Effects of Salinity on Survival Rate and Asexual Reproduction in the Early Life Stages of Aurelia coerulea

This study examined the effects of salinity on survival in the early life stages (planulae, polyps, and ephyrae) of Aurelia coerulea and on asexual reproduction (budding and strobilation) in polyps. Short-term tolerance experiments, gradual low-salinity exposure experiments, and a 90-day reproduction experiment were conducted across salinities of 0–33 psu. Planulae showed 100% survival at salinities ≥ 21 psu, but metamorphosis into polyps occurred only at salinities ≥ 25 psu. Polyps survived for 48 h at salinities ≥ 17 psu, but normal tentacle morphology and contraction responses were maintained only at salinities ≥ 25 psu. Ephyrae partially survived at salinities ≥ 17 psu, with survival increasing with salinity. Under gradual low-salinity exposure, polyps and ephyrae survived until salinity declined to 17 psu, whereas complete mortality occurred at 13 psu. Sustained budding and strobilation occurred only at salinities of 29 and 33 psu, with the highest reproductive activity observed at 33 psu. Reduced salinity inhibited metamorphosis, altered polyp tentacle morphology, and suppressed budding and strobilation, likely reflecting limited tolerance to osmotic stress. These results indicate that salinity is an important environmental factor regulating survival, asexual reproduction, and potential population dynamics of A. coerulea in coastal environments affected by freshwater-seawater mixing.