WiLD Blog

Seasonal dead zones threaten wildlife from the Washington coast down to California. “The undersea plague appears to be the symptom of global warming…low oxygen waters have extended north into Washington and crept south as far as the California state line…they appear to be as regular as the tides, a lethal cycle that has repeated itself every summer and fall since 2002” (Weiss, 2008).  Dead zones are areas of the ocean where the oxygen has been so depleted, that all life has essentially been suffocated.  The seasonal dead zones that have been forming off our coasts are thought to be caused, again, by global warming.  The atmospheric conditions which produce the nutrient rich California Current are changing.  The California Current’s productivity is driven by the upwelling of nutrient rich waters from the deep, a phenomena made possible by wind. As soon as this nutrient rich water hits the surface and is exposed to sunlight and oxygen, phytoplankton bloom, which is the main food source for many of the world’s small fish and shellfish, which are in turn food for larger marine life, thereby creating a healthy oceanic food web.

The dead zones are produced through the alteration of this natural process.  In increasing the ambient air temperature, “warm, rising air over the land makes the upwelling more frequent and more intense” (Bakun, 2008)   The upwelling is therefore prolonged and phytoplankton populations are in surplus.  Because of this prolonged phytoplankton production, access phytoplankton which are not consumed by fish die and float down to the sea floor where they rot, thereby producing noxious gases such as hydrogen sulfide.  This problem is further exacerbated by the affects of over fishing which cuts down on the natural number of fish who would be potentially feeding on this surplus of phytoplankton.  These anoxic zones are found from June through September and in 2006 covered an area the size of Rhode Island. 

Julie Novak