Individual-Level Trait Responses in Cyanobacterial Populations and Communities.

Trait-based approaches support the mechanistic understanding of individual organism responses to resource availabilities that underlie population and community dynamics. For microbes such as phytoplankton, however, it remains challenging to obtain individual cell traits, particularly in natural communities. Here, we provide a flow cytometry-based approach using a freshwater cyanobacterium Microcystis spp. culture and assessed individual-level trait responses to nitrogen, phosphorus and light limitation and high pCO2. Then, these responses served as 'fingerprints' to describe the main drivers in natural cyanobacterial communities. We observed distinct responses in multidimensional trait space, that is, the integrated phenotype, which differed particularly between nitrogen and light limitation. Notably, cellular contents of the pigments phycocyanin and chlorophyll-a decreased with nitrogen limitation and increased with light limitation, which was confirmed in natural communities. Overall, our results show how individual-trait responses to known environmental conditions can be used to understand natural cyanobacterial population and community dynamics.