Productivity at various levels of a trophic network are critical to the ability of ecosystems to recover from disturbances (e.g. cyclones, heat waves), and maintain key goods and services (e.g. fisheries). Canopy-forming seaweeds play important roles in tropical marine ecosystems, where they are key primary producers, as well as providing food and complex habitats for many other species. In this way, seaweeds influence both primary and secondary productivity within a reef ecosystem, which underpins the biomass of middle and higher order consumers. In this PhD project Alex Chen will investigate how shifts in tropical Sargassum biomass and primary productivity are linked to changes in the secondary productivity of invertebrates and reef fishes over natural seasonal cycles and future scenarios of sea temperature arising from marine climate change.