Distribution and abundance of spatial competition between scleractinian corals and sessile aggressive invertebrates on the west coast of Bonaire

Processes affecting reef ecosystems have three levels of organization: macroscale, mesoscale and microscale. These processes are conducive to interspecific competition amongst various coral and aggressive invertebrate species. Surveys of these organisms’ distribution, abundance and ecological description of their intra/interspecific competition have been conducted throughout the Caribbean. Previous research has found that scleractinian corals in reef slope ecosystems are frequently outcompeted by sessile aggressive invertebrates, such as Clionid sponges, encrusting bryozoans, encrusting gorgonians and overgrowing mat tunicates. Furthermore, interspecific spatial competition between corals and aggressive invertebrates has been observed to increase in frequency with depth. This project analyzed the distribution and abundance of coral-aggressive invertebrate spatial competition along a fringing reef ecosystem on the west coast of Bonaire. Belt transects were laid out between 200 m north and south of the GPS coordinates N 12°09.6 12’ W 068° 16.9 15’, at two depths (10 and 15 m) along the reef slope. Instances of spatial competition involving individuals at least 10 cm in length were photographed for further analysis. Five coral species and 25 aggressive invertebrate species were encountered in a total of 216 coral-aggressive invertebrate interactions. Quantitative data analysis showed that the orange lumpy encrusting sponge (Scopalina ruetzleri) was the most abundant aggressor at 15 and 10 m, although mean total area covered by coralaggressive invertebrate interactions and their frequency did not increase with depth. Findings could be used as a baseline for future scientific marine research, potentially on growth rate of competing species and the underlying mechanisms responsible for their interspecific spatial competition.

This student research was retrieved from Physis: Journal of Marine Science XVII (Spring 2015)19: 17-25 from CIEE Bonaire.