Spawning dynamics in the Hawaiian reef-building coral Montipora capitata

Abstract

The release of gametes into the water column by broadcast-spawning marine inver- tebrates represents the culmination of several physiological events in the parents and the first step in the supply of new recruits to marine ecosystem. The input of new propagules to coral reefs relies on spawning events that display remarkable synchronicity during limited periods each year. Although the timing of spawning is known for most species, other aspects of coral reproduction (polyp fecundity or spawning synchronicity) are less understood. This largely reflects the sporadic nature of reproductive activities and logistical problems of studying the ephemeral coral spawn- ing events in situ on the reef at night. Here, we address this gap by exploring the spatial and tem- poral spawning dynamics of Montipora capitata, a broadcast-spawning, reef-building coral from the central Pacific Ocean, by using the systematic sampling of gametes in the field. Our results indicate that spawning in this species varies among years, months and lunar days, and that the proportion of colonies spawning and synchrony of spawning do not reflect coral colony morphol- ogy, colony size or the differences in environments between sites within a year. Major differences in reproductive outputs (spawned material) were observed between the 2 yr studied, which most probably reflects variability in temperature between years or shifts in the timing of spawning (phenology). This study highlights the complexity of spawning dynamics in corals and suggests that a more comprehensive understanding of interplay between reproduction and environment is fundamentally important to accurately predict the effects of climate change in these important ecosystems.