Phosphate exchanges at the water-sediment interface in a maturation pond (lagunage of Boujaad) and a fry pond (Deroua fisheries farm, Beni-Mellal), Morocco
Sediment samples used in this work were taken from two different sites (maturation pond of Boujaad lagunage and fry pond of the Deroua fish farm) in order to understand and compare the conditions affecting phosphate exchanges across water-sediment interface. This study showed a difference in the chemical composition of the two sediments. In the fry pond, the majority of the phosphate was present as inorganic phosphate (92.5%), especially in forms bound to calcium. On the other hand, total phosphate was divided equally into organic (49.2%) and inorganic (49.8%) phosphorus in the maturation pond. In this pond, phosphate solubility increased in the interstitial water under anoxic conditions. The phosphate released came principally from the inorganic fraction, particularly from Fe(OOH)-P. The maturation pond sediments, which had accumulated much organic matter, liberated more orthophosphate than did the fry pond sediments. Under air flushing, phosphate adsorption is significant particularly in the maturation and fry pond sediments.