[Reconstructed after software failure]
It is finally looking like a trip to Florida is going to take place in April. Ever since moving from there a few years ago, I’ve been yearning to return, if only for the opportunities that it provides to nature photography. And, due to crummy finances and difficulties with work schedules, it hasn’t had the chance to happen until now.
This is far from being an ideal time, and in fact, it falls between two target periods. In February (I hate that word, completely unintuitive to type) and March, the birds are nesting and raising their broods, and Florida attracts a multitude of species. And high summer, despite how most people feel about it, is useful for two reasons: it will give my girlfriend a taste of the worst that Florida has to offer, to see if she can stand to move down there someday; and it produces bioluminescence in the bay waters.
When I first discovered this on my own a few years back, I found it absolutely fascinating, and that hasn’t changed. Certain microorganisms in the Dinoflagellate family produce a brief blue-green flash when agitated past a certain level, and large collections of them will produce a dim glow in turbulent water. Toss a rock in, and you’ll produce a shockwave that delineates the ripples for less than a second – in good conditions, you might actually see the secondary effect from the little fountain that plumes from the center of impact and falls back down. Put your hand in and thrash it around, and you’ll produce a brief cloud of color that wisps away quickly. Chasing this effect in the nearby waters of the Indian River Lagoon led to two rather interesting experiences, which I’m relating out of order just for the drama.
The second took place when I was up over the river (okay, lagoon, but it looks like a river, and that’s generally what it’s called in that area) on the causeway bridge, very late at night. The air was fairly still, still enough that I could hear the approach of at least one dolphin in the darkness. Dolphins make a quiet sound when they break the surface, aside from the ripple of water from their backs – it’s kind of a double-gasp, exhalation and inhalation, within about a second. Once you know it, you can recognize it without having to see them out there. I could hear one approaching, and was waiting until he neared the light spilling from the streetlamps on the bridge. While the bioluminscence was active that evening, fish and gentle waves don’t produce enough turbulence to fire it up, as it were. In most cases.
Until a dolphin happens upon a tasty tarpon and takes off in pursuit. As I watched, a flash of light twisting under the water indicated the presence of the tarpon beating a hasty retreat, followed very quickly by the dolphin. While the tarpon only produced a streak, the much-larger dolphin actually had an outline that followed the dorsal and pectoral fins, traced the hindbody and flashed brilliantly from the tail. Little streamers of turbulence were outlined by the wispy glow from the dinoflagellates and trailed off the fins like smoke. I could see nothing in the darkness of the water save for these aftereffects, but it was awe-inspiring. The show lasted mere seconds and I saw no denouement, but that hardly mattered. And while I would be sorely tempted to try and catch this on videotape, I know this would be impossible without highly specialized equipment – the glow is simply too dim to capture without very long exposures, and it doesn’t last long enough for that. [UPDATE 10/17/09: However, someone certainly managed it, and the result is great!]
The other incident came before that one, and left me puzzled for a long time. On a windy, choppy night, I checked out another location to see if the luminescence was active, poking around until I found a spot with deeper water near shore, and devoid of streetlights. Tossing a stone in close to shore showed nothing of interest, but I sought a larger one to chuck further out. This one weighed about two pounds, and I heaved it about fifty feet from shore. I was rewarded by a nice big splash that was outlined in that lovely blue glow. And something else…
Beginning from the initial splash, the water started to boil in agitation, spreading out in a diagonal line towards the shore to my right and producing a roar audible above the wind. In the darkness, all I saw was the blue glow, but it led me to believe the thrashing water extended at least a foot above the average waterline, and was a few yards wide. The effect grew from the initial splash and extended maybe thirty feet, and lasted start to finish less than ten seconds before fading. I was dumbstruck by what I’d just seen, which was largely because there were no other clues to be seen.
Afterwards, I speculated on two possible causes. The first was that the rock striking bottom had disturbed a patch of gases buried in the bottom, methane or somesuch, that simply burst to the surface – this was the distinct impression that I received. The second, which seemed to make more sense, was that I spooked a very large school of fish.
I’ve discarded both of those now in favor of a third, based on witnessing a similar agitation event in the daylight. Now I believe I spooked a herd of manatees lying near shore. The growing reaction and apparent amount of disturbance seems to fit.
Suffice to say, chucking large rocks in the water isn’t a practice I plan to repeat anymore, and while I’ll be attempting to see the bioluminescence again during the upcoming visit, I’ll find some other method to induce it.