Actividad acetilcolinesterasa, defensas antioxidativas y peroxidación lipídica en el molusco bivalvo Semele solida:: esta especie ¿Podría ser utilizada como bioindicador?

We analyzed the relationships between biochemical parameters: acetylcholinesterase activity (AChE); glutathione S-transferase activity (GST); glutathione concentration (GSH) and lipid peroxidation; in the bivalve mollusc Semele solida, with the effects of environmental stress (anthropogenic activity), from three estuaries in Eastern South Pacific bays: Coliumo estuary (in Coliumo Bay), Lenga estuary (in San Vicente Bay) and Andali¨¦n estuary (in Concepci¨®n Bay). Coliumo is the estuary with minor environmental stress. Thirty juveniles from each site were selected for individual analyses in homogenized of gill or digestive gland tissue to assess AChE activity, GST activity, GSH concentration, malonyldialdehyde concentration (MDA) (lipid peroxidation), and protein content. The biochemical parameters analyzed in specimens from Coliumo estuary, differed significantly from that in Andali¨¦n estuary, with lower AChE activity in gill tissue (2189.9 ¡À 189.6 ¦Ìmol min¡¥1mg protein¡¥1) and intracellular GSH levels (59.8 ¡À 13.3 ¦ÌM), and the highest lipid peroxidation (31.9, 7.4 nmol MDA mL¡¥1) and GST activity (614.9, 92.3 mol mini mg protein). The biochemical parameters in S. solida were closely related to the sector`s stress. Due to this bivalve sensitivity, is recommended as bioindicator for use in programs of environmental alertness in the Eastern South Pacific coastal zone.Se eval¨²a en terreno un conjunto de par¨¢metros bioqu¨ªmicos: actividad acetilcolinesterasa (AChE), glutation-S-transferasa (GST), concentraci¨®n de glutation (GSH) y peroxidaci¨®n lip¨ªdica, en el molusco bivalvo Semele solida, con el objeto de analizar su relaci¨®n con el efecto del estr¨¦s ambiental generada por la actividad antr¨®pica, en tres estuarios del Pac¨ªfico Sureste: estuario Coliumo (Bah¨ªa Coliumo), estuario Lenga (Bah¨ªa San Vicente) y estuario Andali¨¦n (Bah¨ªa Concepci¨®n). Coliumo es el estuario con menor estr¨¦s ambiental. Para ello, se seleccion¨® 30 individuos juveniles de S. solida desde cada sitio. Se analiz¨® en el homogenizado de branquias o tejido digestivo de cada individuo: actividad AChE; actividad GST, concentraci¨®n GSH, concentraci¨®n de malonildialdeh¨ªdo (peroxidaci¨®n lip¨ªdica) y contenido de prote¨ªnas. Los par¨¢metros bioqu¨ªmicos analizados en los organismos recolectados en el estuario Coliumo difirieron significativamente de los recolectados en el estuario Andali¨¦n, los que presentaron menor actividad AChE en tejido branquial (2189,9 ¡À 189,6 ¦Ìmol min¡¥1mg prote¨ªna¡¥1) y concentraci¨®n intracelular de GSH (59,8 ¡À 13,3 ¦ÌM) y en gl¨¢ndula digestiva mayor actividad GST (614,9 ¡À 92,3 ¦Ìmol min¡¥1mg prote¨ªna¡¥1) y mayor grado de peroxidaci¨®n lip¨ªdica (31,9 ¡À 7,4 nmol MDA mL¡¥1). Se observ¨® una estrecha relaci¨®n entre la respuesta de los par¨¢metros bioqu¨ªmicos analizados en S. solida y el nivel de estres ambiental presente en el ¨¢rea. Dado la sensibilidad de S. solida respecto de los par¨¢metros analizados, se recomienda utilizar a esta especie como bioindicador en programas de vigilancia ambiental en la zona costera del Pac¨ªfico sureste

Biogeochemical proxies and diatoms in surface sediments across the Drake Passage reflect oceanic domains and frontal systems in the region

The Antarctic Circumpolar Current is the world's largest current system connecting all major ocean basins of the global ocean. Its flow, driven by strong westerly winds, is constricted to its narrowest extent in the Drake Passage, located between South America and the Antarctic Peninsula. Due to the remoteness of the area, harsh weather conditions and strong bottom currents, sediment recovery is difficult and data coverage is still inadequate. Here, we report on the composition of 51 surface sediments collected during the R/V Polarstern PS97 expedition (Februaryâ-April 2016) across the western and central Drake Passage, from the Chilean/Argentinian continental margin to the South Shetland Islands and the Bransfield Strait (water depth: ∼100–4000 m). We studied microfossils (diatoms), bulk sediment composition and geochemical proxies (biogenic opal, organic carbon, calcium carbonate, carbon and nitrogen stable isotopes, sterols and photosynthetic pigments), and evaluated how they respond to, and reflect oceanic domains and polar to subpolar frontal systems in this region. Our multi-proxy approach shows a strong relationship between the composition of surface sediments and ocean productivity, terrigenous input, intensity of ocean currents, and ice proximity, clearly differentiating among 4 biogeographical zones. The Subantarctic Zone was characterized by warmer-water diatoms, high carbonate (>45) and low organic carbon contents (avg. 0.26), as well as low concentrations of pigments (avg. 1.75 μg/g) and sterols (avg. 0.90 μg/g). A general N-S transition from carbonate-rich to opal-rich sediment was observed at Drake Passage sites of the Polar Front and Permanently Open Ocean Zone. These sites were characterized by low organic carbon content (0.22), high relative abundances of heavily silicified diatoms (≥60% Fragilariopsis kerguelensis), and abundant foraminifera at shallower stations. Approaching the Antarctic Peninsula in the Transitional Zone, an increase in the concentrations of pigments and sterols (avg. 2.57 μg/g and 1.44 μg/g, respectively) and a strong decrease in carbonate content was observed. The seasonal Sea-Ice Zone in the southern section of the study area, had the highest contents of biogenic opal (avg. 14.6) and organic carbon (avg. 0.7), low carbonate contents (avg. 2.4), with the occurrence of sea-ice-related diatoms and sterols. In all zones, terrigenous input was detected, although carbon/nitrogen ratios and δ13Corg suggest a predominance of marine-derived organic matter; lower values of δ13Corg occurred south of the Polar Front. The new results presented here constitute a highly valuable reference dataset for the calibration of microfossil and geochemical proxies against observational data and provide a useful regional baseline for future paleo-research

Organic and inorganic proxies, and concentration of diatoms from surface sediment PS97/ Sterols preserved in surface sediments PS97/ Diatoms of surface sediments PS97

The Antarctic Circumpolar Current is the world's largest current system connecting all major ocean basins of the global ocean. Its flow, driven by strong westerly winds, is constricted to its narrowest extent in the Drake Passage, located between South America and the Antarctic Peninsula. Due to the remoteness of the area, harsh weather conditions and strong bottom currents, sediment recovery is difficult and data coverage is still inadequate. Here, we report on the composition of 51 surface sediments collected during the R/V Polarstern PS97 expedition (February-April 2016) across the western and central Drake Passage, from the Chilean/Argentinian continental margin to the South Shetland Islands and the Bransfield Strait (water depth: ∼100-4000 m). We studied microfossils (diatoms), bulk sediment composition and geochemical proxies (biogenic opal, organic carbon, calcium carbonate, carbon and nitrogen stable isotopes, sterols and photosynthetic pigments), and evaluated how they respond to, and reflect oceanic domains and polar to subpolar frontal systems in this region. Our multi-proxy approach shows a strong relationship between the composition of surface sediments and ocean productivity, terrigenous input, intensity of ocean currents, and ice proximity, clearly differentiating among 4 biogeographical zones. The Subantarctic Zone was characterized by warmer-water diatoms, high carbonate (>45%) and low organic carbon contents (avg. 0.26%), as well as low concentrations of pigments (avg. 1.75 μg/g) and sterols (avg. 0.90 μg/g). A general N-S transition from carbonate-rich to opal-rich sediment was observed at Drake Passage sites of the Polar Front and Permanently Open Ocean Zone. These sites were characterized by low organic carbon content (0.22%), high relative abundances of heavily silicified diatoms (≥60% Fragilariopsis kerguelensis), and abundant foraminifera at shallower stations. Approaching the Antarctic Peninsula in the Transitional Zone, an increase in the concentrations of pigments and sterols (avg. 2.57 μg/g and 1.44 μg/g, respectively) and a strong decrease in carbonate content was observed. The seasonal Sea-Ice Zone in the southern section of the study area, had the highest contents of biogenic opal (avg. 14.6%) and organic carbon (avg. 0.7%), low carbonate contents (avg. 2.4%), with the occurrence of sea-ice-related diatoms and sterols. In all zones, terrigenous input was detected, although carbon/nitrogen ratios and δ13Corg suggest a predominance of marine-derived organic matter; lower values of δ13Corg occurred south of the Polar Front. The new results presented here constitute a highly valuable reference dataset for the calibration of microfossil and geochemical proxies against observational data and provide a useful regional baseline for future paleo-research