Massive stranding of Physalia physalis (Hydrozoa: Physaliidae) on the Northwestern coast of Cuba

• Main Authors: Torres-Conde, Eduardo Gabriel, Rodríguez-Martínez, Rosa E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Centro de Investigaciones Marinas 2024
• Subjects: Beach cast; bloom; dimorphism; health risk; juvenile colonies; Portuguese man-of-war; Western Atlantic; Climate change; Human health; North Atlantic
• Online Access: https://doi.org/10.5281/zenodo.11000091

Historically, Physalis physalis (Linnæus, 1758) massive stranding events have been either infrequent or poorly documented. However, their occurrence can significantly affect human health and the stability of coastal ecosystems. This study analyzes a massive P. physalis stranding that affected Cuba’s NW coast in December 2022. During the event, eighty-five people were stung, with 38 having strong allergic reactions. To determine P. physalis abundance, we counted all colonies during the massive event along ~ 3 km coast within a 5 m strip. Density, dimorphic form (left/right-handed), and colony size were quantified using a 0,25 m 2 quadrat placed every 50 m, 10 m from the shoreline. Over ten thousand beach cast colonies were recorded, making this the event with the highest mean colony density (29,3 per m 2 ) ever reported. The massive stranding coincided with the lowest Arctic Oscillation index (-2,59) in the past 11 years during December, which led to northeasterly winds reaching up to 24 km/h, which might have favored the landings. Wind direction and speed, coupled with the dominance of left-handed colonies (71,4%), suggest the North Atlantic Subtropical Gyre as a possible origin source of the bloom. The high prevalence of juvenile P. physalis colonies (68%) likely aligns with the autumn breeding season in the northern hemisphere. The potential causes of P. physalis blooms are still poorly understood. Systematic monitoring of the distribution and abundance of this species should be a research priority considering the potential risk to human health and the fact that the blooms could become more frequent on the Atlantic coasts due to its eutrophication and climate change.