Xiang et al. present a clear study that shows how the combined effect of temperature and DOC disrupts the diazotrophs community of two octocoral holobionts. The project is well designed, the data analysis sufficient and the manuscript well written, therefore, I think that it only needs a few fixes before being ready for publication.

Main concerns

Could the author explain in the M&M; how the tanks were divided across the experiment (control vs experimental)?

Could the lack of feeding have affected the metabolism of the mixotrophic X. umbellate? I feel that some discussion on this point is needed.

Minor comments

Line 42: could the author make a more specific statement? How labile DOC loading should be lowered in the ocean?

Line 221: could the authors report how many folds the diazotrophs increased in P. flava?

Line 222: change significantly with significant

Line 238: change potentially with possibly

Line 259: what corals are the authors referring to? Scleractinian corals?