Euryhalinity and thermal tolerance of Phyllorhiza punctata (Scyphozoa) scyphostomae: life history and physiological trade-offs

Phenomena such as global warming, rising sea temperatures and extreme weather and climate anomalies such as floods and heat waves have been shown to alter absolute salinity values. While affecting marine and estuarine population dynamics, these scenarios may also favour the invasion and proliferation of opportunistic and potentially harmful species in new geographical areas—such as blooming jellyfish. These organisms are one of the less studied taxa, particularly the proliferative asexual benthic phase, to which effects of in situ and experimental global change scenarios are poorly addressed. Acclimation and plasticity to global change scenarios were individually assessed through life history and physiological responses (survival, settlement time, time until maturity, feeding activity, asexual reproduction and behaviour) of laboratory-reared ciliated buds and polyps (= scyphostomae) of the invasive Phyllorhiza punctata (Cnidaria: Rhizostomeae). The present study evaluated the effects of two temperature levels (21 °C—current thermal scenario, or 25 °C—warming scenario) and six salinity regimes resembling estuarine and marine conditions (15, 20, 25, 30, 35 or 40) during 21 days. Under warming, P. punctata scyphostomae showed faster development and budding rates upon estuarine-like salinities, but higher mortality and reduced development under marine-like conditions—an ecological niche trade-off since at 21 °C such pattern was not found. Overall, our results suggest that global changes might prompt P. punctata proliferation through polyp colonisation mainly in estuarine areas and potentially increase blooming events with further implications at local and regional scales.