The Sulfurous Slopes of Daikoku Seamount

Located 67 miles northwest of the northernmost island of the Commonwealth of the Northern Mariana Islands, Daikoku Seamount rises 2,500 m (8,202 ft) meters from the seafloor to a summit only about 323 m (1,060 ft) below sea level.

Making the third visit to the seamount’s hydrothermal vents since an eruption in 2014, this dive explored the unique high-sulfur and carbon dioxide rich venting in and around the summit caldera. As ROV Hercules flew up the slopes, the team spotted super dense communities of the flat tonguefish, Symphurus thermophilus. The only flatfish known to be be vent-obligates — found only in this habitat — these approximately six-inch long fish were spotted darting across the thin sulfurous sediment layer. Lots is yet to be known about this species as scientists speculate the habitat may provide food for them in the form of bacterial mats. 

Also thriving in this ecosystem rich in chemical streams, the team found bushes of tubeworms (Lamellibrachia satsuma). The tubeworms use a crown of plumes to extract dissolved oxygen and hydrogen sulfide from the surrounding sea water so bacteria in their body can produce food. With the help of these internal symbionts, tubeworms grow in large bundles providing habitats for other organisms like crabs and Hormathiidae anemones. Gathering data from depths which intersect with bottomfish habitat in the protections of the Volcanic Unit of the Mariana Trench Marine National Monument is a way exploration supports community-elevated resource management needs in the region.

The Mattingan: Mariana Arc Volcanic Exploration (NA171) expedition is exploring deep-sea areas identified by the local management and science community, including sites with signatures of active volcanism, abyssal plain habitats, and areas in and around the Monument where new data can support resource management priorities. This expedition is supported by NOAA Ocean Exploration, the Bureau of Ocean Energy Management, and the US Geological Survey via the Ocean Exploration Cooperative Institute.