Mark W. Denny, W. Wesley Dowd
Owing to its unique combination of extreme physical severity and exceptional biological diversity, the intertidal zone of rocky shores has long served as a model system for development of ecological theories and experimental tests of their predictions. This narrow interface between marine and terrestrial environments is a natural microcosm that presents organisms with rapid, extensive and often unpredictable variation in hydrodynamic forces, temperature, pH, oxygen availability and salinity. As ecologists struggle to predict the physical environment's effects on future community structure and function, it is essential to understand the physiological interactions among these factors and their role in ecology. Thus, the dynamic and heterogeneous nature of wave-swept rocky coasts provides an opportunity to exploit shoreline microcosms as a bellwether of climate change. Here, we review aspects of the intertidal environment that distinguish it from other microcosms and explore the nature of three smaller, embedded microcosms-tidepools, splashpools and the internal microcosms of individual organisms. Each of these systems comes with a distinct suite of physiological challenges and experimental potential. The variety of environmental interactions embodied by these microcosms positions rocky shores to continue serving as a model system for investigating environmental physiology, community ecology and the interplay between the two. This article is part of the theme issue 'Life in natural microcosms'.