科学美国人60秒:Plankton Pee May Alter Ocean's Chemistry

Every day, the largest mass migration on the planet happens—in the world's oceans. Tiny fish, jellies and shrimpy things feed at the water's surface by night. And by day, they hide in darker waters a few hundred meters below. "The ocean is a dangerous place, and so swimming down to depth is your best bet to avoid predators." Daniele Bianchi, an oceanographer at the University of Washington.

Bianchi and his team tracked these ocean migrations with sonar data. And they found that the creatures descend to areas of deep water where certain species of bacteria hang out. Those bacteria snack on nutrients that float down from the surface—so-called "marine snow."

But Bianchi says the migrating creatures may also deliver food to the bacteria—in the form of ammonia in the creatures’ urine. The bacteria metabolize the ammonia to produce energy and nitrogen gas—effectively removing the nitrogen from the food chain, and sending it in gaseous form back into the atmosphere. Then other bacteria fix that nitrogen gas back into food chains—on land and in the ocean—where it eventually finds its way into amino acids. Some of which make up the proteins in us. The findings appear in the Proceedings of the National Academy of Sciences. [Daniele Bianchi et al, Enhancement of anammox by the excretion of diel vertical migrators]

"There are about 20 times more of these tiny fish than there are humans on the planet." Meaning that these miniscule creatures could play an important role in the ocean's nitrogen cycle, Daniele says—simply by taking a leak.

—Christopher Intagliata