Phytoplankton community changes in a coastal upwelling system during the last century

Phytoplankton communities in coastal upwelling systems are influenced by the interplay between human-induced and natural climate forcing that vary regionally and the two factors have not been well quantified. Combining lipid biomarker analyses in 23 sediment cores from the Zhejiang coast of the East China Sea and a physical-ecological model, we found that during the 1960s–2000s there was a 42 ± 4% increase in diatom proportions and a 17 ± 8% decrease in dinoflagellate proportions within the core upwelling area that is attributed to changes in Kuroshio Current transport and coastal upwelling. During the 1950s–2000s there was a 16 ± 8% increase in dinoflagellate proportions and 12 ± 4% decrease in diatom proportions outside the core upwelling area which is attributed to anthropogenic nutrient inputs and climate warming. Our results provide a novel approach to quantify mechanisms of past and future changes in marine phytoplankton communities.