Macrofaunal diversity in high-bottom current environments at the Vesturdjúp Seamounts (Northern Irminger Sea, Iceland)

The Vesturdjúp Basin is located at the northeastern edge of the Irminger Sea, bordered by southern Greenland to the west, the Denmark Strait and Iceland to the north, and the Reykjanes Ridge to the east. To the south, it opens into the North Atlantic Ocean. The basin’s bathymetry is characterized by large sediment rafts shaped by intense bottom-water currents, a distinctive ocean floor fabric, and numerous cone-shaped volcanoes¹. In the summer of 2024, Meteor Expedition M201 explored the seamounts of the Vesturdjúp Basin¹. In addition to a comprehensive geological sampling and geophysical program, all studied volcanoes were surveyed using a towed camera system (OFOS – Ocean Floor Observation System). A total of 21 dives were conducted, covering 24.3 km of seafloor and resulting in over 65,000 still images and 38 hours of video footage. Observations revealed that lithified sediments and some manganese crusts extensively cover the seamounts of the Vesturdjúp Basin, with occasional rocky outcrops accompanied by abundant talus material and drop stones. No evidence of recent lava was detected. However, the seamounts host diverse and vibrant ecosystems that vary with depth and, more notably, with current exposure. While some seamounts show sparse macrofaunal presence, many are rich in species, such as sea pens, corals, diverse sponges, crinoids, crustaceans, octopods, and fish. This study presents the faunal diversity of the Vesturdjúp Basin seamounts, highlighting how species distribution and abundance appear to be more influenced by current dynamics and sedimentation patterns - particularly south of the Denmark Strait in the northern Irminger Sea - than by the geological features of the volcanoes.

¹Augustin, N.,  Palgan, D., Hübscher, C.P., van der Zwan, F.M., et al., (2024) Volcanism in the Vesturdjúp Basin - Flank Igneous System or Intraplate Volcanism Off-Shore Western Iceland, Cruise No. M201, 09. June - 18. July 2024, Reykjavik (Iceland) - Praia da Vitoria (Azores, Portugal), METEOR-Berichte, M201, 1-91, https://doi.org/10.48433/cr_m201