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Paleoclimate records from the Atacama Desert are rare and mostly discontinuous, mainly recording runoff from the Precordillera to the east, rather than local precipitation. Until now, paleoclimate records have not been reported from the hyperarid core of the Atacama Desert (

The impacts of natural- and human-induced processes on lake ecosystems in remote oceanic islands remain to be fully elucidated. These lakes are excellent candidates to analyze the importance of anthropogenic vs. natural forces driving lacustrine long-term ecological evolution from previous pristine pre-colonized conditions. Disentangling the effects of both is particularly relevant in highly active volcanic areas, where catastrophic eruptions can act as an atypical natural driver altering the lake's long-term ecological trajectories. In this paper we study past ecological changes occurring in Lake Azul (São Miguel island), a crater lake from the remote Azorean archipelago, to address which were the main causes of its long-term trophic history. We analyzed diatom assemblages, sedimentology, and bulk organic matter of sediments deposited since ca. 1290 CE, when a huge local eruption occurred. This episode drove the evolution of Lake Azul through six distinct phases, commencing with a restart of ecological succession after tephra deposition disrupted biogeochemical cycling. The alteration was so profound that the lake underwent a state of oligotrophic conditions for approx. 650 yr. Nutrients were sourced by fish-induced internal recycling and the overflow of the near Lake Verde during this period, rather than by allochthonous nutrient inputs modulated by climate variability and/or vegetation cover changes in the watershed after the official Portuguese colonization. It was only after recent artificial fertilization when the system overcame the volcanic-induced long-term resilience. This over-fertilization and a reduction in water turnover exacerbated the recent symptoms of eutrophication after 1990 CE. Contrary to other studies, Lake Azul constitutes an uncommon case of long-term resilience to trophic change induced by a cataclysmic volcanic eruption. It brings new insights into the fate of lake ecosystems which might be affected by similar events in the future., This research was funded by the Ministry of Economy and Competitiveness projects PaleoNAO, RapidNAO and PaleoModes (CGL2010-15767, CGL2013-40608-R and CGL2016-75281-C2, respectively) and by the Fundação para a Ciência e a Tecnologia (PTDC/CTA-AMB/28511/2017). David Vázquez-Loureiro, Armand Hernández, María Jesús Rubio and Pedro Raposeiro benefited with grants from the Xunta de Galicia (I2C Programme co-funded with the European Social Fund), Generalitat de Catalunya (Beatriu de Pinós - Marie Curie cofund programme), Ministry of Economy and Competitiveness (Programa de Formación de Personal Investigador, FPI), and Fundação para a Ciência e a Tecnologia (SFRH/BPD/99461/2014), respectively.

Estuaries are sensitive to changes in global to regional sea level, to climate-driven variation in rainfall and to fluvial discharge. In this study, we use source and environmentally sensitive proxies together with radiocarbon dating to examine a 7-m-thick sedimentary record from the Sado estuary accumulated throughout the last 3.6 kyr. The lithofacies, geochemistry and diatom assemblages in the sediments accumulated between 3570 and 3240 cal. BP indicate a mixture between terrestrial and marine sources. The relative contribution of each source varied through time as sedimentation progressed in a low intertidal to high subtidal and low-energy accreting tidal flat. The sedimentation proceeded under a general pattern of drier and higher aridity conditions, punctuated by century-long changes of the rainfall regime that mirror an increase in storminess that affected SW Portugal and Europe. The sediment sequence contains evidence of two periods characterized by downstream displacement of the estuarine/freshwater transitional boundary, dated to 3570-3400 cal. BP and 3300-3240 cal. BP. These are intercalated by one episode where marine influence shifted upstream. All sedimentation episodes developed under high terrestrial sediment delivery to this transitional region, leading to exceptionally high sedimentation rates, independently of the relative expression of terrestrial/marine influences in sediment facies. Our data show that these disturbances are mainly climate-driven and related to variations in rainfall and only secondarily with regional sea-level oscillations. From 3240 cal. BP onwards, an abrupt change in sediment facies is noted, in which the silting estuarine bottom reaches mean sea level and continued accreting until present under prevailing freshwater conditions, the tidal flat changing to an alluvial plain. The environmental modification is accompanied by a pronounced change in sedimentation rate that decreased by two orders of magnitude, reflecting the loss of accommodation space rather than the influence of climate or regional sea-level drivers. FCT by Spanish Ministry of Science and Innovation [SFRH/BD/110270/2015, HAR2014-51830-P, HAR2011-29907-C03-00] FCTPortuguese Foundation for Science and Technology [PTDC/HISARQ/121592/2010] Instituto Dom Luiz-IDL [UID/GEO/50019/2013] info:eu-repo/semantics/publishedVersion

We examine the Holocene environmental changes in a wet dune slack of the Portuguese coast, Poco do Barbarroxa de Baixo. Lithology, organic matter, biological proxies and high-resolution chronology provide estimations of sediment accumulation rates and changes in environmental conditions in relation to sea-level change and climate variability during the Holocene. Results show that the wet dune slack was formed 7.5 cal. ka BP, contemporaneous with the last stages of the rapid sea-level rise. This depositional environment formed under frequent freshwater flooding and water ponding that allowed the development and post-mortem accumulation of abundant plant remains. The wetland evolved into mostly palustrine conditions over the next 2000 years, until a phase of stabilization in relative sea-level rise, when sedimentation rates slowed down to 0.04 mm yr(-1), between 5.3 and 2.5 cal. ka BP. Later, about 0.8 cal. ka BP, high-energy events, likely due to enhanced storminess and more frequent onshore winds, caused the collapse of the foredune above the wetlands' seaward margin. The delicate balance between hydrology (controlled by sea-level rise and climate change), sediment supply and storminess modulates the habitat's resilience and ecological stability. This underpins the relevance of integrating past records in coastal wet dune slacks management in a scenario of constant adaptation processes. Faculdade de Ciencias da Universidade de Lisboa [FCT UID/GEO/50019/2013]

The location of the Azores Archipelago in the North Atlantic makes this group of islands an excellent setting to study the long-term behavior of large oceanic and atmospheric climate dynamic patterns, such as the Atlantic Multidecadal Oscillation (AMO) and the North Atlantic Oscillation (NAO). Here, we present the impacts of these patterns on Lake Empadadas (Azores Archipelago) from the Medieval Climate Anomaly (MCA) - Little Ice Age (LIA) transition to the present based on sedimentological, geochemical and biological characterizations of the sedimentary record. Multivariate analyses of a number of proxies including X-ray fluorescence (XRF), X-ray diffraction (XRD), total organic and inorganic carbon (TOC and TIC) and diatom life forms abundance reveal that the sedimentary infill evolution has been controlled by (i) fluctuations in the lake level and (ii) variations in organic matter accumulation. Both processes are governed by climate variability and modulated by anthropogenic activities associated with changes on the lake catchment. Changes in these two sedimentary processes have been used to infer five stages: (i) the MCA-LIA transition (ca. 1350–1450 CE) was characterized by a predominantly positive AMO phase, which led to intermediate lake levels and high organic matter concentration; (ii) the first half of the LIA (ca. 1450–1600 CE) was characterized by predominant lowstand conditions and intermediate organic matter deposition mainly related to negative AMO phases; (iii) the second half of the LIA (ca. 1600–1850 CE) was characterized by negative AMO and NAO phases, implying intermediate lake levels and high organic matter deposition; (iv) the Industrial era (ca. 1850–1980 CE) was characterized by the lowest lake level and organic matter accumulation associated with negative AMO phases; and (v) the period spanning between 1980 CE and the present reveals the highest lake levels and low organic matter deposition, being associated with very positive AMO conditions. At decadal-to-centennial scales, the influence of the AMO on Azorean climate plays a larger role than previously thought. In fact, the AMO appears to exert a stronger influence compared to the NAO, which is the main mode of climate variability at shorter time scales. © 2017 Elsevier B.V., This work was financed by the Spanish Ministry of Economy and Competitiveness through the PaleoNAO project (CGL2010-15767/BTE) and the RapidNAO project (CGL2013-40608-R). Armand Hernández and Pedro Raposeiro were supported by the Portuguese Science Foundation (FCT) through a post-doctoral grant (SFRH/BPD/79923/2011 and SFRH/BPD/99461/2014, respectively). The support of the Generalitat de Catalunya to MERS (2014 SGR-1356) is also acknowledged.

Diatom-based carbon and oxygen isotope analyses (δ13Cdiatom and δ18Odiatom) were performed on diatomrich laminated sediments of Lake Chungará (Andean Altiplano, northern Chile) deposited during the Lateglacial and Early Holocene (12,400e8300 cal years BP) to reconstruct climate change and environmental response across this major climate transition. The δ13Cdiatom data show both centennial-tomillennial scale changes related to fluctuations in lake productivity and CO2 concentration in the lake water, and variations in carbon sources to the lake through time. The δ18Odiatom data reflect changes in lake hydrology and climate. The combination of δ13Cdiatom and δ18Odiatom data reveals interactions between the internal lake processes and its catchment runoff. During wet periods (low δ18Odiatom values) δ13Cdiatom indicates an enhanced contribution of allochthonous carbon, whereas during dry periods (high δ18Odiatom) δ13Cdiatom values suggest more autochthonous carbon production and recycling. These decadal-to-centennial oscillations are not recognized after 10,000 cal years BP, possibly as a result of ENSO-like phenomenon weakening. Humid conditions during the LateglacialeEarly Holocene transition (12,400e10,100 cal years BP) were possibly due to the establishment of La Niña-like conditions in the tropical South Pacific. Whereas, dry conditions in the Early Holocene (10,100e9100 cal years BP) may be caused by the northward migration of the ITCZ due to both ENSO-like weakening and an insolation minimum. Finally, a return to humid conditions at the end of the Early Holocene (9100e8300 cal years BP) is coincident with an increase in summer insolation. © 2012 Elsevier Ltd., The Spanish Ministry of Science and Innovation funded the research at Lake Chungará through the projects ANDESTER (BTE2001-3225), Complementary Action (BTE2001-5257-E), LAVOLTER (CGL2004-00683/BTE), GEOBILA (CGL2007-60932/BTE), PALEONAO (CGL2010-15767) and CONSOLIDER-Ingenio 2010 GRACCIE (CSD2007-00067). Armand Hernández is supported by a BPD fellowship (SFRH/BPD/79923/2011) from Portuguese Foundation for Science and Technology (FCT).

We analyzed the patterns of nucleotide sequence variation at three mitochondrial DNA loci, the noncoding mitochondrial control region and two genes (cytochrome b and cytochrome oxidase I) of Gavia immer in the largest collection of wintering individuals from Southern Europe to date. The sample consisted of 33 birds, oiled during the 2002/2003 Prestige tanker spill and washed ashore on the Galician coast (NW Iberian Peninsula). The aims of the study were to investigate the levels of standing genetic variation in the species, and to identify the geographic origin of these wintering birds. To do this, all available sequences of these loci, mostly from North American specimens collected from both the Atlantic and Pacific coasts, were retrieved from GenBank and included in the analysis. Overall, only 14 genetic variants were detected in the nearly 2 Kb surveyed, which reflects very low levels of nucleotide site diversity in this species. Interestingly, all variants were found at very low frequencies, and there was no indication of any clear subdivision in the G. immer population. This genetic profile is consistent with G. immer being a single panmictic population of small effective population size as compared with other seabirds. These circumstances preclude identification of the breeding regions of these wintering birds relying solely on genetic data. In the light of these results, possible causes, and the genetic and ecological consequences, of this demographic scenario are discussed.

Biogeochemical cycles and sedimentary records in lakes are related to climate controls on hydrology and catchment processes. Changes in the isotopic composition of the diatom frustules (δ18Odiatom and δ13Cdiatom) in lacustrine sediments can be used to reconstruct palaeoclimatic and palaeoenvironmental changes. The Lago Chungará (Andean Altiplano, 18°15′S, 69°10′W, 4520masl) diatomaceous laminated sediments are made up of white and green multiannual rhythmites. White laminae were formed during short-term diatom super-blooms, and are composed almost exclusively of large-sized Cyclostephanos andinus. These diatoms bloom during mixing events when recycled nutrients from the bottom waters are brought to the surface and/or when nutrients are introduced from the catchment during periods of strong runoff. Conversely, the green laminae are thought to have been deposited over several years and are composed of a mixture of diatoms (mainly smaller valves of C. andinus and Discostella stelligera) and organic matter. These green laminae reflect the lake's hydrological recovery from a status favouring the diatom super-blooms (white laminae) towards baseline conditions δ18Odiatom and δ13Cdiatom from 11,990 to 11,530cal years BP allow us to reconstruct shifts in the precipitation/evaporation ratio and changes in the lake water dissolved carbon concentration, respectively. δ18Odiatom values indicate that white laminae formation occurred mainly during low lake level stages, whereas green laminae formation generally occurred during high lake level stages. The isotope and chronostratigraphical data together suggest that white laminae deposition is caused by extraordinary environmental events. El Niño-Southern Oscillation and changes in solar activity are the most likely climate forcing mechanisms that could trigger such events, favouring hydrological changes at interannual-to-decadal scale. This study demonstrates the potential for laminated lake sediments to document extreme pluriannual events. © 2010 Elsevier B.V., The Spanish Ministry of Science and Innovation funded the research at Lago Chungará through the projects ANDESTER (BTE2001-3225), Complementary Action (BTE2001-5257-E), LAVOLTER (CGL2004-00683/BTE), GEOBILA (CGL2007-60932/BTE) and CONSOLIDER-Ingenio 2010 GRACCIE (CSD2007-00067).

47 páginas, 2 tablas, 6 figuras, A multiproxy study of sediments cores from Zoñar Lake (37º29’00’’N, 4º41’22’’ W, 300 m a.s.l.) supported by 11 14C AMS dates provides the first high-resolution centennial-scale reconstruction of past humidity changes in southern Spain during the last 4000 years. Arid periods occurred prior to 2.9 cal. kyr BP and during 1.3-0.6 cal. kyr BP (Medieval Climate Anomaly). The most humid period occurred during 2.6-1.6 cal. kyr BP encompassing the late Iron Age-Iberian and Roman epochs. Two humid periods of lower intensity occurred between 0.8 – 0.6 cal kyr BP (1200 – 1400 AD) and about 400 cal. yr BP (around 1600 AD) coinciding with the onset of the Little Ice Age. Humid conditions are synchronous with a decline in solar output and seem to correspond to atmospheric patterns similar to negative NAO phases. Arid conditions show better correlation with northern Africa climate evolution suggesting a possible link to subtropical dynamics. The geographic location of Zoñar Lake and the robust chronology provides an opportunity to improve our understanding of the climate evolution in mid latitudes during the Late Holocene and to evaluate subtropical and high latitude factors in Mediterranean climate evolution., Financial support for this study was provided by the Spanish Ministry of Science and Education (projects LIMNOCLIBER REN 2003-09130-CO2-02, IBERLIMNO CGL2004-20236-E, CALIBRE CGL2006-13327-C04/CLI and CGL-2006-2956-BOS) and Andalusian Government (PAI group RNM-328). A. Moreno acknowledges the funding from the European Commission’s Sixth Framework Program (Marie Curie Outgoing International Fellowships, proposal 021673-IBERABRUPT).We thank comments and suggestions from Herb Wright, who helped with a previous version of the manuscript, Francisco Mezquita and Javier Marco for their advice on ostracod identification and José.S. Carrión and Noemí Fuentes for pollen samples preparation. We also thank Achim Brauer for his support and dedication during the varve counting. We are also very grateful to the LRC (Minnesota, USA), and particularly to Doug Schnuremberger, Mark Shapley and Anders Noren for making possible the 2004 expedition. A.C. Stevenson and an anonymous reviewer provided constructive criticisms and suggestions.

18 páginas, 10 figuras, 3 tablas., High-resolution geochemical analyses obtained using an X-ray fluorescence (XRF) Core Scanner, as well as mineralogical data from the Lago Chungará sedimentary sequence in the northern Andean Chilean Altiplano (18°S), provided a detailed reconstruction of the lacustrine sedimentary evolution during the last 14,000 cal. yr BP. The high-resolution analyses attained in this study allowed to distinguish abrupt periods, identify the complex structures of the early and mid-Holocene arid intervals and to compare their timing with Titicaca lake and Sajama ice records. Three main components in the lake sediments have been identified: (a) biogenic component, mainly from diatoms (b) volcanics (ash layers) from the nearby Parinacota Volcano and (c) endogenic carbonates. The correlation between volcanic input in Lago Chungará and the total particles deposited in the Nevado Sajama ice core suggests the Parinacota Volcano as the common source. The geochemical record of Lago Chungará indicates an increase in siliceous productivity during the early Holocene, lagging behind the rise in temperatures inferred from the Nevado Sajama ice core. The regional mid-Holocene aridity crisis can be characterized as a number of short events with calcite and aragonite precipitation in the offshore lake zones., The Paleostudies programme (European Science Foundation) provided the necessary funding to carry out the analyses at the University of Bremen. This study is supported by the projects BTE2001-3225 and BTE2001- 5257-E and CGL2004-00683/BTE funded by the CICYT, the Spanish Ministry of Science and Technology. A. Moreno and P. González-Sampériz are the recipients of a CSIC research contract (I3P postdoctoral programme). S. Giralt acknowledges the Spanish Ministry of Science and Technology for his postdoctoral contract in the Ramón y Cajal programme.

48 Pag., 2 Tabl., 7 Fig. The definitive version is available at: http://www.springerlink.com/content/0921-2728/, The multidisciplinary study of sediment cores from Laguna Zoñar (37°29′00′′ N, 4°41′22′′ W, 300 m a.s.l., Andalucía, Spain) provides a detailed record of environmental, climatic and anthropogenic changes in a Mediterranean watershed since Medieval times, and an opportunity to evaluate the lake restoration policies during the last decades. The paleohydrological reconstructions show fluctuating lake levels since the end of the Medieval Warm Period (ca. AD 1300) till the late 19th century and a more acute dry period during the late 19th century – early 20th century, after the end of the Little Ice Age. Human activities have played a significant role in Laguna Zoñar hydrological changes since the late 19th century, when the outlet was drained, and particularly in the mid-20th century (till 1982) when the spring waters feeding the lake were diverted for human use. Two main periods of increased human activities in the watershed are recorded in the sediments. The first started with the Christian conquest and colonization of the Guadalquivir River Valley (13th century) particularly after the fall of the Granada Kingdom (15th century). The second one corresponds to the late 19th century when more land was dedicated to olive cultivation. Intensification of soil erosion occurred in the mid-20th century, after the introduction of farm machinery. The lake was declared a protected area in the early 1980s, when some agricultural practices were restricted, and conservation measures implemented. As a consequence, the lake level increased, and some littoral zones were submerged. Pollen indicators reflect this limnological change during the last few decades. Geochemical indicators show a relative decrease in soil erosion, but not changes in the amount of chemical fertilizers reaching the lake. This study provides an opportunity to evaluate the relative significance of human vs. climatic factors in lake hydrology and watershed changes during historical times. Paleolimnological reconstructions should be taken into account by natural resources agencies to better define lake management policies, and to assess the results of restoration policies., Financial support for research at Laguna Zoñar was provided by the Spanish Inter-Ministry Commission of Science and Technology (CICYT)(REN2000-1136 Project “Arid periods in the Mediterranean areas of the Iberian Peninsula since the last glacial maximum: chronology, characterization and paleoclimate implications”). Funding by projects REN 2003-02499GLO and PI 17/739/FS is also acknowledged.

A sedimentary and micropaleontological study of the Quillagua Formation provides a detailed paleohydrological reconstruction of the lacustrine system which occupied the present-day hyperarid Quillagua–Llamara fore-arc Basin (Northern Chile) from lattermost Miocene (5.8±0.4 Ma) to Early Pliocene times. Diatom and lithofacies analyses were carried out in two correlated stratigraphic sections of the lacustrine system. The Quebrada Temblor section is located at the southern margin of the ancient lake and is directly influenced by the freshwater inputs of a northward flowing fluvial system draining the Precordillera and Calama regions. The Cerro Mogote section occupies a western marginal location in the northern zone sheltered from direct fluvial inputs from the south but subjected to the activity of the alluvial fan systems of the Coastal Range. A mostly shallow oligosaline waterbody occupied the basin during the interval studied, though with fluctuations in salinity and the extent of the inner, open waters. The southern margin sector — represented by Quebrada Temblor — had, in general terms, a palustrine oligosaline character with almost freshwater conditions during certain periods, which favoured the establishment of semi-permanent to permanent freshwater plumes overlying a saline waterbody. Development of shoreline facies subjected to desiccation events was also characteristic at the top of this section. The innermost shallow lacustrine areas — represented by Cerro Mogote — maintained more homogeneous oligosaline characteristics and more persistent open waters. They were also subjected to freshwater pulses mediated in this case by the activity of the terminal alluvial fan zones. Paleohydrological evolution of the basin was strongly conditioned not only by shifts in the climatic–tectonic system but by variations in the local hydrological parameters. Four hierarchical orders of variability in the lake level of the basin were distinguished both by stratigraphic analysis of lithofacies and from changes undergone by the diatom record. Strong intrasample mixing of diatoms of incompatible salinity spectra and the presence of fine laminated lacustrine facies in some terms define the highest order short-term intra- or inter-annual pulses experienced by the lacustrine system (higher than 6th order). Diatom-based punctuated interruptions of the minor order bathymetrical trends highlight the high frequency variability in the basin (probably 6th order, 0.001–0.01 Ma), while the deepening/shallowing facies defined by the arrangement of the decimetre thick lithological sequences revealed a lower order of variability (5th order, 0.01–0.1 Ma). Combined lithofacies and diatom analyses delineate the lowest order of variability (4th order, 0.1–1 Ma) allowing the reconstruction of two well-established highstand and lowstand situations which implied the existence of a regressive trend between two transgressive trends. This order of variability is related to the interplay of tectonic events in the Calama Basin, and the regional climatic evolution during late Neogene to Pliocene times. European Union (CI1-CT 94-0069) Cataluña. Generalitat; SGR 1997-00073 Ministerio de Economía y Competitividad; PB94-0901

12 páginas, 6 figuras, 1 tabla, Local characteristics in the upwelling of Galicia (NW Iberian Peninsula) are studied in terms of dissolved silicate patterns in the seawater column and opal distribution in the sediments. Freshwater input, upwelling, remineralization and sedimentation are considered. The freshwater silicate input is not important during the upwelling season. Upwelling is the main process controlling silicate biogeochemistry activity in the coastal zone. Areas of silicate remineralization in the seawater column and opal abundance in surface sediment practically coincide. These together define the coastal limit of upwelling influence and its diverse local effects. Galician upwelling is important in the area surrounding three well-defined zones; Cape Finisterre, Cape Prior and La Corufia Canyon. South of Finisterre upwelling is more intense and closer to the coast. To the north, it is discontinuous and keeps distant from the coast, being near to the edge of the continental shelf, This paper is a contribution to the Spanish project APC95-0010: "El afloramiento de Galicia durante el cuaternario", financed by DGICYT and the EU project "Ocean Margin Exchange (OMEX)" ref. MAS2-CT93-0069.