Rich biodiversity at the newly discovered Jøtul hydrothermal field off Svalbard

MARUM – Center for Marine Environmental Sciences described this hydrothermal vent as the most beautiful of the MSM109 expedition in 2022. It consisted of several vents and flanges and the escaping fluid shimmered everywhere. They named the complex structure Yggdrasil hydrothermal spring, after the name of the tree of life in Norse mythology. Photo: MARUM – Center for Marine Environmental Sciences, University of Bremen

The Jøtul hydrothermal field, newly discovered in July 2022 in the Arctic mid-ocean ridge system, lies several kilometers away from the volcanically active ridge – atypical for hydrothermal fields – and offers diverse habitats for numerous specialized species.

“[…] We were very happy when we discovered an active black smoker. The metal-containing liquid, which was over 300 degrees Celsius, shot out as if from a stovepipe and turned into a black cloud, the spread of which we could no longer monitor with the ROV,” said Professor Gerhard Bohrmann from MARUM – Center for Marine Environmental Sciences at the University of Bremen, chief scientist of the expedition MSM109 on board the Maria S. Merian in 2022, in the MARUM press release at the time.

The study on the discovery of the Jøtul hydrothermal field on the Knipovich Ridge west of Svalbard, published in Nature Scientific Reports at the beginning of May, now shows how extraordinary its location is. On the one hand, the discovery itself is a little sensation, as no hydrothermal activity had previously been detected at the Knipovich Ridge, which has extremely low spreading rates of just 1.4 centimeters per year. On the other hand, the Jøtul vents are located about five kilometers east of the crest of the Brøgger Axial Volcanic Ridge and are more related to the bounding fault of the rift valley. Typically, hydrothermal fields associated with volcanic activity are located near submarine volcanic ridges. This special location indicates a complex interplay of tectonic and magmatic activities. The discovery by the German-Norwegian research team is a significant step forward for marine geology.

A – The locations of the active centers of seabed spreading are marked on the map of the Norwegian-Greenland Sea. The study area is located west of Svalbard. B – Detailed map of the study area. The Jøtul hydrothermal field lies well away from the volcanic Brøgger Ridge. C – Bathymetry of the Jøtul hydrothermal field. The black lines mark the dives of the MARUM-QUEST robot. Hydrothermal activity was detected in the areas marked in yellow. Figure: Bohrmann et al. 2024

In the study, the authors emphasize that the discovery of the Jøtul hydrothermal field is significant, because it represents a new link between the active hydrothermal systems of Loki’s Castle at the bend of Mohns and Knipovich Ridges and the Aurora hydrothermal field of the Gakkel Ridge”.

The Knipovich Ridge is a 500-kilometer-long spreading ridge that forms the interface between the North American and Eurasian continental plates in the European part of the Arctic Ocean. Unlike the mid-ocean ridges in the Atlantic or Pacific, which generally spread at speeds of between two and five or, in extreme cases, up to 14 centimetres per year, the Knipovich Ridge is one of the ultra-slow spreading ridges, about which very little is known to date.

The researchers discovered the black smokers and other hydrothermal vents after analyzing water samples in the water column above the Knipovich Ridge. After the chemical composition of the water indicated hydrothermal activity, they searched the ocean floor at a depth of 3,000 meters with the MARUM-QUEST ROV and finally discovered numerous different vents with temperatures of over 300°C.

“Warm fluid leaks associated with white precipitates, microbial flocs and filaments, and many small organisms were observed, shimmering in the ROV’s headlights. Other vents have led to massive chemical precipitation and sometimes form several meter-high mounds on the sea floor,” reads the MARUM press release from 2022.

The rich mineral deposits around the vents are of great importance as they provide the basis for unique chemosynthetic communities. These in turn are the basis for species that are adapted to such high-temperature environments, such as tubeworms, mussels, shrimps and others.

The Ocean Census team, which is currently investigating the biodiversity of the Arctic deep sea as part of the “Arctic Deep” expedition, made a remarkable discovery a few days ago. At one of the vents of the Jøtul hydrothermal field, they discovered a coral species that belongs to the Octocorallia and is very likely a new discovery. And the icing on the cake of their find is that this octocoral had settled on a stalked crinoid, or sea lily, a living fossil.

“Every new species we find has a particular function in the ocean. When we loose species we loose those functions and eventually it’s us who are affected,” said Professor Alex Rogers, head of the study at Ocean Census, in the following video created for the International Day of Biological Diversity.