Nutrient Dynamics in Bottom Sediment of a Reservoir in the Semi-Arid Region

Aims: This research was developed to quantify the dynamics of the stocks of organic carbon, phosphorus and nitrogen in sediments, as well as the retention or release of nutrients in the water column of a reservoir in the tropical semi-arid region.

Place and Duration of Study: To achieve these goals, trenches were opened in the two tributaries (the Canindé and Capitão Mor Rivers) of the Pereira de Miranda reservoir, Pentecoste, in the State of Ceará (CE), Brazil. The trenches were located 500 m upstream from the waterbody. Samples were collected from each sediment deposition profile. After collection, the total organic carbon, labile carbon, granulometry, and total and assimilable phosphorus were analysed.

Results: The Canindé and Capitão Mor display different dynamics for the contribution of carbon, phosphorus and nitrogen, and it is evident that the Canindé River contributes more nutrient to the sediments, a fact that is mainly related to the greater deposition of fine sediment found in the Canindé.

Conclusion: Sediment granulometry has a strong influence on the retention or release of TOC, P and N, and reservoirs with a predominance of fine sediments display greater fixation of these elements and become a nutrient sink within the ecosystem.