Upwelled plankton community modulates surface bloom succession and nutrient availability in a natural plankton assemblage

Abstract. Upwelling of nutrient-rich waters into the sunlit surface
layer of the ocean supports high primary productivity in eastern boundary
upwelling systems (EBUSs). However, subsurface waters contain not only
macronutrients (N, P, Si) but also micronutrients, organic matter and seed
microbial communities that may modify the response to macronutrient inputs
via upwelling. These additional factors are often neglected when
investigating upwelling impacts on surface ocean productivity. Here, we
investigated how different components of upwelled water (macronutrients,
organic nutrients and seed communities) drive the response of surface plankton
communities to upwelling in the Peruvian coastal zone. Results from our
short-term (10 d) study show that the most influential drivers in
upwelled deep water are (1) the ratio of inorganic nutrients
(NOx : PO43-) and (2) the microbial community present that can
seed heterogeneity in phytoplankton succession and modify the stoichiometry of
residual inorganic nutrients after phytoplankton blooms. Hence, this study
suggests that phytoplankton succession after upwelling is modified by
factors other than the physical supply of inorganic nutrients. This would
likely affect trophic transfer and overall productivity in these highly
fertile marine ecosystems.
