RT Journal Article SR Electronic T1 Impacts of reduced inorganic N:P ratio on three distinct plankton communities in the Humboldt upwelling system JF bioRxiv FD Cold Spring Harbor Laboratory SP 550046 DO 10.1101/550046 A1 Kristian Spilling A1 Maria-Teresa Camarena-Gómez A1 Tobias Lipsewers A1 Alícia Martinez-Varela A1 Francisco Díaz-Rosas A1 Eeva Eronen-Rasimus A1 Nelson Silva A1 Peter von Dassow A1 Vivian Montecino YR 2019 UL http://biorxiv.org/content/early/2019/02/14/550046.abstract AB The ratio of inorganic nitrogen to phosphorus (NP) is projected to decrease in the Eastern Boundary Upwelling Systems (EBUS) due to warming of the surface waters. In an enclosure experiment, we employed two levels of NP ratios (10 and 5) for three distinct plankton communities collected along the coast of central Chile (33°S). The primary effect of the NP treatment was related to different concentrations of NO3, which directly influenced the biomass of phytoplankton. Additionally, low inorganic NP ratio reduced the seston NP and Chl a-C ratios, and there were some effects on the plankton community composition, e.g. benefitting Synechococcus spp in some communities. One of the communities was clearly top down controlled and trophic transfer to grazers was up to 5.8% during the 12 day experiment. Overall, the initial plankton community composition was more important for seston stoichiometry and trophic transfer than the inorganic NP ratio. Any long term change in the plankton community structure will likely have greater impact than direct effects of a decreasing inorganic NP ratio on the Humboldt Current ecosystem.