Consecutive Strandings of Porpita porpita Colonies at Different Developmental Stages Along the Coast of Jeju Island

Abstract

Porpita porpita, a pleustonic colonial hydrozoan, underwent unprecedented large-scale strandings on Jeju Island in June and October 2025. Colonies stranded in June were approximately 30 mm in diameter, whereas the October event was dominated by colonies smaller than 5 mm. Based on published growth models, the October colonies likely represented recently developed colonies, suggesting local recruitment following the initial influx. Elevated sea surface temperatures around Jeju may have facilitated rapid population expansion.