Since the publication, in 1961, of the seminal paper “The Paradox of the Plankton” by G.E. Hutchinson, the scientific literature has offered many examples of investigations aimed at clarifying the factors contributing to microalgal (amazing) diversity. The richness of microalgae (phytoplankton and phytobenthos) is widely recognized to depend on species-specific competition skills (e.g. allelopathy, abilities in resource acquisition and in avoiding predation) in a fast-changing environment driven by the turbulent mixing of water masses. This vision considers the single water body as the arena where diversity is built. More recently, the vision was enlarged by considering the role of immigration through passive dispersal as an important factor shaping microalgal diversity in freshwater ecosystems. This new approach is resulting in the idea that communities in different water bodies are not isolated and self-driven, but they are part of a larger metacommunity and continuously interacting thanks to dispersal mechanisms. Several conceptual models, developed in the frame of community ecology, have been recently applied to try to better understand microalgae diversity patterns within and among water bodies at different geographical scales. To better understand the influence of spatial variables and local environmental conditions, this special session is intended as a call for phytoplankton and phytobenthos ecologists to gather information on biodiversity patterns and drivers in relation to the spectrum of local environmental patterns AND considering the spatial variables that may affect microalgae dispersal (e.g. distance among water bodies and their spatial connections beside local environmental filtering). We cordially invite all those involved in microalgae ecology to look at their data under a “spatial” perspective and to submit their contribution to this special session.