Abyssal foraminifera attached to polymetallic nodules from the eastern Clarion Clipperton Fracture Zone: a preliminary description and comparison with North Atlantic dropstone assemblages

• Published in: Marine Biodiversity
• Main Authors: Gooday, Andrew J., Goineau, Aurélie, Voltski, Ivan
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2015
• Subjects: Pacific; North Atlantic
• Online Access: https://eprints.soton.ac.uk/383596/

We examined encrusting organisms on seven polymetallic nodules from the eastern Clarion Clipperton Fracture Zone (CCFZ, ?4070 m water depth, eastern equatorial Pacific). Apart from occasional sponges and a single bryozoan, all the organisms were foraminifera or foraminifera-like protists. A total of 75 morphotypes (presumed to be morphospecies) was recognised, with between 9 and 19 being present on individual nodules. Additional species were observed during shipboard examination of the nodules, bringing the total number of species to 86. The assemblage was dominated by a variety of mat-like formations, clusters of patches, isolated domes, broad trails, anastomosing networks and branched or unbranched tubular structures that either lay flat against the nodule surface or projected away from the surface. These forms were interpreted as monothalamous foraminifera (monothalamids). Most have mainly agglutinated walls but a few are predominately organic. Some can be assigned to the Komokiacea (notably the genus Chondrodapis) or families such as the Hemisphaeramminidae ('domes'), while others (e.g. many of the mats and patch-like forms) are difficult to place into existing monothalamid groupings. Some of the branching and anastomosing tubes resemble the genus Rhizammina. The most easily recognisable morphotypes include Telammina, in which tiny chambers are linked by extremely thin tubes to form a network, and sinuous orange tubes that incorporate sponge spicules and can be assigned to the genus Saccorhiza based on the occasional presence of a proloculus. Polythalamous foraminifera are also fairly common. They include various calcareous species (mainly Cibicides spp.), as well as agglutinated forms such as Hormosina, ?Placopsilina and trochamminaceans. Similar assemblages, including some morphospecies that are clearly identical to ours, have been described previously from somewhat deeper sites (4500–5000 m) in the CCFZ. In order to explore distributions at a global scale, we compared our Pacific nodule assemblages to ...