Something beautiful, and almost magical, happens in the Reserva Marina Tres Palmas in the early evening a few nights after the full moon in August, which is unknown to most Rincoeños.

For a brief few minutes large areas of the water’s surface turns pink! This is caused by the release of billions of tiny gamete (egg and sperm) sacs which float to the surface and take on this pastel hue before dissolving, in another round of the ancient game of fertilization and conception, of life and death.

The annual spawning of the elkhorn coral (acropora palmata) in the RMTP is a very significant event, for several reasons. Primarily, because it is an indication these critically threatened corals are healthy! Elkhorn, and its related species staghorn coral (acropora cervicornis) are the principle reef-building coral in the Caribbean, fast growing (up to 11 cm a year!) structures whose branching ‘arms’ provide habitat and shelter for many juvenile fish and form the base of the reef ecosystem (think of trees in a forest). Alas, the past decades have shown more than a 90% die-off of these corals for various reasons. The RMTP still contains the highest concentration of healthy elkhorn in Puerto Rican waters… quite possibly because most of the coral colonies to be seen out there are genetically distinct- the result of sexual reproduction by gametes instead of the far more common asexual cloning of other reefs, where pieces of a colony break off and continue to grow in a new location. This unusual genetic diversity is what is quite likely allowing the RMTP elkhorn to survive the diseases and environmental stresses that have devastated most Caribbean reefs. It is one of the unique features of the RMTP.

Secondly, a successful spawning event indicates the local marine environment is healthy! Many factors will prevent the coral from forming gamete sacs or, if formed, prevent them from releasing them. Higher water temperature is the most significant known factor, however water acidity, salinity, and biological or chemical contaminants may also play a role. So a robust spawning is a handy yardstick to measure the over all status of the local waters.

Third, it is a great opportunity for fish watching! Of these billions of gamete sacs, far fewer than 1% will actually cross-fertilize to form a genetically unique individual coral polyp and begin a new colony. Most of the rest will be eaten. Every fish that lives in or around the RMTP (even those that are usually active only during the day) comes out to feed for a half hour or so, and it is quite the show.

Fourth, for all these reasons, it is just a very very cool thing to watch!

Tips for watching the spawning: My best guess is that the spawning, if it occurs (it didn’t last year) will happen this year the evenings of August 18 and 19, usually between 8:30-9:30 pm.

What you will need: The best way I’ve found to watch the show is to have your snorkel gear and a small body board, with a dive light (or flashlight in a ziplock plastic bag). This way you can float above the action but still get a good view. Please DO NOT wear fins! You’ll be in shallow water, with not much depth perception at night- it is way too easy to be kicking against the coral behind you while trying to stay in place! Of course as a safety factor you will want to stay close to shore, unless you are an experienced night diver. But I do not think the current water clarity will make exploring areas more than 3 or 4 meters deep very rewarding.

Story and Photos by Steve Tamar

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El Coqui