Using satellite remote sensing of primary production and in-depth analysis of photosynthetic processes at the celluar and sub-cellular level he has been able to estimate global algal production from space. He has developed a new hypothesis about the factors controlling phytoplankton blooms focusing on the balance between phytoplankton growth and grazing, and seasonally varying physical proceses. In a recent perspectives paper in Nature Climate Change  he explains that changes in phytoplankton populations are governed by periods of accelerating and decelerating division rates. Environmental factors that are impacted by climate change are also responsible for changes in the plankton ecosystem.