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Spatiotemporal information is crucial for cetacean research and conservation, particularly for wide-ranging and migratory species. Sperm whales (Physeter macrocephalus) are distributed worldwide in deep oceans; however, little is known about the species in the western margin of the Pacific Ocean. Here, we examined the available information related to the occurrence, distribution, and potential habitats of sperm whales in the waters off China. Historical whaling information (18th-20th century) indicates that sperm whales have been captured in the East China Sea (ECS) and South China Sea (SCS). Furthermore, sporadic strandings have been recorded since the 1910s, and more frequently from 1990 onwards. Since 1990, accidental sightings have been documented in the eastern ECS, northeastern and southern SCS, and their adjacent waters. More recently (2019-2022), field encounters have been reported in dedicated ship-based investigations in the Xisha and Nansha waters, providing robust evidence of the regular existence and potential residency of sperm whales in the northwestern and central areas of the SCS. Female nursery groups suggest that the Xisha waters might be an important nursing ground for sperm whales. Satellite tracking data from four adults showed that sperm whales in the SCS might display both fine-scale and long-distance movements. Taken together, it appears that sperm whales are currently active in the waters off China, and that deep waters (depth >200 m) in the ECS and SCS may provide the species with critical habitats. This review provides crucial baseline information on sperm whales in the waters off China, which may help to facilitate future research efforts and conservation initiatives for the species at national and cross-regional scales. More field investigations and other monitoring approaches including acoustic monitoring, biologging, photo-identification, and genetics are required to reveal the distribution, movement, and habitat use patterns of sperm whales in these waters. [ABSTRACT FROM AUTHOR]

Deep ocean regeneration of dissolved silica (DSi) is an essential part of the ocean silica cycle and is driven by a complex series of biogeochemical processes. Here we compare the distributions of DSi and other environmental parameters in several western Pacific marginal seas to explore the role of marginal seas in deep ocean DSi regeneration. Results show that in oligotrophic marginal seas (such as the South China Sea), the DSi content in deep waters is similar to that of the adjacent Pacific waters. However, in productive marginal seas (such as the Bering Sea), the DSi content in deep waters is markedly higher than that in adjacent Pacific waters at the same depths. This is mainly due to deep ocean DSi regeneration in the marginal sea basin, which is fueled by the high biogenic particle flux from the productive surface waters. On a global scale, deep ocean DSi regeneration is accelerated in productive marginal seas, causing marginal seas such as the Bering Sea to have the highest DSi concentrations of all global waters.

This study analyzes the pH of surface-sediment porewater (i.e. 2–3 cm below the water-sediment interface), and concentrations of CaCO 3 and organic carbon (OC) in 1192 sediment cores from the northern South China Sea, in water depths ranging from 137 to 3702 m. This is the first study in the literature to analyze the large-scale spatial variability of deep-water surface-sediment pH over a large ocean basin. The data showed strong spatial variations in pH. The lowest pH values (<7.3) were observed south of Hainan Island, an area that is affected by summer upwelling and freshwater runoff from the Pearl and Red Rivers. Moderately low pH values (generally 7.3–7.5) occurred in two other areas: a submarine canyon, where sediments originated partly from the Pearl River and correspond to a paleo-delta front during the last glacial period; and southwest of Taiwan Island, where waters are affected by the northern branch of the Kuroshio intrusion current (KIC) and runoff from Taiwan rivers. The surface sediments with the highest pH (⩾7.5, and up to 8.3) were located in a fourth area, which corresponded to the western branch of the KIC where sediments have been intensively eroded by bottom currents. The pH of surface-sediment porewater was significantly linearly related to water depth, bottom-water temperature, and CaCO 3 concentration ( p < 0.05 for the whole sampling area). This study shows that the pH of surface-sediment porewater can be sensitive to characteristics of the overlying water column, and suggests that it will respond to global warming as changes in surface-ocean temperature and pH progressively reach deeper waters. [ABSTRACT FROM AUTHOR]

A deep-sea pedunculate barnacle of the family Scalpellidae, subfamily Arcoscalpellinae, collected from deep waters of the South China Sea is studied.Sinoscalpellumgen. nov. is erected to accommodateSinoscalpellum sinensissp. nov. The new genus differs from the other genera by the inframedian latus narrow and long, umbo at basi-rostral angle and protruded to below rostrum. A key to genera of the subfamily Arcoscalpellinae is provided. http://www.zoobank.org/urn:lsid:zoobank.org:pub:061A3277-012E-4808-B7BA-3180CF910CD7 [ABSTRACT FROM AUTHOR]

A new species of deep-water barnacle that belongs to the family Scalpellidae is described from the South China Sea. Arcoscalpellum liui sp. nov. is morphologically similar to Arcoscalpellum gryllum Zevina, but differs from the latter by the absence of longitudinal striae on the capitular plates and the presence of caudal appendages with few terminal setae. [ABSTRACT FROM AUTHOR]