Deep midwater Annelida from the NORI-D exploration area of the Clarion-Clipperton Zone, Pacific Ocean

Midwater ecosystems represent a substantial knowledge gap in baseline biodiversity surveys of the Clarion-Clipperton Zone of the Pacific Ocean, where deep-sea mining of seafloor polymetallic nodules is anticipated to impact the water column via sediment discharge plumes. In the first midwater surveys by remotely operated vehicle of the Nauru Ocean Resources Inc. exploration contract area D (NORI-D), we documented nine annelid species: Poeobius meseres (Flabelligeridae), Tomopteris sp. (Tomopteridae), Tomopteridae sp., Pelagobia sp. (Lopadorrhynchidae), Lopadorrhynchidae sp., and Typhloscolecidae sp. from the mesopelagic oxygen minimum zone and vicinity; and Swima bombiviridis (Acrocirridae), Swima fulgida, and Flota sp. (Flabelligeridae) from greater depths. Five species were vouchered, and the ranges of occurrence for four species were extended substantially, by 1,400–2,900 km across the northeastern Pacific (Swima bombiviridis, Swima fulgida, Flota sp., and Tomopteris sp.). We also report an image of benthopelagic Polynoidae and the first record of parental care of juveniles in Tomopteridae. These specimens, live images, and reference DNA sequences will support the identification of pelagic annelids from video surveys for biodiversity research and environmental impact monitoring.