Molecular diversity of coral microbiomes along a latitudinal transect in the western Pacific Ocean
Reef-building corals are holobionts composed of dinoflagellates, prokaryotes, and other microorganisms, and this symbiotic relationship enables corals to respond to environmental factors such as light and water temperature. We investigated community structures of dinoflagellates and prokaryotic microorganisms in Acropora digitifera sampled along a latitudinal transect including Kuroshima, Irabujima, Akajima, Okinawajima, Amami Oshima (Naon and Kusuno), and Tanegashima in the Nansei Islands, Japan. We also investigated the relationship between microbial community structures and environmental parameters using satellite data. The community structures of both dinoflagellates and prokaryotes were distinct at Okinawajima and Tanegashima, but similar at other locations. The community structure at Tanegashima appears to be shaped by environmental isolation due to the Kuroshio Current, whereas community structure at Okinawajima is likely influenced by region-specific factors such as water pollution. Overall, there was no  observed correlation between the community structures of symbiotic microorganisms and latitude. To identify factors determining the symbiotic microbial communities of reef-building corals, further analyses using multivariate analysis with more specific environmental parameters are required. This study provides important insights into the relationship among reef-building corals, their symbiotic microorganisms, and their habitats. Additionally, it emphasizes the necessity of on-going research on reef-building corals and their symbiotic microorganisms in the coastal waters of Japan.