Are bright blue jellyfish really swarming off the San Diego coast?
SAN DIEGO (FOX 5/KUSI) — Some San Diegans may have stumbled across a recent viral video on Instagram apparently depicting bright blue jellyfish swarming in shallow waters described as near the city’s coast.
The video, which was posted by the account “@socalbucketlistaddicts” earlier this month, showed hundreds of Catostylus mosaicus, or blue blubber jellyfish, swimming in calm waters. The video included a locator that claimed it was captured in the Mission Bay area.
The video on its face appeared to mark an incredibly rare instance of a non-native species of jellyfish blooming in the region, but experts say San Diegans should not pay it any heed: To date, there has not been any record of the blue blubber jellyfish in the region’s waters.
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As jellyfish expert Linsey Sala with Scripps Institution of Oceanography explained, the blue blubber jellyfish is a species that is mostly known for residing in the warm waters of the Indo-Pacific, particularly those around Australia and the Philippines.
According to the biodiversity data website iNaturalist, the blue blubber jellyfish is considered the most common type of medusae that can be found along the eastern coastline of Australia.
The species particularly favors estuaries, semi-enclosed lagoons and shallow bays of this region due to their often higher salinity, iNaturalist added. Higher salinity helps support their feeding and better control their osmoregulation, or the regulation of their body’s water content.
A nearly identical video of a bloom of blue blubber jellyfish, which was posted to TikTok two weeks prior to the one showing the jellyfish with a San Diego locator, appeared to trace back to shallow waters in the Indo-Pacific region.
FOX 5/KUSI reached out to the Instagram account for more details on where the video came from, but its owner did not respond to the inquiry.
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But that’s not to say San Diego does not have its fair share of invertebrates in the region’s coastal waters.
Frequent beachgoers may have stumbled upon the jelly-like Velella velellas, or “By-the-wind Sailor,” that have washed up on the region’s shores in recent weeks. San Diego is also known to have a population of Aurelia labiata, or Greater Moon Jelly, according to iNaturalist.
Velella velellas as spotted in Imperial Beach on Apr. 27, 2024. Moon jellyfish were spotted near Coronado Kays in June 2023. (Photo: Vishwas Lokesh)
San Diego’s naturalists have also observed the tiny Phylum Ctenophora, or comb jellies, near the region’s waters. Comb jellies, which are closely related to sea jellies, are incredibly common and can be found inhabiting waters worldwide.
Most of these species seen in our waters are not dangerous to humans, even though they still might sting. Experts say the greater moon jellyfish’s sting, for instance, is only slightly venomous for humans, producing prickly sensations or mild burning in the worst cases.
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