This hydromedusa was documented during our midwater transects at 800 meters over a newly discovered petite-spot volcano - the first ever discovered in the U.S. Exclusive Economic Zone. The water column the largest biome on Earth and one of the least explored. Almost every time scientists spend time documenting midwater fauna, they make new discoveries.
Image courtesy of the NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas.Download larger version (jpg, 235 KB).
Dive 18: Petite-spot Volcano
20°37.174'N, 147°19.457'E, 5,692 meters July 5, 2016
This shrimp, seen swimming in the water column, had very long antennae! Long antennae like this are not uncommon in the deep sea, as they help to increase the area around which an animal can sense, which is important in the deep sea where there is little to no light for seeing.
Video courtesy of the NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas.Download (mp4, 55.4 MB)
Dive 18 documented the first ever petit-spot volcano discovered outside of Japan. Scattered subangular to angular rocks were observed on the surface, suggesting they were recently (geologically speaking) deposited on the seafloor. Rocks showed thin to heavy manganese-oxide coating as the remotely operated vehicle Deep Discoverer (D2) moved up the slope. Fauna at these depths were more abundant than was expected. Sessile animals encountered included carnivorous and hexactinellid sponges, anemones, tube-dwelling polychaetes, a long (10-centimeter) scaleworm, an equally long and translucent holothurian, and a brisingid seastar with parasites (gastropods and barnacles). Documented swimmers and crawlers included cusk eels, Abyssopelagic crustaceans (mysids, shrimp, and long-legged isopods), polynoid polychaetes, a chaetognath (arrow worm) and an acorn worm. During the midwater dive, D2 encountered chaetognaths, forams, radiolarians, hydromedusae, ctenophores, larvaceans, salps, and siphonophores.
