High bacterivory by the smallest phytoplankton in the North Atlantic Ocean

Small planktonic algae contribute hugely to the ocean ecosystem by fixing carbon dioxide through photosynthesis. A new study of water samples from the North Atlantic Ocean in summer challenges the assumption that the phytoplankton are wholly dependent on inorganic nutrients by revealing that they also consume bacteria, obtaining about a quarter of their cell biomass from grazing on bacterioplankton. Previously, specialized protozoons had been thought to be the main predators of bacteria, but despite a comparatively sedate rate of bacterial consumption, the small algae are so numerous that at times they perform between 40 and 95% of total bacterivory in the near-surface ocean waters. Bacterivory may go some way towards explaining the dominance of the smallest algae in the oceans.