Efecto de las áreas de protección especial en la comunidad de macroinvertebrados de los ríos de la cuenca alta del Manzanares (Sierra de Guadarrama, Madrid)

Abstract

Effect of special protected areas in the rnacroinvertebrate cornrnunity in the Manzanares upper basin (Sierra de Gua­darrarna, Madrid) This contribution focuses on studying the quality and diversity of the three main rivers of the Upper Manzanares basin in Central Spain: the Samburiel-Navacerrada River, the Mediano River, and the Manzanares River. The main objective is the diagnosis of it's alterated state and to evaluate the current deterioration of the biological diversity of macroinvertebrates. To this effect a sampling was carried out during the most critical time of year for the system, summer of 2001. Despite the fact that the physical environment is rather homogeneous in the whole area, there are differences in the characteris­tics and functional features of the streams. Those differences seem mainly related to land-use and water management, factors themselves dependent on whether the sub-basin is located inside or outside the protected area of 'Cuenca Alta del Manzana­res' Regional Park (PRCAM). The Manzanares river is the one presenting the highest state of conservation and water quality, with high values for richness, diversity, and biotic indexes. The Samburiel river, on the other hand, is the one presenting the worst conditions and the greatest degree of deterioration, due to f10w regulation as well as pollution. It's macroinvertebrate communities are extremely impoverished and present high spatial heterogeneity. The Mediano stream shows an intermediate condition, partly due to its artificial temporary f10w (water withdrawals in its middle reach). This explains and the fact that the macroinvertebrate communities have low-density populations, with diminishing species richness as well as water qualjty.