Biological controls on marine volatile organic compound emissions: A balancing act at the sea-air interface

Volatile organic compounds (VOCs) comprise a vast pool of low molecular weight and rapidly diffusible chemicals that are emitted from all cells as well as by photolysis of dissolved organic matter and burning of fossil fuels. In the ocean, VOCs are an important component of the marine carbon cycle, serving as plankton growth products and substrates and also as info-chemicals that influence phytoplankton life cycles. When VOCs are emitted from the ocean into the atmosphere, they alter Earth's radiative budget through oxidation reactions and secondary aerosol formation. Marine phytoplankton are the primary biotic source of marine VOCs, many of which are exploited as nutrient resources by ubiquitous bacterioplankton that have evolved specific mechanisms to consume these compounds. Thus, the balance of VOC production and consumption exerts control on the concentrations of dissolved VOCs at the sea-air interface. Current simulations of atmospheric chemistry do not take into account biological controls of dissolved VOCs. Linkages between phytoplankton communities, VOC composition, and surface ocean properties are promising avenues for improving the next generation of chemical transport models that quantify and predict VOC emissions. We suggest that VOC accumulation may be pre-dictable by identifying periods when plankton communities are disrupted by biological or physical processes. Layered models that use remote sensing and ocean physics to measure the states and trajectories of plankton assemblages have promise for predicting ocean sea-air VOC transfer.