Expert: Walter Hintz - 4/15/2010

Question
Mr. Hintz,

Cold water contains more oxygen than warm water. However, warm water contains more life. I asked my teacher why this was and she simply told me that the reason was that the warmer water is closer to the sun. This makes sense since warm water is found mostly in the tropics which are near the equator and the Earth is tilted in a way that allows for the equator to get the most sun. However, wouldn't this mean that there should be more oxygen in the warm water? I realize that cold water holds more oxygen, however, shouldn't the warm water, because of the abundant sunlight, be filled with photosynthetic creatures which are constantly adding oxygen? Cold water does not have this and yet it still contains more oxygen. Also, oxygen is necessary for most life but cold water, even though it is abundant with oxygen, does not have a very high variety of species. What I am basically trying to ask is why are the abundant oxygenated cold waters not filled with life? Thanks!

Mark

Answer
Hi Mark;
Of course the areas closest to the sun are warmer.  But The amount of dissolved O2 has to do with solubility and it is a property of water that is is more soluble in colder water.  The abundance of aquatic life is affected by temperature. Temperatures are a factor in metabolism because enzymes are temperature sensitive. Just because there is more O2 in cold water does not mean there is a greater diversity of life