Total carbohydrates: organic carbon in lagoon sediments as an indicator of organic effluents from agriculture and sugar-cane industry

Sediments from the Altata-Ensenada del Pabellón lagoon system, were analysed for their total carbohydrate (TCH) and organic carbon (TOC) contents, and the TCH:TOC ratio (expressed as percentage of the TOC) was used to give an indication of the amount of organic matter derived from agriculture and sugar-cane industry in the sediments. The (TCH:TOC)100 values found in the marine region Altata, Culiacan river and the estuarine region Ensenada del Pabellón were comparable ranging from 7.7% to 26.5%. The inner water bodies (channels and small lagoons) showed values (20.7–43.2%), significantly higher than those obtained in the other locations. This indicates that the organic residues derived from the agriculture and sugar-cane industry constituted a significant fraction of the organic matter only in the sediments from the inner water bodies. This study shows that the high values of the TCH:TOC ratio in sediments indicate not only the presence of sewage sludge as previously noted, but also the presence of residues from the agriculture and the sugar-cane industry.