Most days on the little island consisted of digging holes, setting traps (plastic soda bottles with the top 3 inches sawn off), inserting the bottles into holes, baiting traps with sardines, returning an hour later to retrieve and measure lizards, repeat again and again, usually in 85-90 degree heat, relative humidity almost a hundred percent.
It was occasionally suggested by a Bermudian colleague that we “take a ride out to the boilers,” which were visible not far off shore as patches of foam where waves broke. The boilers (boiler reefs) form a dotted line along the wave-washed south coast of Bermuda. They mark the locations of now-submerged rocky prominences that had been above sea level during the most recent ice age. We never went, however, which was okay with me because there were lizards to measure, and, as I had found out in previous well-intentioned jaunts, being out in the surf in an open Boston Whaler did not agree with mid-continental constitution.
Boiler reefs near Horseshoe Beach, south shore of Bermuda.
Eastern end of Bermuda, showing Nonsuch Island, Cooper's Point, and lines of boiler reefs.
A boiler reef is a relatively small feature, a few metres in diameter at the ocean’s surface. Circular, with a hollow centre, it has inched its way up from the bottom as thrashing seas have done likewise, as polar ice has oh-so-slowly melted away. Boilers resemble lumpy, reddish inverted cones. Spongiform martini flasks. A bit-squashed upside-down wizard hats. The technical name is “algal-vermitid cup reef,” which hints at both shape and composition. There are three biological structural components to a boiler: an algal mat, dominated by Herposiphonia secunda, encrusting calcareous organisms, such as the coralline alga Lithophyllum intermedium, and to provide a little more “backbone,” the vermiform worm snail, Dendropoma corrodens.
The worm snail, upon settling from a planktonic larval stage, cements itself to a surface, including other worm snails, and starts growing in an irregular, twisting fashion. Where there are many worm snails glued together, growing madly off in all directions, a rock-hard conglomeration resembling frozen macaroni is the result. Other organisms, including hydrozoans, polychaete worms, crustaceans, and burrowing sea urchins live on or within this mollusk-algae matrix.
Click to see, the thin white line of surf is the line of boilers. From Nonsuch Island.
Relatives from Europe arrived on the island for a visit. And the way it is when someone from far away visits and you go somewhere nearby of note you would otherwise not bother to go, with no hesitation whatsoever five or six of us piled into the Whaler and headed out into the pounding surf, up to the lip of a boiler. Masks and flippers were pulled on, and over the side we went.
I fell out on the boiler side, so ended up closest to it. We had not discussed a plan of attack, but I assumed the point of visiting one was to somehow get inside it, either through a fissure, or over the top. Hopefully it would be less turbulent in there. During a wave trough I saw a break in the rim where I might slip over, and timed my approach for the next crest. I swam with the wave, up over and in. I was in a boiler! The next step, I supposed, was to swim down into it. I did my best head-first duck-dive, and kicked down as far as I could go, then turned upright. I was in a black-red, shadowy chamber, the blue sky above. A flurry of motion rose from below to surround me, a school of silver, big-eyed fish, one to two feet long, with strongly forked tails. They circled me in a dense, gleaming helix. It was a stunningly beautiful moment, the kind that makes you emit a gleeful noise into your snorkel. I slowly floated to the surface in their midst. By the time the others had entered the boiler, the fish had melted away, out to open water. I found out later the fish were Horse-eye Jacks, in the family Carangidae.
Today I look out the window at the grey sky. Hundreds of gulls are winging back to the shore for the night. Impressive in their way, but not a moment I’ll remember years from now. Oh, I hope the sun returns soon. Word of advice: if you have a chance to visit a boiler, jump in!
Thomas, M.L.H. and J. Stevens. 1991.Communities of constructional lips and cup reef rims in Bermuda Coral Reefs 9(4):225-23.
Sterrer, W. 1992. Beruda’s Marine Life. Bermuda Zoological Society, Bermuda.307 pp.