Camila Mota

Thanks, Marnie.

I've got tacos and moose goes for lunch, I think, later today instead.

But I'm going to go a bit off topic here to talk about coral reefs.

OK, you win.

So one thing we all know about coral reefs, of course, is that they're in trouble.

There's bleaching, fewer fish, you name it.

But scientists have found that something weirder that's harder to notice is also going on.

It turns out that the food chains on Caribbean reefs, which is right where I am now, have basically shrunk significantly.

You're spot on.

But a recent study basically published in the journal Nature has found that 7,000 years ago, the ladder used to have more rungs and fish are basically kind of all eating the same stuff right now.

do scientists know what fish were eating 7 000 years ago yes so they looked at these tiny structures in fish called otoliths they're all also known as ear stones they're basically little calcium bits in a fish's ear that help with hearing and balance but also trap chemical signals from what the fish ate during its life now the researchers compared these otoliths

trapped in fossilised reefs from 7,000 years ago with those today.

And they used chemistry to reconstruct the whole food web.

So Katie, exactly what did they find?

So they found that the food chain had compressed so that big fish are eating lower on the chain while small fish are creeping up.

And also fish have just lost their individuality.

They used to specialise, now they don't.

And this matters because?

Because variety means that a species can be resilient.

So if you lose one food source, it wouldn't wipe out all the fish.