Split spawning realigns coral reproduction with optimal environmental windows.

Area of Science:

• Marine Biology
• Coral Reef Ecology
• Reproductive Biology

Background:

• Split spawning, gamete maturation and mass spawning over consecutive months, is observed in corals but its frequency and significance are poorly understood.
• Understanding split spawning is crucial for coral population dynamics and conservation efforts.

Purpose of the Study:

• To investigate the frequency and predictability of split spawning events over a decade at Scott Reef.
• To determine the environmental cues and lunar cycles influencing split spawning.
• To assess the significance of split spawning for coral reproductive success.

Main Methods:

• Long-term monitoring of coral spawning events at Scott Reef over ten years.
• Analysis of lunar cycles and their correlation with spawning timing.
• Comparison of spawning dates with regional environmental conditions.

Main Results:

• Split spawning was found to be frequent and predictable at Scott Reef over a decade.
• Split spawning events were linked to full moons occurring in the early or late weeks of the typical spawning month.
• In split years, most coral species spawned in the month following the usual spawning period, often after a 13-month lunar cycle.
• Split spawning prevents a ~10-day annual shift in spawning dates, maintaining alignment with optimal environmental windows.

Conclusions:

• Split spawning in corals is driven by a decoupling of lunar and seasonal cues.
• This reproductive strategy functions as a 'leap year' mechanism, ensuring coral spawning aligns with favorable environmental conditions.
• Split spawning is vital for maintaining reproductive success and population resilience in coral communities.