Interactive comment on “Photo-lability of deep ocean dissolved black carbon” by A. Stubbins et al

Stubbins et al provide a concise study on photolability of dissolved black carbon (DBC) in seawater. The discussion paper is timely and the presentation of the study was well conceived; it was very easy to follow this paper and to understand the importance of DBC in global carbon cycling. A major outcome of this paper was the tight coupling between CDOM (the absorptive property of DOM) and DBC. In fact, Stubbins et al provide a convincing argument that DBC rather than lignin is a key chemical tracer of terrestrial CDOM. The aim of this paper was to investigate its photoreactivity, and I think here the authors have show a more direct link between chemistry and optical properties than in studies that focus on lignin, especially for seawater.