HR: 1400h
AN: OS23B-15    [Abstracts]
TI: Distribution of organic-walled dinoflagellate cysts in recent marine sediments from the Gulf of Tehuantepec, South Pacific of Mexico.
AU: * Vasquez-Bedoya, L F
EM: luis@ola.icmyl.unam.mx
AF: Universidad Nacional Autónoma de México. Posgraduate Program of Marine Sciences and Limnology. Mazatlan Academic Unit., Calz. J. Montes Camarena s/n, Mazatlan, Sin 82040, Mexico
AU: De Vernal, A
EM: devernal.anne@uqam.ca
AF: Centre de Recherche en Géochimie et en Géodynamique (GEOTOP-UQAM-McGill), 201 avenue du Président-Kennedy. PK-7150 , Montreal, Qc H2X 3Y7, Canada
AU: Ruiz-Fernandez, A C
EM: caro@ola.icmyl.unam.mx
AF: Universidad Nacional Autonoma de Mexico. Instituto de Ciencias del Mar y Limnologia. Unidad Academica Mazatlan., Calz. J. Montes Camarena s/n, Mazatlan, Sin 82040, Mexico
AU: Machain-Castillo, M L
EM: machain@mar.icmyl.unam.mx
AF: Universidad Nacional Autonoma de Mexico. Instituto de Ciencias del Mar y Limnologia. Ciudad Universitaria, Circuito Cuidad Universitaria s/n, Mexico City, DF 04510, Mexico
AU: Radi, T
EM: radi.taoufik@courrier.uqam.ca
AF: Centre de Recherche en Géochimie et en Géodynamique (GEOTOP-UQAM-McGill), 201 avenue du Président-Kennedy. PK-7150 , Montreal, Qc H2X 3Y7, Canada
AU: Hillaire-Marcel, C
EM: chm@uqam.ca
AF: Centre de Recherche en Géochimie et en Géodynamique (GEOTOP-UQAM-McGill), 201 avenue du Président-Kennedy. PK-7150 , Montreal, Qc H2X 3Y7, Canada
AB: A qualitative and quantitative study of recent organic-walled dinoflagellate dinocysts recovered in sediments has been undertaken in the coastal zone of the Gulf of Tehuantepec, Mexico. A sediment core was collected in 2004 with a Reineck-type corer using a plastic tube (7 cm i.d); and it was subsampled at 0.3 cm intervals down to 10 cm depth and then at 1 cm intervals at further depths. The ²¹⁰Pb and ¹³⁷Cs-derived sedimentation and mass accumulation rates at the site were found to vary from 0.033 to 0.209 cm yr^-1, and from 0.05 to 0.29 g cm^-2 yr^-1., respectively. The cysts concentrations ranged between 477 and 2300 cysts g^-1 and the cysts fluxes between 68 a 494 cysts cm^-2 yr^-1. Twenty-three cyst taxa were identified: Brigantedinium spp., Polysphaeridium zoharyii, Bitectatodinium spongium, Spiniferites delicatus, Quinquecuspis concreta, Echinidinium transparantum, Operculodinium centrocarpum, Selenopemphix quanta, Type Echinidinium granulatum, Echinidinium aculeatum, Protoperidinium americanum, Echinidinium delicatum, Selenopemphix nephroides, Cyst of Protoperidinum stellatum, Lingulodinium machaerophorum, Islandinium spp., Votadinium spinosum, Polykrikos kofoidii, Pentapharsodinium dalei, Tuberculodinium vancampoe, Spiniferites mirabilis, Votadinium calvum and Nematosphaeropsis labyrinthus. The assemblages included cysts of both phototrophic and heterotrophic species, with variation of their respective abundance reflecting changes in the trophic structure of the upper water mass, especially after 1950, with a decrease from ~30% to 15% of photototrophic species, likely as a response to pollution (including cultural eutrophication) created by the industrial development of the adjacent coastal zone. Brigantedinium spp., Polysphaeridium zoharyii and Bitectatodinium spongium, were the dominant species found in the core and are most likely influenced by the seasonal upwelling that characterize the study area, as indicated by the predominance of planktonic foraminiferal species Globigerina bulloides and Globigerinita glutinata throughout the core. Potentially toxic species such as Polysphaeridium zohary (cyst of Pyrodinium bahamense var. compressum) were also observed all along the sediment core and new analysis are to be performed to further investigate their presence in the zone.
DE: 4860 Radioactivity and radioisotopes
DE: 4863 Sedimentation (1861)
DE: 4924 Geochemical tracers
DE: 4944 Micropaleontology (0459, 3030)
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly