Conrad et al have tried to understand the change in Fe speciation in terms of particulate, colloidal and soluble phases across a salinity gradient along the Lena river plume. The Fe concentration data are also coupled with Fe- isotope data showing fractionation attributed to precipitation of bulk of the Fe. The residual colloidal Fe -oxyhydroxide in the outer Lena plume has positive del 56Fe values in contrast to the precipitated Fe. Although the outcome is promising it suffers from low number of data points. The relationship between DOC and truly dissolved Fe (<1kDa) is also not clear. This is an important issue from the point of view of iron bioavailability and productivity. Authors may shade more light on this aspect.

Both the reviewers have suggested major revision. You may kindly incorporate the suggestions from the reviewers and submit the annotated manuscript for further review.

Corrections are suggested by the referee. Those correction should be incorporated by the author