Significance Viruses often carry genes acquired from their host. In the present work, we show that a virus of a marine alga carries a gene encoding a transporter protein that mediates nutrient uptake. We confirm that the viral transporter protein is expressed during infection and show that the protein functions to take up sources of nitrogen. This is important because acquisition of nutrients often determines the ecological success of phytoplankton populations. This work demonstrates how a virus can amend host–viral dynamics by modulating acquisition of nutrients from the environment.