Examining the Interaction Between Juvenile Diadema antillarum and the Caribbean Coral Reef at Two Contrasting Sites

Abstract

In the 1980s, a mass mortality event in the Caribbean coral reefs, targeted the keystone herbivore, D. antillarum. Since then, persistently low population densities of D. antillarum are evident. By comparing Banco Capiro, an atypical reef system with much higher population density of D. antillarum and Utila, a more representative reef system for the Caribbean, previous research has suggested that juvenile D. antillarum may be facing a barrier to maturation. However, no studies have explored the interaction between the coral reef and juveniles in order to elucidate the effects of juveniles on the reef and vice versa. This study indicates that a barrier to maturation continues to exist on Utila but Banco Capiro’s juveniles overcome this barrier allowing for the replenishment of D. antillarum’s population density. In order to determine which ecological factors of the reef may be influencing the suppression of juveniles’ maturation, the interaction with E. viridis and the interaction of habitat quality and predation pressure on juveniles were investigated. E. viridis, the common sea urchin, had a stronger, positive relationship with juveniles on Utila, showing that Utila’s different ecosystem may elicit this beneficial relationship. Furthermore, a significant interaction between Panularis, the spiny lobster, and both rugosity and refuge size existed on Utila, but not on Banco Capiro. This suggests that habitat is especially important for juveniles on Utila with increasing predation pressure. Although, both Banco Capiro and Utila showed no direct effects of juveniles on the benthic cover of the reef, the structural complexity of the reef and reef ecology interact with juvenile populations differently between the two sites.