The Phycosphere-Living and Dying in Close Quarters

The phycosphere, the immediate environment of a phytoplankton cell, is enriched with bacteria and viruses that interact in close and complex ways. Compounds released by phytoplankton are used by the bacteria, and the bacteria, in turn, may provide the phytoplankton with essential micronutrients and vitamins. Some bacteria provide direct benefits, while others may indirectly benefit or even harm algae. Bacteria may also switch between algal stimulation or inhibition depending on the algal growth stage. Although the interactions within the phycosphere are at the microscale level, they have the potential to impact fundamental processes including nutrient cycling, toxin production, and biogeochemical cycling.