to identify these East Scotia Ridge hydrothermal vent sites to within ten metres of where they were.

Doug showing Alfred the method for sampling methane from the water samples collected
in the grey Niskin bottles on the CTD profiler in the background.
Alfred collecting water samples from a Niskin bottle on the CTD profiler
Having found these sites, we now use the CTD to look at the complex flow of chemicals exiting the vents. By collecting water samples in 10 litre plastic bottles on the CTD, we can investigate which chemical species are present in vent fluids and how they may affect the wider ocean including the impacts of nutrients like iron. Iron has a strong effect on primary productivity and consumption of CO2 in shallower waters. With this research we will see if our small hydrothermal vents have a much wider, global impact on marine life and our planet.

In addition to the chemical species being investigated, the microbiologists are particularly interested in the changes in the microbial community and the effects these microbes have on communities living in the plume environment.

On Saturday night, a CTD was used to pinpoint the major black smoker on E2. We sampled at various depths where the hot buoyant chemically-rich plume rose through the water column. We collected water samples to analyse for gases, metals and nutrients. Some of these will be analysed on board and others will be taken back to respective labs in the UK. Last night a series of CTD dips were conducted over the northern end of the E2 site to prospect for a new site for which evidence was found in 2009/2010.

This type of work normally leads to very excited geochemists and biologists catching up on their sleep!

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