Heo Jin Suk1, Lee Hak-Jeung1, Hwang Mi Sook1 and Hwang Eun Kyung1
1Fisheries Seed and Breeding Research Institute,
National Institute of Fisheries Science, Haenam 59002, Republic of Korea
Discoloration of Pyropia by nutrient deficiency in seawater has been occurring periodically in various regions since the first report at 2010 in the western coast of Korea. However, an unusual discoloration event of Pyropia observed between end of December 2021 and February 2022 in Haenam, southwestern coast of Korea. Reason of the event presumed to be due to the outbreak of occurrence of large-size phytoplankton Cylindrortheca closterium in winter. The phenomenon has serious economic damage about 13 million US$ to the local fishermen and adversely affects the production of the Pyropia industry. Korean Pyropia industry is a national core one that is moving forward with the goal of exporting 1 billion US$. In addition, it is estimated to be worth about 4 billion US$ due to an continuous increase exports. Therefore, this kind of unusual event could be an obstacle of Pyropia industry. In this study, we investigated that phytoplankton density, environmental factors (seawater temperature, salinity, DO and nutrient concentrations) and growth of Pyropia. To test recovery of discolored thalli, culture experiment conducted under supplying nutrients. According to nutrient deficiency period, color of thalli was significantly recovered within 7 days. We report that the first occurrence of winter diatom blooms with discoloration of Pyropia in Korea.