Abstract
Coastal lagoons are very sensitive to anthropogenic impacts and sedimentary records may provide valuable temporal reconstructions of the environmental changes in the lagoon, the coastal zone, and the catchment area. The Alvarado Lagoon (Veracruz, southwestern gulf of Mexico) belongs to an extensive complex of wetlands recognized as a Ramsar site. However, its catchment basin has one of the highest deforestation rates in Mexico due to the transformation of lowlands for agriculture and grazing, thus causing siltation of the surrounding aquatic bodies. To evaluate the impact of land use change on Alvarado Lagoon, sediment fluxes and provenance were reconstructed by studying the elemental composition (determined by X-ray fluorescence spectrometry) of a sediment core dated radiometrically (210Pb, 137Cs, 239,240Pu). The sedimentary record showed an acceleration of the sediment accumulation rate during more than 134 ± 17 years; however, the changes in elemental composition during the past 40 years (i.e., 1972–2011) indicated the incorporation of continental weathered sediments and an increment of sediment accumulation of circa 470%, in coincidence with the period of higher deforestation and siltation. The recent increase in sediment accumulation rates and changes in geochemical features are attributed to erosion caused by land use changes in the Alvarado Lagoon drainage basin.
Highlights
Global change refers to changes in the structure and functioning of the Earth System, caused by the rapid increase in human population
To evaluate the impact of land use change on Alvarado Lagoon, sediment fluxes and provenance were reconstructed by studying the elemental composition of a sediment core dated radiometrically (210Pb, 137Cs, 239,240Pu)
The sedimentary record showed an acceleration of the sediment accumulation rate during more than 134 ± 17 years; the changes in elemental composition during the past 40 years (i.e., 1972–2011) indicated the incorporation of continental weathered sediments and an increment of sediment accumulation of circa 470%, in coincidence with the period of higher deforestation and siltation
Summary
Global change refers to changes in the structure and functioning of the Earth System, caused by the rapid increase in human population. Ciencias Marinas, Vol 40, No 4, 2014 effects is the increased erosion due to land-use changes (Vitousek 1994, Ruiz-Fernández et al 2014) and to the loss of vegetation cover associated with the growing human demand for natural resources. Land-use changes can be recognized in sedimentary records of coastal ecosystems because they generally increase soil erosion, which is reflected in increased sediment accumulation rates in aquatic systems (e.g., Ruiz-Fernández et al 2009) and in the geochemical composition of sediments (e.g., Koinig et al 2003, Ruiz-Fernández et al 2012). It has a half-life (T1⁄2) of 22.23 years and can be used to date sediments deposited over the last 100–150 years, period during which the diverse effects of climate change are more noticeable (e.g., pollution, sea level rise, eutrophication)
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