Los Farallones

Dispatches from Point Blue’s field station on the Farallon Islands National Wildlife Refuge

Glowing Sea Gherkins!

On the morning of January 7th, the field team stumbled across a curious sight to behold… thousands of tubular gelatinous creatures washed up on the rocky shorelines of the island. After a bit of sleuthing, we determined these creatures are a species of pyrosome commonly called sea pickles (Pyrosoma alanticum), or as we affectionately call them “sea gherkins!” Pyrosomes are colonial, asexual tunicates, meaning that the finger-sized, bumpy, tube-like sea pickles shown above are not actually individual organisms, but rather a group of tiny multi-cellular animals called zooids! (Welch 2017)  Working together, they filter-feed on plankton in the upper water column and orient themselves using small hair-like appendages called cilia (Welch 2017). The animals are also capable of bioluminescence; the zooids all simultaneously produce a glowing bright blue light when disturbed, as a defense mechanism against potential predators. After learning about this fact, the whole team was lucky enough to observe this mesmerizing phenomenon in Sewer Gulch. We stood in awe as the crashing waves triggered the pickles’ illuminating blue light. Although sea pickles typically reside in warm tropical waters, they have been found blooming in the colder waters of the Eastern Pacific ever since ‘The Blob,’ a large mass of abnormally warm water in 2014 and 2015 (Cornwall 2019). Although The Blob eventually receded, the invading sea pickles that came with it have stuck around. To this day, it is uncertain what kind of ecological impact these mysterious creatures may be having on the Eastern Pacific and whether if they are here to stay.


Welch, Craig (June 13th, 2017). “Bizarre, Glowing Sea Creatures Bloom in the Pacific”.  Nat Geo.

Cornwall, Warren (Feb. 1st, 2019) “Invasion of the glowing sea pickles”. Science Magazine. DOI: 10.1126/science.363.6426.445