A more acidic ocean might make more sea creatures glow in the dark

Scientists have reported that some bioluminescent organisms might get brighter, while some might lose their brightness due to the increasing effects of climate change.

The report was shared at the virtual annual meeting of the Society for Integrative and Comparative Biology.

PH's effect on bioluminescence varies

Bioluminescence is a common trait among organisms in parts of the ocean. The ability to light the dark has evolved more than 90 times in different species. As a result, the chemical structures that create bioluminescence vary wildly—from single chains of atoms to massive ringed complexes.

As a result of such variability, changes in pH of the world’s oceans due to climate change could have unpredictable effects on creatures’ ability to glow.

Due to global warming, the average ocean pH is expected to drop from 8.1 to 7.7 by 2100.

Scientists measure the effect of pH on bioluminescence

To determine the effect of pH on bioluminescence, sensory biologist Tom Iwanicki and colleagues at the University of Hawaii at Manoa gathered 49 studies on bioluminescence across nine different phyla.

Data from those studies were then analyzed to see how the brightness of the creatures’ bioluminescent compounds varied at pH levels from 8.1 to 7.7.

The team discovered that bioluminescent chemicals in some species, such as the sea pansy (Renilla reniformis) increased light production twofold as the pH dropped.

Other compounds, such as those in the sea firefly (Vargula hilgendorfii), increased only about 20 percent, while some species, like the firefly squid (Watasenia scintillans), appeared to have a 70 percent decrease in light production.

Effect of the decrease in bioluminescence in organisms

The pH change could affect mating rituals, communication, feeding habits, etc. carried out among organisms in the ocean.

For the sea firefly—which uses glowing trails to attract mates—a small increase in pH could give it an advantage, but the increase will be harmful for the Firefly squid which uses luminescence for communication.