Quarterdeck 3.3

Love on the Rocks


by Stephen R. Gittings

Also see "Down Under. . . Out Yonder" for more information about the Flower Gardens National Marine Sanctuary.

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Montastrea annularis corals release packets of egg and sperm during the annual spawning event at the Flower Gardens. The packets break apart on the surface to allow fertilization, and resulting larvae drift for days or weeks before sinking. If the larvae settle on a reef or other suitable substrate they can begin growing into mature corals. (Photos by Joyce and Frank Burek)


In 1990 recreational divers at the Flower Gardens first witnessed "mass spawning," the dramatic, annual, synchronous release of gametes by a variety of coral species. Spawning by any corals was rarely seen before this time, and mass spawning in the Atlantic had never been witnessed under water. The divers reported their experience to scientists and now the two groups mount scientific expeditions every year to study the phenomenon.

The Flower Gardens' reefs exhibit some of the most prolific and highly predictable spawning found anywhere. It happens each year eight evenings after the August full moon, generally between 8:00 and 11:00 p.m. In recent years reports from the Flower Gardens have stimulated "spawning expeditions" and scientific observation there and on reefs in the Caribbean Sea. They have also enabled studies of important controversies in coral-reef science.

For example, the dominant reef-building coral species in the Atlantic Ocean, Montastrea annularis, was recently divided into three species based on differences in colony shape, protein content, and other characteristics. Mass spawning by the three "species" at the Flower Gardens allowed researchers to find out if the corals can reproduce with one another-the definitive attribute of a true species.

Preliminary studies at the Flower Gardens and in Panama suggest that interspecific fertilization is rare and in all likelihood, the three do not reproduce with each other to any substantial degree. In fact, the three have slightly different spawning times within the already limited "spawning window" of several hours each year.


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Oceanography, Texas A&M University

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URL=http://oceanography.tamu.edu/Quarterdeck/QD3.3/Gittings/gittings-sidebar.html
Updated January 8, 1996