Coastal Environments in the Bahía Blanca Estuary, Argentina

Abstract

The Bahía Blanca Estuary is a coastal system placed in a sharp transition betweenhumid subtropical and semiarid climates, shaped by a unique combination oflarge interanual climatic variations and a transgressive sea level during theHolocene. In the region, the late Holocene marine transgresion resulted inlow coastal landforms inherited from the former estuarine dynamics. Theseenvironments are commonly occupied by coastal ecosystems that can be roughlyclassified into intertidal and inland (perimarine) wetlands. Within the intertidalzone, most of the area is covered by extensive barren mudflats, and marshesare dominated by Spartina alterniflora or Sarcocornia perennis. A supralittoralzone can be defined in an intermediate position, irregularly inundated by seawater. Vegetation in this zone is sparse, with a mosaic of salt flats, halophyticsteppes and shrubs forming mound-intermoundcomplexes. The Old MarinePlain, in the inland limits of the marine transgression is not affected by tidalflooding, but an irregularly humid zone develops due to saline seepage fromthe uplands. These wetlands are subjected to episodic disappearance, and mayget dry for several years, relying on the occurrence of rainy years during humidperiods to resurge. Because of their highly dynamic nature, and the particularclimatic settings of the area, these wetlands are sensitive indicators of climatechange and variations in large scale circulation patterns. This chapter describesclimatic patterns, geomorphological settings, and plant communities, as wellas the major physical and biological interactions defining landscape structure.