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Bioluminescent Bays of St. Croix

St. Croix 100 Night KayakSt. Croix is home to not one, but TWO of the Caribbean’s rare bioluminescent bays!  Both Salt River Bay National Historical Park and Ecological Preserve and Altona Lagoon offer visitors a chance to witness nature’s “living lights” at night. For those of you not familiar with this concept, a bioluminescent bay (or bio bay) is a natural occurrence caused by a high concentration of bioluminescent micro-organisms called dinoflagellates.

Depending on the night and location, there are actually three different types of bioluminescent organisms that may be seen: dinoflagellates (the most common), glow worms and/or ctenophora (or comb jelly fish).  At night, the dinoflagellates are often seen as tiny sparkles or as individual flashes of light as water is disturbed.  In fact, when kayaking through the bio bays, the movement of the kayak through the water makes the dinoflagellates appear like stars flying past you as you move.  The comb jelly fish on the other hand light up neon green like a glow stick when they are disturbed with your paddle or touched. And don’t worry, comb jellies do not sting so you can touch them, just remember to be gentle because they are VERY fragile creatures!

A combination of factors creates the necessary conditions for bioluminescent bays to form with the most important factor being the presence of red mangrove trees, which surround the Salt River Bay.  In fact, research being conducted at the Salt River Bay by the University of South Carolina, the University of North Carolina Wilmington and the University of the Virgin Islands is focused on analyzing the quality and nutrient composition of the bay’s water, the distribution of the dinoflagellates, and the abundance of “cysts” (or dormant dinoflagellates) embedded in the sea floor.  Bioluminescent bays are extremely rare with “only seven year-round lagoons known to exist in the Caribbean” according to Dr. Michael Latz of the Scripps Institute of Oceanography at the University of California San Diego, an expert on bioluminescent organisms; “Any place that has a bioluminescent bay should cherish it like a natural wonder, like a treasure”.

If you have the opportunity, don’t miss visiting St. Croix’s breathtaking bioluminescent bays.  Keep in mind that you can’t see bioluminescence every night due to weather conditions and the cycle of the moon, which also determine how vivid the “living lights” will be when they are visible!  Whether you are visiting the bio bays by foot or by kayak, check with your local guide or tour company when planning your trip to ensure you find the best time to go.  Also, remember to be ecologically responsible when you visit because many of the Caribbean’s bio bays are in danger of having their lights put out permanently!  You can do your part when you visit by NOT wearing insect repellent, deodorant, perfumes or sunblock as these can kill the bioluminescence.  For additional information, conservation tips and news concerning St. Croix’s bio bays, please visit

– Jennie Ogden, Editor
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