Soyun Choi

Aquaculture farms cultivating Saccharina japonica are highly active in Wando, Korea, and Rongcheng, China. However, the yield of S. japonica significantly declined in the Rongcheng region in 2022 compared to previous records, whereas that in Wando remained at a normal level, presumably due to the presence of a pathogenic microbiome. We used environmental DNA (eDNA) metagenomic analysis to compare the microbial compositions of seawater from aquaculture farms in Wando and Rongcheng. Seawater samples were collected from one Korean site in Wando (WA) and two Chinese sites in Ailian Bay (AB) and Lidao Bay (LB). Metagenomic analysis focusing on the microbial 16S rRNA identified 38 phyla and 58 families of microbiomes in all regions. Potentially pathogenic bacterial groups associated with S. japonica in AB and LB were more abundant than in WA, suggesting their potential influence on mortality and the decline in the harvest yield of S. japonica. The microbial composition of WA was distinguished from those of the other two sites, which clustered together with higher similarity. Since the S. japonica aquaculture industry is important for both countries, this comparative eDNA monitoring is a valuable initiation towards the next step of problem-solving practices in coastal management in these two aquaculture systems.

The crocodile icefish, Chionobathyscus dewitti, belonging to the family Channichthyidae, is an endemic species of the Southern Ocean. The study of its biological features and genetics is challenging as the fish inhabits the deep sea around Antarctic waters. The icefish, the sole cryopelagic species, shows unique physiological and genetic features, unlike other teleosts. It lacks hemoglobin and has evolved antifreeze proteins. Here, we report the genome sequencing data of crocodile icefish produced using the Illumina Novaseq 6000 platform. The estimated genome size was 0.88 Gb with a K-value of 19, and the unique sequence, heterozygosity, error, and duplication rates were 57.4%, 0.421%, 0.317%, and 0.738%, respectively. A genome assembly of 880.69 Mb, with an N50 scaffold length of 2401 bp, was conducted. We identified 2,252,265 microsatellite motifs from the genome assembly data, and dinucleotide repeats (1,920,127; 85.25%) had the highest rate. We selected 84 primer pairs from the genome survey assembly and randomly selected 30 primer pairs for validation. As a result, 15 primer pairs were validated as microsatellite markers.

The increasing number of elderly people who live alone has raised serious social issues such as isolation, care problems, and lonely death. In particular, since elderly people who live alone have a higher rate of depression than general elderly people due to disconnection from good health and social life, it is necessary to promote health, form a social network, and increase leisure activities to prevent depression. Therefore, this study used data from the Korea Welfare Panel in 2020 and conducted a regression analysis to determine how much the health status, leisure life, and social relationship satisfaction of senior citizens who live alone explain the degree of depression. As a result of this study, it was found that the higher the education level of elderly people who live alone, the lower the feeling of depression, and the worse the health status, the higher the depression. The effect of education level on depression was significant with adjusted R2 .020 (p>.001), but the impact was not so great. However, in the regression model with health status added, ΔR2 increased by .151, confirming the effect of health status on depression. The explanatory power of the regression model, in which the variables of social relationship satisfaction and leisure life satisfaction were added, showed that the adjusted R2 was .203 (p>.001). That means that the higher the satisfaction with the social relationship and the higher the satisfaction with leisure activities, the lower the level of depression. Based on the results of analysis, this study proposes measures to prevent and respond to depression of elderly people who live alone.