Primer estudio sobre fraccionamiento de fósforo en sedimentos supramareales del estuario de Bahía Blanca (Argentina)

Estuarine sediments play a key role in the processes of nutrient remineralization; among them, phosphorus (P) is an essential element for life. In this work, we evaluated the levels of P in sediments of the surface layer (S: 0-5mm depth) and sub-surface layer (SS: 5-10mm depth) of the low supratidal plain of Puerto Rosales (middle zone of the Bahia Blanca estuary, Argentina). This is also the first study of P speciation in this area. In order to assess the relationship among physico-chemical parameters and the different fractions of P analyzed, we determined granulometric composition, percentage of moisture and organic matter, pH, Eh and temperature in the sediments. The results showed high levels of total P (up to 1.055 mg P g -1 dw) and there were no significant differences between layers, reflecting the ability of these sediments to retain native and / or anthropogenic P. In general, P tended to remain as P linked to phosphate minerals of Ca and as refractory or residual P (40% and 35%, and 20% and 31% in S and SS, respectively). The granulometric composition of the sediment would favor the retention of P while the flood would be affecting it, especially in the fraction corresponding to the labile o adsorbed P (11% and 23% for S and SS, respectively). In both layers, the variability observed in the proportions of P-Fe and the moderately labile P seems to be related to the dissolution of PO 4 3- and its diffusion towards the water column through porewater.