Updates From Sea | Cruise 2007
February 1st
By Eric Simms, Education Outreach Coordinator
Hot Vents = Cool Chemistry
At any given second, millions of chemical reactions are taking place in the cells of your body. Without them you wouldn't be able to think, breathe, eat, walk, talk, listen, feel, see, smile, or even blink. Chemicals and their reactions are essential to everything that happens on our planet, including the hydrothermal vent ecosystems found in the deep sea.
Chimneys venting super hot, chemical-rich fluids. Image taken in April, 2005. Photo © DSV Alvin
A group of chemists here on the ship, led by Dr. George Luther, are measuring the chemistry of the hydrothermal vent fluids that originate deep beneath the seafloor. Why? Because the chemicals in these fluids support most of the life found at vents - and more specifically, because these scientists are interested in learning if the chemistry of the fluid changes after a large eruption.
It used to be that chemists would have to collect water samples and bring them back to the surface for analyses before they could get measurements of the chemicals. But new instruments now allow them to get instant measurements for many chemicals right on the seafloor using a chemistry probe. The probe can be placed next to any vent or animals the scientists choose using the manipulator arm on the Alvin submersible. These instant, or in situ, measurements are valuable because they can help the scientists 'test' the vents and decide which are the most interesting ones for collecting biological samples. Another instrument (nicknamed the Insect because it has long probes that look like legs) can be left on the seafloor for days or weeks to continuously collect chemistry measurements and tell scientists how the chemistry changes over time.
Edouard Metzger, Mustafa Yucel and Heather Nees analyze samples for dissolved iron concentrations. Photo © DSV Alvin
And just what are the chemists discovering on this cruise? So far they have found levels of dissolved hydrogen sulfide in the lower temperature vent fluids as much as five to ten times higher than they were before the eruption. These high levels of sulfides appear to create conditions that attract the first bacteria and animals to new vents after an eruption. For example, Tevnia tubeworms seem to be one of the first animals to arrive and grow at new vents. Chemical measurements of fluids at vents where Tevnia are found have been showing high levels of hydrogen sulfide and low levels of oxygen. Along with carbon dioxide, these two chemicals are used by symbiotic bacteria that live in the guts of Tevnia to create sugars and other compounds the worms can use for energy.
Vents where Tevnia are found have also had low measurements of iron, which also appears to be good for the worms and bacteria. Iron can react with hydrogen sulfide and prevent it from being used by the bacteria to create energy by chemosynthesis.
The peak in the green line indicates the high level of hydrogen sulfide in the fluids. Photo © E. Simms
The chemical measurements taken on this cruise are not only important to help understand what happens soon after an eruption - they will also be valuable to make comparisons to future measurements to see if the fluid chemistry changes over time. Will the chemistry of the vents change in the next few weeks, months and years? Will the types of animals at the vents change as the chemistry changes? Only time, and many more measurements, will tell ...
