Development of estuarine wetlands under decadal and long-term climate variations

SCHUERCH M.; SCHOLTEN J.; CARRETERO, S; BERGAMINO L.; GARCIA RODRÍGUEZ F.

Londres

Conferencia; 55th Conference of Estuarine Coastal Sciences Association; 2015

Estuarine wetlands are subject to a wide range of natural and anthropogenic drivers. The local tide and wave regime, estuarine sediment transport processes and long-term sea level rise (SLR) range among the major natural drivers. Modifications in the river catchment areas and coastal protection measures are the major anthropogenic influences. In estuarine systems, a pronounced spatial and temporal variability is observed with respect to these drivers and, hence, the resulting local tidal range and sediment availability. To a large extent, this variability is driven by decadal fluctuations in riverine sediment discharge as well as changes in the storm climate in combination with the location of the wetland relative to the river mouth.For a selection of marshes along the Rio de la Plata (Argentina, Uruguay), we investigated how El Niño-driven decadal variations in river discharge and associated sediment discharge as well as changes in storm activity affect their long-term morphological development. We performed extensive grain-size analyses on 15 cores along the Rio de la Plata and assessed the long-term vertical accretion rates, using radioisotope analysis, for five of these marshes. Comparison of the variability of accretion rates with historic data on river discharge and storm activity reveals a distinct spatial pattern of temporal variability in accretion rates that can be related to the wetlands location within the estuary.For the marshes in the inner estuary and along the Argentinean coast, accretion rates seem to be related to variations in river discharge. Accretion rates on marshes in the outer estuary and along the Uruguayan coast are subject to reduced temporal variability with maximum rates in periods of high storm activity. These preliminary results highlight the importance of decadal climate variability on estuarine wetland development and concurrently demonstrate how the natural estuarine gradient affects the spatial pattern of sediment accretion rates.