Friday, 22 February 2013

15 - Vent energy and chocolate cake

We’ve just had a few birthdays on board, meaning great quantities of delicious chocolate cake for everyone. We’ve also been sampling the fantastic Beebe Vent site fluids, and so it seems a good opportunity to make some food comparisons.

The vents are furiously spewing out an estimated 300 kg of water every second, and that water contains about 12 millimoles (mM) of hydrogen sulfide, the main food for the bacteria which feed the shrimp. We’ll say 12 mM is about 1.25 Calories (kcal; after great calculations by McCollom and Shock in 1997).

Our chocolate cake, which is ginormous, is probably at least 15000 kcal – so a little maths tells us that our vents are serving up about a slice of cake every second – and more than 2,000 delicious chocolate cakes each day. Plenty of food for bacteria – if only they can get to the fluids – which (unfortunately for them) are more than 400°C. It’s probably safer for them to stay in the diffuse areas, which have less hydrogen sulfide, but much more comfortable temperatures around 50°C. Funnily enough, this is where we find the majority of the shrimp – which carry the bacteria in their gills and other convenient parts of their bodies. Personally, I prefer chocolate cake to rotten-egg smelling hydrogen sulfide – but each to their own!

By Jeff Hawkes

Jeff taking a sample from the CTD carousel to analyse methane – another great food source for bacteria

2 comments:

  1. Would you venture to guess that if these vents were not spewing the hot water and hydrogen sulfide out into the ocean at that depth that there could be a volcano formed there. So because the vents are releasing the high pressure liquid and gas, the probability of a volcano building, as they do in the Pacific Ocean with some regularity, likely be remote and the vents are a good thing for the inhabitants in the area of the vents?

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  2. Hello! The water is heated by the magma at depth below the seafloor. Because of the high temperatures and pressure, chemical reactions occur between the water and rock and the fluid gets more acidic and dissolves metals and gases like hydrogen sulfide. So actually, the hot water isn't there waiting to get out - it's showing us where there is hot magma beneath the surface and where there are conduits for the water to flow. Vents often occur on active volcanoes too - check out the Brothers Volcano and NW-Rota-1 Volcano near New Zealand!

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