| 1 | Some aspects of the nitrogen cycle in mangrove and estuarine waters The seasonal changes of nitrogen nutrients, regeneration rates and uptake rates of nitrogen nutrients were investigated in a mangrove ecosystem on the west coast of India during 1997-1998. The changes of nutrient concentrations followed clear seasonal cycles. In case of NOd3u-@@ and NO@d2@@ @u-@@, advection with freshwater in monsoon and in situ biological processes during the rest of the year controlled concentration changes. In case of reduced forms, they were regulated by biological in situ production rates. The gradual increase in concentrations of the reduced forms in the dry months was mainly due to intense microbial decomposition of organic matter. Particulate organic nitrogen (PON) concentrations showed clear seasonal variations and ranged from 12.1 to 207.9 mu g. Litterfall appeared to be the major source of PON to the water column. Unlike that the PON, chlorophyll @ia@@ followed a different seasonal trend and concentration ranged from 0.1 to 21.6 mu g. The seasonal patterns of uptake rates were distinct, with a dominance of NO@d3@@ @u-@@ and NO@d2@@ @u-@@ uptake in the post-monsoon, followed by dominance of NH@d4@@ @u+@@ and urea uptake in pre-monsoon. Ammonium and nitrite production rates were among the highest known for nearshore waters and showed clear seasonal patterns Source: Heredia, A.M. 2000; 201; pp. 1136.
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