December 18, 2012
Reproduction In Coral Colonies Affected By Tissue Damage
April Flowers for redOrbit.com - Your Universe Online
New research from the University at Buffalo reveals that coral colonies in the Bahamas that have suffered tissue damage were still producing low numbers of eggs four years after the initial injuries. The study, recently published in the Journal of Experimental Marine Biology and Ecology, showed that tiny sperm-producing factories called spermaries were in short supply as well.
UB geology professor Howard Lasker, PhD led the study on the coral species Antillogorgia elisabethae. Lasker said the slow recovery of the coral colonies was surprising.
"The really interesting finding was that four years later, these colonies were still displaying an effect," Lasker said. "They don't necessarily look damaged anymore, but it takes some time to get back to where they were in terms of reproduction."
"This research has broader repercussions," Lasker said. "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."
Lasker, and his colleague Christopher Page — formerly a master's student in UB's Graduate Program in Evolution, Ecology and Behavior and currently a biologist at the Mote Marine Laboratory — examined the species A. elisabethea, formerly known as Pseudopterogorgia elisabethae. The species is a Caribbean gorgonian coral, which forms male and female colonies.
During reproduction, the female colonies release eggs that remain on the colony's surface to be fertilized and develop into larvae.
Lasker and Page looked at egg and sperm production to study the effect of tissue damage on sexual activity in colonies near Cross Harbour, Abaco. To obtain an anti-inflammatory chemical used in a skin care product, the coral is harvested by pruning branches from large, sexually mature colonies in this area.
Harvests were performed in 2002 and 2005. The researchers returned in 2009 before the annual spawning, which occurs in November and December, to compare 24 colonies that had been cropped to 20 that had not. They dissected 24 individual coral polyps from each of the 44 colonies to count the reproductive organs.
Lasker and Page found that in the cropped female colonies, approximately one in three polyps had no eggs at all. In the uncropped colonies, the females had more than double the number of polyps producing three or more eggs. The uncropped colonies had 120 polyps in all, compared to 53 in the cropped colonies.
In the male colonies, the team found that more than three quarters of polyps in the uncropped colonies house 11 or more spermaries in contrast to the cropped colonies where less than 60 percent of polyps had 11 or more spermaries.
For most coral colonies, scientists understand sexual maturity to be a product of colony size, not age. Most large corals reproduce as a general rule and small ones don't. The results of this study support the idea that damaged coral may have lower fecundity because they divert resources away from reproduction to support growth and injury repair.
"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 wrote in their study.