Variation of nitrification rates in Chelem lagoon, Yucatan, Mexico

Abstract

Sedimentary nitrification rates were measured by incubation of cores collected from Chelem lagoon (located in the Yucatan peninsula on the coast of the Gulf of Mexico). Analyses of <i>p</i>H and total sulfide in the pore water and total nitrogen

<span style="font-size:14.0pt;line-height:115%;font-family:" times="" new="" roman";="" mso-fareast-font-family:"times="" roman";color:black;mso-ansi-language:en-in;="" mso-fareast-language:en-in;mso-bidi-language:hi"="" lang="EN-IN">and total phosphorous in the sediments were also carried out. Effects of human interference were discernible in the zone of the lagoon more used by man. Peak values of total nitrogen and total phosphorous with the latter exhibiting significative correlation with the sediment <i>p</i>H, were observed in this zone. Very low <i>p</i>H values were measured in Chelem sediments probably due to the high ambient hydrogen sulfide levels. The high sulphide concentrations resulted in the absence of nitrification at 5 of the 14 stations sampled; however, on the western side of the lagoon high nitritication rates (30.2 ± 36.9 μmol/m²/h) were measured. These rates presented significative correlation with total phosphorous content of the sediment and with the reported phosphate flux between sediment and water. The reported ammonium release from the sediments, was four times the nitrification rate, indicating that just a fraction of the ammonium produced in Chelem sediments is converted to nitrate.</span>