Allee effects limit coral fertilization success

Area of Science:

• Marine Biology
• Conservation Science
• Reproductive Ecology

Background:

• Climate change is causing coral population decline, increasing the risk of reproductive failure due to Allee effects.
• Fertilization success in corals is known to improve with spawning intensity and synchrony, but local density effects are poorly understood in natural settings.

Purpose of the Study:

• To investigate the local dependence of fertilization success on coral density in wild populations of Acropora hyacinthus.
• To quantify the impact of spatial Allee effects on coral reproductive output.

Main Methods:

• Field study measuring fertilization success of individual Acropora hyacinthus colonies in Palau, Micronesia.
• Analysis of fertilization rates in relation to colony proximity, local density, and spawning synchrony.

Main Results:

• Strong evidence of spatial Allee effects was found, with fertilization success declining sharply as colony separation increased from <0.5m to 15-20m.
• The distance to the nearest neighboring gravid colony was a better predictor of Allee effects than local colony density.
• Fertilization success decreased significantly on a second spawning night with higher winds, despite more intensive spawning.

Conclusions:

• Spatial Allee effects significantly impact Acropora hyacinthus fertilization success, with close proximity being vital for reproduction.
• Spawning synchrony and environmental factors like wind can exacerbate or mitigate Allee effects.
• Restoration efforts focusing on reconnecting depleted coral populations may be crucial for safeguarding reproductive success against climate change impacts.