Microecosystems can exist in locations which are precisely defined by critical environmental factors within small or tiny spaces. Microecosystems can exist in locations which are precisely defined by critical environmental factors within small or tiny spaces. Such factors may include temperature, pH, chemical milieu, nutrient supply, presence of symbionts or solid substrates, gaseous atmosphere (aerobic or anaerobic) etc. These microecosystems with limited water volume are often only of temporary duration and hence colonized by organisms which possess a drought-resistant spore stage in the lifecycle, or by organisms which do not need to live in water continuously. The ecosystem conditions applying at a typical pond edge can be quite different from those further from shore. Extremely space-limited water ecosystems can be found in, for example, the water collected in bromeliad leaf bases and the 'pitchers' of Nepenthes.