okay let's talk about polluted rivers biggest river in the United States is the Mississippi this is the Mississippi River and together with its major tributaries the Missouri the Ohio the Tennessee it drains basically everything from the Appalachians to the Continental Divide which means that anything that gets on the ground over three-quarters of the United States why ends up coming down the Mississippi and going into the Gulf of Mexico through the Mississippi Delta here down by New Orleans so what kind of things are coming down the river well animal waste some potentially human waste sediment runoff pesticides industrial waste toxic heavy metals you named what is it though that does the most damage when it gets into the ocean it's something I haven't mentioned yet it's fertilizer farmers put fertilizer on their fields the plants use some of it rain or irrigation water whatever washes the rest off homeowners put fertilizer onto their lawns so the grass will grow better and they left a couple levels more often never quite figured out that but again the grass uses solvent and awful lot of it washes away when the sprinklers are on into the gutters into the storm drains into the river that takes it to the ocean so what's the problem with fertilizer it makes things grow better it's not toxic right it makes everything grow much better in particular it makes all the plankton in the ocean here grow magnificently and we wind up with huge blooms have you heard of algal blooms red tides eutrophication all words for basically the same problem all those rapidly growing microorganisms use up most of the oxygen in the water and they don't live very long after a few days or weeks of the most they are dying rotting down falling to the bottom and the decay process uses up the last by 15 percent of the option in the water now there's zero option with water and with zero oxygen zero life nothing can live that the region in front of the Mississippi Delta here is called the dead because nothing lives there the dead zone can be up to 250 miles this way 50 miles that way no while spill has ever produced devastation on a fraction of that scale this is the Mississippi its largest river in the United States but on a world list of big rivers it's not that big there of any bigger of the spermatic and many of those also the great agricultural areas so dead zones are getting bigger and more important and more numerous they are part of course out in the middle of the ocean they're found around the coastal islands but near the coastline is where the ocean is most productive it's where we get most of the resources from so this