Dissolved Oxygen

One of the most important factors of freshwater health is dissolved oxygen (DO), which is measured in milligrams per liter (mg/L). Levels above 5 mg/L are essential to support aquatic life.There are many biotic and abiotic factors that affect levels of dissolved oxygen in water such as temperature and streamflow.

Can you figure out what's happening?

On the graph, the dark blue bars represent the maximum amount of dissolved oxygen in the river in a 24 hour period, while the light blue bars are the minimum amount in the same 24 hour period. How do the minimum and maximum amount of dissolved oxygen change over the year?
QUESTION: Can you figure out what natural process is affecting the levels of dissolved oxygen in the river?

Directions:

Hover over the graph and compare the changes in dissolved oxygen with the visible changes that are occuring in the river system.

hint: It's not just the two factors that were already mentioned!
hint: What is the biggest change of color in the images?