 A 2010 study considered whales to be a positive influence to the productivity of ocean fisheries , in what has been termed a " whale pump . " Whales carry nutrients such as nitrogen from the depths back to the surface . This functions as an upward biological pump , reversing an earlier presumption that whales accelerate the loss of nutrients to the bottom . This nitrogen input in the Gulf of Maine is " more than the input of all rivers combined " emptying into the gulf , some 23 @,@ 000 metric tons ( 25 @,@ 000 short tons ) each year . Whales defecate at the ocean 's surface ; their excrement is important for fisheries because it is rich in iron and nitrogen . The whale faeces are liquid and instead of sinking , they stay at the surface where phytoplankton feed off it . 
