We demonstrated in our recent Communications Biology paper how marine photosynthetic bacteria, Prochlorococcus, are adversely affected by leachates from commonly used plastics. This study was one of the first to consider how substances leaching from plastics may affect marine primary producers and demonstrated that plastic pollution has the potential to negatively impact a wider range of organisms than previously appreciated. We outline here key outstanding questions regarding how ocean plastic pollution may impact small, but essential, marine microbes and discuss how these can be addressed.