The following post is an article by Robert Krulwich written as a featured post "Krulwich Wonders" for NPR, posted
The Power Of Poop: A Whale Story
The problem was with the middle group — the krill.
Too much for Professor Smetacek.
Krill need iron to grow and multiply. Given what we know about ocean chemistry, , there's not enough iron in the southern ocean water to support that many krill. So either the whales had smaller meals a century ago, or somehow the oceans got an extra kick or boost of iron to create more krill.
Nobody was willing to consider a food pyramid that looked like this:
The 'Whale Poop Hypothesis'
And that's when Smetacek proposed what he delicately called in his paper, the whales' extra nutritious "manuring mechanism." (Or, as it's come to be known, his "whale poop hypothesis.") It begins with this obvious observation: Whales poop. In fact, they poop mightily.
Poop With 10 Million Times More Iron
Nicols' team analyzed 27 fecal samples from four species of baleen whales, . "He found that on average whale faeces had 10 million times as much iron as Antarctic seawater." Basically, that's iron concentrate. And strategically emitted — which would have to be up near the ocean surface, where the sun shines — that extra iron would create blooms of phytoplankton, which would then be eaten by krill, leading to a boost in the krill population, leading to ... yes ... bigger whale dinners!
Then, if something nasty were to happen, like ocean-going terrestrials invent boats, harpoons, trawlers, nets and kill masses of whales — instead of the krill population expanding ("Hooray! Those giants who eat us are gone — let's multiply!"), the krill population might shrink. ("Oh no! Those big animals who gave us iron are gone! We're going to starve.")
And guess what? When Antarctica's great whales were nearly destroyed in the 1960s, the krill population, instead of expanding, collapsed, by some 80 percent.
Smetacek got it right. Whales do, in fact, garden the ocean, fertilizing the seas to grow their own food.
Whales recirculate the iron. Even the bits that slip down to the dark bottom get pulled back up by whales. Sperm whales dive to terrifying depths, 3,000 feet below, to hunt iron-rich prey like giant squid. Pressed by the weight of the ocean, their digestion stops; they don't excrete. They consume the iron below, hold it in, climb back to the surface, and that's where they poop. Every sperm whale, , draws 50 tons of iron to the surface every year.
Recycling Yourself Into Abundance
So who knew? A couple of centuries ago, the southern seas were packed with baleen whales. Blue whales, the biggest creatures on Earth, were a hundred times more plentiful than they are today. Biologists couldn't understand how whales could feed themselves in such an iron-poor environment. And now we may have an answer: Whales are extraordinary recyclers.
What whales consume (which is a lot), they give back. As science writer J.B. MacKinnon writes in his book , "Whales may have been boosting the productivity of the entire ocean, making their own extraordinary abundance possible."
|Robert Krulwich/NPR||ch is a lot), they give back. As science|