Multispecific coral spawning events and extended breeding periods on an equatorial reef

Scleractinian corals often reproduce in synchronized spawning events to maximize gamete fertilization and coral larval production. The extent of spawning synchrony and its timing vary among coral taxa and among biogeographic regions. Information is, however, limited, especially for equatorial reefs, hindering the identification of environmental cues that influence gametogenic cycles and spawning. To investigate the timing of gamete maturation and spawning in Palau and their association with environmental cues, we monitored tagged colonies from 11 common coral species within three families over 21 months. We then combined our findings with previous available information to more broadly summarize the known coral spawning patterns in Palau. In combination with previous observations, our data confirmed the occurrence of an extended coral spawning season in Palau, spreading over 9 months. Some coral taxa participated in synchronous multispecific spawning events, with the largest occurring throughout April and May. Other coral taxa, including Montipora corals, displayed inter- and intra-specific spawning asynchrony. Consequently, environmental cues associated with spawning patterns differed among species. The largest Acropora spawning event of the year (March-April) was associated with the lowest yearly high tides and a monthly mean sea surface temperature around 29 degrees C. Massive Porites spawned predominantly in April and May, associated with increased monthly levels of solar insolation. Porites rus spawned in June-August and was associated with longest monthly day length. Our study demonstrates that Palauan coral assemblages have complex patterns of multispecific spawning events throughout most of the year, which may have important implications for larval dispersal, supply and recruitment patterns, influencing the resilience of coral reefs in this region.