This study presents the unusual mass mortality of Rhizostoma pulmo occurred on the coast
of İstanbul in the Sea of Marmara in the first week of December 2020. The density of dead
R. pulmo was 45±5 ind./m2
in the area and the mean diameter was 24.3 cm. The role of
physical parameters, marine pollution, nutrient influx, climate change, overfishing,
invasive species on jellyfish blooms and its effect on human health are discussed briefly
in this study