Level 2
Understanding Dissolved Oxygen
Although water molecules contain oxygen atoms, this oxygen is not accessible to fish and other organisms, because it is locked up in the water molecule. Instead, air from the surrounding atmosphere dissolves in the water, and it is this dissolved oxygen that supports aquatic life. Different factors influence the amount of dissolved oxygen in water. For example, fast-flowing water may absorb more dissolved oxygen than slower-moving water. Organisms in the water that use oxygen for respiration will also deplete oxygen levels.
Below is a graph of water temperature and dissolved oxygen recorded over one year at the ACE Basin National Estuarine Research Reserve in South Carolina. Use this graph to check your understanding. Then try making your own graphs to compare two quality parameters.
