Prof. Macreadie's research focuses on understanding and responding to the impacts of global change in aquatic ecosystems (namely marine, but also freshwater), and addressing all biotic components – from microbes to plants, to fish, to megafauna. Most of his research effort is presently directed towards capitalizing on 'blue carbon', which refers to the powerful ability of coastal vegetated ecosystems to sequester carbon and thereby help mitigate climate change.

His approach is multi-disciplinary, spanning the fields of chemistry, ecology, microbiology, economics, molecular biology, and policy.