BG-2019-455

Dear Jerome Kaiser,

First of all I would like to thank Tom Jilbert and the anonymous referee for their thorough reviews and you for you reply. I think it would be worthwhile for you to make the changes according to the reviewers comments as you have indicated in your reply. Although I would not use the term trap sediments for material collected in sediment traps, perhaps sediment rap material or trapped material? I would advise you to check some of the older microbial mat literature as well, there are two nice overview tables, species and settings, on mid chain branched n-alkanes in Shiea et al. 1990. Together with several other interesting references. One of the reasons why there was such an interest in these compounds in the past is because they were found in 1.7 billion year old samples (e.a. Summons et al., 1988). You yourself mentioned that they are assumed to be quite resistant to degradation, which is a bit contradictory to you response to the anonymous reviewer. I think you might need to reconsider your explanation for the mismatch, perhaps I should say, the lack of a “1 to 1” relationship between biomarker and organism, there is, of course, a relationship. A better explanation for this species that were not accounted for or environmental conditions favoring mid chain branched n-alkane production or not might also help with the phosphorus versus temperature discussion, although I assume both will probably play a role. It would have been really great if you had another biomarker record for heterocystous cyanobacteria and/or an even more general cyanobacterial biomarker and/or a general primary productivity marker to compare your branched n-alkane record with. I think a HG record for the same samples would have been really useful in this case.

I am looking forward to reading your reply and modified manuscript.

Best regards,

Marcel

Dear Jerome Kaiser,

Thanks again to Tom Jilbert and the anonymous referee for their thorough reviews and you for you reply. I think it can be published subject to technical corrections.

Kind regards,

Marcel