Trophic assessment of red seabream (Pagrus major) as a possible bioindicator of human activities in the South Sea of Korea using stable C and N isotopes.

To assess the impact of sand mining on resource utilization by the red seabream (Pagrus major) and the trophic structure of fish assemblages two years after mining activities, we compared stable isotope ratios (δ13C and δ15N) and isotopic niches between aggregated mining and control sites in April and August 2022. Our results showed no spatial differences in the δ13C and δ15N values of red seabream between the sand mining and control sites, suggesting that the mining did not affect their dietary resources. Furthermore, the considerable overlap among fish consumers suggested that the fish food web in mining areas has trophic functions similar to those in natural habitats after mining activities. Overall, our study enhances our understanding of ecosystem conservation and the ecological-based management of coastal areas.

Pseudoruegeria limi sp. nov. isolated from mud flats in the Yellow Sea in Korea.

A Gram-negative, aerobic, non-motile and rod-shaped bacterial strain, D-17(T), was isolated from mud flats in the Yellow Sea in Korea. Phylogenetic trees based on the 16S rRNA gene sequence showed that strain D-17(T) belongs to the genus Pseudoruegeria and it shared 97.5 % similarity with the type strain of Pseudoruegeria haliotis WM67(T). The sequence similarities with Pseudoruegeria litimaris HD-43(T) and Pseudoruegeria aquimaris SW-255(T) were 96.9 and 96.1 %, respectively. Strain D-17(T) was found to grow with 0.5-6 % (w/v) NaCl, at 20-30 °C, and at pH 6.5-8.0. Strain D-17(T) was determined to contain Q-10 as the predominant ubiquinone and summed feature 8 (C18:1 ω7c and/or C18:1 ω6c, as defined by the MIDI system) as the major fatty acids. The major polar lipids were identified as phosphatidylglycerol, diphosphatidylglycerol, an unidentified aminolipid, an unidentified glycolipid, an unidentified lipid and four unidentified phospholipids. The DNA G+C content was determined to be 63.6 mol%. The DNA-DNA relatedness with P. haliotis WM67(T) was 32.5 %. The differential phenotypic properties revealed that strain D-17(T) can be separated from other Pseudoruegeria species. Based on the data presented in this study, strain D-17(T) represents a novel species, for which the name Pseudoruegeria limi sp. nov. is proposed. The type strain is D-17(T) (=KCTC 32460(T) =JCM 19487(T)).

Aestuariibaculum scopimerae sp. nov., isolated from the globular ghost crab, Scopimera globosa.

A Gram-staining-negative, non-motile, catalase- and oxidasepositive bacterium, designated strain I-15(T), was isolated from a crab of the Yellow Sea, Korea. On the basis of a 16S rRNA gene sequence analysis, strain I-15(T) was shown to belong to Bacteroidetes, related to the genus Aestuariibaculum. Sequence similarity between strain I-15(T) and the only type strain of the genus Aestuariibaculum, Aestuariibaculum suncheonense SC17(T), was 96.7%. Strain I-15(T) grew at 0.5-6.0% (w/v) NaCl, at 10-42°C and at pH 4.5-8.0. It could hydrolyze starch and Tweens 80. Menaquinone-6 was the only respiratory quinone, and summed features 3 (C16:1 ω7c/C16:1 ω6c) (16.4%), iso-C15:0 (15.6%), and iso-C15:1 G (12.6%) were the major cellular fatty acids. The major polar lipids were phosphatidylethanolamine, two unidentified aminolipids and two unidentified lipids. The DNA G+C content was 39.0 mol%. Polyphasic data allowed genotypic and phenotypic distinction of strain I-15(T) from the only validly published Aestuariibaculum species. Therefore, the organism is considered a novel species of the genus Aestuariibaculum, for which the name Aestuariibaculum scopimerae sp. nov. is proposed. The type strain is I-15(T) (=KCTC 32459(T) =JCM 19486(T)).