Once students have completed the introduction to the Hudson River and basic aquatic ecosystem science, we can move on to the exciting next step of using the tools that scientists use to understand aquatic ecosystems including the Hudson River.

A key measurement tool for aquatic ecosystems is dissolved oxygen, abbreviated DO. By understanding the dynamics of DO, scientists can know how the aquatic animals and plants relate to each other and the chemistry and physical parameters of the water in which they're living. Plants produce oxygen in photosynthesis and both plants and animals use oxygen during respiration. Those plants and animals and the oxygen levels in the water respond to temperature in important ways.

This section focuses largely on this very important measure of aquatic ecosystem health and balance: dissolved oxygen.