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Geochemistry of trace metals in shelf sediments affected by seasonal and permanent low oxygen conditions off central Chile, SE Pacific (∼36°S).

Autores:

Muñoz, P., Dezileau, L., Cardenas, L., Sellanes, J., Lange, C., & Inostroza, J. et al.

Resumen:

Trace metals (Cd, U, Co, Ni, Cu, Ba, Fe, Mn), total organic carbon (TOC) and C and N stable isotope signatures (δ13C and δ15N) were determined in short sediments cores from the inner and outer shelf off Concepción, Chile (∼36°S). The objectives were to establish the effect of environmental conditions on trace metal distributions at two shelf sites, one affected by seasonal oxygenation and the other by permanent low oxygen conditions due to the presence of the oxygen minimum zone (OMZ). We evaluate trace metals as proxies of past changes in primary productivity and the bottom water oxygen regime. Concentrations of pore water sulfides and NH4+ were also measured as indicators of the main diagenetic pathways at each site. Our results for the inner shelf (seasonal suboxia) suggest that the oxidative state of the sediments responds to seasonal pulses of organic matter and that seasonal oxygenation develops during high and low primary productivity in the water column. Here, positive fluxes (to the water column) estimated from pore water concentrations of several elements were observed (Ba, Co, Ni, Fe and Mn). The less reduced environment at this site produces authigenic enrichment of Cu associated with the formation of oxides in the oxic surface sediment layer, and the reduction of U within deeper sediment sections occur consistently with negative estimated pore water fluxes. In the outer shelf sediments (permanent suboxia, OMZ site), negative fluxes (to the sediment) were estimated for all elements, but these sediments showed authigenic enrichments only for Cd, Cu and U. The short oxygenation period during the winter season did not affect the accumulation of these metals on the shelf. The distribution of Cu, Cd and U have been preserved within the sediments and the authigenic accumulation rates estimated showed a decrease from the deep sections of the core to the surface sediments. This could be explained by a gradual decrease in the strength of the OMZ in the last 100 years, in combination with periods of strong oxygenations during El Niño events.

Año: 2012

Palabras claves: Trace metals; Sediments; Oxygen minimum zone; Organic carbon; SE Pacific; Concepción shelf.

Referencia APA: : Muñoz, P., Dezileau, L., Cardenas, L., Sellanes, J., Lange, C., & Inostroza, J. et al. (2012). Geochemistry of trace metals in shelf sediments affected by seasonal and permanent low oxygen conditions off central Chile, SE Pacific (∼36°S). Continental Shelf Research, 33, 51-68.

Mining of EST-SSR from 454 pyrosequencing in the surf clam Mesodesma donacium (Lamark, 1818).

Autores:

Aguilar-Espinoza, A., Guzmán-Riffo, B., Haye, P., & Gallardo-Escárate, C.

Resumen:

Novel simple sequence repeats (SSR) were identified from 454 transcriptome pyrosequencing ESTs in the surf clam Mesodesma donacium. From 7,734 ESTs annotated with SSR motives, 75 putative EST-SSRs were selected according their repetitive DNA sequence and functional annotation (Gene ontology), of these, 15 were characterized on 45 individuals of two wild populations located in two different biogeographic transition zones of the coast of Chile (30 and 42°S). Most loci were in Hardy–Weinberg equilibrium, and the polymorphic information content (PIC) ranged from 0.243 to 0.634. Pairwise Fst between sampled populations was estimated in 0.478. These EST-SSR markers promise to be useful for future management strategies of this overexploited species.

Año: 2012

Palabras claves: Pyrosequencing 454, Expressed sequence tag (EST), Microsatellite, Mesodesma donacium

Referencia APA: Aguilar-Espinoza, A., Guzmán-Riffo, B., Haye, P., & Gallardo-Escárate, C. (2012). Mining of EST-SSR from 454 pyrosequencing in the surf clam Mesodesma donacium (Lamark, 1818). Conservation Genet Resour, 4(4), 829-832.

The marine brooder Excirolana braziliensis (Crustacea: Isopoda) is also a complex of cryptic species on the coast of Chile.

Autores:

Varela, A. & Haye, P.

Resumen:

Speciation is a direct consequence of isolated populations in taxa with low dispersal potential. The brooding crustacean Excirolana braziliensis, with a presumably wide geographic range of distribution (~16° N-41° S in the Pacific and ~19° N-35° S in the Atlantic), has been detected to correspond to cryptic species on the coast of Panama. Latitudinal variations in reproductive features in E. braziliensis have been attributed to phenotypic plasticity, however, the differences may be the result of divergent populations. Considering that the taxon has been reported to be a complex of cryptic species in other geographic areas and given the phenotypic differences detected along its distribution range, we hypothesized that E. braziliensis is a complex of species in the coast of Chile. We used partial cytochrome c oxidase subunit I (COI) sequences from 132 individuals with the diagnostic morphology of E. braziliensis collected along ~2200 km of coast to determine the genetic structure of E. braziliensis. Phylogenetic and phylogeographic analyses showed three distinct clades with 14 to 19 % of genetic divergence and high values of genetic differentiation. Intra and inter-clade divergence revealed the existence of a species complex of E. braziliensis on the coast of Chile, supporting growing evidence of the high abundance of cryptic species in marine invertebrate taxa.

Año: 2012

Palabras claves: cryptic species, genetic differentiation, genetic distance, marine peracarids, phylogenetics.

Referencia APA: Varela, A. & Haye, P. (2012). The marine brooder Excirolana braziliensis (Crustacea: Isopoda) is also a complex of cryptic species on the coast of Chile. Rev. Chil. Hist. Nat., 85(4), 495-502.