Dead Zone is a common term for hypoxia. Hypoxia occurs when dissolved oxygen absorption reduces. It occurs when a water body gets multifold nutrients, especially nitrogen or phosphorus which feed the growth of an organism called cyanobacteria or blue-green algae which with too multiple nutrients can grow out of control. When a water body gests hypoxic conditions, underwater vegetation and fauna change their conduct in order to reach an area with improved absorption of oxygen. 

EFFECTS

--> Dead zones have some fatal effects, a dead zone is like a discreet trap that there's no escaping from for marine life and fish can not descry dead zones before entering the area.

--> It's also hard for other ocean habitats similar to lobsters and clams as they move sluggishly. 

--> The oxygen dearth causes marine creatures to lose consciousness and die shortly thereafter. 

-->The algae overgrowth blocks the light from the sun and the blocking of sunlight is dangerous to animals submerged plants still go through photosynthesis submerged. 

--> Fish suffer greatly from dead zones as changes in oxygen position change their entire biology. 

--> Less the biodiversity that exists submerged, the more the balance of the entire ocean is disintegrated. 

~ SANIDHYA GUPTA (SMSMB)