Molecular diversity of coral microbiomes shows no relationship with latitude in the western Pacific Ocean

Reef-building corals are holobionts that include dinoflagellates, prokaryotes, and other microorganisms, and these symbiotic relationships enable corals to respond to environmental factors such as light and water temperature. We investigated community structures of dinoflagellates and prokaryotes in Acropora digitifera sampled along a latitudinal transect that included 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 variables using satellite data. Community structures of both dinoflagellates and prokaryotes were distinctly different 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 regional factors such as water pollution. Overall, there was no observed correlation between community structures of symbiotic microorganisms and latitude. This study provides important insights into relationships among reef-building corals, their symbiotic microorganisms, and their habitats. Additionally, it emphasizes the necessity for on-going research on reef-building corals and their microsymbionts.