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Paleoclimatological information derived from the study of lacustrine sedimentary records is not only biased by taphonomical processes but also by potential differences in the expression of climate variability in the sediments due to site-specific factors. Using a multiproxy approach (the elemental and isotopic compositions of organic matter, diatom assemblages, and marker pigments of algae and cyanobacteria), we study the different environmental signatures recorded since the Little Ice Age (LIA) in the sediments of two volcanic lakes located within the same caldera on S~ao Miguel Island (Azores Archipelago). Lake Santiago is a crater lake whose eutrophic status in the last stage of the LIA was linked to external nutrient inputs associated with this humid period. Its post-LIA evolution was forced by changes in the thermal structure of the water, which determined its degree of mixing and therefore nutrient availability through recycling from the hypolimnion. In contrast, the decadal to centennial limnological evolution of Lake Azul, a caldera lake 2.5 km from Lake Santiago, shows geochemical and micropaleontological signatures disconnected from climate variability until 1980/1990 CE due to its greater exposure to the fallout of tephra after a catastrophic eruption in c. 1290 CE. Only after 1980/1990 CE did a global warming scenario induce a common ecological restructuring of both lakes, involving the replacement of turbulence-loving algal taxa by species adapted to strengthening water column stratification. Nevertheless, this shift was relatively gradual in Lake Azul but more sudden in Lake Santiago, indicating that the local site-specific components still had an effect on the expression of climate change in the sediments. Despite the short history of anthropogenic pressure (compared to their continental counterparts) and the large atmospheric patterns operating over the Azores Archipelago, the sedimentary records of these two adjacent oceanic volcanic lakes reacted quite differently to climate changes., Spanish Ministry of Economy and Competitiveness projects PaleoNAO, RapidNAO and PaleoM-odes CGL 2010-15767 CGL 2013-40608-R, Fundacao para a Ciencia e a Tecnologia (FCT) PTDC/CTA-AMB/28 511/2017, Xunta de Galicia, European Social Fund (ESF), Spanish Ministry of Science and Innovation through the Ramon y Cajal Scheme RYC 2020-029253-I, Fundacao para a Ciencia e a Tecnologia (FCT) DL57/2016/ICETA/EEC 2018/25, Universidade da Coruna/CISUG

Despite the multidisciplinary and comprehensive approach taken in ref. 1, we acknowledge that there are still open questions that require further research. We emphasize that our study relies on multiple records that show the synchronous arrival of humans on multiple islands before ca. 1400 CE. Elias et al. (2) raise specific concerns about the record from Peixinho Lake, one of the five lakes included in the study, while ignoring the other multiproxy lake sediment records. The arguments presented by Elias et al. (2) do not undermine in any way the main conclusions of our paper, but still we would like to explicitly address the main criticisms with regard to the only record in question

15 pages, 4 figures.-- Under a Creative Commons license, A multiproxy approach was applied to a sediment core retrieved from the deep crater Lake Funda, located in the middle of the North Atlantic Ocean on Flores Island, Azores archipelago (Portugal). The purpose of this study was to determine how this ecosystem responded to natural and anthropogenic forces over the last millennium. We distinguished three main phases in lake evolution using multiproxy reconstructions and documentary sources. (A) Climate and lake catchment processes, as well as internal ones, were the main drivers of ecosystem variability before 1335 CE, when human disturbances were absent in the Lake Funda catchment. (B) The second phase is marked by unprecedented changes in all studied proxies between 1335 and 1560 CE, including abrupt changes in the composition and diversity of diatom and chironomid assemblages. Synergistic effects from high climate variability and the onset of human disturbances in the catchment (e.g., introduction of livestock) during the Medieval Climate Anomaly-Little Ice Age transition, led to an increase in lake trophic state from mesotrophic to eutrophic conditions. (C) In the last phase (1560 CE to the present), the eutrophic conditions in Lake Funda were maintained through a positive feedback loop between lake productivity and in-lake phosphorous recycling. Variability within the lake ecosystem was mainly associated with climate variability and internal lake dynamics (e.g., phosphorus remobilization). Our results show that a paleoecological approach is crucial to understanding lake ecological states in the present-day in order to develop locally adapted management and restoration strategies. A long-term perspective enables us to understand the harmful consequences of ongoing climate change and human disturbances on lake ecosystems, The research was funded by the Portuguese Science Foundation (FCT) (DL57/2016/ICETA/EEC2018/25) and the DISCOVERAZORES (PTDC/CTA-AMB/28511/2017), together with the PaleoModes project (CGL2016-75281-C2) funded by the Spanish Ministry of Economy and Competitiveness, and the Luso-American Foundation. AH is funded by the Spanish Ministry of Science and Innovation through the Ramón y Cajal Scheme (RYC2020-029253-I)

[Abstract] Coastal dunes evolve in direct response to primary drivers, such as wind and waves, which can significantly influence the landscape. Here, we examine the effects of the wind and wave regimes on the vegetation cover and shoreline position of the dune system that makes up the Doniños barrier on the rocky NW Iberian coast since the middle of the 20th century. By studying a series of aerial images, we determined that the vegetated dunes experienced net seaward shoreline advance at an average rate of 1.28 ± 0.01 m/year and an overall dune vegetation coverage expansion of 50.5 %. Available local atmospheric data indicated that wind stilling was the main factor responsible for these trends. However, the shoreline evolution process included annual-to-decadal periods dominated by stalled or reversed advances in energetic winters when waves could reach the foredune, causing erosion and vegetation cover deterioration. Consecutive energetic winters resulted in severe foredune erosion and slow to no recovery of shoreline advance thereafter. This work presents a case study in which a new conceptual model of the opposite and unbalanced effects of wind stilling and storm surges on foredune evolution dynamics is discussed and established under the current climate change scenario. This work was supported by the PALEOMODES (CGL2016-75281-C2) and IMPACOM (PID2019-107424RB-I00) projects of the Spanish Ministry of Economy and Competitiveness and the Ministry of Science and Innovation, respectively. The authors also thank Puertos del Estado for providing SIMAR point data and the Agencia Estatal de Meteorología (AEMET) for providing climate data. AH is funded by the Spanish Ministry of Science and Innovation through the Ramón y Cajal Scheme (RYC2020-029253-I). This work is a contribution to IGCP Project 725 ‘Forecasting Coastal Change’. Funding for open access charge was provided by the Universidade de Vigo/CISUG

Humans have made such dramatic and permanent changes to Earth's landscapes that much of it is now substantially and irreversibly altered from its preanthropogenic state. Remote islands, until recently isolated from humans, offer insights into how these landscapes evolved in response to human-induced perturbations. However, little is known about when and how remote systems were colonized because archaeological data and historical records are scarce and incomplete. Here, we use a multiproxy approach to reconstruct the initial colonization and subsequent environmental impacts on the Azores Archipelago. Our reconstructions provide unambiguous evidence for widespread human disturbance of this archipelago starting between 700-60+50 and 850-60+60 Common Era (CE), ca. 700 y earlier than historical records suggest the onset of Portuguese settlement of the islands. Settlement proceeded in three phases, during which human pressure on the terrestrial and aquatic ecosystems grew steadily (i.e., through livestock introductions, logging, and fire), resulting in irreversible changes. Our climate models suggest that the initial colonization at the end of the early Middle Ages (500 to 900 CE) occurred in conjunction with anomalous northeasterly winds and warmer Northern Hemisphere temperatures. These climate conditions likely inhibited exploration from southern Europe and facilitated human settlers from the northeast Atlantic. These results are consistent with recent archaeological and genetic data suggesting that the Norse were most likely the earliest settlers on the islands., This research is funded by Fundação para a Ciência e Tecnologia (DL57/2016/ ICETA/EEC2018/25) grant, DISCOVERAZORES research project (PTDC/CTA-AMB/28511/2017), the Spanish Ministry of Economy and Competitiveness research projects PaleoNAO (CGL2010-15767), RapidNAO (CGL2013-40608-R), and PaleoModes (CGL2016-75281-C2), and by the Luso-American Foundation. This work is contributing to the Institut de Ciència i Tecnologia Ambiental (ICTA) - Universitat Autonoma de Barcelona “Unit of Excellence” Maria de Maetzu (CEX2019-000940-M) grant. The International Atomic Energy Agency is grateful for the support provided to its Environment Laboratories by the Government of the Principality of Monaco.

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 (

[Abstract] The Atacama Desert in northern Chile is one of the driest deserts on Earth. Hyperaridity persists at least since the Miocene and was punctuated by pluvial phases. However, very little is known about the timing, regional spread and intensities of precipitation changes. Here, we present a new precipitation record from a sedimentary sequence recovered in a tectonically blocked endorheic basin that is located in the hyperarid core of the Atacama Desert. The chronostratigraphic framework of the record is given by a multi-disciplinary dating approach, suggesting an age of ca. 68 ka BP for the core base. The sequence consists of three sediment types, whose sedimentological and geochemical characteristics suggest different depositional processes that reflect different degrees in humidity. First, particularly fine-grained sediments with high clastic but low calcium sulfate and carbonate contents reflect a particularly dry climate with only sporadic precipitation events and fluvial supply via channel systems. Second, more coarse-grained sediments with lower clastic and higher calcium sulfate and carbonate contents reflect more moist conditions with stronger precipitation events that lead to fluvial activity not restricted to the channels but involving the slopes and plains in the catchment. Third, normally graded layers with an equally high proportion of calcium sulfate and carbonate reflect occasional high-precipitation events that caused sediment supply also from most distant parts of the catchment via severe flash floods. The sedimentary succession suggests that precipitation changes took place on orbital but also on millennial time scales. Rather moist periods occurred during most of MIS 2, several shorter periods within MIS 3 and parts of MIS 4. Comparison of the findings from the Huara record with selected climate records from continental and marine sites in South America suggests a strong precipitation heterogeneity across the Atacama. This heterogeneity is caused by pronounced differences in the dominating climate patterns and a shift from predominant summer rain in the north to winter rain in the south. Precipitation supply to the Huara clay plan is controlled by the atmospheric circulation rather than the surface temperature of the adjacent ocean.

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.

Coastal back‐barrier perched lakes are freshwater bodies that are elevated over sea‐level and are not directly subjected to the inflow of seawater. This study provides a detailed reconstruction of the Doniños back‐barrier perched lake that developed at the end of a small river valley in the rocky coast of the north‐west Iberian Peninsula during the Holocene transgression. Its sequence stratigraphy was reconstructed based on a core transect across the system, the analyses of its lithofacies and microfossil assemblages, and a high‐resolution radiocarbon‐based chronology. The Doniños perched lake was formed ca 4·5 ka bp. The setting of the perched lake was favoured by Late Holocene sea‐level stabilization and the formation of a barrier and back‐barrier basin, which was contemporaneous with the high systems tract period. This basin developed over marine and lagoonal sediments deposited between 10·2 ka bp and 8·0 ka bp, during rapidly rising sea‐level characteristic of the transgressive systems track period. At 1·1 ka bp, the barrier was breached and the perched lake was partially emptied, causing the erosion of the back‐barrier basin sediments and a significant sedimentary hiatus. Both enhanced storminess and human intervention were likely to be responsible for this event. After 1 ka bp, the barrier reclosed and the present‐day lake was reformed, with the water level reaching as high as 5 m above mean sea‐level. The depositional evolution of the Doniños system serves as a model of coastal back‐barrier perched lakes in coastal clastic systems that have developed over gently seaward‐dipping rugged substrates at small distances from the shoreline and under conditions of rising sea‐level and high sediment supply. A review of estuaries, back‐barrier lagoons, pocket beaches and back‐barrier perched lakes in the rocky coast of north‐west Spain shows that the elevation of the bedrock is the main factor controlling the origin and evolution of these systems., This study was funded by the Spanish Ministry of Economy and Competitiveness through the projects CONSOLIDER‐ Ingenio 2010 GRACCIE (CSD2007‐00067), RapidNAO (CGL2013‐40608‐R) and PaleoMODES (CGL2016‐75281‐C2‐1‐R). AH and ML were supported by the Portuguese Science Foundation (FCT) through post‐doctoral SFRH/BPD/79923/2011 and SFRH/BPD/82103/2011, respectively. RC is grateful for a PhD fellowship from the Xunta de Galicia (Plan I2C) co‐financed by the European Social 94 Fund.

Raposeiro et. al., Little is known about the effect of top predator introduction in historically fishless communities, especially on remote islands. This issue is important because it might strongly affect climate reconstructions derived from biota assemblages such as chironomids. Head capsule larval remains of chironomids have been studied in a 660 years lacustrine sedimentary sequence from Lake Azul (Sao Miguel Island, Azores archipelago) to assess the extent and timescale of the effect of the predator introduction occurring in this historically fishless lake. Analysis of similarity showed that the chironomid assemblage was statistically different before and after predator introduction (R = 0.78; p < 0.001). Abundance of chironomids was about 40% greater in the fishless lake period compared to the period in the presence of predator. Results show major change in chironomid assemblage coinciding with the first time of goldfish introduction (around 1790 CE), followed by carp (1890 CE) and pike (1979 CE) introductions. The composition of feeding group guilds changed following a pattern characterized by a decrease in abundance of detritivorous and predaceous taxa and an increase in abundance of grazing chironomid taxa. This study suggests that predator introduction was the most important factor affecting the chironomid assemblages in this natural, Azorean fishless lake, but predators did not affect all chironomid species. Other external forcings like major climate oscillations, anthropogenic activities in the catchment basin, and volcanic eruptions seem to play an additional role. The latest stage of the warm and arid Medieval Climate Anomaly (1000–1300 CE) favoured the occurrence of some warm-adapted chironomid taxa, which were absent through the Little Ice Age (ca. 1450–1850 CE) cool period. © 2016, Part of this study was financed by the Fundo Regional da Ciência e Tecnologia (M3.1.7/F/009/2011) and the PaleoNAO and RapidNAO projects of the Spanish Ministry of Education (CGL2010-15767 and CGL2013-40608-R, respectively). PMR was supported by Fundação para a Ciência e Tecnologia (SFRH/BPD/99461/2014). AH was supported by the Portuguese Science Foundation (FCT) through a post-doctoral grant (SFRH/BPD/79923/2011). This work was also funded by FEDER funds through the Operational Programme for Competitiveness Factors - COMPETE and by National Funds through FCT - Foundation for Science and Technology under the UID/BIA/50027/2013 and POCI-01-0145-FEDER-006821.

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 rocky and indented coast of NW Iberia is characterized by the presence of highly valuable and vulnerable, small and shallow barrier–lagoon systems structurally controlled. The case study was selected to analyse barrier–lagoon evolution based on detailed sedimentary architecture, chronology, geochemical and biological proxies. The main objective is to test the hypothesis of structural control and the significance at regional scale of any high-energy event recorded. This work is also aimed at identifying general patterns and conceptualizing the formation and evolution of this type of coastal systems. The results allowed us to establish a conceptual model of Holocene evolution that applies to rock-bounded barrier–lagoon systems. The initial stage (early Holocene) is characterized by freshwater peat sedimentation and ended by marine flooding. The timing of the marine flooding depends on the relation between the elevation of the basin and the relative mean sea-level position; the lower the topography, the earlier the marine inundation. Thus, the age of basin inundation ranged from 8 to 4 ka BP supporting significant structural differences. Once marine inundation occurred, all systems followed similar evolutionary patterns characterized by a phase of landward barrier migration and aeolian sedimentation towards the back-barrier (i.e. retrogradation) that extended circa 3.5 ka BP. The later phases of evolution are characterized by a general trend to the stabilization of the barriers and the infilling of the lagoons. This stabilization may be temporally interrupted by episodes of enhanced storminess or sediment scarcity. In this regard, washover deposits identified within the sedimentary architecture of the case study explored here suggest pervasive high-energy events coeval with some of the cooling events identified in the North Atlantic during the mid- to late Holocene.

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.

The late glacial-Holocene transition from the Lago Chungara sedimentary record in northern Chilean Altiplano (18°S) is made up of laminated sediments composed of light-white and dark-green pluriannual couplets of diatomaceous ooze. Light-white sediment laminae accumulated during short-term extraordinary diatom blooms whereas dark-green sediment laminae represent the baseline limnological conditions during several years of deposition. Diatom oxygen isotope ratios (δ18Odiatom) from 40 consecutive dark-green laminae, ranging from 11,990 to 11,450 cal year BP, show that a series of decadal-to-centennial dry–wet oscillations occurred. Dry periods are marked by relatively high isotope values whereas wet episodes are indicated by lower values. This interpretation agrees with the reconstructions of terrigenous inputs and regional effective moisture availability carried out in the lake but there is a systematic temporal disagreement between them owing to the non-linear response of the lacustrine ecosystem to environmental forcings. Furthermore, the δ18Odiatom record tracks effective moisture changes at a centennial scale. Three major phases have been established (11,990–11,800, 11,800–11,550, and 11,550–11,450 cal year BP). Each phase is defined by an increasing isotope trend followed by a sudden depletion. In addition, several wet and dry events at a decadal scale are superimposed onto these major trends. Spectral analyses of the δ18Odiatom values suggest that cycles and events could have been triggered by both El Nino-Southern Oscillation (ENSO) and solar activity. Significant ENSO frequencies of 7–9 years and 15–17 years, and periodicities of the solar activity cycles such as 11 years (Schwabe), 23 years (Hale) and 35 years (Bruckner) have been recognised in the oxygen isotope time series. Time–frequency analysis shows that although solar and ENSO forcing were present at the onset of the Holocene, they were more intense during the late glacial period. The early Holocene might have been mainly governed by La Nina-like conditions that correspond to wet conditions over the Andean Altiplano.

Lake Chungara´ (18 15¢S, 69 09¢W, 4520 m above sea-level) is the largest (22AE5 km2) and deepest (40 m) lacustrine ecosystem in the Chilean Altiplano and its location in an active volcanic setting, provides an opportunity to evaluate environmental (volcanic vs. climatic) controls on lacustrine sedimentation. The Late Quaternary depositional history of the lake is reconstructed by means of a multiproxy study of 15 Kullenberg cores and seismic data. The chronological framework is supported by 10 14C AMS dates and one 230Th/234U dates. Lake Chungara´ was formed prior to 12AE8 cal kyr bp as a result of the partial collapse of the Parinacota volcano that impounded the Lauca river. The sedimentary architecture of the lacustrine succession has been controlled by (i) the strong inherited palaeo-relief and (ii) changes in the accommodation space, caused by lake-level fluctuations and tectonic subsidence. The first factor determined the location of the depocentre in the NW of the central plain. The second factor caused the area of deposition to extend towards the eastern and southern basin margins with accumulation of high-stand sediments on the elevated marginal platforms. Synsedimentary normal faulting also increased accommodation and increased the rate of sedimentation in the northern part of the basin. Six sedimentary units were identified and correlated in the basin mainly using tephra keybeds. Unit 1 (Late Pleistocene-Early Holocene) is made up of laminated diatomite with some carbonate-rich (calcite and aragonite) laminae. Unit 2 (Mid-Holocene-Recent) is composed of massive to bedded diatomite with abundant tephra (lapilli and ash) layers. Some carbonate-rich layers (calcite and aragonite) occur. Unit 3 consists of macrophyte-rich diatomite deposited in nearshore environments. Unit 4 is composed of littoral sediments dominated by alternating charophyterich and other aquatic macrophyte-rich facies. Littoral carbonate productivity peaked when suitable shallow platforms were available for charophyte colonization. Clastic deposits in the lake are restricted to lake margins (Units 5 and 6). Diatom productivity peaked during a lowstand period (Unit 1 and subunit 2a), and was probably favoured by photic conditions affecting larger areas of the lake bottom. Offshore carbonate precipitation reached its maximum during the Early to Mid-Holocene (ca 7AE8 and 6AE4 cal kyr bp). This may have been favoured by increases in lake solute concentrations resulting from evaporation and calcium input because of the compositional changes in pyroclastic supply. Diatom and pollen data from offshore cores suggest a number of lake-level fluctuations: a Late Pleistocene deepening episode (ca 12AE6 cal kyr BP), four shallowing episodes during the Early to Mid-Holocene (ca 10AE5, 9AE8, 7AE8 and 6AE7 cal kyr BP) and higher lake levels since the Mid-Holocene (ca 5AE7 cal kyr BP) until the present. Explosive activity at Parinacota volcano was very limited between c. >12AE8 and 7AE8 cal kyr bp. Mafic-rich explosive eruptions from the Ajata satellite cones increased after ca 5AE7 cal kyr bp until the present.

This paper examines the interdependence among the different forcing factors in the evolution of the Traba coastal wetland (Galicia, NW Spain) based on lithofacies and diatom analyses of three cores reaching the basement. According to radiocarbon data, the wetland originated 5700 cal yr BP, a time when similar systems on the Atlantic coast of the Iberian Peninsula were formed. Diatom assemblage data allow the estimation of the sea level position at 5700 cal yr BP at least 7 m below present-day mean sea level. Attenuation of the sea-level rise at that time was a major driving mechanism that permitted the establishment of an incipient beach–dune complex, causing water-logging in the Traba basin. However, the location of this incipient wetland on a basement high, which prevented an open connection to the sea, made topographic inheritance the main forcing factor in the subsequent evolution of the wetland. Thus, Traba was never a coastal lagoon system, as it has sometimes been defined. The maximum permeability of the beach–dune complex enclosing the wetland was recorded after its origin until 2900 cal yr BP, when increased stormy conditions affected the Galician shelf waters. Since then, the evolution of the wetland has been mainly controlled by more local factors, especially the continental sediment supply. Changes in land use in the basin have accelerated the infilling of the water body since the 19th century. This rapid infilling makes the whole system more prone to total encroachment in the short term, rather than to sea drowning. Palaeoenvironmental analyses showing the main trends in the long-term evolution of coastal wetlands can be of key importance in any management decisions aimed at preserving these kinds of sensitive coastal environments. Ministerio de Ciencia y Tecnología; REN2000-0468 Ministerio de Ciencia y Tecnología; CGL2004-0048BTE

Engel et al. (2014) present a new approach to understand Holocene climate changes in the Central Andes. They reconstruct the relative temperature changes in the Western Cordillera for the last 4,300 years by characterizing the 13C composition of a plant species occurring in the Carhuasanta peat sedimentary record (Peru, 15º 30' S.

15 páginas, 6 figuras, 1 tabla, The coupling of lake dynamics with catchment biogeochemistry is considered the key element controlling primary production in mountain lakes at time scales of a few decades to millennia, yet little is known on the impacts of the morphometry of lakes throughout their ontogeny. As Lake Chungará (Central Andean Altiplano, northern Chile) experienced long-term lake-level fluctuations that strongly modified its area:volume ratio, it is an ideal system for exploring the relative roles that long-term climatic shifts and lake morphometry play on biosiliceous lacustrine productivity. In this paper, we review previous data on the percent contents of total organic carbon, total inorganic carbon, total nitrogen, total biogenic silica, isotopic composition of organic matter, carbonates, and diatom frustules, as well as data on the abundance of the chlorophycean Botryococcus braunii in this lake for the period 12,400–1300 cal yr BP. We also include new data on organic carbon and biogenic silica mass accumulation rates and the diatom assemblage composition of an offshore core dated using 14C and U/Th. Biosiliceous productivity in Lake Chungará was influenced by shifts in allochthonous nutrient inputs related to variability in precipitation. Humid phases dated at approx. 12,400 to 10,000 and 9600 to 7400 cal yr BP coincide with periods of elevated productivity, whereas decreases in productivity were recorded during arid phases dated at approx. 10,000 to 9600 and 7400 to 3550 cal yr BP (Andean mid-Holocene Aridity Period). However, morphometry-related in–lake controls led to a lack of a linear response of productivity to precipitation variability. During the late Glacial to early Holocene, lowstands facilitated complete water column mixing, prompting episodic massive blooms of a large centric diatom, Cyclostephanos cf. andinus. Thus, moderate productivity could be maintained, regardless of aridity, by this phenomenon of morphometric eutrophy during the early history of the lake. The subsequent net increase in lake level introduced modifications in the area of the epilimnion sediments versus the total volume of the epilimnion, preventing complete overturn. Surpassing a certain depth threshold at approx. 8300 cal yr BP caused cessation of the morphometric eutrophy conditions associated with Cyclostephanos cf. andinus superblooms. After 7300 cal yr BP, the lake experienced a decrease in biosiliceous productivity and a change of state that involved a stronger dependence on precipitation variability, with a lesser contribution of diatoms to the total primary productivity. Our results show that the interpretation of lacustrine paleoproductivity records as paleoclimatic archives needs to take into account the effects of changes in the epilimnion sediment area to epilimnion volume ratio in association with lake ontogeny, The Spanish Ministry of Science and Innovation funded this research 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)

Benthic foraminiferal, ostracod, calcareous nannoplankton and diatom assemblages have been analysed from the 25.45 sedimentary succession of a borehole drilled in the Santo André lagoon (southwestern Portugal). The zones and subzones recognized according to their microfossil content have been used to define six palaeoenvironmental stages extending from the Lateglacial to the present. Stage A and the lower part of stage B (14.2 to 10.0 ka) represent a postglacial terrestrial environment when sea level was below present. Following eustatic sea-level rise, a normal marine, open-bay environment established during the upper part of stage B (10.0 to 5.4 ka). Before 5.4 ka, a coastal lagoon developed as a consequence of a sandy barrier formation. Since then, natural variation in the permeability of the detrital barrier through time has been the primary control of the physical, chemical and biological features of the lagoonal environment: during stage C (5.4 to 3.6 ka) as a freshwater-dominated lagoon, stage D (3.6 to 1.6 ka) as a brackish lagoonal environment, and stage E (1.6 to 0.5 ka) as a return to a freshwater-dominated lagoon. Finally, in the last 400 years (stage F), human intervention on the sandy barrier (artificial open- and closed-inlet conditions) has provoked rapid and dramatic environmental changes in Santo André.

Subfossil biotic assemblages in lakes' surface sediments have been used to infer ecological conditions across environmental gradients. Local variables are usually the major drivers of assemblage composition, but in remote oceanic islands biogeographic filters may play a significant role. To assess the contribution of local and regional filters in the composition of subfossil diatom and chironomid assemblages in surface sediments, 41 lakes in Azores archipelago were studied and related to environmental variables. Ordination techniques were used to identify the forcing factors that best explain the composition of these assemblages. Both assemblages are influenced by multiple limnological variables (conductivity, pH and nutrients). However, diatom assemblages differed mainly in the proportion of planktonic versus benthic species along lakes' depth gradient while chironomids differed significantly among islands but not among lake depths. Thus, biogeographic filters play an important role in shaping islands' freshwater communities, particularly insect ones, more influenced by geographic variables. Results demonstrate the accuracy and potential of biotic remains in sediments for applied studies of lake ecology, trophic status, climatic trends and ecological reconstruction and evolution of lakes. In the Azores, the application of this information for the development of inference models is envisaged as a further step to accomplish these goals. © 2014 Springer International Publishing Switzerland., Part of this study was financed by the Fundo Regional da Ciencia e Tecnologia (M3.1.7/F/009/2011)and the PaleoNAO project of the Spanish Ministry of Education (CGL2010-15767).

Continental slopes are presumed key areas for deposition of organic carbon exported from the shelf. Analysis of across-slope differences in diatom and silicoflagellate fluxes recorded in bottom sediments of the Goban Spur margin, a typical North Atlantic slope environment, was carried out to test if they can provide information on the magnitude of advection of material from the shelf into deeper waters. Total diatom and silicoflagellate accumulation rates showed strong across-slope differences. Minimum values are recorded at the shelf break where maximum surface productivity conditions occur while the deeper sampling stations record fluxes as high as 183×106 valves cm–2 ka–1. While high diatom fluxes show a clear correspondence with the activity of a permanent bottom nepheloid layer operating in the region, they do not correlate with productivity patterns observed in the water column. Diatom assemblages are mainly composed of Chaetoceros resting spores and Thalassionema nitzschioides (Grunow) Grunow ex Hustedt, typical indicators of spring bloom conditions in the area. The absence of clear across-slope trends in the diatom assemblages is interpreted as the effect of random mixing driven by the strong hydrodynamic regime provoked by the activity of the bottom nepheloid layer. The dominance of Chaetoceros resting spores across the slope is related to important exportation of shelf-derived production. However, due to the broad ecological tolerances of the main taxa composing the diatom assemblages, they do not allow precise estimations on the magnitude of the primary vertical flux vs. the secondary lateral flux in this slope environment. Use of the tychoplanktonic and benthic diatoms, which are restricted to the neritic realm, allows only the estimation of the minimum amount of shelf-derived diatoms reaching the slope sediments (at least 13% of the total diatom assemblage for the upper slope area of the Goban Spur). This study shows that major limitations exist for the use of diatoms preserved in surface sediments of this area as tracers of shelf-derived production transported to the continental slope.

Diatom and sedimentological analyses of a 7.6-m core of the Albufeira coastal lagoon, western Portugal, provide information about the forcing factors and environmental history of the evolution of this lagoon during the last 2500 years. At this timescale, eustasy is considered to be a minor environmental control on the dynamics of the barrier-lagoonal system. Instead, these dynamics are forced by local factors, such as changes in the sand-barrier permeability. Lithological and diatom facies are compared with present-day environ ments and show that the lagoon evolved essentially as a slightly brackish water body with a salinity of around 1‰. This pattern was disturbed by three major episodes of sedimentation associated with threshold responses in the permeability of the barrier. The first ( c. 2370 BP) did not produce a specific lithological signal and is characterized by a peak in freshwater euplanktonic diatoms, implying an almost permanent isolation of the basin and freshwater flooding. A second episode was identified at c. 1600 BP, when a dramatic opening of the tidal inlet provoked a significant change in the sedimentation regime, which became dominated by inorganic, minerogenic sediments and allowed marine/brackish epiphytic diatoms to flourish together with allochthonous marine planktonic species. Finally, a third threshold occurred at c. 1225 BP corresponding to the establishment of the present-day muddy or sandy-muddy sedimentation pattern. Both the sedimentological features and the diatom assemblages indicate the establishment of a more tidally influenced environment. This reflects regular artificial breaching of the barrier associated with increasing anthropogenic intervention in the system.

Diatom distribution on continental shelf sediments from the upwelling area off Galicia (NW Iberian Peninsula) has been determined in 78 surface sediment samples. Three well defined biofacies with a close relationship to upwelling influence along the coast have been distinguished from both the absolute diatom abundances in the sediments and assemblage diatom composition based on multivariate statistics: Rias Baixas and the shelf areas south and north to Cape Finisterre. Chaetoceros resting spores as well as highest absolute diatom content in the sediments are recorded in the highly productive Rias Baixas where most of the primary production is due to intense upwelling phenomena. The western shelf, south of Cape Finisterre. is characterized by Thalassionema nitzschioides and Thalassiosira cf. leptopus. Both taxa reflect a minor influence of upwelling conditions and productivity related to more persistent nutrient input due to coastal outwelling rather than upwelling. Minor and patchy upwelling conditions as well as lower productivity in the northern shelf are characterized by the lowest absolute diatom content in the sediments and the important increase in relative abundance of the resistant Paralia sulcata. Caution must be taken in the interpretation of Paralia sulcata dominated biofacies in downcore studies since a juxtaposition of discontinuous upwelling conditions and dissolution effects may be the factors responsible for the relative increase on the taxon in the sediments. The obtained results show the extent and limitations of fossil diatom distribution in surface sediments as tracers of regional coastal upwelling conditions in continental shelves where the existence of extensive areas of relict sediments and transported diatoms may mask the present-day upwelling signal of the photic zone., This work was supported by the European Union in the framework of the MAST programme, contract no. MAS2-CT93-0069 (Ocean Margin Exchange, OMEX). It is also a contribution to projects XUGA10307B93 (Xunta de Guliciu) and APC-950010 (Direccibn General de Znvestigacibn Cien tljica y Ticnica)

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).

19 pages, The annual variation of the dissolved silica contributions to the ria of Vigo and its spatial distributions on the silicate sediment is considered using a box model. During winter, the silicate freshwater flux is high, about 10 mol Si s-l. This mixes with the ria water and is exported to the ocean. During the rest of the year, the most important source of dissolved silicate is the subsurface incoming flux of marine water to the ria which provides from 52% to 65% of the total. In these seasons, the redissolution of biogenic silicate is the second source and causes up to 46% of silicate inputs to the photic zone. The utilisation of dissolved silicate by the diatoms was 1 mol Si s-1, but increased to 11 mol Si s-1 in the event of upwelling. The abundance of silicate in sediments in different parts of the ria of Vigo is a consequence of the cited fluxes. The bottom of the inner middle zone in the ria receives diatoms in spring and summer when no upwelling occurs (from 50 to 120 mg Si m-2 d-1), and silicate is resupended due to sediment stirring during winter. The external mid-zone of the ria is richer in remains of diatoms and opal, there being no resuspension and sedimentation is greater than in other areas during upwelling events (172 mg Si m-2 d-1), as indicated by the relative abundance of Chaetoceros spp. spores.

Inputsofoiltotheseafromtankerincidentshavebeenmuchreducedinthelast20years,butarestillaregularoccurrence(Clark,2001).Recentmajorshippingdisasters were the sinking of the Erika off Brittany(France)in1999andofthePrestigeoffNWSpainin2002.Thedamagedonebytankerincidentsandotheroilspillshasvariedwiththetypeandvolumeofoil,weatherconditionsandtheareaandtimeofyearwheretheincidentstookplace,buttherearealwayseconom-ical,politicalandenvironmentalconsequences.Aswithothershipping,manyaccidentsinvolvingtankershap-pen every year and some areas (notably those nearmajorshippinglanes)aremorelikelytoexperiencelargespillsthanothers.Yetonaregionalscale,majoroilincidentsarestillsorarethatfewcountriescanclaimtobefullypreparedtocopewiththeresultantchaos.ThemannerinwhichboththeErikaandthePrestigeinci-dentsweretreatedbytheFrenchandSpanishauthori-ties,respectively,highlightedthislackofpreparedness.One of the most visible environmental effects of oilspills, not to be confused with necessarily the mostprofoundimpactonthe(marine)environment,issea-birdmortality.Theauthorshavebeeninvolvedinassessingtheim-pactofoilspillsonseabirdsinEuropeandinNorthAmericaoverthepast25years.Withfewexceptions,theneed toproperly assessthe impactofthese spills onseabirdshasnotbeenfullyappreciatedduringincidents,despitepressure from themedia and other interestedpartiesforaccurateanduptodateinformationonthedamage done. Consequently, the number of seabirdcasualtiesinvolvedinmanymajorspillshasonlybeenestimatedapproximately,whileimpactsatthepopula-tionlevelhavebeendifficulttodetermine.Mostseabirdspeciesarehighlymobileandarecapableoftravellinggreatdistances,eitheroutsidethebreedingseasonorsimplyinsearchforfood.Intheabsenceofaccuratefiguresandwithnoknowledgeofagestructuresandthepossibleoriginofthebirdsinvolved,itisverydifficulttopredictorinterpretpost-spillpopulationtrends.There are two inter-linked aspects to dealing withoiled seabirds during major spills. The first involvesbirdsfoundalive,andthehumanitarianeffortsmadetoclean,rehabilitate,andsuccessfullyreleasethemintothewild.Thiscanbearelativelyexpensiveandlogisticallycomplicatedprocess.Thesecondinvolvesassessingthelikelyimpactofthespillonthepopulationsofthosespeciesaffected.The successful rehabilitation of oiled seabirds re-quireshighqualityfacilitiesandexpertskills(includingveterinary).Fewoilspillsoccurwherebotharereadilyavailable,butinrecentyearstherehavebeensomerel-atively successful attempts to clean, rehabilitate, andreleasebirdswiththehelpofexpertteamsbroughtinfromabroad.Theneedtoestablishproperlyequippedrescuecentresisusuallyappreciatedveryrapidly,par-ticularly when images of heavily oiled seabirds arebroughttotheattentionofthepublicthroughthe(in-ternational)media.Oil spill impact assessment (OSIA) requires morethanthis,particularlysincemostseabirdcasualtiesinoilspillsdonotreachthecoastalive.Therefore,intheveryearlystagesofaspill,systematiccollection,recordingandscientificexaminationofdeadseabirdshastobeestablished.Themaininterfacebetweenthisprocessandrehabilitationeffortsisintegratingdataonseabirdsre-ceivedatrehabilitationcentres(andtheirfate)intoanoveralldatabaseofseabirdcasualties.TheprincipalaimoftheOSIAistoproperlyassessthedamagedonebythespill,intermsofrecordingthenumberofcasualties

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).

Easter Island (SE Pacific, 27°S) provides a unique opportunity to reconstruct past climate changes in the South Pacific region based on terrestrial archives. Although the general climate evolution of the south Pacific since the Last Glacial Maximum (LGM) is coherent with terrestrial records in southern South America and Polynesia, the details of the dynamics of the shifting Westerlies, the South Pacific Convergence Zone and the South Pacific Anticyclone during the glacial–interglacial transition and the Holocene, and the large scale controls on precipitation in tropical and extratropical regions remain elusive. Here we present a high-resolution reconstruction of lake dynamics, watershed processes and paleohydrology for the last 34 000 cal yrs BP based on a sedimentological and geochemical multiproxy study of 8 cores from the Raraku Lake sediments constrained by 22 AMS radiocarbon dates. This multicore strategy has reconstructed the sedimentary architecture of the lake infilling and provided a stratigraphic framework to integrate and correlate previous core and vegetation studies conducted in the lake. High lake levels and clastic input dominated sedimentation in Raraku Lake between 34 and 28 cal kyr BP. Sedimentological and geochemical evidences support previously reported pollen data showing a relatively open forest and a cold and relatively humid climate during the Glacial period. Between 28 and 17.3 cal kyr BP, including the LGM period, colder conditions contributed to a reduction of the tree coverage in the island. The coherent climate patterns in subtropical and mid latitudes of Chile and Eastern Island for the LGM (more humid conditions) suggest stronger influence of the Antarctic circumpolar current and an enhancement of the Westerlies. The end of Glacial Period occurred at 17.3 cal kyr BP and was characterized by a sharp decrease in lake level conducive to the development of major flood events and erosion of littoral sediments. Deglaciation (Termination 1) between 17.3 and 12.5 cal kyr BP was characterized by an increase in lake productivity, a decrease in the terrigenous input and a rapid lake level recovery, inaugurating a period of intermediate lake levels, dominance of organic deposition and algal lamination. The timing and duration of deglaciation events in Easter Island broadly agree with other mid- and low-latitude circum South Pacific terrestrial records. The transition to the Holocene was characterized by lower lake levels. The lake level dropped during the early Holocene (ca 9.5 cal kyr BP) and swamp and shallow lake conditions dominated till mid Holocene, partially favored by the infilling of the lacustrine basin. During the mid- to late-Holocene drought phases led to periods of persistent low water table, subaerial exposure and erosion, generating a sedimentary hiatus in the Raraku sequence, from 4.2 to 0.8 cal kyr BP. The presence of this dry mid Holocene phase, also identified in low Andean latitudes and in Patagonian mid latitudes, suggests that the shift of storm tracks caused by changes in the austral summer insolation or forced by “El Niño-like” dominant conditions have occurred at a regional scale. The palm deforestation of the Easter Island, attributed to the human impact could have started earlier, during the 4.2–0.8 cal kyr BP sedimentary gap. Our paleoclimatic data provides insights about the climate scenarios that could favor the arrival of the Polynesian people to the island. If it occurred at ca AD 800 it coincided with the warmer conditions of the Medieval Climate Anomaly, whereas if it took place at ca AD 1300 it was favored by enhanced westerlies at the onset of the Little Ice Age. Changes in land uses (farming, intensive cattle) during the last century had a large impact in the hydrology and limnology (eutrophication) of the lake., The Spanish Ministry of Science and Education funded the research at Raraku Lake through the projects LAVOLTER (CGL2004-00683/BTE) and GEOBILA (CGL2007-60932/BTE) and CONSOLIDER GRACCIE (CSD2007-00067). The Limnological Research Center and the Large Lake Observatory (University of Minnesota, USA) are acknowledged for technical assistance with the XRF-Core Scanner analyses. We acknowledge fellowship to A. Moreno from the European Commission's Sixth Framework Program (Marie Curie Fellowship 021673 IBERABRUPT).

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.

Oxygen isotopes of diatom silica and petrographical characterisation of diatomaceous laminated sediments of Lago Chungará (northern Chilean Altiplano) have allowed us to establish its palaeohydrological evolution during the Lateglacial-early Holocene (ca. 12 000-9400 cal. yr BP). These laminated sediments are composed of light and dark pluriannual couplets of diatomaceous ooze formed by different processes. Light sediment laminae accumulated during short-term diatom blooms whereas dark sediment laminae represent the baseline limnological conditions during several years of deposition. Oxygen isotope analysis of the dark diatom laminae show a general 18O enrichment trend during the studied period. Comparison of these 18Odiatom values with the previously published lake-level evolution suggests a correlation between 18Odiatom and the precipitation:evaporation ratio, but also with the evolution of other local hydrological factors as changes in the groundwater outflow as well as shifts in the surface:volume ratio of Lago Chungará. The lake expanded (probably increasing this ratio) during the rising lake-level trend due to changes in its morphology, enhancing evaporation. Furthermore, the lake's hydrology was probably modified as the groundwater outflow became sealed by sediments, increasing lake water residence time and potential evaporation. Both factors could cause isotope enrichment., The Spanish Ministry of Science and Education funded the research at Lago Chungara´ through the projects ANDESTER (BTE2001-3225), BTE2001-5257-E, LAVOLTER (CGL2004-00683/BTE) and GEOBILA (CGL2007-60932/BTE).

A high resolution multiproxy study (magnetic susceptibility, X-ray diffraction, XRF scanner, gray-colour values, Total Organic Carbon, Total Inorganic Carbon, Total Carbon and Total Biogenic Silica) of the sedimentary infill of Lago Chungará (northern Chilean Altiplano) was undertaken to unravel the environmental forcings controlling its evolution using a number of different multivariate statistical techniques. Redundancy analyses enabled us to identify the main provenance of the studied proxies whereas stratigraphically unconstrained cluster analyses allowed us to distinguish the “outsiders” as result of anomalous XRF scanner acquisitions. Principal Component Analysis (PCA) was employed to identify and isolate the main underlying environmental gradients that characterize the sedimentary infill of Lago Chungará. The first eigenvector of the PCA could be interpreted as an indicator of changes in the input of volcaniclastic material, whereas the second one would indicate changes in water availability. The chronological model of this sedimentary sequence was constructed using 17 AMS 14C and 1 238U/230Th dates in order to characterize the volcaniclastic input and the changes in water availability in the last 12,300 cal years BP. Comparison of the reconstructed volcaniclastic input of Lago Chungará with the dust particle record from the Nevado Sajama ice core suggested that the Parinacota volcano eruptions were the main source of dust during the mid and Late Holocene rather than the dry out lakes as has previously been pointed out. The comparison of the water availability reconstruction of Lago Chungará with three of the most detailed paleoenvironmental records of the region (Paco Cocha, Lake Titicaca and Salar Uyuni) showed an heterogeneous (and sometimes contradictory) temporal and spatial pattern distribution of moisture. Although the four reconstructions showed a good correlation, each lacustrine ecosystem responded differently to the moisture oscillations that affected this region. The variations in the paleoenvironmental records could be attributed to the dating uncertainities, lake size, lake morphology, catchment size and lacustrine ecosystem responses to the abrupt arid events., This research work was funded by the projects BTE2001-3225, BTE2001-5257-E and GCL2004-00683 from the Spanish Science and Technology Ministry.

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.

The Azores archipelago has provided significant clues to the ecological, biogeographic and evolutionary knowledge of oceanic islands. Palaeoecological records are comparatively scarce, but they can provide relevant information on these subjects. We report the palynological reconstruction of the vegetation and landscape dynamics of the São Miguel Island before and after human settlement using the sediments of Lake Azul. The landscape was dominated by dense laurisilvas of Juniperus brevifolia and Morella faya from ca. 1280 CE to the official European establishment (1449 CE). After this date, the original forests were replaced by a complex of Erica azorica/Myrsine africana forests/shrublands and grassy meadows, which remained until ca. 1800 CE. Extractive forestry, cereal cultivation (rye, maize, wheat) and animal husbandry progressed until another extensive deforestation (ca. 1774 CE), followed by the large-scale introduction (1845 CE) of the exotic forest species Cryptomeria japonica and Pinus pinaster, which shaped the present-day landscape. Fire was a significant driver in these vegetation changes. The lake levels experienced a progressive rise during the time interval studied, reaching a maximum by ca. 1778–1852 CE, followed by a hydrological decline likely due to a combination of climatic and anthropogenic drivers. Our pollen record suggests that São Miguel were already settled by humans by ca. 1287 CE, approximately one century and a half prior to the official historically documented occupation of the archipelago. The results of this study are compared with the few palynological records available from other Azores islands (Pico and Flores). © 2017 Elsevier Ltd, This research was funded by The Ministry of Economy and Competititvity, projects PaleoNAO (CGL2010-15767), RapidNAO (CGL2013-40608-R) and PaleoMODES (CGL2016-75281-C2-1-R). Arantza Lara is especially grateful to Jacqueline van Leeuwen, Florencia Oberli, Willi Tinner and Pim van der Knaap, for their help in different aspects of sample processing and pollen identification during her short stay in the Institute of Plant Science, University of Bern (Switzerland). Armand Hernández was supported by the Portuguese Science Foundation (FCT) through a post-doctoral grant (SFRH/BPD/79923/2011).