Apply the Data - When Things Heat Up

Sample graphs and data sets for use with the activity When Things Heat Up.

The figure below shows temperature and DO concentrations at 4:00 am and again at 4:00 pm in the same stream throughout one year. The stream has slow moving water and aquatic plants growing in the stream from spring through fall. Download the data here.

 

 

You can use the following questions to guide a discussion about this graph. 

1. How do temperature and dissolved oxygen change throughout the year?
Temperature is highest in summer, while DO is lowest in summer. This is because saturation concentration of dissolved oxygen decreases as the water temperature increases.

2.  Why was the dissolved oxygen lower at 4:00 a.m. than at 4:00 p.m.?
The plants in the water consume oxygen at night (due to metabolicrespiration), but cannot produce oxygen from photosynthesis at night when there is not light. Therefore DO can be substantially lower in water at one time of day than another.

  

The graph below shows the relationship between temperature and dissolved oxygen concentration.  Download the data here.