One of the reasons that I'm fascinated（兴奋的） by the ocean is that it's really an alien（外国的） world on our own planet. From our perspective（透视画法） sitting on the shoreline（海岸线） or even out on a boat, we're given（做） only the tiniest glimpses（一瞥） at the real action that's happening beneath（在……下面） the surface of the waves. And even if you were able to go down there, you wouldn't see very much because light doesn't travel very far in the ocean. So to answer questions about how the ocean works（使工作）, in my research we use sound. We use sonars（声纳） that send out pulses（脉搏） of sound made up of a number of different frequencies（频率） or pitches that are shown with different colors. That sound bounces（弹跳） off things in the habitat（(动植物的)生活环境） and comes back to us.

  If it were to bounce off this dolphin, the signal we got back would look very much like the one we sent out, where all the colors are represented pretty evenly. However, if we were to bounce that same sound off of a squid, which in this case is about the same size as that dolphin, we'd instead only get the lowest frequencies back strongly, shown here in the red. And if we were to look at the prey（捕食） of that squid, the tiny little krill（[动]磷虾(单复同)） that they're eating, we would instead only get the highest frequencies back. And so by looking at this, we can tell what kinds of animals are in the ocean. We can look at how dense（密集的） they are, where they're distributed（分发）, look at their interactions（相互作用） and even their behavior to start to study the ecology of the ocean. When we do that, we come up with something sort of surprising.

  On average, there isn't very much food in the ocean. So even in places which we think of as rich, the coasts, we're talking about two parts out of every million contained food. So what does that mean? Well, that means that in the volume（卷） of this theater, there would be one tub（浴盆） of movie theater popcorn available to be eaten. But of course, it wouldn't be collected for you neatly in this bucket. Instead, you'd actually have to be swimming through this entire（全部的） volume（卷） Willy Wonka style, picking off individual kernels（(硬壳果)仁） of popcorn, or perhaps if you were lucky, getting a hold（把握） of a few small clumps（丛）.

  But of course, if you were in the ocean, this popcorn wouldn't be sitting here waiting for you to eat it. It would instead be trying to avoid becoming your dinner. So I want to know how do animals solve this challenge.