Linking patterns of freshwater discharge and sources of organic matter within the Rı´o de la Plata estuary and adjacent marshes

BERGAMINO L.; SCHUERCH M.; TUDURI A.; CARRETERO S.; GARCÍA-RODRÍGUEZ F.

MARINE AND FRESHWATER RESEARCH

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2017 vol. 68 p. 1 - 12

1323-1650

We investigated carbon isotopic ratios δ13C vs. C/N forsurface sediments throughout a large estuarine system (Río de la Plata, RdlP),combined with sediment cores from adjacent marshes to infer main carbonsources. We also evaluated the influence of the El Niño-Southern Oscillation(ENSO) and associated high freshwater discharge events on the organic mattertransport within the estuary. The isotopic pattern in surface sediments of theRdlP showed the upper reaches to be influenced by riverine particulate matter (δ13C range -24 to -26?). Similarly,in the sediment cores from marshes of the upper reaches, δ13C valuesdecreased from -24? in ancient sediments to -28? in recent sediments reflectingan increased contribution of organic matter from land including C3 plants andfreshwater phytoplankton during the last 50 years. However, the lower reachesrepresent a depositional environment of marine algae (δ13C ranged -21 to -23?),with no influence of detritus from adjacent marshes indicating minor erosion ofthe marshes in the lower reaches operating as carbon sink habitats. Ourisotopic analysis point that the transport and deposition of terrigenous organicmatter within the RdlP and adjacent marsh habitat appear to be both temporallyand spatially linked to hydrology patterns.