A blue whale defecating off the coast of California. (IMAGE)
Caption
Because whales eat more than previously thought, they also poop more, and whale poop is a crucial source of nutrients in the open ocean. By scooping up food and pumping out excrement, whales help keep key nutrients suspended close to the surface where they can power blooms of the carbon-absorbing phytoplankton that form the base of ocean food-webs. Without whales, those nutrients more readily sink to the seafloor, which can limit productivity in certain parts of the ocean and may in turn limit the capacity of ocean ecosystems to absorb planet-warming carbon dioxide. Restoring whale populations to levels seen before 20th-century whaling could restore lost marine productivity and, as a result, boost the amount of carbon dioxide sucked up by the phytoplankton. The team estimates that the nutrient cycling services provided by pre-whaling populations at the start of the 20th century might fuel a roughly 11% increase in marine productivity in the Southern Ocean and a drawdown of at least 215 million metric tons of carbon, absorbed and stored in ocean ecosystems and organisms in the process of rebuilding. It is also possible these carbon reduction benefits would accrue year over year. New research published today in the journal Nature finds that gigantic baleen whales—such as blue, fin and humpback whales—eat an average of three times more food each year than scientists have previously estimated. By underestimating how much these whales eat, scientists may also have been previously underestimating the importance of these undersea giants to ocean health and productivity.
Credit
Elliott Hazen under NOAA/NMFS permit 16111
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