Marine organisms use previously undiscovered receptors to detect, respond to light

Students with an oceanography instrument — Field samples were collected during a 2015 cruise in the North Pacific. Co-author Bryndan Durham (center) recovers the sampling instrument. The gray bottles open and close at specific depths to collect seawater samples.

Just as plants and animals on land are keenly attuned to the hours of sunlight in the day, life in the oceans follows the rhythms of the day, the seasons and even the moon. A University of Washington study finds the biological light switches that make this possible.

Single-celled organisms in the open ocean use a diverse array of genetic tools to detect light, even in tiny amounts, and respond, according to a study published the week of Feb. 1 in the Proceedings of the National Academy of Sciences.

“If you look in the ocean environment, all these different organisms have this day-night cycle. They are very in tune with each other, even as they get moved around. How do they know when it’s day? How do they know when it’s night?” said lead author Sacha Coesel, a research scientist in oceanography at the UW.

Though invisible to the human eye, ocean microbes support all marine life, from sardines to whales. Knowing these communities’ inner workings could reveal how they will fare under changing ocean conditions.

“This work dramatically expanded the number of photoreceptors — the different kinds of those on-off switches — that we know of,” said senior author Virginia Armbrust, a UW professor of oceanography.