The contribution of phytoplankton to ocean density gradients

Oceanographers have not previously considered plankton as contributors to ocean density gradients, which are conventionally calculated from temperature and salinity alone in the upper ocean. However, we found that phytoplankton density gradients were in some cases comparable to the physical density gradients. As small density gradients drive some ocean currents, and help control gas and heat exchange between ocean and atmosphere, plankton are a hitherto undescribed variable influencing these processes. Density gradients also determine the nutrient input to the upper ocean, thus biological-physical feedback could influence phytoplankton abundance and species composition.