Earth & Sky

Agricultural runoff could harm Gulf of California

Agricultural runoff can trigger enormous blooms of microscopic plants in the Gulf of California.

That’s according to scientists at Stanford University. Virtually all surface water runoff from the Yaqui Valley to the Gulf comes from irrigation. By comparing agricultural records with satellite images of plant blooms, a connection emerged. About two-thirds of the nitrogen in fertilizers finds its way to the coast, where it fuels plant blooms. Earth & Sky spoke to oceanographer Kevin Arrigo.

Kevin Arrigo: That extra “kick” that it got from the agricultural fertilizers was enough to result in some pretty large blooms, for an oceanic region. And these blooms extended all the way across the Gulf, from one side to the other, hundreds of square kilometers in scale.

As the tiny plants die, they leach oxygen from the water. Arrigo told Earth & Sky that he’s concerned about an increasing human imprint near the Gulf of California. It could someday become what’s called a “dead zone,” devoid of nearly anything except bacteria.

Kevin Arrigo: And so what people are working on are ways to fertilize more efficiently, which hopefully will then decrease the amount of nitrogen that ends up in the atmosphere, because that’s still going to end up in the oceans somewhere, or end up in the groundwater, where it will certainly end up in the ocean.

Thanks today to NASA: explore, discover, understand.