Corals are damaged by predators removing tissue, mucus, and skeleton. The response of the coral depends not only on the type of removal, but also on the size, shape, and location of the lesion left by the predator. Large lesions tend to heal more slowly than small ones, as do lesions with a lower perimeter to area ratio. Most studies of coral damage focus on large, reef-building corals. Less is known about smaller corals, including many popular in the aquarium trade. For example, the coral Galaxea fascicularis is a popular coral for aquariums, with large polyps. Most work on this coral focuses on physiological processes, and the coral is amenable for lab work as it is easily fragmented and does well in aquaria. This experiment tested the effects of the perimeter to area ratio of lesions on the response of Galaxea fascicularis as part of an undergraduate coastal ecology course. We placed corals into 3 treatments: no damage, two small scars, or one large scar (all damage treatments had the same area) and removed tissue using a Waterpik. We photographed and weighed the corals to look at lesion recovery and coral growth.
Over the course of the month-long experiment, almost all corals lost mass. Control corals and corals with two small scars lost approximately half a gram of mass over the month-long experiment, while corals with one large scar lost approximately 0.75g. However, these results were not statistically significant. Perhaps another key finding was that student-measured weights varied considerably, even among weights taken for the same coral in the same afternoon. Future iterations of this project will include better quality control during the measurement stage, as well as investigations of water chemistry. Finally, future experiments will examine more spatial arrangements of damage and the effects of environmental conditions on the response of Galaxea fascicularis.