Entering the mangrove forest is like dipping into a strange dream where you’re not quite sure which way is up and your surroundings seem other-worldly. Seated on the boat and looking up, the leafy branches of mangrove trees have come together to form a whimsical archway that blocks the outside climate—whether rain or sun—from penetrating. Tall, gangly prop roots stretch out like stilts from the bases of the small trees and dangle underwater; emerging from the water and scuttling up the roots are crabs, a parallel to the scampering insects and lizards of terrestrial forests. Mollusks foul some of the roots, indicating the height reached by the water at high tide. The place is undoubtedly aquatic, but looking straight up you could fool yourself into believing there is solid ground and soil supporting the foliose trees.
The short boat ride through this surreal habitat at the interface of land and sea was just what we needed after a long, complicated journey over the border from Costa Rica to Panama, involving crossing on foot over a very dicey wooden bridge with tremendous gaps between planks that revealed the crocodile-filled river below. But our habitat of study at the field station on the island of Bocas del Toro was not the mangrove forest; rather, it was the adjoining coral reef.
The first striking thing about the coral reef is that it comes out of nowhere. Bobbing up and down on the waves in the mid-morning drizzle, we couldn’t see to any depth in the turbid water. You wouldn’t think there was anything besides sand beneath the surface, but as soon as we stuck our heads underwater, a vibrant community of fishes, corals, and other marine invertebrates greeted us. Through my snorkel I squealed with delight, taking a hundred mental pictures a second and whipping around in all directions, not sure what to investigate first.
With no trails to follow, as we so comfortably have in terrestrial forests, I decided to pick a fish (a yellow butterflyfish with black stripes stood out) and follow it. We swam over large yellow brain corals, past bright red tunicates puffing sandy squirts of water, between bunches of threatening-looking sea urchins wriggling their sharp spines. It was interesting to see how everything in the habitat seemed to use each other: brittle stars wrapped themselves around coral, and fish munched algae off of the reef or dashed into anemones to hide. The coral growing on the roots of the mangroves provided a seamless transition between the two habitats.
Suddenly, a shimmering something caught my eye. It was a fish, slate blue (nearly fading into the color of the water) with pinkish fins and generally nondescript except for the fact that about every other scale on its body was shimmering with iridescence. The fish looked inexplicably familiar; after a moment I matched it to the illustration from an old childhood book, “The Rainbow Fish”—a heartwarming tale in which a glamorous but egocentric fish learns the virtue of generosity by giving away her flashy scales to friends without. The fish I had spotted resembled this character so strongly that in my excitement I dove to get a better look, inhaling saltwater through my snorkel in the process.
It turns out that the species’ actual name is the stoplight parrotfish (initial phase). The “stoplight” aspect became apparent after witnessing the species’ magnificent ability to change color in order to hide. Farther down the reef I had to do a double-take in order to distinguish one mottled brownish-tan fish taking the color and texture of the coral it was hiding under. I watched as, in an instant, it darted away while simultaneously morphing into a lighter hue with the scaly texture you would normally expect for a fish. This lighter morph was the very same “rainbow fish” I’d spotted earlier.
We explored the reef for hours, gliding over the bustling community below while trying to avoid being pricked by a sea urchin or smashing our fins into the fragile corals. Underwater, we become detached observers, a stark contrast to the sense of oneness you get from walking through a forest. But, as in tropical forests, diversity abounds in the coral reef as organisms are highly specialized for their distinct niches in these astounding “rainforests of the sea.”