Salinization of marshes in Argentina: Natural vs. anthropogenic factors

Abstract

In the littoral zone of Argentina, marsh environments under arid, semi-arid and humid conditions are numerous. In this work, salt marshes located in Río de la Plata Estuary, Bahía Blanca Estuary, San Antonio Bay and San José Gulf were studied aiming which processes determine the occurrence of evaporites in salt marshes, analyzing the importance of natural and anthropogenic factors. QuickBird and Google Earth images were used to identify the geomorphologic, anthropic and hydrological characteristics and, selected samples were examined under a binocular magnifying glass, X-ray diffraction (XRD) and scanning electron microscope (SEM). The four studied marshes are located along a latitudinal gradient on the Argentina Atlantic coast, where the climatic conditions are wet in the northern sector and arid in the marshes of the southern sector. The tidal conditions change from north to south as micro-tidal in Ajó marsh, meso-tidal in Bahía Blanca and macro-tidal in San Antonio and Fracasso marshes. In each area, contrasting climatic conditions, tidal and anthropic influence and hydrological characterization were studied and both the anthropic and the natural factors condition the soils marshes salinization. Although it is expected that a greater amount of salts occur in arid marshes soils, it was observed that salt development in altered marshes with humid climates are more important. This shows the high negative influence that an anthropic modification can have over sensitive ecosystems as the marshes.