He guesses it was six or seven years ago, but Terry Tomalin remembers the details of the event like it was last night.

"I know it was May 31st because it was the last day of snook season," said the avid outdoorsman and writer for the St. Petersburg Times. "It was at the pass near Honeymoon Island, on an incoming tide, and I saw this glow around the bombers," he said, referring to the 6-inch fish-shaped plastic plugs he was using in an attempt to hook a snook.

It's a quick flash that lasts about a second after the water is disturbed.

Tomalin has seen it a handful of times in the 14 years he's been exploring Tampa Bay, especially while kayaking at night, he said. But the fishing experience was by far the most memorable.

"It's kinda freaky the first time you see it," said Tomalin. "You know, you've been out there fishing for hours, and you look down and see something 'nuclear' in the water."

"The water sort of lights up like fireflies," he said.

In reality, this naturally flashy phenomenon has nothing to do with nuclear energy, and there certainly aren't fireflies swimming around in Tampa Bay, but it is the same reason that fireflies glow.

It's called bioluminescence, and it's right here in the waters that bathe our sunny state.

"Actually, anywhere warm temperate or tropical should do it," said Karen Steidinger, senior research scientist at the Florida Marine Research Institute in St. Petersburg. "These are seasonal things, and the best chance to see them is at night from summer through fall."

Bioluminescence is the fancy name scientists have given to the light produced by a chemical reaction that occurs inside all sorts of organisms, but mostly those that live in the sea: bacteria, crustaceans, jellyfish, fish, and more. In the surface waters of Tampa Bay, however, the most likely source of the eerie glow is a tiny dinoflagellate, the same type of critter responsible for those irritating blooms often called red tides.

Dinoflagellates, microscopic organisms, are always present in Tampa Bay, but a prerequisite for a bioluminescent event is that bunches of the right organism reproduce to concentrations above their normal background concentration, Steidinger explained. And the water usually needs to be physically disturbed to see it, she said.

Another word for dinoflagellates is Pyrrhophyta, which literally means "fire plants," but despite the association between light and fire, bioluminescent dinoflagellates are pretty cool. Literally.

Only certain dinoflagellate species have the ability to light up. The reaction that causes it produces a type of "cold light," which means it does not produce heat like most light reactions. The likely sources of the cool light in Tampa Bay even have cool names: Pyrodinium bahamense, Alexandrium monilatum, Gonyaulax polygramma, Noctiluca, and Pyrocystis, among others, said Steidinger.

"I remember a time at Coffee Pot Bayou," Steidinger said. "I was called into work at 7 or 8 pm to identify a bloom. They didn't know if they should be afraid of it, or what, and about 12 people were waiting at the bayou when I showed up with my portable scope (microscope) to identify it." Gonyaulax polygramma was the culprit of that bloom, she recalled, but there was certainly nothing to fear.

"We skipped stones in it," she said.

The flash reaction is caused by two chemicals appropriately called luciferin and luciferase. Lucifer, Latin for "light bearer," might suggest that these dinos have a devilish side, but the dinos doing the flash dance are certainly not all bad.

"Plankton blooms are natural phenomena," said Steidinger in a mantra-like tone. She has studied blooms for nearly four decades. "And bioluminescent organisms are natural where they occur," she added.

Once physically stimulated in any number of ways - as by an oar, fishing lure, or stones - the dinoflagellates in the water give off a blue-green light, she added, because blue-green light travels the farthest in seawater. At peak flash, a single dinoflagellate can release about 1010 photons (light packets) per second, whereas a typical 100-watt lightbulb emits around 1018 photons.

"We've even released sea turtle hatchings in it at Fort DeSoto Park. As soon as the hatchlings hit the water, you could see the blue-green light caused by the movement of their little paddles. It was really kinda cute," Steidinger said.

The "burglar alarm theory" of bioluminescence posits that dinoflagellates do their split-second flash dance to avoid predators. So while you are asleep in bed, Tampa Bay is the site of survival of the fittest at its best (or at least its brightest).

"Think of yourself as a little predator like a copepod (tiny shrimp-like creature)," explained Steidinger, with an infectious enthusiasm that makes you want to know more. "It's nighttime, and you're swimming along trying to eat these dinos from the water, and all of a sudden it lights up from being physically disturbed!"

The flash acts as an alarm that attracts attention of larger fish that might be around, she explained. The fish are like the police that are attracted by the flash of the burglar alarm and then eat the illuminated copepod, thereby sparing the dino its life.

That's a pretty savvy strategy for a single-celled critter.

Bioluminescence is not a 'one size fits all' occurrence. Other marine critters flash for reasons other than self-defense: to help them find food in the sunless depths of the ocean or to help them attract mates. And throughout the sea, bioluminescence comes in all colors of the rainbow: red, orange, yellow, green, blue and violet.

But in Tampa Bay, it's all about the blue-green flash dance of the dinoflagellate. If you're lucky, you can head to the water one evening this summer when the conditions seem right. There's no charge.

And it's a pretty cool show.

- By Kristen M. Kusek