Global challenges in biofuels, chemicals and nutrients stress the need for biomass from marine sources in the near future.Microalgae-derived compounds and their biomass have potential applications from aquaculture and animal feed to human health.Northern diatoms have been shown to serve as important sources of bioactive compounds in our recent achievements, screening for pharmaceutical / drug bioactives.This makes the diatoms excellent models for elucidating biomass production / chemical composition under changing environments, e.g.inorganic nutrients and light quality and quantity.