• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.23 no.2
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• pp.76-90
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• 2018

To determine the distribution of mercury (Hg) in the coastal surface sediments around the Korean peninsula, the baseline concentration of Hg was estimated, the extent of contamination was assessed, and the factors controlling the distribution were discussed. The concentrations of Hg in surface sediments were significantly high in Jinhae-Masan Bay in the South Sea, Ulsan-Onsan Bay and Yeongil Bay in the East Sea, but Hg in other sediments showed a similar distribution to Cs and relatively very low concentration between 0.21 and $39.5{\mu}g/kg$ ($13.6{\pm}7.80{\mu}g/kg$). Compared to the sediment quality guidelines in Korea, 8 % of the surface sediments (n=282) analyzed in this study exceeded the values of the threshold effects level (TEL), and six sediments collected around Onsan Port were higher than the value of the probable effects level (PEL). The contamination levels of Hg were assessed by the enrichment factors using the baseline concentration (2.06Cs+1.75) based on the residual analysis from the linear regression line for Cs, and further, factors controlling the distribution of Hg were discussed by the comparison with geochemical substances depending upon the Hg enrichment level. Hg concentrations were correlated well with Cs concentration in the range of less than 1.69 of EF implying grain size control, while in the range of 1.69 and 4.03 Hg concentrations were correlated well with Fe oxyhyroxide and organic carbon contents, which indicates Hg was enriched by superior sorption capability. On the meanwhile, samples with higher EFs (4.03 to 74.9) showed fairly positive correlations with other metals (Cu, Zn, Pb) rather than geochemical substances. For samples in Youngil Bay and Ulsan-Onsan Bay (n=30), Hg concentrations were correlated only with other metals rather than geochemical substances implying simultaneous supply of metal particles from metal refineries. But samples at Gosung, Sokcho and Uljin coast were correlated well with organic carbon even though they had high EFs. In addition, samples in Jinhae-Masan Bay with high contents of S were enriched by relatively high sulfide formation.

• Korean Journal of Ichthyology
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• v.36 no.1
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• pp.48-57
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• 2024

Distribution status and extinction threat evaluation of an endangered species, Cobitis choii, were investigated from 2015 to 2019. In 2015 and 2018, we investigated past appearance sites of C. choii. In 2015, 163 individuals from nine sites were collected by surveying 19 stations. In 2018, 19 individuals from five sites were collected by surveying 22 sites. In 2019, 156 individuals from 12 sites were collected as a result of a survey of 79 sites of past appearance and potential appearance of C. choii. Appearance regions were Mihocheon (Baekgokcheon (2 sites), Chopyeongcheon (1 sites)), Gapcheon (3 sites), Yugucheon (2 sites), Jicheon (4 sites), and Geumgang mainstream (2 sites). Among these appearing regions, Baekgokcheon, Yugucheon, and Mihocheon mainstreams showed a sharp decline in population. Baekgokcheon was estimated to have a habitat change due to a project to raise the bank of Baekgok Reservoir. Yugucheon was estimated to have a habitat disturbance due to flood-induced collapse and reconstruction of weir. Mihocheon mainstream was estimated to have water pollution and habitat disturbance. On the other hand, Chopyeongcheon and Geumgang mainstream were newly habitat identified and Gapcheon was noted to show an increase in the number of individuals. After performing extinction threat evaluation, C. choii was evaluated as Endangered (EN A2ac) due to its rapid population decline (more than 50%) in its habitats of Baekgokcheon, Yugucheon, and Mihocheon based on criteria A, while it was evaluated as Vulnerable (VU B1ab (iii,v) +B2ab +B2ab (iii,v)) due to its narrow extent of occurrence (EOO, 1,735 km²) and area of occupancy (AOO, 36 km²) in 6 locations with a continuous population decline based on criteria B. Therefore, the final threat of extinction grade was evaluated as Endangered (EN A2ac). In Baekgokcheon, Yugucheon, and Mihocheon mainstream where the population has declined rapidly recently, conservation measures are urgently required to increase its population.