# Individual‐Level Trait Responses in Cyanobacterial Populations and Communities

## TL;DR

This study uses flow cytometry to measure individual cyanobacterial traits and identifies how environmental factors shape their population and community dynamics.

## Contribution

A flow cytometry-based method to assess individual-level trait responses in cyanobacteria and apply them to natural communities.

## Key findings

- Cyanobacteria show distinct trait responses in multidimensional trait space under nitrogen and light limitation.
- Phycocyanin and chlorophyll-a levels decrease with nitrogen limitation and increase with light limitation.
- These trait responses were confirmed in natural cyanobacterial communities.

## Abstract

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.

Trait‐based approaches can elucidate mechanisms underlying dynamics of phytoplankton population and community, but assessing individual‐level traits in natural systems remains challenging. This study used flow cytometry to quantify single‐cell trait responses of Microcystis spp. under nutrient, light and CO2 experiment, and these responses were applied as fingerprints to identify key drivers in natural communities. Distinct integrated phenotypes, particularly under nitrogen and light limitation, revealed contrasting trait responses relevant to the dynamics of cyanobacterial populations and communities.