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Injured coral just not in the mood

U. BUFFALO (US) — Four years after suffering tissue damage, coral colonies in the Bahamas were still producing low numbers of eggs, research shows.

Tiny sperm-producing factories called spermaries were also in short supply, according to the study that shows it can take years for coral to recover their reproductive prowess.

The slow recovery was a surprise, says Howard Lasker, professor of geology at the University at Buffalo, who led the study on the coral species Antillogorgia elisabethae.

“The really interesting finding was that four years later, these colonies were still displaying an effect,” Lasker says. “They don’t necessarily look damaged anymore, but it takes some time to get back to where they were in terms of reproduction.”


Antillogorgia elisabethae colony in the Bahamas. (Credit: Howard Lasker)

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“This research has broader repercussions,” Lasker says. “When you start talking about damage to reefs from events like hurricanes, you might say that the coral survived, that it lost some tissue, but it’s still reproducing. That’s true, but we now know the corals are not quite as healthy as we thought.”

As reported in the Journal of Experimental Marine Biology and Ecology, the species that the researchers examined—A. elisabethae, formerly known as Pseudopterogorgia elisabethae—is a Caribbean gorgonian coral. The coral forms male and female colonies and, during reproduction, the females release eggs which remain on the colony’s surface to be fertilized and develop into larvae.

Lasker’s co-author was Christopher Page, a graduate student at the University at Buffalo at the time of the study. Page is now a biologist at the Mote Marine Laboratory in Florida.

To study the effect of tissue damage on sexual activity, Lasker and Page looked at egg and sperm production in A. elisabethae colonies near Cross Harbour, Abaco, in the Bahamas. In this region, workers harvest the coral, pruning branches from large, sexually mature colonies to obtain an anti-inflammatory chemical used in skin care products.

Such harvests took place in 2002 and 2005. In 2009, Lasker and Page returned to the area before the annual spawning, which for A. elisabethae occurs in November and December. The researchers compared 24 colonies that had been cropped to 20 that had not, carefully dissecting 24 individual coral polyps from each of the 44 colonies to count the reproductive organs within.

What they found:

  • In cropped female colonies, roughly one in three polyps carried no eggs at all, compared with roughly one in six in uncropped colonies. The uncropped colonies also had more than double the number of polyps producing three or more eggs—120 polyps in all, compared with just 53 polyps in the cropped colonies.
  • More than three-quarters of polyps in uncropped male colonies housed 11 or more spermaries, organs that produce sperm. In contrast, less than 60 percent of polyps in cropped colonies had 11 or more spermaries.

In most corals, sexual maturity is understood to be a product of colony size, as opposed to age. As a general rule, large corals reproduce. Small ones don’t. The new research is the latest to support the notion that damaged corals may have lower fecundity because they divert resources away from reproduction and toward growth and injury repair, Lasker says.

“The mechanism controlling resource allocation is unknown, but regardless of the process the important implication of the finding is that populations that appear to have survived and to have recovered from disturbance events may produce fewer gametes than the size and number of colonies would suggest,” Page and Lasker write in their study.

It’s still unknown how changes in egg and spermary production impact long-term population growth.

Source: University at Buffalo

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