It’s going to be a rough day for Puerto Rico, so here’s a post…

It’s going to be a rough day for Puerto Rico, so here’s a post…

It’s going to be a rough day for Puerto Rico, so here’s a post from a nicer day there to offset it a bit.

The Bay of Fire

Imagine entering a quiet tropical bay at night. There are no lights on shore, and on a moonless night the spectacle is unforgettable. As the propeller of your boat churns the black water, an intense blue-green light is left behind, like an eerie trail of cool fire. Outside the bay you see a few sparks of light as you approach, but inside the bay things are very different. Long streaks of light shoot like fireworks beneath the boat. They are created by fleeing fish. A swim in the bay is even more spectacular. Your dive into the water is accompanied by a blinding flood of light, and sparks scatter out as you wave your arms.

Such light effects result from an unusual concentration of bioluminescent dinoflagellates, a natural and permanent phenomenon in a few selected locations such as Bahia Fosforescente, or Phosphorescent Bay, in southwestern Puerto Rico. The bay’s most important source of bioluminescence is Pyrodinium bahamense, a unicellular, photosynthetic dinoflagellate about 40 microns (µm) (0.004 cm, or 0.0015 in) in diameter. As many as 720,000 individuals may be found in a gallon of water, many more than outside the bay. The bay is small, about 90 acres, fan-shaped, and it does not exceed 4.5 m (15 ft) in depth.

The main reason the that dinoflagellates are concentrated there is that the bay is connected to the open sea by a narrow, shallow channel. As water containing the dinoflagellates flows into the bay, evaporation in the shallow water causes the surface water to sink because of the increase in salinity and therefore density. Evaporation is enhanced by the dry and sunny days. Pyrodinium cells stay near the surface and are therefore not carried out as the denser water flows out along the bottom of the shallow entrance. The tidal range is only about a foot at most, so water exchange with the outside is limited. The bay thus acts as a trap that keeps the dinoflagellates from leaving.

Of all the planktonic organisms that enter the bay, why is Pyrodinium favoured? A key factor seems to be thick mangrove trees bordering the bay. They grow along the muddy shores, together with all kinds of organisms living attached to their roots. Mangrove leaves fall into the water, where intense bacterial decomposition increases the organic nutrient levels in the water. Some nutrients essential to the growth of Pyrodinium, perhaps vitamins, may be released by bacteria or other microorganisms.

Bahia Fosforescente is protected to keep the critical natural balance intact, but bioluminescence has noticeably decreased during recent years. A few other bays, termed “bio bays,” in Puerto Rico fortunately show more spectacular bioluminescence, Laguna Grande on the northeastern tip of the island and Puerto Mosquito on the island of Vieques are a few.

~ JM

Image Sourced from: http://bit.ly/1EspeYx

More Info:

Dinoflagellate: http://bit.ly/1EspmHE

Bioluminescence: http://bit.ly/1EnZi12

BioBay Puerto Rico: http://bit.ly/1J1bIBv

HernandezBecerril, D. U., & Navarro, N. (1996). Thecate dinoflagellates (Dinophyceae) from Bahía Fosforescente, Puerto Rico. Revista de Biología Tropical, 44(2 A), 465-475. http://bit.ly/1FdaFPj

We have posted about this before: http://on.fb.me/1QxIjkH