Researchers find that ocean’s glow is unpredictable




Bioluminescence was the buzzword among researchers at Scripps Institute of Oceanography last month, as they prepared for a natural display of fireworks at sea — a phenomenon that is both rare and unpredictable. And they’re talking about it again this week, since it’s returned to local waters.

Put simply, bioluminescence is the emission of light by a living organism. The most popular terrestrial organisms to exhibit visible bioluminescence would probably be the firefly and the glowworm, but bioluminescence also occurs amongst a wide range of aquatic and marine life.

The excitement started during the day on May 6, when a band of red waters, or “red tide,” began to sweep towards the Southern California shore. According to a memo sent that day by Melissa Carter of the Scripps Institute, a phytoplankton known specifically as Lingulodinium polyedrum, which can form dense blooms and discolor the water when enough cells are present, was responsible for the ever-present redness of the water.

The bloom came with little notice. Even the world’s leading oceanographers have a limited ability to predict when these dense blooms of algae will appear.

“The only way I know of to predict that a bloom might become visible at the surface of the ocean is to know that it’s already growing below the surface,” said Professor Peter Franks of SIO. And, he added, that isn’t something that is actively measured in this area.

Years usually elapse between one major bloom and the next. But although the blooms are rare and unpredictable, various environmental factors and interactions within the ecosystem are thought to play a role in forming them.

“We get dense algal blooms (roughly) every five to seven years around here, but to my knowledge they are not correlated with anything we know of,” Franks said. “I don’t think anyone knows why the ‘red tides’ get to such high biomass. It’s probably a combination of nutrient inputs by the ocean physics, physiological and behavioral responses of the organisms, and the possibility of reducing mortality by forming dense subsurface layers.”

In contrast to HABs — “harmful algal blooms” which are also said to also create a “red tide” — blooms dominated by Lingulodinium polyedrum are generally harmless to marine life and humans, said Scripps Ph.D. Student Peter Barry.

Much like certain types of HABs, however, it is highly bioluminescent at night, and this became most apparent when the Southern California ocean waters began to glow. When the glow showed up in early May, it stirred up much excitement among the Scripps community, local scientists and everyday ocean lovers. In fact, the glow of the waves could be seen by anyone with a good set of eyes and a couple minutes of patience.

From the surface, the usually white ruffles of the ocean waves were illuminated with a bluish and greenish glow — an interesting contrast to the redness that had been observed in the daytime.

On the night of May 7, Barry was joined by fellow Scripps Ph.D. Tom Fitzpatrick and James Traer, who suited up in full scuba gear in order to experience the bioluminescence firsthand. As they set off into the soon-to-be midnight water, the presence of the phytoplankton could be seen responding to their motions as they trudged out into the sea. It illuminated the splashes of water with a familiar glow. About an hour and fifteen minutes after departing, the trio emerged from the water all smiles.

Traer recounted his underwater experience with excitement: “I would wave my arms around in the darkness of the ocean floor and observe an explosion of trailing lights,” he noted. “It was amazing.”