Sentence:  Planet Earth Research this year discovered that humans have created at least 50 ‘<WSD>dead zones</WSD>' (zones where there is no oxygen) in the sea through pollution, and have extinguished other species at 1,000 times the natural rate in evolution. 
Meaning of the word marked with <WSD> tags:  An area of the ocean where oxygen levels are too low to support life, especially as a result of pollution.