TY - JOUR A1 - Romero-Viana, Lidia A1 - Kienel, Ulrike A1 - Sachse, Dirk T1 - Lipid biomarker signatures in a hypersaline lake on Isabel Island (Eastern Pacific) as a proxy for past rainfall anomaly (1942-2006 AD) JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - Isabel Lake is a hypersaline crater-lake on Isabel Island, Mexico, situated in the eastern tropical Pacific, an area highly sensitive to hydrological changes. Today, annual rainfall mostly occurs during the wet season, from June to October, when the northern edge of the Intertropical Convergence Zone (ITCZ) extends over the island. In order to evaluate the potential of sedimentary lipid biomarker signatures as a proxy of past hydro-climatic variability we have performed a calibration analysis comparing changes in biomarker distribution in the upper 16 cm of the sediment core with a regional instrumental data set. Annual laminations present in the sediment sequence allow for precise chronological control (1942-2006), More than 80 different lipid compounds were identified in the sediment and could be assigned to three major groups of source organisms: (1) algal populations; (2) a mixed community of ciliates, bacteria and cyanobacteria; and (3) photosynthetic sulfur bacteria. We found that the observed changes in the. relative contribution of the different lipid biomarkers to the sediment record were determined by the regional rainfall variability over the last 65 years. The planktonic community of Isabel Lake was highly sensitive to salinity fluctuations related to rainfall variability; seasonal precipitation results in freshwater input into the lake, driving an annual algal bloom and a relative decrease in the abundance of the more halotolerant populations of (cyano) bacteria and ciliates. Consequently, the concentration ratio between the two most abundant biomarkers in the Isabel Lake sediments, n-alkyl diols and tetrahymanol (which we define as the DiTe index), representing algal and ciliate planktonic populations, respectively, was significantly correlated with the seasonal rainfall anomaly (r = 0.68, p < 0.01). We propose that the DiTe index is a proxy of changes in the aquatic ecosystem of Isabel Lake and, by extension, regional hydrological changes in a sensitive climatic area of the eastern tropical Pacific. KW - Lipid KW - biomarkers KW - Diol KW - Tetrahymanol KW - ENSO KW - Salinity KW - Paleoclimate KW - Mexico Y1 - 2012 U6 - https://doi.org/10.1016/j.palaeo.2012.06.011 SN - 0031-0182 VL - 350 IS - 18 SP - 49 EP - 61 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ángel Puig-Samper, Miguel ED - Ette, Ottmar ED - Knobloch, Eberhard T1 - Humboldt and his geographical album of New Spain JF - HiN : Alexander von Humboldt im Netz ; International Review for Humboldtian Studies N2 - During his trip to New Spain in 1803, Alexander von Humboldt visited large tracts of New Spanish territory, which includes modern Mexico and part of the United States. This trip provided the data for his geographical Atlas of the region, as well as information about the ancient Mexican cultures that he would later include in the general Atlas and in other major works, such as Vues des Cordillères. Likewise, Humboldt’s Political Essay on the Kingdom of New Spain displayed a comprehensive physical, natural, economic, and social description of Mexico in the colonial period, which will also be analysed. With these works, Humboldt presented a new geographical and cultural image of New Spain to the European audiences. In addition to this, his work made important contributions to cartographic knowledge. N2 - Alexander von Humboldt en su viaje a Nueva España en 1803 tuvo la oportunidad de viajar por gran parte del territorio novohispano, que incluye Mexico y parte de del actual territorio de Estados Unidos. Este viaje le permitió preparar un Atlas geográfico de la región, además de obtener información sobre las antiguas culturas mexicanas que luego plasmará en el Atlas general del viaje y en algunas de sus principales obras como Vues des Cordillères. Asimismo, Humboldt hizo una excelente descripción física, natural, económica y social de México en la época colonial en su Ensayo político sobre el Reino de la Nueva España que también será analizado. Con estas obras Humboldt logró ofrecer una nueva imagen del territorio novohispano y sus riquezas al mundo europeo, así como un conocimiento cartográfico de gran importancia. N2 - Alexander von Humboldt, lors de son voyage en Nouvelle-Espagne en 1803, a eu l’occasion de parcourir une grande partie du territoire de la Nouvelle-Espagne, qui comprend le Mexique et une partie du territoire actuel des États-Unis. Ce voyage lui a permis de préparer un Atlas géographique de la région, ainsi que d’obtenir des informations sur les anciennes cultures mexicaines qu'il inclura plus tard dans l’Atlas général du voyage et dans certaines de ses œuvres principales comme Vues des Cordillères. Humboldt a également donné une excellente description physique, naturelle, économique et sociale du Mexique à l’époque coloniale dans son Essai Politique sur le Royaume de la Nouvelle Espagne, qui sera également analysé. Avec ces travaux, Humboldt a réussi à offrir au monde européen une nouvelle image du Nouveau territoire espagnol et de ses richesses, de même qu’une connaissance cartographique de grande importance. KW - New Spain KW - Mexico KW - geographical album Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-592335 SN - 2568-3543 SN - 1617-5239 VL - XXIII IS - 45 SP - 29 EP - 71 PB - Universitätsverlag Potsdam CY - Potsdam ER -