Seventy to eighty percent of the oxygen we breathe comes not from trees but from the earth’s oceans. Actually, it is the phytoplankton in the oceans that create so much oxygen. Scientists are looking for ways to increase phytoplankton to help break down greenhouse gases. They must be careful, however, because too much phytoplankton can create Dead Zones in the Ocean. Dead Zones are areas that have so little oxygen, no sea life can live there. These areas can be created by the overproduction of organic matter by phytoplankton, that sinks to bottom and is broken down by bacteria. This releases carbon dioxide. Bacteria also absorbs oxygen so trying to fix the problem can cause it to worsen if scientists are not very precise and observant.