Since moving to Seattle earlier this year I’ve been looking forward to spending a clear and dark summer night in the San Juan Islands (in Washington’s Puget Sound) – the optimal time to see the incredible phenomenon of marine bioluminescence. A few weeks ago that time finally came, and I went out to Shaw Island (the least populated of the ferry-accessible San Juan Islands) with my girlfriend, Aubrey. For sunset we wandered down to a secluded little cove and waited for twilight to set in. Periodically we tossed a few rocks in the water, hoping something special would happen. After what seemed like ages I impatiently walked up to the shore and waived my hand in the calm water; like miniature Aurora (which, regrettably, I have yet to see) the water exploded with brilliant blueish green sparkles! It was like magical pixie dust!
Click image for larger view!
Of course, the phenomenon was not really a surprise – that’s exactly why we’d come here, and I’d read all about it – but actually seeing the bioluminescence for the first time in person was the most startling and fantastical natural phenomenon I’ve ever experienced. We were out throwing handfuls of pebbles and splashing around in the (rather frigid) water until 1am trying to create a photograph, but it was exceptionally difficult. Although seemingly very bright to the dark-adapted naked eye, it was nearly impossible to capture the effect on camera. Furthermore, the luminescence started to dim a little after repeated disturbances, so we had to give the critters responsible for the light some time to recharge between exposures / rock throwing volleys. In the end, I resorted to taking about ten of the best exposures and blending them together, as well as displacing some exposures to increase the extent of the effect. This was significantly more photoshop tinkering than I’ve ever done before, but ultimately I do think it captures the experience in a way true to the natural phenomenon (which was, after all, controlled by our splashing and rock throwing). Judging from some other images I’ve come across on the web, it can be much brighter under certain conditions, so I’ll have to head out again some time!
Bioluminescence is the emission of light by living organisms through chemical reactions (very different from fluorescence and phosphorescence). There are a number of biological organisms capable of bioluminescence, including fireflies, glow worms, certain fungi, and – the subject of this post – certain marine dinoflagellates.
Dinoflagellates are tiny single celled flagellated protists, some of which, such as Noctiluca scintillans, have the incredible ability to create light through simple chemical reactions. Disturbing the water around them induces an electrical potential across the vacuolar membranes. This potential causes hydrogen ions to enter organelles called scintillons, where a luciferase catalyzed oxidation of luciferin releases energy in the form of blueish green light. Ecologically, the luminescence is thought to be a predatory defense mechanism, either by disrupting predatory swimming, or as a ‘burglar alarm’ to attract other visual predators that might prey on the organisms that have come to feast on the Noctiluca (see Latz, Nauen, and Roh, 2004, which cites a variety of additional sources as well).
Noctiluca scintillans can be found all over the globe, but are particularly abundant in areas of nutrient rich waters. High concentrations of nutrients along with sunlight promotes the growth of plankton, their primary food source, which can result in large algal blooms of Noctiluca, called “red tides”. These can happen just about anywhere along the coast, but can be difficult to predict and can have drastic detrimental effects on marine life. Some areas, such as the San Juan Islands (and the Pudget Sound in general), are extremely reliable for seeing seasonal bioluminescence without the ecological dangers associated with red tides. Just go in the late summer on a dark night (no moon is best), and every time you wave your hand through the water, or watch waves crashing on the shore, you’ll see an eerie and unmistakable blueish green color. Other famous areas to reliably see bioluminescence include Mosquito Bay in Puerto Rico and various spots in Thailand.
If there were one natural phenomenon I’ve experienced that I could suggest you go out of your way to see, this would be it!