Wetlands change dynamics in the Bahía Blanca Estuary (Argentina) and their consequences on the water column primary production

PRATOLONGO, P; GUINDER, V.; MAZZON, C.; PIOVÁN, M.J.; ZAPPERI, G.; MARCOVECCHIO, J.

Mar del Plata

Conferencia; CERF 2012-The changing coastal and estuarine environment: a comparative approach; 2012

Coastal and Estuarine Research federation

Coastal wetlands continuously change in time and space, being long term changes in climate and sea level major driving forces in this evolution. The effects of a rising sea level have been largely studied along the eastern coast of North America and northern Europe, both regions with fully humid climates, and where wetlands developed under a sustained sea level rise during the Holocene. In this presentation, we offer an insight on the processes underlying change in coastal wetlands of the Bahía Blanca estuary, placed in a sharp transition between humid subtropical and semi arid climates, and subjected to a unique combination of large interanual climatic variations and a transgressive sea level during the Holocene. Through the use of historical aerial photographs and modern high resolution satellite images integrated into a geographic information system we describe the direction and quantified the magnitude of recent changes in land cover. Main changes correspond to the replacement of Sarcocornia perennis marshes and halophytic steppes by mudflats, a process that reflects increased erosion. In the inner zone of the estuary, a shallow and turbid environment, marsh erosion is a major source of suspended solids to the water column, and field experiments we are carrying out suggest that benthic communities play a key role in determining a seasonal pattern of higher bioturbation and enhanced erosion in summer, followed by a period of biostabilization and relatively lower turbidity in winter. Changes in water transparency, with a concomitant change in the penetration of solar radiation, seem to be one of the main causes for the development of a recurrent phytoplankton bloom winter. As a final remark, we discuss the relative effects of climate change and human modifications on this particular estuarine dynamics