Biogeography and molecular diversity of coral symbionts in the genus around the Arabian Peninsula.

AIM

Coral reefs rely on the symbiosis between scleractinian corals and intracellular, photosynthetic dinoflagellates of the genus making the assessment of symbiont diversity critical to our understanding of ecological resilience of these ecosystems. This study characterizes diversity around the Arabian Peninsula, which contains some of the most thermally diverse and understudied reefs on Earth.

LOCATION

Shallow water coral reefs throughout the Red Sea (RS), Sea of Oman (SO), and Persian/Arabian Gulf (PAG).

METHODS

Next-generation sequencing of the ITS2 marker gene was used to assess community composition and diversity comprising 892 samples from 46 hard and soft coral genera.

RESULTS

Corals were associated with a large diversity of , which usually consisted of one or two prevalent symbiont types and many types at low abundance. communities were strongly structured according to geographical region and to a lesser extent by coral host identity. Overall symbiont communities were composed primarily of species from clade A and C in the RS, clade A, C, and D in the SO, and clade C and D in the PAG, representing a gradual shift from C- to D-dominated coral hosts. The analysis of symbiont diversity in an Operational Taxonomic Unit (OTU)-based framework allowed the identification of differences in symbiont taxon richness over geographical regions and host genera.

MAIN CONCLUSIONS

Our study represents a comprehensive overview over biogeography and molecular diversity of in the Arabian Seas, where coral reefs thrive in one of the most extreme environmental settings on the planet. As such our data will serve as a baseline for further exploration into the effects of environmental change on host-symbiont pairings and the identification and ecological significance of types from regions already experiencing 'Future Ocean' conditions.