Venomous Foes in Mediterranean Africa: Occurrence of Physalia physalis (Linnaeus, 1758), and First Records of Glaucus atlanticus Forster, 1777 for Algeria and Tunisia

Climate change can promote shifts in species’ biogeographical distribution, but their monitoring is a challenge in the hardly accessible marine environment. In such cases, citizen science allows collecting data on scales unattainable for researchers. This study uses a citizen science approach through social media platforms to describe a high-occurrence event of the siphonophore Physalia physalis in Tunisia during April 2021, which, in addition to literature records, add to more than 50 colonies recorded in 2021 in Algeria and Tunisia. This is the highest abundance ever reported in these countries. Moreover, 20 specimens of Glaucus atlanticus were recorded in August 2022 in Tunisia, and 1 specimen in June 2023 in Algeria, constituting the first record for the species in both countries. For P. physalis, the reported event could result from an increase of citizen science in these countries, driving an increase of reports uploaded to social media, along with a high occurrence of colonies in 2021. Finally, high occurrence events might be partially predicted by westerly wind prevalence in the Strait of Gibraltar and nearby areas, a geographic bottleneck for colony entrance in the Mediterranean Sea. Overall, this study illustrates the key role of citizen science in resource-limited countries and the need of reinforcing these networks to generate eco-environmental awareness and scientific knowledge towards the achievement of UN Sustainable Development Goals.