The world is currently going through a period of rapid change in global environment associated with increases in atmospheric CO 2 , rises in temperature and elevated UVBR fluxes at high and mid latitudes.In this review, we analyse the consequences of such alterations in environmental factors for the microalgae that form the basis of many aquatic food chains.We show that the effects of these changes can be species specific, and so lead to shifts in community composition as well as biomass.These environmental factors also lead to changes in elemental and biochemical composition of microalgae and this can have consequences for the flow of energy and materials to higher trophic levels.