This is acid.
Sulphuric acid to be exact.
A highly corrosive substance, also known as oil of vitriol, H2SO4 is one of those ‘strong acids’ essentially meaning that yes, I actually wear gloves/goggles/lab coat/body armor (if available) when I am using it for legitimate fear of it getting on me and my skin melting off.
While I personally shy away from things that can cause me such bodily harm, certain species of leafy denizens in the genus Demarestia embrace it by actually concocting and harboring Sulphuric acid in their vacuoles. Desmarestia is a hardcore seaweed like that.
Rightly named “Acid Weed,” the internal pH of Desmarestia has been estimated as low as 0.6 pH. For reference, the pH of gastric acid (the stuff in your stomach that liquefies food) sits at roughly 1.5 to 3.5.
These caustic brown seaweeds are found primarily in cold-water habitats and compose the dominant aquatic flora in the Antarctic. Though the primary function of Sulphuric acid in Desmarestia tissues is largely unknown, studies have shown that it works rather effectively as a predator deterrent. Go figure.
In my experience, handling Desmarestia with bare hands will not bring harm to the unsuspecting (though I have held other seaweeds that gave me the finger tingles…pretty impressive for a plant). However, when exposed to physical damage or high temperatures, Sulphuric acid released from broken vacuoles will destroy algal tissues. Similarly, if placed in a bucket of water with other live critters, a bucket of un-live critters will result.
Photos: 1. Shutterstock 2. MBARI 3. An Ocean Garden
Eppley RW, Bovell CR. 1958. Sulfuric acid in Desmarestia. Biol Bull Mar Biol Lab: 115:101–106
Pelletreau, KN; Muller-Parker, G. 2002. Sulfuric acid in the phaeophyte alga Desmarestia munda deters feeding by the sea urchin Strongylocentrotus droebachiensis MARINE BIOLOGY : 141 (1): 1-9