FIG. 1.

Microscopic images of wintertime sea ice from the Chukchi sea near Barrow, Alaska, at −5 (A) and −15°C (B). Ice-grain boundaries and triple-point junctures (upper panels) and details of brine pockets (lower left panels, which are enlargements of the areas boxed in red in the upper panels) are visible by transmitted light. DAPI-stained bacteria (blue) attached to the wall of a brine pocket (A) or to particulate material within the pocket (B) are visible in the same fields as those shown in the lower left panels when examined by epifluorescence light (lower right panels).