Recent sedimentary history of organic matter and nutrient accumulation in the Ohuira Lagoon, northwestern Mexico.
(210)Pb-derived sediment accumulation rates, as well as a suite of geochemical proxies (Al, Fe, delta(13)C, delta(15)N), were used to assess the time-dependent variations of C, N, and P fluxes recorded in two sediment cores collected at Ohuira Lagoon, in the Gulf of California, Mexico, during the last 100 years. Sedimentary C, N, and P concentrations increased with time and were related to land clearing, water impoundment, and agriculture practices, such as fertilization. C:N:P ratios and delta(13)C suggested an estuarine system that is responsive to increased C loading from a N-limited phytoplankton community, whereas delta(15)N values showed the transition between an estuarine-terrestrial to an estuarine-more marine environment, as a consequence of the declining freshwater supply into the estuary due to the channeling and impoundment of El Fuerte River between 1900 and 1956. The recent increases in nutrient fluxes (2- to 9-fold the pre-anthropogenic fluxes of C and N, and 2 to 13 times for P) taking place in the mainland from the 1940s, were related to the expansion of the intensive agriculture fields and to the more recent development of shrimp farming activities.
Ruiz-Fernández
Ana Carolina
AC
Universidad Nacional Autónoma de México, Instituto de Ciencias del Mar y Limnología, Calz. J. Montes Camarena s/n, 82040, Mazatlan, México. caro@ola.icmyl.unam.mx
Frignani
Mauro
M
Tesi
Tommaso
T
Bojórquez-Leyva
Humberto
H
Bellucci
Luca Giorgio
LG
Páez-Osuna
Federico
F
D002244:Carbon / Q000032:analysis / Q000266:history*; D002247:Carbon Isotopes; D019015:Geologic Sediments / Q000032:analysis*; D049672:History, 19th Century; D049673:History, 20th Century; D049674:History, 21st Century; D007856:Lead Radioisotopes; D008800:Mexico; D009584:Nitrogen / Q000032:analysis / Q000266:history*; D009587:Nitrogen Isotopes; D010758:Phosphorus / Q000032:analysis / Q000266:history*; D012623:Seawater; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000266:history*
D002247:Carbon Isotopes; D007856:Lead Radioisotopes; D009587:Nitrogen Isotopes; D014874:Water Pollutants, Chemical; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen