RESEARCH ARTICLE Sedimentary record of water column trophic conditions and sediment carbon fluxes in a tropical water reservoir (Valle de Bravo, Mexico) Vladislav Carnero-Bravo & Martín Merino-Ibarra & Ana Carolina Ruiz-Fernández & Joan Albert Sanchez-Cabeza & Bassam Ghaleb Received: 10 March 2014 /Accepted: 7 October 2014 # Springer-Verlag Berlin Heidelberg 2014 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 im- poundments. Over 1/3 of the total C burial since dam con- struction, 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. Keywords 210 Pb chronology . Eutrophication . Lake sediments . Organic carbon fluxes . Valle de Bravo reservoir Introduction In parallel with population growth and technology develop- ment, environmental change is substantial and increasing. Anthropogenic eutrophication and the resulting hypoxic (O 2 <2.0 mg L -1 ) or anoxic (complete absence of oxygen) condi- tions (Diaz 2001) are amongst the most important environ- mental problems of aquatic ecosystems. Seasonal redox con- ditions are linked to eutrophication because oxygen is con- sumed during organic matter (OM) degradation and this pro- cess enhances nutrient release to the water column Responsible editor: Philippe Garrigues V. Carnero-Bravo Posgrado en Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Cd. Universitaria, México, Distrito Federal, Mexico e-mail: vladislavc@gmail.com M. Merino-Ibarra Unidad Académica de Ecología y Biodiversidad Acuática, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, Mexico, Distrito Federal 04510, Mexico e-mail: mmerino@cmarl.unam.mx A. C. Ruiz-Fernández (*) Unidad Académica Mazatlán, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Calz. J. Montes Camarena s/n, Col. Playa Sur, 82040 Mazatlán, Sinaloa, Mexico e-mail: caro@ola.icmyl.unam.mx J. Sanchez-Cabeza Unidad Académica de Procesos Oceánicos y Costeros, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, 04510 México, Distrito Federal, Mexico e-mail: jasanchez@cmarl.unam.mx B. Ghaleb Centre de Recherche en Géochimie et Géodynamique (GEOTOP), Université du Québec à Montréal, 201 Avenue Président-Kennedy, Montréal H2X 3Y7, Canada e-mail: ghaleb.bassam@uqam.ca Environ Sci Pollut Res DOI 10.1007/s11356-014-3703-0