Spatial and temporal variability of the sedimentary organic matter associated with the Oxygen Minimum Zone (OMZ) in a coastal environment of the northern Humboldt Current, Mejillones Bay, Chile

Marcos Guiñez, Jorge Valdés, Abdel Sifeddine


DOI: https://doi.org/10.3856/vol38-issue2-fulltext-9

This work analyzes the seasonal and spatial variability of the Oxygen Minimum Zone (OMZ) and its influence on the composition of the organic matter deposited on the bottom sediments of Mejillones Bay. The obtained results indicate that the upper limit of the OMZ fluctuated during the year between 20 and 45 m depth. In summer, this limit ranged from 20 to 35 m depth, whereas in winter it ranged from to 40 to 55 m depth. According to a Rock-Eval analysis, the organic matter present in the deepest sediments (100 m) is better preserved than the shalow material (35 m). This analysis revealed that the sediment deposited in the bay is marine phytoplanktonic in origin (Type II) and immature. The ratio of total sulfur to total organic carbon ranges from 0.8 to 3.9% at station A (35 m) and from 5.7 to 10.3% at the deeper stations (70 and 100 m). The Zona de Mínimo Oxígeno y materia orgánica en bahía de Mejillones, Chile243 C:N ratio in the sediments varies between cold and warm periods, with respective averages of 9.13 and 7.74 and a wintertime peak of 11%. The ANDEVA results indicate that the dissolved oxygen (P < 0.001), total carbon (C) (P < 0.001), total nitrogen (N) (P < 0.008), total organic carbon (TOC) (P < 0.001), and hydrogen index (HI) (mg HC g COT-1) (P < 0.019) differ significantly by depth. The dissolved oxygen concentration was found to be related to the conservation of organic matter in the sediments: the organic matter in the deeper sediments was preserved better due to the effect of the OMZ.

Guiñez M, Valdés J, Sifeddine A. Spatial and temporal variability of the sedimentary organic matter associated with the Oxygen Minimum Zone (OMZ) in a coastal environment of the northern Humboldt Current, Mejillones Bay, Chile. Lat. Am. J. Aquat. Res.. 2011;38(2): 242-253. Available from: doi:10.3856/vol38-issue2-fulltext-9 [Accessed 17 Aug. 2019].
Guiñez, M., Valdés, J., & Sifeddine, A. (2011). Spatial and temporal variability of the sedimentary organic matter associated with the Oxygen Minimum Zone (OMZ) in a coastal environment of the northern Humboldt Current, Mejillones Bay, Chile. Latin American Journal of Aquatic Research, 38(2), 242-253. doi:http://dx.doi.org/10.3856/vol38-issue2-fulltext-9