there are numberous issues due to ocean dead zones
The organic matter produced by phytoplankton at the surface of the ocean (in the euphotic zone) sinks to the bottom (the benthic zone) where it is broken down. Bacterial respiration then occurs. The ocean floor water then becomes anoxic, meaning it has very little to no oxygen because the oxygen used by bacteria is the oxygen dissolved in the water, and that’s the same oxygen that all of the other animals on the bottom (crabs, clams, shrimps) and swimming in the water (zooplankton, fish) require for life to go on.16