ALBERT

Description: Here we present the discovery of R. daphneae along the southern Central Indian Ridge, at the Rodriguez Triple Junction, and along the northern Southeast Indian Ridge within the German contract area for the exploration of marine massive sulfide deposits in the Indian Ocean. We used video sled and Remotely Operated Vehicles (ROV) to collect video imagery and recognized a total of eight individuals. The two supplementary videos report on one individual associated with polychaetes on its tentacles and oral disc and, and one individual of the giant anemone that was recorded for the first time, capturing prey, a shrimp of the species Rimicaris kairei. This will provide insight into the basic ecology of the rather elusive giant anemone, R. daphnaea. Supplementary video 1: Video imagery collect by the Remotely Operated Vehicle ROPOS (Remotely Operated Platform for Ocean Science, www.ropos.com) showing commensal polychaetes moving on an individual of Relicanthus daphneae from two different cameras. Arrows in the video indicate position of polychaetes on the giant anemone. Supplementary video 2: Video imagery collect by the Remotely Operated Vehicle ROPOS (Remotely Operated Platform for Ocean Science, www.ropos.com) showing an individual of Relicanthus daphneae capturing prey (Rimicaris kairei). Arrows in the video indicate the position of the shrimp R. Kairei captured by the giant anemone.

Description: The Clarion Clipperton Fracture Zone (CCZ) is an abyssal region in the north-east Pacific that is currently being explored for metal-rich polymetallic nodules, but also harbors a highly diverse megabenthic community. This community is influenced by multiple environmental gradients including bathymetric structures as well as differences in habitat and food availability. This study focuses on the benthic megafauna investigated in an exploration area positioned in the very east of the CCZ, which exhibits the lowest water depths (mean: 4200 m) and the highest flux of particulate organic carbon (POC) of the CCZ. Case studies using seafloor images for the detection of megafauna have revealed differences between seamounts and abyssal hills compared to nodule fields, as well as differences in the community composition between areas with and without nodule coverage and rock outcrop. Extrapolations suggest a richness of more than 300 morphotypes in the study area, including multiple invertebrate groups such as corals, sponges, echinoderms, and crustaceans as well as fish. Focusing on sampled specimens, diversities of Ophiuroidea, Porifera, and Bryozoa are high and more species are likely to be discovered in the study area. This also applies for the taxon Ophiuroidea, which is among the taxa investigated in the greatest detail so far. In the context of deep-sea mining, megafauna has been in the focus of a variety of environmental studies including baseline analyses, disturbance experiments, and/or testing of mining components or systems. These studies identify and address key factors responsible for the observed natural and impacted distribution patterns and thereby help to constrain expected anthropogenic impacts to the deep-sea environment in the context of deep-sea mining. Specifically in the area of focus of this study, 10 years of megafauna analyses have shown that the biodiversity in the selected preservation reference zone (PRZ) is not as similar to that of the impact reference zone (IRZ) as originally hypothesized based mainly on geological parameters. We suggest that recent area-wide habitat classifications and faunal mapping exercises (e.g., Uhlenkott et al. 2020, 2022) are used to designate a new PRZ that is more similar to the IRZ to meet its purpose, but that the current PRZ is maintained for scientific and conservation purposes.