Sargassum species have been reported to be a source of phytochemicals, with a wide range of biological activities. In this study, we evaluated the hepatoprotective effect of a meroterpenoid-rich fraction of the ethanolic extract from Sargassum serratifolium (MES) against tert-butyl hydroperoxide (t-BHP)-treated HepG2 cells. Treatment with MES recovered the cell viability from the t-BHP-induced oxidative damage in a dose-dependent manner. It suppressed the reactive oxygen species production, lipid peroxidation, and glutathione depletion in the t-BHP-treated HepG2 cells. The activity of the antioxidants induced by t-BHP, including superoxide dismutase (SOD) and catalase, was reduced by the MES treatment. Moreover, it increased the nuclear translocation of nuclear factor erythroid 2-related factor 2, leading to the enhanced activity of glutathione S transferase, and the increased production of heme oxygenase-1 and NAD(P)H:quinine oxidoreductase 1 in t-BHP-treated HepG2 cells. These results demonstrate that the antioxidant activity of MES substituted the activity of the SOD and catalase, and induced the production of detoxifying enzymes, indicating that MES might be used as a hepatoprotectant against t-BHP-induced oxidative stress.

The reproduction and population dynamics of Portunus trituberculatus were investigated in 5402 specimens caught on the western coast of Korea, Yellow Sea, during three consecutive years between September 2003 and August 2006. The overall ratio of males to females was 1 : 1.08, although the sex ratio varied slightly from month to month and year to year. Over 90% of the females were in the maturing or mature stages in March-May, the gonadosomatic index was highest in April-May, and ovigerous females peaked in July. These results indicate that the main breeding season was between April and July. The frequency of crab larvae was highest in August, which is clearly supported by the breeding season. At sexual maturity, 50% of females had an estimated carapace width (CW) of 13.12 cm. The relationship between the number of eggs per brood (EN) and CW was ln EN = 3.04 ln CW + 6.83 for non-eyed eggs, and ln EN = 3.31 ln CW + 6.03 for eyed eggs. No brood loss occurred during the incubation period. The reproductive output was 0.34. The growth performance index showed that females grew faster and reached a larger size at the same age than males (L _∞ = 22.1 mm CW and K = 0.66 yr^–1 for females, and L _∞ = 20.4 mm CW and K = 0.72 yr^–1 for males).

We investigated the spatial variability of macrofaunal and meiofaunal assemblages in intertidal flats on the southern coast of Korea. Abiotic and biotic samples were collected at five stations. The species richness, density, and composition of the assemblages differed significantly among stations. Nematoda and Annelida were the most dominant meiofaunal and macrofaunal taxa, respectively, although taxon dominance differed among stations. Distance-based linear models showed that sediment-related variables and heavy metals were the main environmental factors determining the spatial variability of the assemblages. Macrofauna had only sediment-related variables and heavy metals as major environmental factors, but meiofauna were also influenced by other environmental factors such as sea surface temperature, dissolved oxygen-related variables, and salinity. This study can provide basic ecological data for understanding the spatial distribution of macro-meiofaunal assemblages and aid in the development of marine environmental management strategies on the western south coast of Korea.

The feeding habits of the sand shrimp Crangon hakodatei in the East Sea (Korea) were investigated through analysis and comparison of the stomach contents of 602 individuals according to season, shrimp size class, and prey diversity. The diet of C. hakodatei consisted of 17 prey categories mainly comprising crustaceans, molluscs, polychaetes, nematodes, algae, and fishes, with crustaceans dominating the diet. Molluscs, nematodes, and fishes were also important prey, whilst other categories including polychaetes and algae comprised small percentages of the diet. For small C. hakodatei individuals (10 mm CL) tended to be more dependent on amphipods than mysids. Amphipods and mysids together constituted the dominant prey, accounting for more than 50% of the diet in terms of both percent occurrence and relative abundance. The abundance and occurrence of prey showed a seasonal variation, with amphipods and mysids being the predominant prey in autumn (45%), winter (30%), and spring (40%). Amphipods were the dominant prey with regard to season, size class, sex, and area.