Effect of Temperature and Irradiance on Upright Thalli Formation in the Crust Culture of Polyopes lancifolius (Rhodophyta)

The red alga Polyopes lancifolius has traditionally been used in jelly-based foods. We investigated how to optimize indoor cultivation conditions during the seedling crust stage to support their transition to upright thalli formation. Experiments were conducted under five temperatures (10, 14, 18, 22 and 26°C) and three irradiance settings (20, 50 and 80 μmol m-²s-¹). The highest growth rate of the crusts was observed at 26°C and 20 μmol m-²s-¹, achieving 8.7% day-¹. At 22°C, the growth rate increased as irradiance decreased (20 >50 >80 μmol m-²s-¹). The density of upright thalli was most significant at 14°C and 80 μmol m-²s-¹, with 31.3±5.0 individuals mm-² (≥100 μm in length). At 14°C, thalli formation density improved with higher irradiance (80>50 >20 μmol m-²s-¹). During the first 10 weeks, Polyopes adapted to the high-temperature and low-irradiance conditions in the crust stage. After this period, the cultivation environment should be shifted to low-temperature and high-irradiance conditions to facilitate the growth of upright thalli. Lowering the temperature to 14–18°C and increasing the irradiance to over 60 μmol m-²s-¹ will promote upright thalli formation and ensure optimal growth.22Nkc

Seasonal Changes in the Marine Algal Community of the Daejin Coast, Mid-eastern Coast of Korea

The mid-eastern coast of Korea is located at the boundary between cold and warm currents, which causes changes in the distribution and composition of marine organisms in response to fluctuations in the marine environment. To understand the seasonal changes in the seaweed community, we investigated its species composition, biomass, cov- erage, and frequency from November 2022 to August 2023. A total of 45 species (7 green, 18 brown, and 20 red algae) were found in the study area. In the intertidal zone, the number of species decreased from autumn to summer; the biomass peaked during winter (471.94 g wet weight m-2). Seaweed groups were the dominant functional groups, which were coarsely branched, filamentous, and sheet-like during autumn, winter, spring, and summer. The morpho- functional group was dominated by turf species. In the subtidal zone, the number of species increased during autumn to spring, whereas the biomass peaked during spring (655.27 g wet weight m-2). The functional group was dominated by coarsely branched species throughout all four seasons, whereas the morpho-functional group was dominated by canopy species. Consequently, changes in the biomass of brown and red algae are recognized as key drivers of sea- sonal changes in seaweed communities.22Nkc