Some thoughts:
A. You may target a young audience or an older audience.
B. You are not graded upon your art skills, just your accuracy, thoroughness, and creativity.
C. The comic will be six panels to cover the subject and its possible resolution.
D. You may use many different sources for ideas and/or background information.
E. You must mention or illustrate: nitrogen/nitrates, phosphorous/phosphates, nutrients, eutrophication, phytoplankton, algae, dead zones, DO (dissolved oxygen), and decomposition