This activity will help students understand how scientists assess the impacts of iron on ecosystem processes. The amount of iron present affects the amount of phytoplankton growing in an area of the ocean. These producers are extremely small—only one cell in size, so it would not be possible to count them all. Instead, scientists measure the amount of chlorophyll in the water. Since chlorophyll is made by living plant cells, more chlorophyll indicates more phytoplankton present. In this activity, students will look at a spreadsheet of data collected from buoys in Monterey Bay. These buoys collect information on many different chemicals present in the water; the focus of this lesson is the iron and chlorophyll levels. Students will graph the data collected in one year to see if there is a connection between these two factors.