Biogeochemistry of mangrove sediments in the Swamp of Mallorquin, Colombia

Sedimentary environments of the Swamp of Mallorquin in two different settings, one under the influence of mangrove plants and another without plant covering were analyzed in order to establish the incidence that such plants may have on textural, physicochemical (salinity and pH) and geochemical (total carbon, inorganic carbon, total nitrogen and total sulfur) properties of their adjacent sediments. Textural analysis reveals a predominance of mud, especially in the mangrove zone, which at the same time showed higher contents of salts, organic carbon (total carbon is assumed to be total organic carbon due to the nearly total lack of carbonates), total nitrogen and total sulfur, and also a higher acidity. C/N and C/S ratios ranged from 10.7 to 16.6 and from 2.5 to 10.4 respectively in the analyzed mangrove sediments. The results indicate that the sedimentary organic content of the Swamp of Mallorquin would derived from mixed sources (e.g. algal, terrestrial and sewage), and that depositional processes in recent years have taken place under marine and brackish conditions. While mangrove sediments have been considered efficient records of environmental changes (e.g. sources and cycle of organic matter, depositional environments and paleosalinity), this study found that mangrove plants affect such records by modifying the chemistry and the distribution patterns of some variables such as carbon, nitrogen and sulfur in their surrounding sediments.