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A total of 222 surface sediments were collected in the Ulleung Basin, southwestern East/Japan Sea, from the coast to the basin and analyzed for grain size, total organic carbon, biogenic silica and major and trace elements. The metal concentrations of the surface sediments were highly spatially variable, and their distributions were grouped into four types by factor analysis: waste dumping materials (Cr, Cu, Zn, Sn, Sb, and Pb); detrital materials (Al, Fe, and Cs); suboxic diagenetic materials (Mn, Mo, Co, and Ni); and anoxic diagenetic materials (Cd and U). From core samples collected near the dumping site, approximately the top 10 cm was well mixed in the 210 Pb ex profiles and highly enriched in the above metals related to dumping materials. The enrichment factor of Sn indicates dumping materials well, and its distribution can be used to estimate the dispersion range of the dumped material in this basin., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The current phytoplankton community structure is expected to change, with small phytoplankton becoming dominant under ongoing warming conditions. To understand and evaluate the ecological roles of small phytoplankton in terms of food quantity and quality, the carbon uptake rates and intracellular biochemical compositions (i.e., carbohydrates, CHO; proteins, PRT; and lipids, LIP) of phytoplankton of different sizes were analyzed and compared in two different regions of the western East/Japan Sea (EJS): the Ulleung Basin (UB) and northwestern East/Japan Sea (NES). The average carbon uptake rate by the whole phytoplankton community in the UB (79.0 ± 12.2 mg C m -2 h -1 ) was approximately two times higher than that in the NES (40.7 ± 2.2 mg C m -2 h -1 ), although the average chlorophyll a (chl a ) concentration was similar between the UB (31.0 ± 8.4 mg chl a m -2 ) and NES (28.4 ± 7.9 mg chl a m -2 ). The main reasons for the large difference in the carbon uptake rates are believed to be water temperature, which affects metabolic activity and growth rate, and the difference in euphotic depths. The contributions of small phytoplankton to the total carbon uptake rate were not significantly different between the regions studied. However, the rate of decrease in the total carbon uptake with increasing contributions from small phytoplankton was substantially higher in the UB than in the NES. This result suggests that compared to other regions in the EJS, the primary production in the UB could decrease rapidly under ongoing climate change. The calorific contents calculated based on biochemical compositions were similar between the small (1.01 ± 0.33 Kcal m -3 ) and large (1.14 ± 0.36 Kcal m -3 ) phytoplankton in the UB, whereas the biochemical contents were higher in the large phytoplankton (1.88 ± 0.54 Kcal m -3 ) than in the small phytoplankton (1.06 ± 0.18 Kcal m -3 ) in the NES. The calorific values per unit of chl a were higher for the large phytoplankton than for the small phytoplankton in both regions, which suggests that large phytoplankton could provide a more energy efficient food source to organisms in higher trophic levels in the western EJS., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2020 Kang, Jang, Lim, Lee, Lee, Bae, Lee, Kang and Lee.)