How does the species composition of lake phytoplankton respond to environmental variation across large spatial scales? We performed a comprehensive analysis of the phytoplankton community composition of >1,000 lakes across the conterminous USA, using data collected during the National Lakes Assessment of the US Environmental Protection Agency (EPA). Our analysis reveals that geographical variation in phytoplankton community composition is best explained by total phosphorus (TP), water temperature and pH. High TP concentrations were associated with high relative abundances of cyanobacteria and euglenophytes. High temperatures stimulated cyanobacteria, dinoflagellates, desmids and euglenophytes, whereas cryptophytes, golden algae and diatoms were relatively more abundant in colder lakes. Low pH correlated with high dissolved CO2 concentrations, which may explain why it benefitted phytoplankton with inefficient carbon concentrating mechanisms (CCMs) such as golden algae and euglenophytes. Conversely, cyanobacteria increased strongly with lake pH, probably because their CCMs can effectively take up bicarbonate. Biodiversity increased with lake temperature, but decreased at high TP concentrations and high pH. In total, our results illustrate the many insights that can be obtained from the investigation of large-scale patterns, and provide an important baseline to assess how anthropogenic pressures such as eutrophication, global warming and rising atmospheric CO2 may affect the biodiversity and taxonomic composition of lake phytoplankton.

Primary Presenter: Jef Huisman, University of Amsterdam (j.huisman@uva.nl)

Authors:

Jef Huisman, University of Amsterdam  (j.huisman@uva.nl)

Xing Ji, University of Amsterdam  (jxh087@gmail.com)

Quan-Xing Liu, East China Normal University  (qxliu@sklec.ecnu.edu.cn)

Jolanda Verspagen, University of Amsterdam  (j.m.h.verspagen@uva.nl)