A major challenge in contemporary biological oceanography is to reconcile the opposing arguments that nutrient regeneration in the euphotic zone of the open ocean is highly efficient, while at the same time new production is fare greater than previously believed. One hypothesis is that two separate biological systems operate side by side: one composed of small microbes that regenerate most of the nutrients and contribute little to new production and another composed of large phytoplankton species that are ever present in background numbers and that grow rapidly in response to episodic inputs of nutrients at low light levels at the base of the euphotic zone and then sink out quickly. The former system is well studied, but the latter is not. The goal of this research is to study the growth and to gauge the role of large phytoplankton species in new production at very low irradiance. The results will provide a basis for assessing the potential for large phytoplankton species contributing greatly to new production while going unnoticed because of the episodic nature of their growth and sinking.
