The microscopic dinoflagellates that give the Salt River mangrove lagoon its eerie blue glow are finding themselves under the microscope more and more recently. The St. Croix Environmental Association announced it is conducting its own study of the bioluminescent phenomenon that will compliment an ongoing investigation sponsored by the National Park Service.
Dinoflagellates are single-cell organisms that photosynthesize like plants but are able to propel themselves through the water. Whenever they are disturbed, they emit a flash of light.
It is believed this flash is a defense mechanism against the zooplankton that feeds on them. The light acts as a “burglar alarm,” illuminating the attacking creature and bringing it to the attention of larger predators who prey on them.
When dinoflagellates are present in large enough quantities, these flashes are visible to the human eye, resulting in the bioluminescent phenomenon kayakers observe while paddling through the Salt River lagoon.
While the origin of the glow is known, researchers still aren’t sure why some bodies of water are able to support more dinoflagellates than others.
To better understand this, the National Park Service launched a study, which is being conducted by faculty and students from the University of South Carolina, the University of North Carolina Wilmington and the University of the Virgin Islands.
Their research is focused on analyzing quality and nutrient composition of the water, the distribution of the dinoflagellates around the lagoon and the abundance of “cysts,” dormant dinoflagellates embedded in the sea floor.
Paul Chakroff, executive director of SEA, said the organization decided to host its own study because the members felt the scope of the existing research project was not broad enough. They felt it was important to also study the vibrancy of the bioluminescent glow as well.
SEA raised $26,000 from the community to fund the study, which will be led by Dr. Michael Latz of the Cripps Institute of Oceanography at the University of California San Diego, an expert on bioluminescent organisms.
At a public lecture Thursday night, Latz told the crowd that bioluminescent lagoons are “gems.” He said it is an incredibly rare phenomenon, with only seven year-round lagoons known to exist in the Caribbean.
“It’s not every coastal bay that turns into a bioluminescent bay. There’s something really special going on and we need to understand the science behind it,” he said.
Latz said that the intensity of the bioluminescent glow in a body of water is directly proportional to the number of dinoflagellates present and is therefore a measure of the health of the population. By studying variations in the intensity of the glow, scientists can discover factors that promote or impede the growth of the organism.
For instance, during a similar study conducted on a bioluminescent lagoon on Vieques, Latz discovered the intensity of the glow diminished significantly after major storms. He believes this is because the influx of fresh rainwater lowered the salinity of the pond.
Both studies are being conducted to help the National Park Service better understand what it needs to maintain the phenomenon and assess what impact, if any, construction of a proposed maritime research and educational facility on the banks of the lagoon will have on the dinoflagellates community.
During his lecture, Latz cautioned that human activity could have an impact on bioluminescent lagoons. He cited the case of Oyster Bay in Jamaica where the installation of a cruise ship pier required them to dredge the entrance. While no scientific studies have been done on the bay following the construction, anecdotal accounts suggest the glow has diminished.
Latz said that the extreme rarity of bioluminescent lagoons was evidence that they are dependent on a very complicated balance of factors. He said scientists need to better understand those factors to preserve them.
“Any place that has a bioluminescent bay should cherish it like a natural wonder, like a treasure,” he said.