Reproductive patterns of the coral Pocillopora damicornis at Gorgona Island, Colombian Pacific Ocean

Knowing the gametic development of the coral Pocillopora damicornis and its relationship to environmental variation at La Azufrada reef (2 degrees 5810N and 78 degrees 1105W, Gorgona Island, Colombian Pacific Ocean) is essential to understanding the capacity for sexual replenishment of this population. Due to the lack of information about its sexual reproductive process, we collected tissue samples of healthy and unhealthy colonies (with bleaching, or algal or cyanobacterial overgrowth), along with salinity and sea-surface temperature data, between October 2010 and October 2011. During histological analysis we observed four oocyte and three spermary developmental stages in healthy colonies. Colonies were hermaphrodites with synchronous gonadal maturation in May 2011. However, polyps within colonies were either gonochoric, with a 7.8 +/- 11.8:1 (mean +/- SD) female to male polyp sex ratio, or hermaphroditic, with a 2.8 +/- 1.5:1 (mean +/- SD) oocyte to spermary ratio. The low number of spermaries observed may reduce the chance of effective fertilization and could explain the low sexual recruitment observed in the study area. There was a positive correlation between salinity and the mean number of gametes (oocytes and spermaries) produced per polyp, although both oocytes and spermaries increased during the warm water, high-salinity season (March to July 2011). Colonies with bleaching or overgrowth by cyanobacteria or algae had no gametes, suggesting that population recovery after disturbances might not be effective if it depends solely on sexual reproduction.