Hey Mr. Green,

Krill oil is a new health craze because of its heart-healthy omega-3 fatty acids. But how will that affect the ocean's krill populations? I’ve heard that some Antarctic krill populations are already down, and krill is a major source of food for sea life. —Amy in Naperville, Illinois

Humans harvest less than 1 percent of the estimated 100 million metric tons of krill in the Antarctic each year, and only about 20 percent of that harvest becomes krill oil. The rest goes into fish food or—in one of the sillier, Rube Goldberg contrivances of agribusiness—into chicken feed to boost eggs’ omega-3 content. 

Not to let the krillionaires off the hook (or out of their trawler nets), but marine biologists warn that the biggest threat to these shrimplike creatures may be climate change, not health nuts. Krill’s major food source is the mass of microscopic plants and tiny sea animals living right below the Antarctic ice cap. So, shrink the ice, and the food supply could diminish. Krill may also be threatened by the rising acidity of the oceans, caused by carbon dioxide from fossil fuel combustion. And of course, less krill means less food for penguins, seals, and whales.

But I’d lay off krill oil, anyhow. We know that increased demand leads to increased harvest, which was four times higher in the 1980s, before the Soviet fishing fleet collapsed along with the USSR itself. Besides, there are plenty of other omega-3 sources: cheap fish such as mackerel and herring, and, for vegetarians, canola oil, flaxseeds, walnuts, and spinach. —Bob Schildgen

Got a question? Ask Mr. Green!

READ MORE:

Ask Mr. Green: Paper Towels or Hand Dryers

Ask Mr. Green: How Green Is Bamboo?

Ask Mr. Green: What Are the Best Crops for My Backyard?

 --illustration by Little Friends of Printmaking