Effects of organic matter, calcium carbonates and moisture content on availability of nutrients in pond sediments of the Deroua Fisheries Station, Beni Mellal, Morocco

Abstract

Concentration profiles of calcium carbonates (CaCO3) and organic carbon were determined through the pond sediment in different states of moisture. The ponds are being used in fish production and were never limed because the original bottom soil was not acidic. Three horizons in the profile of sediment were clearly identified and defined, from the top of sediment, respectively A (shallow), B (high content of organic matter) and C (original soil). Total calcium carbonates concentrations in both dry (105OC) and wet (fresh) sediments, ranged from 12 to 35% and increases with depth. Organic carbon (OC) concentrations increased with depth in wet sediment and B horizon stored the highest rate; in dry sediment, amounts of OC decreased with depth. Analysis of reactive CaCO3 showed that there were no significant differences between the wet and the dry sediment. When the organic matter was removed, reactive calcium carbonate concentrations in dry sediment became several times greater than those in the wet sediment. In other way, when calcium carbonates were removed, organic carbon concentrations decreased especially in B horizon of the wet sediment. On the opposite, OC contents increase significantly in all horizons of dry sediment. In Deroua station, moisture contents of sediments affect significantly the relationships between calcium carbonates and organic carbon witch is the main source of nutrients in pisciculture ponds. Key Words: Nutrients, Sediment, Calcium carbonates, Organic matter, Moisture. Journal of Aquatic Sciences Vol.19(1) 2004: 33-39