When Is The Best Time To See Bioluminescence In Puerto Rico (2022)

When is the best time to see bioluminescence in Puerto Rico?

This is a question that most people ask themselves when planning a trip to Puerto Rico, but few know the answer to.

Having lived in Vieques, I’ve spent many years kayaking in Puerto Rico’s bioluminescent bays. 

In this article, I will explain when the best time is to see the bioluminescence, and how the moon affects its visibility. I will also cover the following topics:

What is bioluminescence & bioluminescent bays?
When is the best time to go to the bioluminescent bays in Puerto Rico?
How does the moon affect the visibility of the bioluminescence?
Does the rain affect the visibility of the bioluminescence?

 

What is bioluminescence & bioluminescent bays?

Bioluminescence is the term used to describe when a living organism emits light. 

A bioluminescent bay is a shallow bay of water connected to the sea that contains a very high concentration of bioluminescent plankton called “Dinoflagellates”. 

image of two people in a kayak in the water with bioluminescence glowing around them
Image of two people in a kayak in a bioluminescent bay surrounded by bioluminescence.

All over the sea, there are single-celled plankton called “Dinoflagellates”. When pressure is applied to the cell-wall of these Dinoflagellates, a chemical reaction occurs inside the cell, which causes them to emit light.

In regular sea water, you can’t see bioluminescence from these Dinoflagellates because they are in a low concentration. However, in Puerto Rico’s bioluminescent bays, there is a very high concentration of these plankton, which means that when you move the water, you can see bright light (bioluminescence).

These Dinoflagellates naturally drift into these bioluminescent bays since they are connected to the sea. Once they enter these bio bays, they get trapped as the entrance is very narrow, meaning that they can’t escape. They start to multiply inside the bay, which leads to an abnormally high concentration of plankton.

It is this high concentration of plankton that allows humans to see the bioluminescence. 

 

When is the best time to go to the bioluminescent bays in Puerto Rico?

The bioluminescence is visible all year long. 

However, it is only visible for about two-weeks of each month, due to the moon rise/set times. 

The dates that you can view the bioluminescence in Puerto Rico change each month, so it’s best that you contact a tour company to find out when they are operating before you book your flights. 

December to July usually has better visibility for the bioluminescence. 

August to November has higher rainfall and hurricanes that can negatively affect the visibility of the bioluminescence. 

The primary factor (other than the moon) that affects the visibility of the bioluminescence is the concentration of the Dinoflagellate plankton in the bioluminescent bay. The higher the concentration, the brighter the bioluminescence is. The concentration changes from week to week, due to weather, rain & other natural factors. The concentration of the plankton is hard to predict. 

 

How does the moon affect the visibility of the bioluminescence?

One of the most common misconceptions about bioluminescence is that the moon phase is the primary factor that affects the visibility. 

This isn’t true most of the time.

The most important factor that affects the visibility of the bioluminescence is the moon rise & set times, not the moon phase.

screenshot of all the moon rise and set times for a particular month
Image showing when the moon rises and sets in Puerto Rico, as well as the illumination percentage of the moon.

It can be a Full Moon, but if the Full Moon is not in the night sky at the time that you are in the bioluminescent bay, then it will still be pitch black, and you will be able to see the bioluminescence as if it were a New Moon. 

The best conditions to see the bioluminescence is when it is pitch black, and there is no light being reflected from the moon. If there is lots of light in the surrounding environment (such as from the moon), then you can’t see the bioluminescent light being emitted from the Dinoflagellate plankton.

The reason why the moon phase doesn’t matter most of the time is because if the moon isn’t in the night sky at the time that you are in the bioluminescent bay, then it doesn’t matter what the moon phase is, as there will be zero light being reflected by the moon at the specific time, meaning that it is pitch black, which is what you want to ensure optimal viewing. 

If you are planning a trip to Puerto Rico, then I recommend that you contact a bioluminescence tour company to ask which dates the moon won’t be in the night sky at the time of the tour. There is a two-week period each month where the moon isn’t in the night sky at the time of the tour. This is when you can see the bioluminescence.

If a company says that they can take you to the bio bay outside of these two weeks, then they are scamming you and simply trying to take your money.

 

Does the rain affect the visibility of the bioluminescence? 

Heavy rain can negatively affect the visibility of the bioluminescence. 

The concentration of the Dinoflagellate plankton in the bioluminescent bays can decrease when there is heavy rainfall. 

image of woman swimming with bioluminescence
Image of a woman swimming with bioluminescence.

This is why the visibility of the bioluminescence is typically worse from August to November as these months have higher rainfall and hurricanes.



Can you see the bioluminescence all year in Puerto Rico?

Yes, you can see bioluminescence in Puerto Rico all year long. However, the bioluminescence is only visible for about two weeks of each month due to the moon rise/set times.

Which moon phase is best when visiting the bioluminescent bays in Puerto Rico?

Technically the moon phase doesn’t matter most of the time. What matters is when the moon rises and sets. It could be a Full Moon, but if the moon hasn’t risen in the night sky at the time that you are in the bioluminescent bay, then it will still be pitch black and you will be able to see the bioluminescence well as if it were a New Moon.

 

Final thoughts

The bioluminescence is visible in Puerto Rico all year long. 

However, the visibility of the bioluminescence is better from December to July because these months have less rainfall & hurricanes. 

Also, the bioluminescence is only visible for about two weeks of each month, due to the moon rise/set times. 

I recommend that you check out my other article where I talk about the three different bioluminescent bays in Puerto Rico. In this article, I discuss which bio bay is the best, and how you can book a trip to see the bioluminescence.

Article by

Brittany Ashford

Writer at PuertoRico.com. After living in Puerto Rico for seven years, I opened a guesthouse in Rincón and welcomed over 400 guests to the island from around the world. When I’m not writing about travel or spending time with my dog, I’m working towards becoming a pilot with dreams of flying around the islands.

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