Background/Question/Methods Ecosystems and ecosystem boundaries are dynamic. The movement of materials between ecosystems creates important connections that regulate ecosystem function by providing new raw materials and even by transporting organisms. For microorganisms, the movement between ecosystems is perhaps the rule and not the exception, and evidence of continual dispersal can be found in natural, host, and managed ecosystems. As such, the composition of these communities and the function of the ecosystem is going to largely depend on how microbial communities interact and mix. To understand these dynamics, we can use community coalescence theory, which integrates meta-ecosystem dynamics and metacommunity studies. As part of the microbial community coalescence session, this talk will introduce the idea of microbial community coalescence from a theoretical and empirical perspective. In addition, I will present a number of example studies – including mixing water bodies, aquatic and terrestrial linkages, and terrestrial transformations – and reanalyze them through the lens of community coalescence.
Results/Conclusions We find evidence and examples of microbial community coalescence across studies. Using this framework, we can rethink and reinterpret previous results. Evidence of this can be seen in previous studies involving the movement of organisms between terrestrial and aquatic ecosystems, the mixing of fresh and salty waterbodies, and even in the active thaw of permafrost in thermokarst landscapes. Each of these examples provide insights into what happens with microbial communities collide. We find that when communities collide across distinct ecosystem boundaries (e.g., terrestrial and aquatic), the ability of communities to mix is suppressed and many organisms become transient and don’t contribute to ecosystem function. Alternatively, when mixing happens along environmental gradients (e.g., salinity gradient), communities are able to mix, and we observe species sorting dynamics and new interactions. Finally, in ecosystems actively transforming (e.g., thermokarst), we see very high mixing of organisms and resources and this yields novel combination of organisms and unique ecosystem functions. Together, these examples and the others presented in this session will highlight the utility of community coalescence and its ability to understand microbial dynamics and ecosystem processes.