Growth anomalies on Acropora cytherea corals

Area of Science:

• Marine Biology
• Coral Reef Ecology
• Oceanography

Background:

• Coral growth anomalies (CGAs) are disruptions in skeletal formation.
• Acropora cytherea is a key reef-building coral species.
• Understanding CGAs is crucial for coral reef health assessment.

Purpose of the Study:

• To investigate the prevalence and characteristics of CGAs in Acropora cytherea.
• To determine the impact of CGAs on coral colony growth, mortality, fecundity, and photosynthetic capacity.
• To test the hypothesis that CGAs are indicators of coral aging, potentially exacerbated by environmental stress.

Main Methods:

• A ten-year observational study on Acropora cytherea colonies in Amuro Island, Okinawa, Japan.
• Morphological, physiological, and ecological assessments of coral growth anomalies.
• Analysis of colony size, location of anomalies (central vs. peripheral), growth rates, mortality, fecundity, and photosynthetic capacity.
• Contact experiments to assess the contagiousness of growth anomalies.

Main Results:

• Growth anomalies were more prevalent in larger colonies (>2 m diameter) and concentrated in older, central portions.
• Anomalies were associated with reduced productivity and impaired gametogenesis (dysfunctional reproduction).
• Growth anomalies did not significantly affect colony survival, and contact experiments indicated they are not contagious.

Conclusions:

• Coral growth anomalies in Acropora cytherea are likely a manifestation of coral aging.
• Thermal stress may exacerbate the occurrence or severity of these aging-related anomalies.
• While impacting reproductive capacity and productivity, CGAs do not appear to be a primary driver of coral mortality.