Every seed germinating in soils, handshake, tidal change, and stream confluence exemplify common instances of community coalescence - the blending of previously isolated communities. Do dispersal events change how we perceive disturbances, and how might the merging communities scale up to changes in terms of their composition and ecosystem function? In this session, research will examine how previously isolated microbial communities and environmental conditions collide and mix under dynamic conditions. Understanding the isolated community structure and function is needed to accurately predict the resultant microbial community and a range of functions at mixing zones. We will leverage community coalescence theory, which integrates meta-ecosystem dynamics and metacommunity studies. Research will focus on the community coalescence framework for predicting community responses to disturbance in diverse environments and host-associated habitats. The objectives of this session are to (1) understand the importance of community coalescence to ecology and engineered biotic systems, (2) develop innovative approaches to analyzing community mixing during coalescence, and (3) highlight the potential importance of network connectivity and specific biotic interactions in understanding and predicting the consequences of community coalescence.