Benthic foraminifera are excellent environmental indicators; CaCO3 test records the isotopic concentration of their surroundings and can be used to analyze environmental changes that occur during a certain time period. Stable isotopes, particularly those of oxygen (δ18O), are useful for interpreting ancient environments, given that they are used as “proxy” environmental variables (temperature and salinity). In this study, we provide ranges of isotopic variation in benthic foraminifera communities from the Colorado River delta. Four sampling campaigns were conducted in one year (2009-2010) in the adjacent subtidal zone of Baja California. Four transects with a total of sixteen sample station were drawn perpendicular to the coastline. Here, we recorded the following in situ: sand-type, salinity, and temperature. In the laboratory, 300 individuals per sample were separated, and sub-samples were taken for isotopic analysis. Data was processed using the software’s R 2.12.2, PAST 1.81 and Arc Map 9.3. Forty species were identified in the dead assemblages (Thanatocoenosis), whereas thirteen species were found in the living assemblages (Biocoenosis). The most abundant species in both communities belong to the genera Ammonia and Cribroelphidium. In the living assemblages, isotopic variation −2.15% to 5.94% within a temperature interval of 11°C, indicated antiestuarine conditions. In the dead assemblages, isotopic composition −3.04 to −0.74 served as a sign of estuarine conditions prior to damming.
Santa Rosa-del Río, M.A. (2008) Estudio sobre la evolución del Delta del Po (Italia) con análisis sedimentológico y palinológico y comparación bibliográfica con el Delta del Ebro (Espana) durante el Cuaternario [Study on the Evolution of the Po Delta (Italy) with Sedimentological and Palynological Analysis and Comparison with Literature on the Ebro Delta (Spain) during the Quaternary]. Unpublished Master’s Thesis, Universitat degli Studi di Ferrara [University of Ferrara], Ferrara, 93 p.
Bustillos Durán, S. (2004) El agua en la frontera México-Estados Unidos. Araucaria. Revista Iberoamericana de Filosofía, Política y Humanidades, 5.
http://www.redalyc.org/articulo.oa?id=28211509
Thompson, R.W. (1968) Tidal Flat Sedimentation on the Colorado River Delta, Northwestern Gulf of California. Geological Society of America Memoirs, 107, 133.
https://doi.org/10.1130/MEM107-p1
Kowalewsky, M., Avila Serrano, G., Flessa, K.W., and Goodfriend, G.A. (2000) Dead Delta’s Former Productivity: Two Trillion Shells at the Mouth of the Colorado River. Geology, 28, 1059-1062.
https://doi.org/10.1130/0091-7613(2000)28<1059:DDFPTT>2.0.CO;2
Van Andel, T.H. (1964) Recent Marine Sediments of the Gulf of California. In: van Andel, T.J. and Shor, G.G., Eds., Marine Geology of the Gulf of California: A Symposium: American Association of Petroleum Geologists Memoirs, Vol. 3, 216-310.
Baba, J., Peterson, C.D. and Schrader, H.J. (1991) Modern Fine-Grained Sediment in the Gulf of California during the Last Century. In: Dauphin, J.P. and Simoneit, B.R.T., Eds., The Gulf and Peninsular Province of the Californias, AAPG Memoir, Tulsa, Vol. 47, 569-587.
Carriquiry, J.D. and Sánchez, A. (1999) Sedimentation in the Colorado River delta and Upper Gulf of California after nearly a century of Discharge Loss. Marine Geology, 158, 125-145. https://doi.org/10.1016/S0025-3227(98)00189-3
Carriquiry, J.D., Sanchez, A. and Camacho-Ibar, V. (2001) Sedimentation in the Northern Gulf of California after Cessation of the Colorado River Discharge. Sedimentary Geology, 144, 37-62. https://doi.org/10.1016/S0037-0738(01)00134-8
álvarez-Borrego, S. (1983) Gulf of California. In: Ketchum, B.H., Ed., Ecosystems of the World, 26: Estuaries and Enclosed Seas, Elsevier Scientific, New York, 427-449.
Lavín, M.F. and Sánchez, S. (1999) On how the Colorado River Affected the Hydrography of the Upper Gulf of California. Continental Shelf Research, 19, 1545-1560. https://doi.org/10.1016/S0278-4343(99)00030-8
Carbajal, N., Sousa, A. and Durazo, R. (1997) A Numerical Model of the Ex-ROFI of the Colorado River. Journal of Marine Systems, 12, 17-33.
https://doi.org/10.1016/S0924-7963(96)00086-3
Lavín, M.F., Beier, E. and Badán, A. (1997) Estructura hidrográfica y circulación del Golfo de California: Escalas estacional e interannual. Monografía 3 [Hydrographic Structure and Circulation of the Gulf of California: Seasonal and Interannual Scales. Monograph 3]. In: Lavín, M.F., Ed., Contribuciones a la Oceanografía Física en México [Contributions to Physical Oceanography in Mexico], Unión de Geofísica Mexicana [Mexican Geophysical Union], Baja, CA, 41-171.
Santa Rosa-del Río, M.A., Avila-Serrano, G.E., Téllez-Duarte, M.A., Gonzalez-Yajimovich, O. and Cupul-Magana, L.A. (2011) Distribución y abundancia de tanatocenosis de foraminíferos bentónicos en el delta del río Colorado [Death Assemblage Distribution and Abundance of Benthic Foraminifera in the Colorado River Delta]. Boletín de la Sociedad Geológica Mexicana [Bulletin of the Geological Society of Mexico], 63, 429-442. https://doi.org/10.18268/BSGM2011v63n3a6
Alvarez, L.G. and Jones, S.E. (2002) Factors Influencing Suspended Sediment Flux in the Upper Gulf of California. Estuarine, Coastal and Shelf Science, 54, 747-759.
https://doi.org/10.1006/ecss.2001.0873
Rodriguez, C.A., Flessa, K.W. and Dettman, D.L. (2001) Effects of Upstream Diversion of Colorado River Water on the Estuarine Bivalve Mollusc Mulinia Coloradoensis. Conservation Biology, 15, 249-258.
Téllez-Duarte, M.A., Avila-Serrano, G. and Flessa, K.W. (2008) Los Concheros arqueológicos del Delta del Colorado y el uso sustentable de los recursos naturales. Memorias de balances y perspectivas de la historia de la Antropología e Historia de la Baja California 2000-2001 [The Archaeological Middens of the Colorado Delta and Sustainable Use of Natural Resources. Proceedings on the Balance and Perspective of the History of Anthropology and History of Baja California 2000-2001]. Instituto Nacional de Antropología [National Institute of Anthropology], México, D.F., 10-14.
Grossman, E.L. and Teh-Lung, K. (1986) Oxygen and Carbon Isotope Fractionation in Biogenic Aragonite: Temperature Effects: Chemical Geology. Isotope Geoscience Section, 59, 59-64. https://doi.org/10.1016/0168-9622(86)90057-6
Sang-Tae, K. O’Neal, J.R, Hillaire-Marcel, C. and Mucci, A. (2007) Oxygen Isotope Fractionation between Synthetic Aragonite and Water: Influence of Temperature and Mg2+ Concentration. Geochimica et Cosmochimica Acta, 71, 4704-4715.
https://doi.org/10.1016/j.gca.2007.04.019
Téllez-Duarte, M.A., Avila-Serrano, G. and Flessa, K.W. (2008) Environmental Significance of Oxygen Isotopes in the Bivalve Protothaca grata from Archaeological sites in Northeast Baja California. Pacific Coast Archaeological Society Quarterly, 39, 49-56.
Barbieri, R. (2001) Taphonomic Implications of Foraminiferal Composition and Abundance in Intertidal Mud Flats, Colorado River Delta (Mexico). Micropaleontology, 47, 73-83. https://doi.org/10.2113/47.1.73
Ruvalcaba-Baroni, I. (2005) Paleoecología de foraminíferos bentónicos del Pleistoceno en El Faro, Baja California, México [Paleoecology of Pleistocene Benthic Foraminifera in El Faro, Baja California, Mexico]. Unpublished B.A. Thesis, Universidad Autónoma de Baja California [Autonomous University of Baja California], Baja CA, 83 p.
Huerta-Tamayo, L. (2007) Biocenosis y Tanatocenosis de Foraminíferos Bentónicos Como Indicadores de Cambios Ambientales en el Delta del Río Colorado [Living and Death Assemblages of Benthic Foraminifera as Indicators of Environmental Change in the Colorado River Delta]. Unpublished M.S. Thesis, Universidad Autónoma de Baja California [Autonomous University of Baja California], Ensenada, 76 p.
Avila-Serrano, G.E.., Flessa, K.W., Téllez-Duarte, M.A. and Cintra-Buenrostro, C.E. (2006) Distribución de la macrofauna intermareal del Delta del Río Colorado, norte del Golfo de California, México. Revista Ciencias Marinas, 32, 649-661.
Lipps, J.H., Verger, W.H., Bruzas, M.A., Douglas, R.G. and Ross, C.A. (1979) Foraminiferal Ecology and Paleoecology. Society of Economic Paleontologists and Mineralogists, Tulsa, 187 p. https://doi.org/10.2110/scn.79.06
Téllez-Duarte, M.A., Huerta, L., Rubalcaba, I., Avila, G. and Flessa, K.W. (2006) El δ18O en foraminíferos bentónicos como indicador ambiental de la influencia del agua dulce en ambientes estuarinos: el caso del delta del río Colorado [The δ18O in Benthic Foraminifera as an Environmental Indicator of the Influence of Freshwater in Estuarine Environments: The Case of the Colorado River Delta]. Libro de resúmenes del X Congreso Nacional de Paleontología, Instituto de Geología, UNAM, México, D.F., 21-25 noviembre [Book of Abstracts of the Tenth National Congress of Paleontology, Institute of Geology, UNAM, Mexico, DF, 21-25 November].
Abele, L.G. and Walters, K. (1979) Marine Benthic Diversity: A Critique and Alternative Explanation. Journal of Biogeography, 6, 115-126.
https://doi.org/10.2307/3038047
Staines-Urías, F. and Douglas, R.G. (2009) Environmental and Intraspecific Dimorphism Effects on the Stable Isotope Composition of Deep-Sea Benthic Foraminifera from the Southern Gulf of California, Mexico. Marine Micropaleontology, 71, 80-95. https://doi.org/10.1016/j.marmicro.2009.01.007
Celis-Hernández, A.K. (2011) Explotación de Recursos Costeros y Condiciones Ambientales en el Delta del Río Colorado Durante la Prehistoria [Exploitation of Coastal Resources and Environmental Conditions in the Colorado River Delta during Prehistory]. Unpublished M.S. Thesis, Universidad Autónoma de Baja California [Autonomous University of Baja California], Ensenada, 132 p.
Lavín, M.F. and Organista, S. (1988) Surface Heat Flux in the Northern Gulf of California. Journal of Geophysical Research, 93, 14033-14038.
https://doi.org/10.1029/JC093iC11p14033
Usera, J. and Blázquez, A.M. (1998) Interpretación de la Dinámica Poblacional de Ammonia beccarii (Linné, 1758) (Foraminiferida, Protoctista) en el Cuaternario Continental de la Laguna de Villena (Alicante, Espana) [Interpreting the Population Dynamics of Ammonia beccarii (Linné, 1758) (Foraminiferida, Protoctista) in the Quaternary Continental Laguna de Villena (Alicante, Spain)]. Coloquios de Paleontología [Symposia of Paleontology], 49, 145-167.
Townsend, C.H. (1901) Dredging and Other Records of the US Fish Commission Steamer Albatrossa with Bibliography Relative to the Work of the Vessel. US Fish Commission Report for 1900, 387-562.
