There are numerous physical, chemical, and biological factors that come together to create dead zones. A main cause of the spread of ocean dead zones is due to agriculture, primarily fertilizer. Fertilizer from agricultural crops runs off into fields, streams, rivers, and watersheds, eventually reaching the ocean. When the fertilizer gets to the ocean, it gives phytoplankton more nutrients. The phytoplankton then grow and multiply, which leads to more organic matter reaching the benthic zone, more bacterial respiration, and more anoxic water at the bottom of the ocean.This restriction of water flow results in the natural freshwater, that has normal dissolved oxygen concentrations, to decrease. This leads to depleting the rest of the oxygen quicker.13
is fertilization a factor?
"The effects of human behavior is many times reflected at the sea bottom and should be discussed with a louder voice."
-Inger Naslund, WWF Sweden9