Citizen science effectively monitors biogeographical and phenological patterns of jellyfish

Abstract

Jellyfish encounters are set to rise as human activity in the marine environment increases. Although jellyfish pose a threat to human health and the economy, there is limited understanding of their population dynamics. To mitigate the impact of jellyfish and gather information on their biogeographical patterns, we created MedusApp, a citizen science tool for collecting data on jellyfish sightings in the Spanish Mediterranean. From 2018 to 2021, the most commonly sighted species were Pelagia noctiluca, Rhizostoma pulmo, Cotylorhiza tuberculata, and Rhizostoma luteum. Sightings increased for all species, but the Jellyfish Intensity (JI) index showed no significant rise in overall abundance. The JI revealed the inter-annual fluctuations in R. pulmo's nature and more a larger purporting of weight on total JI from C. tuberculata while P. noctiluca decreased. The seasonality of the four species remained stable, providing a basis for time-effective management strategies. MedusApp has further provided new evidence that R. luteum is expanding its range northward in the Western Mediterranean and becoming a commonly observed species. The information collected through MedusApp can be used to improve jellyfish management measures, such as monitoring, control, and alert systems, to reduce conflicts with humans and the environment.