Mean concentrations of total dissolved Fe (TDFe) are plotted as a function of brine volume fraction (Φ_br, upper left), chlorophyll a (Chl-a, upper right), particulate organic carbon (POC, lower right) and particulate Fe (PFe, lower right), and analysed for non-parametric Spearman's rank correlation. The statistical parameters apply to all data points in a given panel. The positive and significant correlations of TDFe concentrations with brine volume fraction Φ_br and biological parameters such as [POC] and [Chl-a] suggest a coupling between the Fe pool and the biota. The strongest correlation shown (lower right), between [TDFe] and [PFe], indicates that particulate Fe largely explains the total dissolvable Fe in sea ice.