Siliceous microorganisms in the upwelling center off Concepción, Chile 36°S: Preservation in surface sediments and downcore fluctuations during the past ~ 150 yearsReport as inadecuate




Siliceous microorganisms in the upwelling center off Concepción, Chile 36°S: Preservation in surface sediments and downcore fluctuations during the past ~ 150 years - Download this document for free, or read online. Document in PDF available to download.

Resumen

We analyzed the temporal patterns of siliceous microorganisms in the water column and their representationin the underlying surface sediments between September 2002 and November 2005, at a fixed stationon the shelf off Concepción, Chile Station 18, 36 30.800S and 73 07.750W, connecting our results toinstrumental records of temperature, salinity, coastal upwelling and freshwater input. The goals of thestudy were to understand the seasonal representation of siliceous microorganisms in surface sedimentsand to evaluate the use of this information in the interpretation of past climatic-oceanographic conditionsin the area. The implications of seasonal and preservational biases are discussed. Additionally, a 30-cmcore collected at the same site and spanning the last 150 years of sedimentation was also studied inorder to provide a record of historical siliceous productivity changes.Firstly, the analyses focused on diatoms since they were numerically the most prominent microorganismsin the water column and the surface sediments, independent of season and year. In both settings,maxima of the key diatom genera Chaetoceros and Skeletonema coincided with the spring–summerupwelling period. For the autumn–winter non-upwelling period, significant plankton–sediment discrepancieswere observed, with enrichment of moderately robust taxa in the sediments, as well as freshwaterdiatoms and phytoliths tracing the increased river discharges in winter. Secondly, the downcoreanalysis revealed a marked decrease in total diatom accumulation rates since the late 19th and throughoutthe 20th century, which was accompanied by increasing concentrations of lithogenic particles andfreshwater diatoms. An alkenone-based sea surface temperature reconstruction in the same core past 150 years and instrumental data show that these changes occurred simultaneously with a generaltrend of increasing temperatures in the upwelling area off Concepción. Taken together, these signalssuggest an intensified influence of ENSO-like variability in the ocean-climate system off central-southernChile.Nota general

Artículo de publicación ISI



Author: Sánchez, Gloria E.; - Lange, Carina B.; - González, Humberto E.; - Vargas Easton, Víctor; - Muñoz, Praxedes; - Cisternas, Car

Source: http://repositorio.uchile.cl/



DOWNLOAD PDF




Related documents