The discovery that some marine life can hitch a ride on a submarine to colonize an otherwise inaccessible ocean area came as an accident which ruined many months of deep-sea species cataloguing. However, that research turned up something completely different, with much larger implications than the original study. It was the first documented case in which a deep-sea alien species had been inadvertently introduced into a new habitat and survived.
Background
Previous research indicated that deep-sea animals generally died when they were brought to the surface, because their bodies could not adapt to drastic changes in temperature and pressure. Animals which are native to deep-sea hydrothermal vents are especially vulnerable to changes in their environment, and do not naturally leave the vicinity of their native hydrothermal vent.
As a result, the biological communities of deep-sea hydrothermal vents represent some of the most isolated and inaccessible ecologies on Earth. The deep-sea animals which live in these parts of the ocean have strong species differentiation between different vents. Until recently, it was thought that these species could be found nowhere else on Earth.
Lateral mobility by submarine
Lead researcher Janet Voight had been leading an Alvin dive to find and catalog previously unknown species native to the Juan de Fuca Ridge, in the Pacific Ocean off the coastline of Washington. This part of the investigation was not near any hydrothermal vents.
When the team examined their findings, they discovered that the suction sampler of the submarine had collected 38 apparently healthy vent limpets, a type of sea snail. However, at that time, vent limpets were believed to live only on hydrothermal vents. It was surprising that they had been found in a non-hydrothermically active area.
During the investigation, another research team published their discovery of a new type of vent limpet in the Gorda ridge system, which they named Lepetodrilus gordensis. Gene sequencing proved that L. gordensis was genetically the same species as the vent limpet which had just been discovered by Voight’s team.
This was even more puzzling. Each population of L. gordensis was completely isolated from the other. The first population to be identified lived in a limited hydrothermally active area near the Juan de Fuca Ridge, while the other lived 381 miles away in a non-hydrothermically active area.
At the same time, Amanda Bates, another member of Voight’s research team, was working on her doctoral dissertation. She found out that the Lepetodrilus limpets relied on symbiosis with a particular bacterium, which used hydrothermal vent fluids to produce energy. The process would not be sustainable away from a hydrothermal vent.
It was a mystery worthy of Sherlock Holmes. As Holmes once said, “It *is* impossible as I state it, and therefore I must in some respect have stated it wrong.”
Following Holmes’ dictim, Voight suddenly realized that she was looking at the problem the wrong way. Faced with something that must be impossible as stated, she changed the question around. Instead of wondering how 2 independent populations of L. gordensis could exist in separate places, the real question was how her population of L. gordensis could have gotten to an inhospitable place 381 miles from any other population of L. gordensis.
That led her to the conclusion that her own submarine must have been responsible for transferring the limpets. Voight guessed that the limpets must have latched somewhere in the suction sampler, probably in the corrugated hose, during a dive 36 hours earlier in the Juan de Fuca area. Yet for most of that time, the submarine had been on the ocean’s surface or docked at port.
It seemed wildly improbable, because all previous experience had indicated that deep-sea animals died when they were brought to the surface. However, it turned out that it was not impossible for the limpets to survive these changes. In spite of the usual cleaning of the submarine and the sampler, as well as the extreme pressure and temperature changes which resulted from a change of depth of more than a mile, the limpets had survived. There had been just enough seawater in the hose to keep them alive and healthy.
Conclusion
Before Voight’s accidental discovery, no one considered that a potentially invasive species could hitchhike on a submarine. Unlike invasive species which hitch rides in ballast, a hitchhiker on a submarine would have to survive extreme changes in pressure and temperature for extended periods, and then would have to be deposited into a hospitable environment afterwards. Voight’s research has proved that this should no longer be considered impossible.
In this case, a transplanted population of limpets which had hitched a ride on a submarine was unlikely to survive. Unlike the limpets themselves, their symbiotic bacteria would not survive for long away from a hydrothermal vent. The limpets would probably die shortly afterwards.
However, another species might be more adaptable, or might carry parasites or disease. If the next dive had been to a region with hydrothermal vents, even the limpets might have colonized the area. These kinds of invasive species have the potential to disrupt the local ecology, sometimes beyond repair.
If these studies are to continue without causing potentially disasterous anthropogenic alteration, the only alternative may be drastic sterilization of a submarine and its sampling equipment after each location. This will certainly add to the cost of marine research.
