I equate the seasons to being like the flow of time throughout the day. Winter is the still, early hours when you are too cold to get out of bed; spring is the vibrant morning when everything seems full of life; summer is the hot midday; and fall is the beautiful, but ephemeral sunset. As we near the end of August and approach fall, now is the time to get your fill of warm-weather activities to make summer last a bit longer. One of Nantucket’s most unique summer activities is taking a nighttime swim in the bioluminescence.
You may be asking, what is bioluminescence? Before we answer that question, let us first talk about what luminescence is; the emission of light without the material being heated. There are many types of luminescence, including my favorite, triboluminescence; light that is created from a material’s bonds being crushed, scratched, or rubbed. Oil of Wintergreen is famous for this property and I have fond memories from childhood of chomping Wint O Green Lifesavers between my teeth while looking into the bathroom mirror with all the lights off. If you catch it at the right moment, you see a bright green spark when you crush the mint.
Getting back to our main subject, bioluminescence falls under the category of chemiluminescence, and is a result of biochemical reaction in a living organism. Examples of bioluminescence can be found across many taxa, such as fungi and bacteria, but tend to be more common in ocean species such as fish, jellyfish, and crustaceans.
On Nantucket the most common source of bioluminescence originates from dinoflagellates; single-cell marine plankton that are common in surface waters, in particular one species known as Sea Sparkle (Noctiluca scintillans). This is a species where the scientific name makes sense, in Latin, Noctiluca means light at night and scintillans means shining or throwing flashes of light. During the warm, calm nights of August these organisms move close to shore, sometimes in great numbers, and their sparkle is a treat to see.
The best place on island to see the bioluminescence is the north shore beaches, such as Jetties, Steps, and Water Tower. On active nights you can see the dinoflagellates light up from shore, but nothing can surpass the feeling of immersing yourself in the water at night and swimming around engulfed by nature’s nightlights. The coolest part is that often in nature, the more motion you make, the more likely you are to scare away what you are hoping to see. Abruptly point at a warbler and I can assure you that the bird will fly away. But with these bioluminescent dinoflagellates, it is the opposite. Being swirled around catalyzes the Sea Sparkle’s biochemical reaction that makes them glow. In some places around the world, these dinoflagellates can be found in such great quantities that the waves glow bright blue as they pass by.
As you wade in the water, take a moment to relax and look up. On the luckiest of nights with a clear, open sky you will be treated to a two-fold lightshow; the sparkles in the sea and the stars in the sky. Although summer is always fleeting, it does not get much better than that, especially if you have the chance to share this special experience with your friends and family.
Stay tuned for more editions of Current Nature, a bi-weekly column featuring seasonal topics, natural history information, and advice on the outdoors from the staff at the Linda Loring Nature Foundation.