Jars filled with krill line windowsills in a lab. Sailors on a U.S. icebreaker ship collected them. A technician unscrews a lid and pours krill into his hand. A dozen fit in his palm.

They’re tiny. But they’re a big deal.

When you imagine Antarctica, what do you see in your mind? Seals? Penguins? Those White Continent critters need krill to survive. Antarctic krill (which glow in the dark!) feed everything from fish to marine mammals to seabirds. When krill numbers shrink, so do the numbers of other species. Take humpback whales for example. In Antarctica, fewer humpbacks are having babies—possibly due to a lack of krill, their main prey. Chinstrap penguins and fur seals feel the krill squeeze too.

But increasingly, fish all around the world rely on this bitty creature. After harvest, people make krill into tiny pellets. Farmed fish eat the pellets. The krill treat makes fish grow faster. It gives salmon a pinker color.

“The fish love it,” says Brett Glencross. Mr. Glencross is technical director of an organization that sells ingredients from the sea. “It’s like dipping your Brussels sprouts in chocolate to get kids to eat their vegetables.”

God put people in charge “over the fish of the sea.” (Genesis 1:26) But how should krill be used? Who is responsible for them? And who makes sure animals in Antarctica get the food they need?