Revisiting the fauna of the Jan Mayen Vent Fields

Abstract

This thesis investigates the fauna at three hydrothermal vent sites on the Arctic Mid-Ocean Ridge near Jan Mayen: the Troll Wall, Perle & Bruse and the diffuse venting area Gallionella Garden (500-610 m depth). Together with Soria Moria, these vent fields are collectively called the Jan Mayen Vent Fields. There has only been one study previously characterizing the fauna of JMVF, which found very few examples of specialized fauna. However, this study was based on a single sampling event and did not include genetic analyses. Moreover, it did not include the more recently discovered Perle & Bruse vent field. The primary aim of this thesis was to characterize the faunal composition within these hydrothermal vents using video observation, sample processing, morphological identification, and DNA barcoding. The study provides an updated species inventory for the Jan Mayen Vent Fields, identifying 242 taxa, which is a notably higher number compared to other deep-sea hydrothermal vent fields in the region. Most species identified were consistent with known fauna from the surrounding Nordic deep-sea regions but with presence of specialized species. Additionally, this thesis reveals several putative new species to science from JMVF, supported by DNA barcoding, including two species of Ophryotrocha one species of Capitella (Annelida) and three species of Skenea (Gastropoda). The JMVF does not have typical hydrothermal vent foundation species, such as siboglinid worm forests, which differentiates the Jan Mayen vents from other Arctic vent sites like Loki's Castle. However, I found that hydrozoans (Tubularia sp.) generate a habitat for dense colonies of Syllidae (Annelida) and Erichtonius sp. (Amphipoda), serving as an example of a different foundation species. These findings enhance the understanding of deep-sea biodiversity and biogeographical patterns of hydrothermal vent communities, offering insights that could guide future conservation efforts in these fragile environments. Ultimately, shedding light on the fauna of the Jan Mayen Vent Fields not only advances scientific knowledge but also underscores the importance of preserving these understudied ecosystems. Understanding the magnitude of what could be lost is crucial, especially in light of potential threats from deep-sea mining.