Although phosphate has been suggested to be the ultimate control on phytoplankton production , variability in phytoplankton C:P and nitrogen fixation may buffer productivity despite increasing stratification (37, 43). In contrast, increasing nitrogen stress might have greater impacts on marine productivity, as phytoplankton have less ability to acclimate by modifying their C:N 10 ratio . Nonetheless, phosphorus limitation does select for higher C:P in phytoplankton , consequently reducing food quality throughout many marine food webs . These potential changes for marine ecosystems underscore the importance of constraining the rate of rising phosphorus stress throughout the ocean.