This course is focused on the theory and techniques of mathematical model development for marine ecosystems. The focus will be directed towards the philosophy and advances in ecosystem modeling. At the end of the course the students will have a broad view of different ecosystem models ranging from simple NPZD type to complex end-to-end models. Students will be able to run and analyze the results of 3 models of different complexity. The course will give the students a strong insight on how to include models (and modelers) in their research.