This lesson helps students understand the variables that influence the abundance of phytoplankton. Students will make predictions about the timing of the spring phytoplankton bloom in the Gulf of Maine. Furthermore, data from buoy monitoring stations can be graphed and interpreted to assist in making predictions. Examination of the chlorophyll concentration data at each buoy provides further ability to check these predictions. Students will then compare their predictions with reality by obtaining and examining Moderate Resolution Imaging Spectroradiometer (MODIS) images to view the full extent of the bloom over time.