Migrating Animal Urine Impacts Ocean Chemistry

One of the most intense daily migrations occurs not across land or sea, but vertical to it. Countless small animals travel between the ocean's surface to the lightless depths of the deep sea each day. However, researchers have never investigated how this unusual migration impacts our oceans, until now.

According to a study recently published in the journal Proceeding of the National Academy of Sciences (PNAS), the urine of these animals releases significant amounts of ammonia, heavily influencing ocean chemistry, especially in regions low in oxygen.

The lead author of this study, Danielle Bianchi, says that he is fascinated in the massive migrations simply because of how little they have been studied. He argues that it's also important to consider every driving factor of ocean chemistry, especially in these times when researchers are concerned about the Earth's potential for unexpected and radical change.

"To me, it's exciting to think about the effects of animal behavior on a large scale in the ocean," he said in a recent release.

According to the study, after these small migrators - which include zooplankton, crustaceans such as krill, and tiny lanternfish - eat their fill near the ocean's surface at night, they swim between 650 to 2,000 feet deep to escape the rising Sun's light.

And they're not vampires. These creatures adapted this strange migration ritual to escape predators that would otherwise be able to quickly spot and catch them in the light of day.

Interestingly, the animals tend to end their downward journey in regions heavily populated by oxygen-consuming bacteria that decompose carcasses from above.

"The animals really seem to stop in low-oxygen regions, which is sort of puzzling," Bianchi said.

It has since been speculated in past work that these creatures hide here because it is where larger predators would have trouble breathing.

Still, the researcher adds that during their essential migration, there is little time for pit-stops, and the marine life freely urinate as they swim. Results from the new study show that in certain parts of the ocean, ammonia released from animals drives a big part of the oxygen-free conversion of ammonium and other molecules to nitrogen gas, a key chemical transition.

Bianchi says that this can help explain for some mysterious measurements made in the past, in which these processes were thought to be purely facilitated by bacteria. Knowing better takes scientists one step closer to truly understanding the vast ocean that dominates our world.