Bacterial community contribution to nitrogen fixation and nitrous oxides production in the Sontecomapan Lagoon

Nitrogen fixation and denitrification are processes poorly studied in Mexican coastal lagoons. In this study the N incorporation and loss rates of the bottom water and sediments were analyzed in six zones of Sontecomapan lagoon during “Nortes” and rainy seasons and their relation with the rivers outflows and the coastal marine waters entrance. The rate of N2 fixation was calculated through acetylene reduction and the denitrification through N2O production techniques. The N2 fixation was lower than the nitrogen loss as N2O production (denitrification). The greatest fixation rate was registered in the “Nortes” season; being favored by oxic conditions and high organic matter concentrations in the sediments. In the rainy season, the N2 fixation was lowered by 80 % compared to the “Nortes” season. Denitrification was favored by low salinities in November and was 23 % higher than in February, 2005. In the rainy season the nitrous oxide production was related to the high N-NO3- concentrations and decreased by 18 % when the salinity increased from 13 to 22 PSU