Carbon accumulation driven by anthropogenic activities within wetland environments associated with Lake Titicaca

To assess the anthropogenic impact on carbon and nitrogen accumulation rates in wetlands associated with Lake Titicaca, sediment cores recording the past century in contrasting environmental conditions were analyzed using elemental and isotopic proxies. Duplicate 50-cm sediment cores were collected from wetlands within the National Reserve environment of Lake Titicaca, and from a wetland area under the direct influence of a sewage plant. Subsamples were analyzed for total organic carbon (TOC), total nitrogen (TN), δ¹³C, and δ¹⁵N. Sediment accumulation rates (SAR) and Mass accumulation rates (MAR) were calculated from ²¹⁰Pb-excess activity using the Constant Flux Constant Sedimentation method (CFCS). The SAR in the impacted area averaged 0.38 cm yr⁻¹, up to twofold higher than in the “National Reserve”, likely due to increased organic matter influx from anthropogenic activities. Although δ¹³C values showed no significant differences between the study areas, abrupt shifts in organic matter sources and significantly heavier δ¹⁵N values were observed in the impacted area after the 1970s, indicating that carbon and nitrogen sources derive from a mix of terrestrial vegetation, algae, and cyanobacteria, fertilized by nutrient enrichment from anthropogenic activities. Despite no significant differences in carbon and nitrogen fluxes between both studied areas, the lower stocks in the impacted area indicate a lower accumulation capacity due to a higher contribution of labile organic matter. This study underscores the crucial role of wetlands associated with Lake Titicaca in the deposition and accumulation of organic carbon driven by both natural and anthropogenic factors and highlights the importance of wetland preservation in maintaining the accumulation capacity of these ecosystems in the context of global wetland eutrophication.