Coral Reefs Depend on Big Fishes’ Pee

None of us live, or pee, in a vacuum.* The substances that leave our body interact with our environments in a million little ways. Traces of prescription drugs in our waste travel through the waterways and affect the way shrimp live their lives. Someone else’s pee in a public pool can raise your risk of developing asthma. But not all excrement is harmful. Scientists say that fish pee is a necessary—and threatened—component of healthy marine ecosystems. The researchers published their findings in the journal Nature Communications. 

Lead author Jacob Allgeier studies ecology at the University of Washington’s School of Aquatic and Fishery Sciences. “Part of the reason coral reefs work,” he said in a press statement, “is because animals play a big role in moving nutrients around.” 

Researchers have been working since the 1980s to understand the relationship between fish and the health of their homes on the reef. Recent research has suggested a primary link: fish waste. Their pee is rich in phosphorus, and their gills give off ammonium—two chemicals corals need to stay healthy and strong. 

Allgeier and his colleagues wanted to test this hypothesis by looking at reefs where fish had been removed. They visited 43 different coral reefs in the Caribbean, ranging from pristine to over-fished. Allgeier caught and measured hundreds of live fish. He placed each one in a bag of water for a half-hour, then analyzed the water once the fish were gone.

Fish in a bag. Image credit: Jacob Allgeier

He found that large, carnivorous fish peed out more phosphorus than smaller herbivores, and that bigger fish almost always gave off more ammonium, making them especially desirable to a community of coral. Unfortunately, these same fish are also quite desirable to fishers, who yank the big ones right out of the ecosystem equation. 

“Simply stated, fish biomass in coral reefs is being reduced by fishing pressure,” Allegeier says. “If biomass is shrinking, there are fewer fish to pee.” 

He and his colleagues say these findings should influence future thinking about fishery management. “Fish hold a large proportion, if not most of the nutrients in a coral reef in their tissue, and they’re also in charge of recycling them,” he said. “If you take the big fish out, you’re removing all of those nutrients from the ecosystem.”

*This is not a challenge. Do not pee in your Dyson.

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Watch How a Bioluminescence Expert Catches a Giant Squid

Giant squid have been the object of fascination for millennia; they may have even provided the origin for the legendary Nordic sea monsters known as the Kraken. But no one had captured them in their natural environment on video until 2012, when marine biologist and bioluminescence expert Edith Widder snagged the first-ever images off Japan's Ogasawara Islands [PDF]. Widder figured out that previous dives—which tended to bring down a ton of gear and bright lights—were scaring all the creatures away. (Slate compares it to "the equivalent of coming into a darkened theater and shining a spotlight at the audience.")

In this clip from BBC Earth Unplugged, Widder explains how the innovative camera-and-lure combo she devised, known as the Eye-in-the-Sea, finally accomplished the job by using red lights (which most deep-sea creatures can't see) and an electronic jellyfish (called the e-jelly) with a flashy light show just right to lure in predators like Architeuthis dux. "I've tried a bunch of different things over the years to try to be able to talk to the animals," Widder says in the video, "and with the e-jelly, I feel like I'm finally making some progress."

[h/t The Kid Should See This]

Big Questions
Why Are There No Snakes in Ireland?

Legend tells of St. Patrick using the power of his faith to drive all of Ireland’s snakes into the sea. It’s an impressive image, but there’s no way it could have happened.

There never were any snakes in Ireland, partly for the same reason that there are no snakes in Hawaii, Iceland, New Zealand, Greenland, or Antarctica: the Emerald Isle is, well, an island.

Eightofnine via Wikimedia Commons // Public Domain

Once upon a time, Ireland was connected to a larger landmass. But that time was an ice age that kept the land far too chilly for cold-blooded reptiles. As the ice age ended around 10,000 years ago, glaciers melted, pouring even more cold water into the now-impassable expanse between Ireland and its neighbors.

Other animals, like wild boars, lynx, and brown bears, managed to make it across—as did a single reptile: the common lizard. Snakes, however, missed their chance.

The country’s serpent-free reputation has, somewhat perversely, turned snake ownership into a status symbol. There have been numerous reports of large pet snakes escaping or being released. As of yet, no species has managed to take hold in the wild—a small miracle in itself.

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