Aquatic Dead Zones

Click to enlarge.

NASA posted on its Earth Observatory Image of the Day page the above Map of the Ocean’s Dead Zones on July 17. These zones are principally at the mouths of great river systems along large, industrially-developed population centers. This is so because nitrogen-laden fertilizers which overrun into the rivers are dumped into the oceans at their mouths. This causes great blooms of algae that eventually die and cause detrivorous microbe populations to greatly increase. These microbes reduce the dissolved oxygen content of the waters to the point that larger animals are unable to live in the area (as a result, the name “dead zones”) and large fish kills can be observed. The dead zones are more prominent in industrially-developed areas, where the availability of relatively cheap fertilizers causes farmers to err on the side of over-fertilizing crops.

The map has two other layers of information: the particulate carbon concentration of the oceans (first signs of potential dead zones) and population density.

The map was created by Robert Simmon & Jesse Allen based on data from Robert Diaz from the Viriginia Institute of Marine Science.

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