How do you bring organisms back from deep depths like the Mariana Trench without the organisms exploding from the change in outside pressure?
– Bryce K., 13, San Diego
Researchers have had success bringing organisms from the deep sea to the surface intact since at least the 1970s, when Scripps Institution of Oceanography, UC San Diego marine biologist Art Yayanos designed unique, pressure-compensated, pressure-retaining traps made of titanium with quartz viewing ports designed and fabricated at Scripps. The traps were baited to attract small crustaceans called amphipods, which were recovered from the Mariana Trench at a pressure of 16,000 pounds per square inch. The scientists were able to culture deep-sea microbes living on the amphipods.
The challenge of devising ways to retrieve deep-sea organisms alive remains before us. Decompression can affect organisms recovered from great depths in two possible ways: (1) expanding their interior gas volumes, and (2) destabilizing the membranes enclosing their cells. Thus collection usually results in the death of the organism. Deep-sea fishes, for example, often come back with their swim bladders (a gas-filled organ used for buoyancy) hanging out their mouths due to the expansion of this organ with decompression. It’s not clear whether any deep-sea microbes have any gas-containing structures inside their cells, but at least so far this does not appear to be the case. Many high pressure-requiring deep-sea microbes have been recovered alive from great depth following repressurization after recovery. These cells do die with decompression, but it is a slow enough process that many survive the impacts of decompression long enough to be recovered if the scientists on board research vessels act quickly enough to restore them to their preferred pressure state. The cause of decompression-associated death in this case appears to stem from the destabilization of the membrane, which becomes more liquefied with the loss of pressure.
We don’t yet know, however, what we are missing when we collect deep-sea samples with decompression. Some deep microbes may lose membrane stability and fall apart faster than others during the ascent and recovery process. With Alexander Bochdansky at Old Dominion University, Scripps scientists have started developing and testing a pressure-retaining sampler. With this instrument connected to our autonomous deep-diving/ascending landers, we should be able to collect microbes from the deepest ocean depths and bring them back to the surface without decompression. The plan is to look and see what happens to the distribution of microbial species recovered from ocean trenches with and without decompression. This will allow us to directly address your question, so stay tuned for more discoveries in the deep by Scripps scientists.
– Doug Bartlett, marine microbiologist (and chief scientist on James Cameron’s 2012 DEEPSEA CHALLENGE voyage to the 11-kilometer [36,000-foot] -deep Mariana Trench), Marine Biology Research Division