Two- to four-centimeter-deep circular depressions created by differential thermal absorption by dark algal growths on the glacial surface. These circular algal growths are common in ablation zones of Bylot Island glaciers. Organic debris collected from the ablation zones of Aktineq and Sirmilik glaciers is dominated by fragments of the black algae Ancyclonema nordenskioidii, which is probably the algal growth in the image (Bouchard and Shilts, 1991). Tip of ice pick for scale.