Fig. 17. Aulococtena acuminata. A cydippid ctenophore from the deep-sea which uses two tentacles to snare its prey. (15 cm long). (Photo: Marsh Youngbluth)
Jellyfish, members of a group also known as gelatinous zooplankton, are amazing creatures. They occur in all the oceans from the surface to the seafloor.
In addition to being beautiful, these drifters are capable of eating enormous amounts of prey and may compete with fishes for these natural resources. Many species grow quickly and produce large populations. When numerous, jellyfish are hostile toward humans or any other animals that swim into their stinging tentacles.
Fig. 18. Bathycyroe fosteri. A lobate ctenophore found at intermediate depths in all the oceans. This species is very common and abundant near the mid-Atlantic ridge. (5 cm tall). (Photo: Marsh Youngbluth).
But what happens in the deep sea, a place where people rarely visit? We don’t know the answer yet. This environment is the largest and darkest habitat on our planet. How many gelatinous forms live there? The MAR-ECO project has provided opportunities to explore with a suite of modern technologies that enable us to enter, watch, photograph, record, capture and respire a variety of jellyfish.
Segregates in layers with regard to depht
In the span of two weeks we have descended more than 2000 m to the seafloor around the mid-Atlantic ridge. We’ve learned that jellyfish segregate in layers with regard to depth. Animals like comb jellies and medusae are often numerous in a zone 300 to 600 m below the surface and were most diverse just north of the Azores.
Each time we splashed into the sea with an ROV we encountered wondrous and apparently undescribed animals that behave in unexpected ways.
Scientists to be credited: Marsh Youngbluth, Aino Hosia, Tom Soernes.