 Sperm whales increase levels of primary production and carbon export by depositing iron @-@ rich faeces into surface waters of the Southern Ocean . The iron @-@ rich faeces cause phytoplankton to grow and take up more carbon from the atmosphere . When the phytoplankton dies , it sinks to the deep ocean and takes the atmospheric carbon with it . By reducing the abundance of sperm whales in the Southern Ocean , whaling has resulted in an extra 2 million tonnes of carbon remaining in the atmosphere each year . 
