Prior analysis of whale carbon dioxide emissions attributes 25 percent of carbon dioxide emissions total to the animals in the Southern Ocean region. Subsequent computation lowers the whales’ carbon dioxide emissions estimate to 0.3 percent, which is equivalent to 17 million tons of carbon a year. Lavery and team explain that there are low levels of iron in the Southern Ocean, and the sperm whales each contribute about 10 grams of iron to the surface. Since the iron comes from the whales’ waste material, it takes the form of liquid plumes, effectively acting as a fertilizer and encouraging growth of plankton. Depending on the exact values and environmental conditions, sperm whales can then be classified “either a net carbon sink or as carbon-neutral,” Discovery writes.