英语听力：自然百科 海洋“死亡地带”

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Alright, buddy⁵, we're gonna go whisk this out. Here we go! Excellent! Ready, Now! The main things were measuring our temperature, salinity⁶ and importantly the dissolved oxygen of the water. And that's what tells us how that low oxygen zone looks.

 

With National Science Foundation funding, Barth is studying low oxygen for dead zones which appear each summer after the Oregon Washington coast. 

 

So in 2006, we actually went to zero oxygen and it extended many miles across the seafloor. And that's when we partnered with the Oregon Department of Fish and Wildlife to send a camera down on a remotely-operated vehicle, and we got these images of dead crabs⁷ everywhere.

 

Worldwide ocean dead zones now number about 400. Major manmade cause is agricultural runoff in rivers into the ocean. In addition, winds and currents move nutrient-rich but oxygen-poor water from the deep ocean to the coast. Microscopic⁸ organisms called phytoplankton thrive but then die, decompose⁹ and the cycle continues. Climate change may also come in to play.

 

We think there are two scenarioes that global warming is potentially affecting this. So, under the deep ocean, there are measurements that show that the oxygen levels are going ever so slightly down with time. When that water's brought toward ashore¹⁰, it's already low in oxygen. 

 

Global warming may also be influencing wind patterns and changing ocean circulation. Barth says these smart robots provide new insight to understand our oceans. 

 

To me, it's often this whole new view under the sea. I think it's really revolutionized how we can keep a tab on what's going on out there.

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