Salinization and plant zonation in Argentinian salt marshes: Natural vs. anthropic factors

Abstract

Four salt marshes located in the Río de la Plata Estuary, Bahía Blanca Estuary, San Antonio Bay and Fracasso Beach in the Peninsula Valdés were studied. Water balances, tidal regime, geomorphology, anthropic modifications, salts in the soils and vegetation in each salt marsh were compared in order to determine how the natural and anthropic factors condition the salinization of the marshes. In addition, the way in which these factors affect the distribution of the communities of plants was studied. The climatic conditions are humid and arid along the northern and southern Argentine Atlantic coast. The tidal conditions were micro-tidal in the Ajó River associated with the Río de la Plata Estuary, meso-tidal in Bahía Blanca, and macro-tidal in San Antonio and Fracasso salt marshes. It is expected that, under natural conditions, the formation of salts in soils will present a higher increase in the south (arid and macro-tidal) than in the north (humid and micro to meso-tidal). However, the results obtained show that the anthropic factors associated with the construction of embankments in the northern marshes modify their hydrological functioning, and generate conditions which favour the processes of salinization, causing considerable changes in the distribution of the communities of plants. Thereby, future research should be aimed to improve the development of engineering structures that will not affect the salt marsh environments nor the ecosystem services the salt marshes provide.