Vertical distribution of photosynthetic parameters in the sea ice. Distribution of each parameter is presented for landfast (A, C, E) and pack ice (B, D, E) over three layers of the ice column: surface, interior and bottom. Average values for combined Arctic and Antarctic data are plotted for maximum photosynthetic capacity, Pmax (A, B), α (C, D), and Ik(E, F); error bars indicate standard error. Significance was tested within each layer by Kruskal-Wallis test. Different letters (a–f) indicate significant differences; same letters indicate no significant difference (t-test, p < 0.05). DOI: https://doi.org/10.1525/elementa.267.f5