# Multistability and regime shifts in microbial communities explained by competition for essential nutrients

## TL;DR

This study introduces a resource-explicit model for microbial communities competing for essential nutrients, revealing how multistability and regime shifts depend on nutrient stoichiometry and supply balance, with implications for understanding community resilience.

## Contribution

It applies game-theoretical methods to identify all community states and their stability, advancing understanding of multistability mechanisms in microbial ecosystems.

## Key findings

- Multistability requires different nutrient stoichiometries among species.
- Balanced nutrient supply promotes multistability and diversity.
- Community states become less stable with balanced nutrient supply.

## Abstract

Microbial communities routinely have several possible species compositions or community states observed for the same environmental parameters. Changes in these parameters can trigger abrupt and persistent transitions (regime shifts) between such community states. Yet little is known about the main determinants and mechanisms of multistability in microbial communities. Here we introduce and study a resource-explicit model in which microbes compete for two types of essential nutrients. We adapt game-theoretical methods of the stable matching problem to identify all possible species compositions of a microbial community. We then classify them by their resilience against three types of perturbations: fluctuations in nutrient supply, invasions by new species, and small changes of abundances of existing ones. We observe multistability and explore an intricate network of regime shifts between stable states in our model. Our results suggest that multistability requires microbial species to have different stoichiometries of essential nutrients. We also find that balanced nutrient supply promote multistability and species diversity yet make individual community states less stable.