Effects of Feeding and Light on the Growth of Juvenile Colonies of the Atlantic Coral Porites Astreoides

Abstract

Coral species sustain one of the most ecologically and economically important ecosystems in the world. Ecosystem services provided by reefs are worth over hundreds of thousands of dollars as they provide coastal protection, safe fish juvenile rearing zones, as well as ecotourism revenue. Successful coral recruitment is critical to the resilience of coral reefs, especially with rapid environmental change now a principal threat to coral survival. However, there is limited information on the effects of environmental parameters on the survival and growth of juvenile corals. Larvae from twenty colonies of the brooding Atlantic coral Porites astreoides were collected over several days and immediately settled onto terracotta clay tiles. The new recruits reared for two weeks under the same conditions as the adults. The juveniles were then transferred to controlled aquaria treatments and reared for 8 weeks under two light (50 and 200 µmol photons m-2 s-1) and two feeding regimes (once every week and four times a week) using freshly cultured brine shrimp. Frequent feeding of the juvenile corals had a strong effect on growth rate under both light regimes, increasing growth rates by over 50% compared to low fed conditions. Light levels did not have a significant effect on growth rates, but did have a significant effect on symbiont density, and both symbiont- and area-normalized chlorophyll a content. Highly fed corals had greater symbiont densities and area-normalized chlorophyll a content than low fed corals, possibly due to increased internal nutrient recycling. Food availability has a strong influence on the success of juvenile corals.