This TED Talk features marine scientist and educator Nancy Rabelos, recorded live at TED Women 2017.

Good evening. Welcome to New Orleans. I don't know if you knew this, but you are sitting within 15 minutes of one of the largest rivers in the world,

the Mississippi River.

Old Man River, Big Muddy.

And it goes as far north as the state of Minnesota,

as far east as the state of New York,

as far west as Montana.

And 100 miles from here, river miles, it empties its fresh water and sediments into the Gulf of Mexico.

That's the end of Geography 101.

Now we're going to go to what is in that water. Besides the sediment, there are dissolved

molecules, nitrogen and phosphorus. And those through a biological process lead to the formation

of areas called dead zones.

Now, dead zone is a quite ominous word,

if you're a fish or a crab,

even a little worm in the sediments,

which means that there's not enough oxygen for those animals to

survive. So how does this happen? The nitrogen and the phosphorus stimulate the growth of

microscopic plants called phytoplankton. And small animals called zooplankton eat the phytoplankton. And small animals called zooplankton, eat the phytoplankton, small fish eat the zooplankton,

large fish eat the small fish, and it goes on up into the food web.

The problem is that there's just too much nitrogen and phosphorus right now,

too much phytoplankton falling to the bottom,

and decomposed by bacteria that use up the oxygen.

...