Foraminiferal Fauna in the Late Pleistocene Core Sediments of the Ulleung Basin, East Sea (Sea of Japan) of South Korea

Abstract Foraminifera are classified based on the diverse morphologies of their calcium carbonate shells (tests) and exhibit different community structures depending on environmental conditions, making them valuable bioindicators for changes in marine environments. Morphological studies and faunal records of foraminifera are essential for understanding species distribution and their relationship to changing marine environments. This study represents the first attempt to document the foraminiferal fauna in Korean waters by describing the morphological characteristics and diversity of foraminiferal species observed in core sediments from the Ulleung Basin in the East Sea, along with accompanying images. A total of 48 species of foraminifera belonging to 1 phylum, 3 classes, 8 orders, 20 families, and 33 genera were identified. Among them, 15 species were planktonic foraminifera, while 33 species were benthic foraminifera. Notably, seven species were previously unreported in Korea and are newly documented in this study. The discovery of previously unreported species suggests that research on foraminifera in Korean waters has been somewhat neglected. In addition, the identification of five distinct morphological types of N. pachyderma sinistral indicates significant environmental changes in the Ulleung Basin of the East Sea in the past. Future studies evaluating and tracking the morphological diversity and distribution patterns of these species could contribute to stratigraphic research and the reconstruction and interpretation of past marine environments in the East Sea.