A few years ago, my son and I went kayaking in Morro Bay. As we were coming back that evening, my son noticed “blue-green sparks” flying off his paddle. He was probably seeing a type of dinoflagellate plankton that emits flashes of blue-green light in response to agitation. This is called bioluminescence.
Acting like light sticks at Halloween, it’s the production of light by living organisms through an internal chemical reaction. This can be seen in fireflies back East or even in glow worms that live in canyons along the Central Coast.
Almost all marine bioluminescence is blue-green in color, probably because blue-green light travels farthest in water. On the other end of the light spectrum, red and yellow hues are quickly absorbed by the water column as you descend. Bioluminescent plankton inhabit all the world’s oceans but not its freshwater lakes.
Upwelling brings cold and nutrient-rich water to the surface along the immediate shoreline. When the northwesterly winds relax and upwelling diminishes, the bioluminescent plankton can multiply rapidly. Combined with the interactions of the deep scattering layer, they can produce just the right conditions for bioluminescence. The light of just a single dinoflagellate can be seen at night. When millions upon millions of tiny plankton give off their light at the same moment, the ocean can turn into a nearly indescribable light show.
One night, we were diving off San Clemente Island during a period of high bioluminescence activity, and a pod of Pacific white-sided dolphins came swimming by. The dolphins resembled a gaggle of fast-moving, brilliant blue torpedoes with trails of glowing bubbles corkscrewing toward the surface.
One moonless night, while serving in the U.S. Navy and traveling through the Strait of Hormuz — situated between the Persian Gulf and the Gulf of Oman — on the guided-missile frigate USS Estocin back in the early 1980s, the bioluminescence was frightfully strong. The greenish wake of our ship could be seen from miles away as an ever-expanding chevron on the surface of an absolutely flat and calm sea as billions of agitated plankton gave off their light.
A few years later, during a nighttime anti-submarine warfare exercise at a sonar range off the Bahamas, we haphazardly took advantage of bioluminescence. Our aircrew was tasked with tracking a British fast-attack submarine with our trusty but outdated H-2 Seasprite Helicopter.
During our briefing, we were told we would probably be able to keep in contact for only a few minutes before the sub would disappear in the dark void of the ocean. Sure enough, we deployed an active sonobuoy from our helicopter on the sub’s last known position and got a couple of pings or echoes from it before we lost contact.
As we were getting ready to deploy another buoy, one of the pilots saw the distinctive blue-green light coming from one area of the ocean. We immediately flew to where the light was coming from and deployed another buoy. Unbelievably, I got a couple of pings. No doubt the British sub commander was startled and surprised that we still had contact and started to make very aggressive maneuvers. That only caused his sub to produce more bioluminescence, making it easier to track him.
After a few hours of tracking this guy, we ran out of buoys. With our fuel beginning to run low, we decided to return to our ship. From that night on, our helicopter crew was considered the anti-submarine warfare masters of the fleet.