Abstract
During RVMS Merianexpedition MSM75, an international, multidisciplinary team explored the Reykjanes Ridge from June to August 2018. The first area of study, Steinahóll (150–350 m depth), was chosen based on previous seismic data indicating hydrothermal activity. The sampling strategy included ship- and AUV-mounted multibeam surveys, Remotely Operated Vehicle (ROV), Epibenthic Sledge (EBS), and van Veen grab (vV) deployments. Upon returning to Steinahóll during the final days of MSM75, hydrothermal vent sites were discovered using the ROV Phoca (Kiel, GEOMAR). Here we describe and name three new, distinct hydrothermal vent site vulnerable marine ecosystems (VMEs); Hafgufa, Stökkull, Lyngbakr. The hydrothermal vent sites consisted of multiple anhydrite chimneys with large quantities of bacterial mats visible. The largest of the three sites (Hafgufa) was mapped, and reconstructed in 3D. In total 23,310 individual biological specimens were sampled comprising 41 higher taxa. Unique fauna located in the hydrothermally venting areas included two putative new species of harpacticoid copepod (Tisbesp. nov. andAmphiascussp. nov.), as well as the spongeLycopodina cupressiformis(Carter, 1874). Capitellidae Grube, 1862 and Dorvilleidae Chamberlin, 1919 families dominated hydrothermally influenced samples for polychaetes. Around the hydrothermally influenced sites we observed a notable lack of megafauna, with only a few species being present. While we observed hydrothermal associations, the overall species composition is very similar to that seen at other shallow water vent sites in the north of Iceland, such as the Mohns Ridge vent fields, particularly with peracarid crustaceans. We therefore conclude the community overall reflects the usual “background” fauna of Iceland rather than consisting of “vent endemic” communities as is observed in deeper vent systems, with a few opportunistic species capable of utilizing this specialist environment.
Highlights
Iceland is one of only two areas on Earth where a mid-ocean ridge has been elevated above the sea level, making it a remarkable laboratory for studying spreading-associated geological, biological, chemical, and physical processes (Sæmundsson, 1979)
The Reykjanes Ridge lacks first-order transform offsets (Keeton et al, 1997), but instead shows a short-wavelength segmentation composed of individual Axial Volcanic Ridges (AVRs) (Murton and Parson, 1993; Keeton et al, 1997; Searle et al, 1998)
In addition to the bathymetric maps, Steinahóll was surveyed by the Autonomous Underwater Vehicle (AUV) Abyss from GEOMAR equipped with an Edgetech sidescan sonar 2200-S 120/410 kHz and with turbidity, CTD, and redox potential sensors
Summary
Iceland is one of only two areas on Earth where a mid-ocean ridge has been elevated above the sea level, making it a remarkable laboratory for studying spreading-associated geological, biological, chemical, and physical processes (Sæmundsson, 1979). The Reykjanes Ridge (Figure 1A) is the longest oblique, hotspotinfluenced section of the global mid-ocean ridge system (Talwani et al, 1971; Searle et al, 1998; Sandwell et al, 2014) This ∼950 km segment of the northern Mid-Atlantic Ridge is spreading at 1 cm y−1 half rate (Talwani et al, 1971; DeMets et al, 1990) and is located between Iceland (64◦N) and the Bight Fracture Zone near 57◦N. Further south along the ridge, historic activity has not been documented and is unknown
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