Reef coral reproduction in the eastern Pacific: Costa Rica, Panamá, and Galápagos Islands (Ecuador). III. Agariciidae (Pavona gigantea and Gardineroseris planulata)

Abstract

The reproductive ecology of Pavona gigantea Verrill and Gardineroseris planulata (Dana) was investigated in the equatorial eastern Pacific region from 1985 to 1994. These zooxanthellate scleractinian corals were adversely affected in this region during the 1982–1983 El Nino warming event. Both species were hermaphroditic, with individual colonies showing sequential cosexual development, thus resulting in dominantly outbreeding reproduction. Sexuality was mixed, with high percentages of gonochoric and hermaphroditic colonies in both species. Approximately 1:1 male-to-female gonad ratios were found in gonochoric and hermaphroditic colonies combined. Broadcast spawning was observed in P. gigantea in the Galapagos Islands, and the sudden disappearance of mature gametes and the presence of spent gonads suggest that G. planulata is also a broadcast spawner. Colonies of both species with ≲200 cm2 (10 cm diam) live tissue were nonreproductive. Estimated ages of the youngest reproductive colonies were 11 yr for P. gigantea and 20 yr for G. planulata. The percentage of all colonies of P. gigantea with gonads at nonupwelling sites (Cano Istand, Costa Rica and Uva Island, Panama) ranged from 37 to 47%, respectively; colonies with gonads from upwelling environments (Saboga and Taboga Islands, Panama) ranged from 31 to 39%, respectively, and reproductively active colonies from the thermally variable Galapagos islands comprised 40% of the collections. Compared with P. gigantea, the numbers of sexually active G. planulata colonies were roughly onehalf at nonupwelling Cano Island (20%) and Uva Island (25%) sites, or less (10%) at the upwelling Saboga Island site. Peak reproductive activity in P. gigantea occurred during the rainy season at all study sites. In the nonupwelling Costa Rican (Cano Island) and Panamainan (Uva Island) sites, mean monthly sea-surface temperatures (SSTs) were high (28 to 29°C), but slightly lower than in the dry season (29°C). In the upwelling Gulf of Panama (Saboga and Taboga Islands), reproduction occurred after mean monthly SSTs increased from 24 to 28–29°C. In the Galapagos Islands, reproductive activity peaked during sea warming, when mean monthly SSTs reached 25°C. Sexually active colonies of G. planulata, present only at the main collection sites of Cano and Uva Islands, were also observed during the wet season. The presence of mature or spawned gonalds in both species mostly around new and full lunar phases suggests that spawning is at least weakly synchronized with moon phase. Fecundity estimates disclosed the following nonsignificant differences between sites for P. gigantea, expressed as egg production cm-2 colony surface surface yr-1: Galapagos (10 300 to 30 800), Uva Island (4900 to 9800), Cano Island (1800 to 7400), Saboga Island (600 to 1300) Taboga Island (1200 to 2400). Fecundity estimates for G. planulata were considerably lower: Uva Island (700 to 1400), Cano Island (500 to 1000). The sexual recruitment of P. gigantea into El Nino-Southern Oscillation (ENSO) 1982–1983-disturbed, equatorial eastern Pacific coral communities has been low, with only moderate recovery evident since 1983. G. planulata has revealed no sexual recruitment where seed populations are absent or rare (Cano Island, Galapagos Islands), and only low recruitment (Panama) in areas with colonies that survived the ENSO disturbance.