What is the dead zone about? Answer Please?

Question

Dont Spoil

Answer 1

Since you added "don't spoil" to the details in your question, I'm going to assume you weren't talking about the Gulf of Mexico.  But when you post a question in the Botany section, you probably will get that answer.

I'm thinking you were asking about either the book by Stephen King, or the movie ot TV series.  If so, you'd probably get an answer more related to your question if you were to post the question again, this time using the "Arts & Humanities" > "Books & Authors" for the book, or the "Entertainment & Music", then either "Movies" or "Television".

Answer 2

I assume you are referring to the area in the Gulf of Mexico in which all macroscopic life dies.  It is believed to be due to nutrients in the Mississippi River water that empties into the Gulf.  As microbes use the nutrients, it depletes the oxygen in the sea water and all those organisms that have to have oxygen die.