Abundance and morphology of Paleodictyon nodosum, observed at the Clarion-Clipperton Zone

Abstract

Paleodictyon is an important trace fossil characterised by a regular hexagonal structure and typical of ancient deep-ocean habitats as far back as the Ordovician. It is represented in modern deep-sea settings by Paleodictyon nodosum, known from the Mid-Atlantic Ridge, the South Atlantic, and off eastern Australia. Here we report the occurrence of P. nodosum in the Clarion Clipperton Zone (CCZ), abyssal equatorial Pacific, an area characterised by polymetallic nodule fields. At the study site within the International Seabed Authority northeastern Area of Particular Environmental Interest (APEI-6), P. nodosum appeared as a compact, regular pattern of small circular openings on the seafloor, each pattern interpreted as reflecting the activity of an individual organism. The patterns had a mean size (maximum dimension) of 45 mm ± 16 mm SD (n = 841) and occurred at a density of 0.33 individuals m . Most (82%) were interrupted by nodules, but those that were not displayed both regular (59%) and irregular (41%) forms, the former having equal numbers of rows along the three axes (6 x 6 x 6 and 8 x 8 x 8). In both size and morphology, our Paleodictyon traces were more similar to the Australian examples than to those from the Mid-Atlantic Ridge.

Editorial: Biodiversity of the Clarion Clipperton Fracture Zone

“…Durden et al (2017) provide the first in situ observation from the CCZ. Although Paleodictyon nodosum creates a distinct symmetric pattern and is commonly found on the abyssal seabed, its origin and function remains elusive.…”

“…New species descriptions, in particular for previously neglected groups, illustrate a taxonomically more balanced view and represent one of many smaller steps for diversity estimations (Kamenskaya et al 2016;Markhaseva et al 2017;Molodtsova and Opresko 2017;Zinssmeister et al 2017). In situ observations from video and still imagery using manned and unmanned (ROV, AUV) submersibles have led to discoveries of new habitats and also yielded valuable biogeographic information (Amon et al 2016a;Durden et al 2017;Vecchione 2016), while community analyses provide important insights into the patterns and processes driving (macro-)faunal diversity and turnover at local to regional scales (Wilson 2017).…”

“…Although Paleodictyon nodosum creates a distinct symmetric pattern and is commonly found on the abyssal seabed, its origin and function remains elusive. Therefore, Durden et al (2017) discuss the potential use of time-lapse imagery, among other techniques, to elucidate unresolved questions.…”

“…& Among the first biological data from APEIs (Amon et al 2016a;Durden et al 2017) & The first study of dinophysoid dinoflagellates from the CCZ (Zinssmeister et al 2017) & The first record of wood falls from the CCZ (Amon et al 2016a) & The first record of Paleodictyon nodosum from the eastern equatorial Pacific (Durden et al 2017) & New species and/or new distributional records of xenophyophores, benthopelagic calanoids, antipatharian corals and cirrate octopods (Kamenskaya et al 2016;Markhaseva et al 2017;Molodtsova and Opresko 2017;Vecchione 2016) …”

Inactive Sulfide Ecosystems in the Deep Sea: A Review

“…It is the association of P. nodosum with the margins of the massive sulfides that is of relevance, since this distribution suggests a sphere of influence of the inactive sulfides that extends beyond the exposed massive sulfides. However, traces similar to those of Paleodictyon nodosum are reported from abyssal locations remote from inactive sulfides, including the manganese nodule beds of the Clarion-Clipperton Zone (Durden et al, 2017b). Systematic mapping of distributions of P. nodosum traces along transects away from inactive sulfides at the TAG Field is needed before association of this trace with inactive sulfide ecosystems can be confirmed or rejected.…”