[EN] Populations of one or several species of planktonic freshwater algae were inoculated uniformly on culture media solidified with agar-agar and lacking nitrate or nitrate and phosphate. The cultures were exposed to continuous gradients of the limiting nutrients and sampled after an incubation time ranging from several weeks to a few months. Cell numbers and amount of photosynthetic pigments per unit surface were determined. In general, the values of these parameters decreased from the nutrient source, according to a negative exponential pattern. A simple mathematical model is proposed for the interpretation of the results, and their ecological significance is discussed. [...] Ankistrodesmus falcatus, Scenedesmus quadricauda, Stichococcus sp., Nitzschia palea

[ES] Para el estudio de la dinámica de los ecosistemas es fundamental la consideración de las características de su distribución espacial. En el medio acuático, la elevada heterogeneidad espacial del fitoplancton plantea interesantes problemas ecológicos; en este contexto, la experimentación con cultivos de laboratorio puede servir para poner de manifiesto mecanismos semejantes a algunos de los que actúan en la naturaleza, como por ejemplo los efectos de la limitación por nutrientes difundidos a partir de un punto de aporte. […]

19 pages, 12 figures, 5 tables

Peer reviewed