Only a unique group of marine animals can tolerate the 400 degree Celsius temperatures of deep sea hydrothermal vent fields. In order to better safeguard these animals, researchers from the Okinawa Institute of Science and Technology Graduate University (OIST) calculated the dispersal of larvae from these ecosystems.
The goal, researchers say, is to learn more about these hydrothermal vent fields, as they emit chemicals that are vital to the survival of marine life such as vent crabs and eyeless vent shrimp.
"We are trying to understand how these western Pacific vent fields are connected," explained professor Satoshi Mitarai, first author and principal investigator of OIST's Marine Biophysics Unit. "And we want to know how the creatures are migrating from one site to another, as well as how they are evolving."
Researchers also hope to learn more about these unique environments so that they can protect native vent species from deep-sea mining, which is a process that retrieves metals from the ocean floor that could negatively affect the animals living near these hydrothermal vents.
"Deep ocean mining would destroy these habitats," Mitarai added.
Researchers chose to quantify larval dispersal because the larval stage is the only time at which these creatures can freely move through the ocean via the currents. Knowing that the vent animals remain in the larval stage for an average of 83 days and travel at a depth of about 1,000 meters, researchers deployed 10 deep-ocean profiling floats off the coast of Ishigaki Island in southern Okinawa. These floats, designed to drift along with the ocean's current, were released every other month for a period of two years.
"This is the first time we could see how deep ocean circulation processes potentially transport materials from hydrothermal vents," Mitarai said.
Researchers then quantified larval dispersal on a larger scale using simulated "model" floats. Combining the data revealed larvae could be transported over long distances to far off vent fields. These findings will help researchers predict where vent species travel during larval stage, which in turn sheds light on the creatures' gene flow and evolutionary history.
"We have provided concrete background information that population geneticists can use to set up their hypotheses to understand gene flows," Mitarai said. "This information can help marine ecologists to design optimum plans to protect these areas from deep ocean mining."
Their study was recently published in the Proceedings of the National Academy of Sciences.
