Large, enigmatic foraminiferan-like protists in the eastern part of the Clarion-Clipperton Fracture Zone (abyssal north-eastern subequatorial Pacific): biodiversity and vertical distribution in the sediment

Komokiaceans and similar large (millimetre-sized to centimetre-sized) testate protists resembling Foraminifera are a ubiquitous and often dominant component of abyssal macrofaunal assemblages. Yet they are often overlooked and many forms are undescribed, often at the genus or higher taxon level. As a result, they represent a major source of unknown biodiversity in the deep sea. We studied the diversity and vertical distribution of these delicate, often fragmentary organisms in sediment samples (0- to 6-cm layer) collected from three sites in the eastern part of the Clarion-Clipperton polymetallic nodule field (subequatorial NE Pacific) during the 1997 cruise of the RV Professor Logachev organised by the Interoceanmetal Joint Organization (IOM). A total of 102 morphospecies and morphotypes was recorded (28-69 per station), indicating an extremely diverse assemblage. Although most were found in the uppermost 2 cm, deeper sediment layers also yielded some species. This is one of only a few studies of komokiaceans and related organisms in this part of the Pacific. It contributes to baseline knowledge of abyssal communities in an area targeted for future commercial nodule mining operations.