Spatiotemporal variation in coral recruitment and its association with seawater temperature

The supply of propagules mediates recruitment and population dynamics, thereby driving community resilience following disturbances. These relationships are of interest on tropical reefs, where coral populations have drastically declined in abundance and sexual recruitment is the only means by which they will recover. To better understand the causes and implications of variation in this vital rate (i.e., recruitment), coral recruitment was measured in Mo'orea, French Polynesia, and St. John, U.S. Virgin Islands, using settlement tiles deployed from 2005 to 2019. The results were used to test two hypotheses: (1) annual variation in recruitment is a weak predictor of long-term variation in recruitment, but (2) it is associated with seawater temperature. Coral recruitment varied over space and time, so that differences in recruitment between consecutive years were uninformative of long-term trends. Recruitment varied among years in an apparently chaotic manner, but the variation reflected linear and quadratic associations with mean annual temperature and the daily variation in temperature. These associations are consistent with theory addressing the mechanisms by which temperature affects coral larvae and recruitment. Comprehension of these mechanisms is required to accurately interpret evidence of coral recruitment collapse, and to elucidate the conditions favoring recovery of coral communities through recruitment.

Automated summary

The study found that coral recruitment is influenced by seawater temperature and varies spatially and temporally. Therefore, relying solely on consecutive years' recruitment data is not informative for long-term trends. Recruitment showed linear and quadratic associations with mean annual temperature and daily temperature variation.