Effects of Light and Sedimentation on a Juvenile Coral in Bermuda

Abstract

Constantly threatened by environmental, marine, and human factors, coral reefs must maintain growth and calcification rates in order to remain resilient and diverse ecosystems. The links between light, sedimentation, and adult coral growth have been well established, identifying light as a positive factor and excess sedimentation as a negative one. The effects of light and sedimentation on juvenile corals, however, are less clear and require further investigation. This study seeks to discern these effects on the growth and mortality of juvenile Favia fragum corals by assessing changes in surface area over a three-week period. Additionally, the relationship between light, sedimentation level and zooxanthellae densities will be examined. We investigated the effects of artificial shading on juvenile F. fragum using three treatment levels, zero-, one-, and three-shade, to alter light and sedimentation conditions in situ. Although the one- and three-shade treatments significantly altered the amount of light available to corals, results were largely insignificant. Growth rates were marginally higher for the one-shade than for the control treatment, but the three-shade rates did not differ significantly from those of the control treatment. The proportion mortalities and zooxanthellae densities were not significantly different between the three treatments. These predominantly insignificant results suggest directions for further study into the ideal conditions for juvenile coral growth and therefore the resilience of coral reefs.