JC010: Mud volcanoes and submarine canyons


A taste (or a sniff?) of microbiology

John, Barry ( from Cardiff University) and Lois ( from Gent University) are the microbiologists on the team and they were very pleased with a core that they got late last night. Their research is almost like trying to build up a story of the sediment; what is going on deep down in the sediment and what living things are found in it. They have to piece together the evidence and act as detectives.

After Barry sniffed the length of it with his highly attuned nose trying to detect hydrogen sulphide, a sign of microbe activity, they set to work. They worked through the night until 6am. This is painstaking work. They use sterile syringes and plunge them into the core as quickly as possible to collect the sample of the mud. The organisms they are investigating do not thrive on oxygen and so they need to keep the environment free from it. These bacteria are called anaerobic methane oxidising bacteria and oxygen will kill them. There is a video clip below that shows how this is done. The sediment has to be kept cold to mimic the conditions the bacteria live in so as soon as possible it is put into the fridge. What they are investigating is the bacteria which use methane as an energy source, in combination with sulphates. Initially they put some of the bacteria into preservative so that they can estimate their numbers when they return to Cardiff, using powerful microscopes. They are expecting to find thousands of millions per cubic centimetre.

When they have preserved some of the sample, they inject the rest of the bacteria with radioactive methane and radioactive sulphates. For safety they use a specially adapted containerised van on board. Using these tracers they learn how the bacteria use these compounds in their metabolism. The samples are also analysed for DNA, in back at University, so they can assess their growth rate. Bacteria that we are more familiar with on land have a very high reproductive rate but these bacteria seem to be reproducing much more slowly possibly 7 months to, some speculate, 200,000 years!

So what do the scientists think may be happening?  Way down in the sediment bacteria are using organic compounds in the rocks and this produces a gas called methane. Or maybe the methane they use has bubbled up from thermogenic activity below in the crust. Anaerobic methane oxidising bacteria use the methane and sulphates found in the sediment to gain energy in a complex redox reaction and the end products are carbon dioxide and hydrogen sulphide. The carbon dioxide bubbles up into the water column where it can be used by the phytoplankton, whereas the hydrogen sulphide accumulates as a smelly, toxic waste product.    If methane were not used by these anaerobic bacteria it may be released into the atmosphere and as it is 21 times more potent than carbon dioxide it could cause even more problems for the climate, so it is important research work for the future. We know oceans absorb carbon dioxide but are they a source of carbon as well? Microbiologists may be able to find the answer.

Barry, John and Lois hard at work in the lab

The radioactive van!

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