A dynamic perspective of shallow lakes of arid Patagonia as habitat for waterbirds

JULIO L. LANCELOTTI; MIGUEL A. PASCUAL; GAGLIARDINI ANTONIO

Ponds: Formation, Characteristics and Uses

Nova Science Publishers, Inc.

Lugar: New York; Año: 2010;

<!-- @page { margin: 2cm } P { margin-bottom: 0.21cm } --> In arid regions, where water availability imposes significant constraints on many species, shallow lakes and ponds have a particularly important ecological role. Meanwhile, these aquatic environments have been listed among the most threatened habitats of the world. With an area of over 6.000.000 km2, the Patagonian steppe is one of the largest arid extensions of South America. Running intermittently along the steppe, a system of basaltic plateaus or mesetas, holding thousands of lakes and ponds, provides primary habitat for numerous species, including a rich waterbird community and numerous endemism. We characterized the array of shallow lakes of the Strobel meseta, analyzing their dynamics along temporal and spatial gradients. Using multivariate analyses, based on limnological, topographic, and geographic variables of 32 water bodies, we identified four lake types: large unvegetated, large vegetated, turbid, and ponds. Based on 114 bird censuses we evaluated the relative importance of each lake type as waterbird habitat. Ponds hold the highest density of waterbirds and, together with large vegetated lakes, the highest number of species. Using satellite images corresponding to periods with contrasting precipitation, we analyzed the hydrologic dynamic by lake type and by location throughout the meseta. Whereas most lakes, <!-- @page { margin: 2cm } P { margin-bottom: 0.21cm } --> including large ones, are concentrated on the west side of the meseta, above 900m of elevation, ponds are distributed throughout the whole area, but are less stable from a dynamic point of view. The total area covered with water on the meseta is strongly affected by seasonal and inter-annual changes in precipitation. During dry periods, most ponds, and particularly those located at lower altitudes, undergo a drastic reduction in water level or even dry out. Variations in water level impinge on the limnological configuration of lakes and ponds, particularly on the emergence of macrophytes, a key habitat attribute for most species of waterbird. Given this strong dependency of hydrology and habitat provision on precipitation, temperature, and wind, meseta shallow lakes and the communities they sustain appear particularly vulnerable to climate change.