How does sunlight effect the amount of dissolved oxygen in a lake?

Question

It's a mesotrophic lake, if that helps.

Answer 1

Sunlight would indirectly increase the amount of dissolved oxygen in your mesotrophic lake.  These lakes have aquatic plants, bottom-growing algae, and even bottom-dwelling photosynthetic cyanobacteria.

The oxygenic photosynthetic activity of these organisms will increase the dissolved oxygen content of the water, with sunlight.

Edit:  thumbs down to the other two responders.  They are correct about temperature and oxygen solubility, but totally missed the point of "mesotrophic."

Answer 2

Oxygen solubility is inversely related to temperature. As the water warms its hydrogen bond lattice structure is lost and the oxygen no longer fits between the ranked polar water molecules. When the water is cooler its polar nature forms some latticing as the molecules pose plus charge to negative. Oxygen fits in the pockets formed by the H2O as it forms the hydrogen bonded network. The oxygen is flanked by water molecules whose charged regions pen it lightly in place. Solubility is impacted by the pressure of the atmosphere (the partial pressure of oxygen in the air) so the exact figure depends on the lakes altitude as well as the temperature.

At 0 C and sea level 457 uM of oxygen is dissolved  but raise the temperature to 25C and there is only 258 uM O2 in the same body of fresh water.

Here are the charts for the solubility of oxygen in both fresh and saline water at psi from 14.7 to 58.7.

http://www.engineeringtoolbox.com/oxygen...

Hydrogen bond structure of water

http://antoine.frostburg.edu/chem/senese...

More detail on the interaction of the dipole water and nonpolar oxygen molecules is described here under the procedure section

http://waterontheweb.org/curricula/bs/te...

Answer 3

The hotter the water, the less oxygen can be dissolved in the water. Therefore, dissolved oxygen concentrations are lower in the summer. Sunlight heats the water so that's how it affects it.