Abstract
Reef-building corals have evolved for adapting to tropical/subtropical ocean by establishing the obligate symbiotic relationship with dinoflagellates, commonly known as zooxanthella. It is not widely appreciated that coral harbor multiple species of microalgae within their skeleton. Its ecological function as well as impacts on the host corals has remained as a subject to be explored. Here we compare microalgal flora in the skeleton of corals inhabited eutrophic and oligotrophic environments. 10 coral colonies of Goniastrea aspera were collected from eutrophic and oligotrophic environments in Okinawa (Japan) and Great Barrier Reef (Australia). Microalgal species profile was analyzed with the PCR-DGGE method. We detected cyanobacteria and photosynthetic bacteria in all samples collected from the oligotrophic environments. However, such photosynthetic organisms were detected in only half of the samples collected from the eutrophic environments.
