The role of salt-marsh sediments on nutrients, organic matter and pollutants transference to the estuarine system: sources or sinks?

JORGE MARCOVECCHIO; VANESA NEGRIN; SANDRA BOTTE; CARLA SPETTER; GERARDO PERILLO,

Foz de Iguaçú

Congreso; 2010 The Meeting of the Americas ? AGU (American Geophysical Union); 2010

AGU (American Geophysical Union)

Wetlands play a significant role within biogeochemical cycles considering that valuable biological, chemical and sedimentary processes are performed there. In addition, salt-marshes largely developed in coastal marine and estuarine systems are usually highly productive environments, acting as source or sink of materials, depending on different factors including tidal energy, salinity, oxygen release, etc. Global climate change, with the consequent sea level rise, could threaten salt marshes and their ecological roles. Bahía Blanca Estuary, which is our study case, includes many salt-marshes associated to large tidal flats ; these salt-marshes have different exposure time to tidal flood within the semidiurnal tide regime which characterizes the estuary. The production of halophyte vegetation, important (specially the belowground one) to determine retention capacity of these environments as well as the transference processes of nutrients, organic matter and several pollutants from salt-marshes sediments to the estuarine water are analyzed in the present communication, highlighting the influence of physical-chemical parameters (i.e. Eh and pH, salinity, dissolved oxygen) on the final direction of the process. Bahía Blanca salt-marshes show low production rates and seasonal differences in biomass of the macrophytes. The content of nutrients and heavy metals in plant tissues is a similar range as observed in other salt-marshes. The sediments are highly reduced and rich in organic matter and nutrients. Several heavy metals (i.e. Cu, Ni, Fe, Zn) showed to be accumulated in the aboveground tissues of the halophytes, while others (i.e. Cd, Pb, Mn) do it on aerated ones. The analyzed data set allows sustaining that it is not possible to define just a permanent role of these sub-systems within the estuary, considering that these functions could be modified according to the corresponding environmental changes in the estuarine conditions, as well as seasonal changes in vegetation. Consequently, the ability of several physical-chemical processes as indicators of the transference dynamics within the estuary is fully discussed.