Why is The Vieques Mosquito Bay so brightly Bioluminescent?

A Delicate Balancing Act:

To create a bioluminescent bay you need a lagoon surrounded by Red Mangroves (which occur in the tropics and semi tropics only). The roots of the red mangroves release tannins that are rich in Vitamin B12, one of the important nutrients for these light emitting dinoflagellates. The decomposing mangrove leaves release many other nutrients which add to the nutrient rich environment.

The Bay must also be relatively free of pollution, which generally requires protected lands surrounding the bay. Special zoning for all the land in the watershed of the biobay is essential. The zoning must assure sufficient forest cover to hold back the sediment whenever there is significant rain.

The Bay requires enough size and depth to enable the water to stay relatively cool in the daytime, it does, however, remain warmer than the ocean outside. It also requires a restrictive channel to the ocean, with a relatively small tidal exchange. This biobay has the channel to the ocean at the windward end of the bay which may also serve to restrict the outflow of the dinoflagellates to the sea as the tide goes out, while allowing sufficient water exchange to avoid overheating and stagnancy.

Any alterations to the size of the channel to the ocean (such as shallower or deeper or wider) can destroy a biobay. Pollution flowing into the bay from chemicals in groundwater and flood waters can ruin a biobay. Sufficient fluorocarbons from motorboats adversely affects the bioluminescent dinoflagellates, as would waste from any boats anchored in the bay. People swimming, who have sprayed themselves with DEET, adversely affect the biobay.

Lights seen from the bay and ambient light in the sky ( reflected from clouds) greatly reduce the visibility of the bioluminescence at night. It is a real treat to be in the biobay when the electricity goes out on the island! It is also considerably better to see the biobay when there is no moon visible in the sky.

So why is this particular biobay (perhaps) the brightest in the world? Because all these factors are perfectly balanced, creating ideal circumstances for a constant 'super bloom' of Pyrodinium bahamense dinoflagellates, over 700,000 per gallon of water!

How fragile is this ecosystem? Well, the factors being constant, this bay recreates itself continuously (for now). A recent rainfall, of over 30 inches, poured sediment into the bay turning it into a giant mud puddle... and killed most of the dinoflagellates. The sediment flushed out with the tides over a few weeks period, the dinoflagellates reproduced like crazy, and repopulated themselves, and the bay became, just as bright all over again.

Three important factors need control to protect the bay:

1. Too much sediment is washing out of the hills above, due to lack of forest ground cover. This sediment is building up in the biobay and the bay is changing slowly. However, should agricultural chemicals to be added to the sediment it would dramatically destroy the dinoflagellates.

2. An increase in motorboats entering the bay, especially any boats overnighting in the bay, adding fluorocarbons and sewage containing human bacteria.

3. Increasing light pollution in the nearby hills.

The legislature of Puerto Rico needs to look into the protection needed for the biobays of Puerto Rico, or the Biobay needs the protection of becoming a United Nations Biosphere Reserve. In short the legislature of PR must pass specific laws of protection to insure the continuation of a biobay into the modern, developing world.

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Above left : Artists depiction of bioburst of light. Swim in the Fairy Dust! photo Doug Meyerscoff!

The Bioluminescent Bay in Vieques is one of the unspoiled wonders of the world. Just to experience this phenomena is, in itself, worth the entire journey.About Bioluminescence:

The bioluminescent dinoflagellates Pyrodinium bahamense are a photosynthesis using plankton. They are one celled and measure about 1/500 th of an inch. The tiny burst of light it gives off is a hundred times bigger than itself. Each dinoflagellate bursts into light when it feels pressure against its cell wall. The light is given off in an instantaneous process; when you add the light bursts of 700,000 dinoflagellates per cubic foot of water together the effect is spectacular!

Almost all marine bioluminescence is (greenish) blue in color, for two related reasons. First, blue-green light (wavelength around 470 nm) transmits furthest in water. The reason that underwater photos usually look blue is because red light is quickly absorbed as you descend. The second reason for bioluminescence to be blue is that most organisms are sensitive only to blue light. The luminescence of a single dinoflagellate is readily visible to the dark adapted human eye.

The intensity of luminescence by photosynthetic dinoflagellates is strongly influenced by the intensity of sunlight the previous day. The brighter the sunlight the brighter the flash. (maybe you can discern this, maybe it is hard to notice the difference)

Bioluminescence is production of light by living organisms. Organisms that are bioluminescent include certain fungi and bacteria that emit light continuously. The dinoflagellates, a group of marine algae, produce light only when disturbed.

The production of light in bioluminescent organisms results from the conversion of chemical energy to light energy.

Bioluminescent fish are common in ocean depths; the light aids in species recognition in the darkness. Other animals use luminescence in courtship and mating and to divert predators or attract prey.The chemical reaction responsible for the production of light bursts begins with a luciferin, a light emitter.

The luciferin reacts with another chemical, called the luciferase, salt and oxygen resulting in a burst of light and water. Luciferin + Luciferase + Oxygen + Salt ----> Light + Water. Bioluminescence is a primarily marine phenomenon. It is the predominant source of light in the largest fraction of the habitable volume of the earth, the deep ocean . In contrast, bioluminescence is essentially absent (with a few exceptions) in fresh water, even in Lake Baikal. On land it is most commonly seen in the few families of luminous insects. Bioluminescence has evolved many times in the sea as evidenced by the several distinct chemical mechanisms by which light is emitted and the large number of only distantly related taxonomic groups that have many bioluminescent members.

Moon Phases Schedule

"We attribute the cause to the heat of the sun, which has, as it were, impregnated and filled the sea during the day with an infinity of fiery and luminous spirits. These spirits, after dark, reunite to pass out in a violent state..." 1688 - Pere Guy Tachard [about the bioluminescent ocean during a cruise to Siam]

The most unique night to go is the first and second nights after the full moon, as the moon rises an hour after sunset the first night and almost two hours the second night. This gives you time to experience the bioluminescence with no moon and then watch the moon rise. A spectacular experience... Remember that the week before the full moon the moon is very bright and does diminish the experience a little bit. ( but don't let that stop you if that is when you must visit Vieques)

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