Spatial variation of denitrification in Mara wetland, Tanzania

Wetlands worldwide play an important role in global biogeochemical cycles. Mara wetland in Tanzania is the source of livelihood for people living around the wetland. The communities living around this wetland are completely dependent on wetland functions and services. Mara wetland serve as a buffer between Lake Victoria and upstream of Mara River basin. Besides many ecological functions and services like nutrient retention by this wetland is very important for water quality of the Lake, which in turn is fundamental requirement for the fishing community. However this wetland is now under stress from the land use changes along the Mara River basin. Therefore it is very crucial to understand nutrient dynamics of the wetland for developing sound management practices. The aim of this study was to quantify the potential denitrification rates along the cross-section of wetland and determination of limiting factors for denitrification in different hydrogeomorphological units (HGMUs). Other factors effecting potential denitrification were also reported. Study area was divided into three different HGMUs namely permanently flooded, temporarily flooded and agriculture/grazing area. Acetylene inhibition method was used for denitrification enzyme assay in soil samples from different HGMUs. Agriculture/grazing HGMU have the lowest potential denitrification rate 0.03 (± 0.22)æg N2O/g DW/hour. The highest potential denitrification rate was 3.08 æg N2O/g DW/hour in permanently flooded HGMU. However variability in rates of potential denitrification rate was very high because of technical limitation in all the methods to measure denitrification rates. Designing studies to capture seasonal variation of denitrification rate is highly recommended