title: Sedimentary record of water column trophic conditions and sediment carbon fluxes in a tropical water reservoir (Valle de Bravo, Mexico).
abstract: Valle de Bravo (VB) is the main water reservoir of the Cutzamala hydraulic system, which provides 40% of the drinking water consumed in the Mexico City Metropolitan Area and exhibits symptoms of eutrophication. Nutrient (C, N and P) concentrations were determined in two sediment cores to reconstruct the water column trophic evolution of the reservoir and C fluxes since its creation in 1947. Radiometric methods ((210)Pb and (137)Cs) were used to obtain sediment chronologies, using the presence of pre-reservoir soil layers in one of the cores as an independent chronological marker. Mass accumulation rates ranged from 0.12 to 0.56 g cm(-2) year(-1) and total organic carbon (TOC) fluxes from 122 to 380 g m(-2) year(-1). Total N ranged 4.9-48 g m(-2) year(-1), and total P 0.6-4.2 g m(-2) year(-1). The sedimentary record shows that all three (C, N and P) fluxes increased significantly after 1991, in good agreement with the assessed trophic evolution of VB and with historic and recent real-time measurements. In the recent years (1992-2006), the TOC flux to the bottom of VB (average 250 g m(-2) year(-1), peaks 323 g m(-2) year(-1)) is similar to that found in highly eutrophic reservoirs and impoundments. Over 1/3 of the total C burial since dam construction, circa 70,000 t, has occurred in this recent period. These results highlight the usefulness of the reconstruction of carbon and nutrient fluxes from the sedimentary record to assess carbon burial and its temporal evolution in freshwater ecosystems.
authors.affiliation: Posgrado en Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Cd. Universitaria, México, Distrito Federal, Mexico, vladislavc@gmail.com.
authors.forename: Vladislav
authors.initials: V
authors.lastname: Carnero-Bravo
authors.forename: Martín
authors.initials: M
authors.lastname: Merino-Ibarra
authors.forename: Ana Carolina
authors.initials: AC
authors.lastname: Ruiz-Fernández
authors.forename: Joan Albert
authors.initials: JA
authors.lastname: Sanchez-Cabeza
authors.forename: Bassam
authors.initials: B
authors.lastname: Ghaleb
mesh_terms: D002244:Carbon / Q000032:analysis*; D057486:Carbon Cycle; D002947:Cities; D017753:Ecosystem; D004784:Environmental Monitoring; D005068:Eutrophication; D005618:Fresh Water / Q000737:chemistry*; D019015:Geologic Sediments / Q000032:analysis* / Q000737:chemistry; D008800:Mexico; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D002244:Carbon